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Developmental Defects of the Axial Skeleton in Paleopathology Barnes, Ethne. University Press of Colorado 0870813161 9780870813160 9780585030197 English Paleopathology, Skeleton--Abnormalities. 1994 R134.8.B37 1994eb 616.07 Paleopathology, Skeleton--Abnormalities.
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Developmental Defects of the Axial Skeleton in Paleopathology Ethne Barnes UNIVERSITY PRESS OF COLORADO
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Copyright © 1994 by the University Press of Colorado Published by the University Press of Colorado, P.O. Box 849, Niwot, Colorado 80544 All rights reserved. The University Press of Colorado is a cooperative publishing enterprise supported, in part, by Adams State College, Colorado State University, Fort Lewis College, Mesa State College, Metropolitan State College of Denver, University of Colorado, University of Northern Colorado, University of Southern Colorado, and Western State College of Colorado. Library of Congress Cataloging-in-Publication Data Barnes, Ethne. Developmental defects of the axial skeleton in paleopathology / Ethne Barnes. p. cm. Includes bibliographical references and index. ISBN 0-87081-316-1 1. Paleopathology. 2. Skeleton Abnormalities. I. Title. R134.8.B37 1994 616.07 dc20 93-48329 CIP The paper used in this publication meets the minimum requirements of the American National Standard for Information SciencesPermanence of Paper for Printed Library Materials. ANSI Z39.48-1984 10 9 8 7 6 5 4 3 2 1
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For Arthur and little Ethne
Page vii
Contents Figures
xv
Tables
xxiii
Foreword
xxv
Preface
xxix
1. Introduction
1
The Morphogenetic Approach
3
Purpose
5
Methodology
6
2. The Development of Defects
9
Morphogenesis of the Axial Skeleton
14
A. Blastemal Stage
15
1. Notochord
16
2. Neural Tube
16
3. Paraxial Mesoderm
18
4. Prechordal Cranial Base
19
5. Blastemal Desmocranium
21
6. Branchial Arches
23
7. Frontonasal Process
25
8. Sternal Precursors
25
B. Cartilaginous Stage
27
1. Vertebral Column
27
2. Ribs
28
3. Chondrocranium
28
C. Osteogenic Stage
28
1. Vertebral Column
28
2. Ribs
30
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3. Chondrocranium
30
4. Membranous Skull
30
5. Mandible and Maxilla
30
6. Styloid Process
31
7. Sternum
31
Summary 3. Developmental Field Defects of the Vertebral Column, Ribs, and Associated Parts of the Cranium Part I. Notochord Field Defects A. Failure of the Notochord to Regress
31 35 35 36
1. Coronal Cleft Centrum
36
2. Sagittal Cleft Centrum
36
3. Mesenchymal Diastematomyelia
39
Summary Outline: Notochord Field Defects Part II. Neural Tube Field Defects A. Neurulation Defects
40 41 43
1. Cranium: Anencephaly
44
2. Vertebral Column: Meningomyelocele
44
B. Postneurulation Defects
46
1. Vertebral Column
46
a. Spinal meningocele with spina bifida cystica
46
b. Spinal meningocele with spina bifida occulta
47
c. Sacral agenesis
50
2. Cranium: Encephalocele and Meningocele
52
Summary Outline: Neural Tube Field Defects
54
Part III. Developmental Ectodermal Inclusion Cysts
55
A. Epidermoid Cysts
55
B. Dermoid Cysts
56
C. Dermoid Sinus
56
Summary Outline: Developmental Ectodermal Inclusion Cysts
57
Part IV. Paraxial Mesoderm Field Defects A. Segmentation Errors 1. Asynchronous Development of Hemimetamere Pairs
59 59
a. Hemimetamere shifts: hemivertebra
60
b. Hemimetamere hypoplasia-aplasia
62
2. Failure of Segmentation a. Block vertebra
58
63 63
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b. Klippel-Feil syndrome
67
3. Irregular Segmentation of Ribs
71
4. Neural Arch Joint Failure of Segmentation
76
5. Numerical Errors of Segmentation
78
B. Cranial-Caudal Border Shifting 1. Occipitocervical Border
79 81
a. Cranial shift
82
b. Caudal shift
88
c. Basilar impression
92
2. Cervicothoracic Border
99
a. Cranial shift
100
b. Caudal shift
102
3. Thoracolumbar Border
104
a. Cranial shift
104
b. Caudal shift
105
4. Lumbosacral Border
108
a. Cranial shift
108
b. Caudal shift
110
5. Sacrocaudal Border
114
a. Cranial shift
114
b. Caudal shift
114
6. Patterns of Border Shifting C. Developmental Delay of Vertebral Elements
116 117
1. Hypoplasia-Aplasia of the Neural Arch Complex 117 a. Cleft neural arch
117
b. Other neural arch defects
122
c. Transverse elements
125
2. Hypoplasia-Aplasia of the Centrum a. Hypoplasia
126
b. Aplasia
126
Summary Outline: Paraxial Mesoderm Field Defects 4. Developmental Field Defects of the Skull Part I. Prechordal Cranial Base Field Defects Summary Outline: Prechordal Cranial Base Field Defects Part II. Blastemal Desmocranium Field Defects A. Failure to Coalesce 1. Primary Suture Ossicles
126
129 134 134 138 138 140 141
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a. Patterned extra sutural ossicles
141
b. Fontanelle bones
142
c. Retention of the mendosa suture
142
d. Multiple interparietal bones of the occipital
143
2. Enlarged Parietal Foramina
143
3. Developmental Thinness of the Parietals
146
4. Metopism
148
B. Failure to Differentiate: Sutural Agenesis
152
C. Microcephaly
157
Summary Outline: Blastemal Desmocranium Field Defects
159
Part III. Branchial Arch I Field Defects
160
A. Field Defects of the Mandible
161
1. Developmental Delay
161
a. Cleft mandible
161
b. Hypoplasia-aplasia of the mandible
161
2. Bifid (Double-Headed) Condyles
163
3. Developmental Excess: Hyperplasia
167
a. Condylar hyperplasia
167
b. Coronoid hyperplasia
169
4. Developmental Inclusion Cyst (Stafne Defect)
170
B. Field Defects of the Maxilla
171
1. Developmental Delay
171
a. Cleft palate 2. Developmental Fissural (Inclusion) Cysts a. Median anterior maxillary cyst
171 175 177
b. Median palatal cyst
178
c. Globulomaxillary cyst
178
Summary Outline: Branchial Arch I Field Defects
179
Part IV. Blastemal Frontonasal Process Field Defects
180
A. Facial Clefts
180
1. Nasomaxillary Cleft
182
2. Naso-Ocular Cleft
182
3. Median Cleft
182
4. Bilateral/Unilateral Cleft Lip
184
5. Midline Cleft Lip
189
6. Hypoplasia of the Median Nasal Prominence: Binder's Syndrome
192
B. Nasal Bone Hypoplasia-Aplasia
192
C. Lacrimal Bone Hypoplasia-Aplasia
194
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Summary Outline: Blastemal Frontonasal Process Field Defects Part V. Branchial Arch I Ectodermal Groove Field Defects
196 197
Developmental Delay of the External Auditory Meatus 197 Summary Outline: Branchial Arch I Ectodermal Groove Field Defects
201
Part VI. Branchial Arch I Closing Membrane Field Defects
202
A. Developmental Defects of the Tympanic Plate: Tympanic Aperture/Cleft
202
B. Developmental Excess of the Styloid Sheath
204
Summary Outline: Branchial Arch I Closing Membrane Field Defects
205
Part VII. Branchial Arch II Field Defects
205
A. Failure of Bony Elements of Stylohyoid Chain to Ossify
207
B. Failure of Reichert's Cartilage to Differentiate
207
Summary Outline: Branchial Arch II Field Defects
208
5. Developmental Field Defects of the Sternum A. Failure to Differentiate
210 211
1. Manubrio-Mesosternal Joint Fusion
211
2. Misplaced Manubrio-Mesosternal Joint
212
3. Xiphisternal Joint Fusion
213
B. Developmental Delay 1. Cranial Fusion Delay Defects
215 215
a. Suprasternal ossicles
215
b. Delayed cranial cohesion of sternal bands
215
2. Caudal Fusion Delay Defects
217
a. Delayed caudal cohesion of sternal bands
218
b. Incomplete caudal cohesion of sternal bands
221
C. Developmental Excess of Sternal Bands
227
Summary Outline: Developmental Field Defects of the 227 Sternum 6. Developmental Field Defects of the Axial Skeleton in the 231 Puye and Central Pajarito Plateau Skeletal Population A. Paraxial Mesoderm Field Defects 1. Asynchronous Development of Hemimetamere Pairs
234 234
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2. Errors in Segmentation: Block Vertebrae
237
3. Irregular Segmentation of Ribs
241
4. Numerical Errors in Segmenation
241
5. Border Shifting in the Vertebral Column
244
a. Occipitocervical border shifting
244
b. Thoracolumbar border shifting
248
c. Lumbosacral border shifting
250
d. Sacrocaudal border shifting
255
6. Developmental Delay of the Vertebral Elements
259
a. Sacral neural arch defects
259
b. Atlas: posterior arch defects
265
c. Other vertebral element defects
267
B. Prechordal Cranial Base Field Defect
269
C. Blastermal Desmocranium Field Defects
271
1. Failure to Coalesce a. Primary suture ossicles
271 271
2. Metopism
277
3. Sutural Agenesis
277
D. Branchial Arch I Ectodermal Groove Field Defect: 278 Partial Atresia of the External Auditory Meatus E. Branchial Arch I Closing Membrane Field Defects: 278 Tympanic Aperture/Cleft F. Developmental Delay Field Defects of the Sternal Plates 1. Failure to Differentiate a. Manubrio-mesosternal joint fusion
281 282 282
b. Misplaced manubrio-mesosternal joint
284
c. Xiphisternal joint fusion
284
2. Caudal Fusion Delay Defects
287
a. Delayed caudal cohesion
287
b. Incomplete caudal cohesion
288
Conclusions Based on the Data 7. Puye and the Pajarito: Historical Background
298
Pajarito Plateau
301
Pajarito Plateau Prehistory
302
Ethnohistory
304
Pajarito Plateau Burials
307
Puye Burials
291
307
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Otowi Burials
309
Tsankawi Burials
311
Tsirege Burials
312
Summary of Pajarito Plateau Burials
312
Puebloan Socio-Religious Organization
313
Genetic Aspects
315
8. Summary and Interpretations
318
Glossary
323
Literature Cited
335
Index
351
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Figures The axial skeleton: skull, vertebral column, ribs, and 1.1sternum 2.1Stages of development of the axial skeleton
4 15
2.2Blastemal stage of development Schematic drawing of the development of the vertebral 2.3 anlage Schematic drawing of the development of the 2.4exoccipitals, atlas, and axis from the first and second cervical sclerotomes 2.5Development of the blastemal prechordal cranial base Stages of embryonic development, twenty-four days to 2.6 four weeks Stages of embryonic development, five weeks to nine 2.7 weeks 2.8Embryonic development of the face
17
2.9Development of the sternum Failure of the notochord to regress sagittal cleft centrum 3.1 (butterfly vertebra) Failure of the notochord to regress sagittal cleft T11 3.2 vertebra from the Trigg site in Virginia 3.3The human embryo at twenty-three days Neurulation neural tube defect: craniorhachischisis (brain 3.4 and spinal cord fissure) with anencephaly 3.5Different types of neural arch defects Neural arch defects of the sacrum: neural tube defect 3.6(spina bifida) versus developmental delay defect in the paraxial mesoderm (cleft neural arch) 3.7Neural tube defect: sacral agenesis
27
20 21 22 23 24 26
37 39 43 44 45 48 51
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Neural tube defect: postneurulation cranial meningocele 3.8 at bregma 53 3.9 Dermoid cyst from Amoxiumqua, New Mexico 58 3.10Variations of hemimetameric shift defects 61 Hemimetameric unilateral double shift in adult male 3.11 63 from Paucarcancha, in the highlands of Peru Hemimetameric shift with solitary hemivertebra of the 3.12fifth lumbar vertebral segment from Quarai, New 64 Mexico 3.13Variations of hemimetamere hypoplasia-aplasia 65 Mild unilateral multiple hemimetamere hypoplasia in 3.14 66 Chinese cannery worker from Alaska 3.15Failure of segmentation of the sclerotomes 68 3.16Type II block vertebra from Hawikku, New Mexico Type I block vertebra from Yellow Jacket outlying 3.17 village in southwest Colorado 3.18Variations of irregular segmentation of the ribs
69 73 74
3.19Examples of irregular segmentation of the ribs 75 Unilateral (L) merging of the first and second ribs from 3.20Heshotauthla, 76 New Mexico Merged first and second ribs, and cervical rib merged 3.21 77 with first rib 3.22Occipitocervical border shifting 83 Partial expressions of the occipital vertebra resulting 3.23 85 from cranial shifting of the occipitocervical border Precondylar tubercle resulting from cranial shifting at 3.24 86 the occipitocervical border Basilar transverse clefts and bifid condylar facets 3.25resulting from cranial shifting at the occipitocervical 87 border Type II odontoid defect resulting from cranial shifting at 3.26the occipitocervical border, with the separated apical tip 90 attached to the anterior rim of the foramen magnum
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Type V odontoid defect resulting from cranial shifting 3.27at the occipitocervical border Variations of occipitalization of the atlas resulting from 3.28caudal shifting of the occipitocervical border, from Peru Precondylar facet resulting from caudal shifting of the 3.29 occipitocervical border Occipitalization of the atlas resulting from caudal shifting of the occipitocervical border, with 3.30 pathological fusion of C2C3 block vertebra to the atlas 3.31Cervicothoracic border shifting Class III cervical ribs resulting from cranial shifting of 3.32 the cervicothoracic border Class IV cervical ribs resulting from cranial shifting of 3.33 the cervicothoracic border 3.34Thoracolumbar border shifting Lumbar rib resulting from caudal shifting of the 3.35 thoracolumbar border 3.36Lumbosacral border shifting Incomplete sacralization of L5 resulting from cranial 3.37 shifting of the lumbosacral border Incomplete and complete lumbarization of first sacral 3.38segment resulting from caudal shifting of the lumbosacral border 3.39Sacrocaudal border shifting Variations of developmental delay defects of the 3.40 vertebral elements Cleft atlas resulting from developmental delay of the 3.41 neural arch Bifurcated neural arch of T11 and T12 resulting from 3.42 developmental delay of the neural arch Bifurcated neural arch of L5 with cleft first and second 3.43sacral segments resulting from developmental delay of the neural arches Mild ventral hypoplasia of T11 and T12 vertebrae
91 93 97
98 103 106 107 109 110 112 113 115 118 121 122 123 124
3.44resulting from developmental delay of the centra
127
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3.45Developmental delay defects of the centrum 128 4.1 Elements of the prechordal cranial base 135 Defects of the basioccipital resulting from 4.2 developmental disturbance of the parachordal cartilages 137 Failure to coalesce defects in the blastemal 4.3 140 desmocranium 4.4 Enlarged parietal foramina 145 4.5 Developmental thinness of the parietals
147
4.6 Developmental thinness of the parietals from Egypt
149
4.7 Developmental thinness of the parietals from Peru
150
4.8 Metopism
151
4.9 Variations of sutural agenesis 153 Agenesis of the right side of the coronal suture without 4.10 156 plagiocephaly Agenesis of the sagittal suture with scaphocephaly in a 4.11 157 child Agenesis of the sagittal and lambdoidal sutures with 4.12 158 scaphocephaly and bulging occipital 4.13Cleft mandible resulting from developmental delay 162 Variations of mandibular hypoplasia-aplasia associated 4.14 164 with hemifacial microsomia Unilateral mandibular hypoplasia associated with type 4.15 165 II hemifacial microsomia Variations of bifid (double) mandibular condyles from 4.16 167 Hrdlicka (1941) Unilateral bifid mandibular condyle from Heshotauthla, 4.17 168 New Mexico 4.18Hyperplasia of the coronoid processes 169 Solitary developmental cyst (Stafne defect) in the 4.19mandible from developmental delay defect of the 170 mucosa 4.20Normal development of the palate 172
4.21Variations of cleft palate resulting from developmental 173 delay of the palatal processes of the maxilla
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4.22Bilateral cleft palate from Kentucky Developmental cysts of the mandibular and maxillary 4.23 mucosa 4.24Developmental components of the face Variations of facial clefting resulting from 4.25developmental delay defects involving the frontonasal process 4.26Median cleft face with hypertelorism
176
4.27Variations of cleft palate secondary to cleft lip
186
4.28Unilateral cleft lip and palate from Nazca, Peru Unilateral hypoplasia of the premaxilla with mild 4.29midline cleft lip and associated unilateral cleft palate from southwestern Colorado Unilateral hypoplasia of the premaxilla, creating cleft 4.30nares and associated unilateral cleft palate, from Pachacamac, Peru Mild hypoplasia of the median nasal prominence, 4.31 producing midface hypoplasia (Binder's syndrome) Variations of developmental delay defects of the nasal 4.32 bones 4.33Nasal bone hypoplasia and aplasia from Hawaii Normal development of the external auditory meatus 4.34 from the branchial arch I ectodermal groove 4.35Hypoplasia and aplasia of the external auditory meatus Unilateral atresia (aplasia of the ectodermal groove) 4.36 from Chicama, Peru 4.37Development of tympanic plate defects Variations of failure of portions of Reichert's cartilage 4.38 to differentiate 5.1 Immature sternum (manubrium and sternebrae)
188
5.2 Failue of sternal precursors to differentiate Manubrio-mesosternal joint fusion and xiphisternal 5.3 joint fusion from Hawikku, New Mexico
213
177 181 183 185
190
191 193 194 195 198 199 200 203 206 212
214
5.4 Development of suprasternal ossicles
216
5.5 Suprasternal ossicle from Hawikku, New Mexico
217
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Variations of delayed cranial cohesion defects of the 5.6 sternal plates 218 Variations of sternal types I, II, III, and IV based on 5.7 219 Ashley's method (1956) Large type III sternum contrasted with a small type I 5.8 220 sternum from Hawikku, New Mexico Sternal variations of types I, II, and III from Giusewa, 5.9 221 New Mexico Immature and mature type I sterna with hypoplasia of 5.10last sternal segment (sternebra) from Hawikku, New 222 Mexico Sternal variations of types I, II, and III from 5.11 223 Amoxiumqua, New Mexico 5.12Delayed caudal cohesion defects of the sternal plates 224 Sternal variations of types I and II from Heshotauthla, 5.13 225 New Mexico Sternal variations of type II from Pueblo Bonito, New 5.14 226 Mexico Large xiphoid aperture from Pueblo Bonito, New 5.15 228 Mexico Unusually large mesosternum from unknown Puebloan 5.16site in New Mexico compared to normal type II 229 sternum from Hawikku, New Mexico Asynchronous development of hemimetamere pairs for 6.1 T4 and T5: contralateral balanced shifting with failure 235 of segmentation (block vertebra) of T3, T4, and T5 6.2 Type II block vertebrae from Puye 238 6.3 Irregular segmentation of ribs from Puye Supernumerary vertebra at the thoracolumbar border 6.4 with transitional rib from Puye Precondylar facets resulting from caudal shifting at the 6.5 occipitocervical border from Puye and Tsankawi Paracondylar process resulting from caudal shifting at 6.6 the occipitocervical border from Puye Lumbar rib resulting from caudal shifting at the 6.7 thoracolumbar border from Puye
242 243 245 247 249
Page xxi
Sacralization of fifth lumbar vertebra resulting from 6.8 cranial shifting at the lumbosacral border from Puye 253 Unilateral incomplete sacralization of fifth lumbar 6.9 vertebra resulting from unilateral cranial shifting at the 254 lumbosacral border from Puye Incomplete sacralization of first caudal segment 6.10resulting from caudal shifting at the sacrocaudal border 256 from Puye Incomplete sacralization of first caudal segment 6.11resulting from caudal shifting at the sacrocaudal border 257 from Tsankawi 6.12Variations of sacral cleft neural arch from Puye 260 Sacrum with cleft first and second sacral segments 6.13 261 from Puye 6.14Cleft and bifurcated neural arches of sacrum from Puye 262 Variations of sacral cleft neural arch from Otowi and 6.15 263 Tsankawi 6.16Complete cleft sacra from Otowi and Tsankawi 264 6.17Posterior arch defects of the atlas from Puye Aplasia of the left side of the neural arch of C7, with 6.18 failure to completely segment from C6, from Tsankawi Scoliosis of cervical spine resulting from unilateral 6.19 aplasia of the neural arch of C7 from Fig. 6.18 6.20Abnormally small basioccipital from Puye Occipital with numerous lambdoidal ossicles and 6.21 occipital with interparietal bones from Puye 6.22Bregma fontanelle bones from Puye
266
6.23Metopism from Tsirege
276
6.24Tympanic cleft from Puye
279
6.25Variations of sternal defects from Puye
282
6.26Variations of sternal defects from Puye
283
6.27Variations of sternal defects from Puye
286
268 270 271 272 274
6.28Variations of sternal defects from Otowi
290
7.1 Maps of site locations
299
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Puye Mesa from the east looking west toward the mesa7.2 top pueblo and cliff house ruins along the south face 300 Reconstructed cliff house along south face of Puye 7.3 301 Mesa Map showing a: Four Corners region, and b: Pajarito 7.4 304 Plateau Map showing area where northern Rio Grande pueblos 7.5 305 are located Sketch map of Puye Pueblo and burial mound, 7.6 excavated by E. L. Hewett 308 in 1909 Sketch map of Otowi Pueblo and burial mounds, 7.7 excavated by E. L. Hewett in 1905 (redrawn from 310 Hewett 1906) Sketch map of Tsankawi Pueblo and burial mounds A, 7.8 B, and C excavated by E. L. Hewett in 1900 and 1905 311 (redrawn from Hewett 1906) Sketch map of Tsirege Pueblo and burial mound 7.9 excavated by E. L. Hewett in 1905 (redrawn from 313 Hewett 1906) Crania of a: adult female (NMNH 269281) and b: adult 7.10 316 male (NMNH 262947) from Puye
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Tables 2.1 Developmental Fields of the Axial Skeleton 2.2 Morphogenesis of the Axial Skeleton
13 33
6.1 Skeletal Collections Analyzed Developmental Fields Affected by Disturbances in the 6.2 Puye and Central Pajarito Plateau Skeletal Collections Frequency of Asynchronous Development of 6.3 Hemimetamere Pairs 6.4 Frequency of Block Vertebrae Frequency of Minor Occipitocervical Border Shifting 6.5 Associated with Failure of Segmentation (Block Vertebra) Frequency of Numerical Errors in Segmentation: Extra 6.6 Vertebral Segments Found in Complete Vertebral Columns Frequency of Precondylar Facets (minor Caudal 6.7 Shifting At the Occipitocervical Border) 6.8 Frequency of Minor Occipitocervical Border Shifting
232
6.9 Frequency of Thoracolumbar Border Shifting
250
6.10Frequency of Lumbosacral Border Shifting
251
6.11Frequency of Total Shifts At the Lumbosacral Border
252
233 236 239 240
243 246 247
6.12Frequency of Sacrocaudal Border Shifting 257 Trends in Border Shifting of the Vertebral Column For 6.13 258 Puye 6.14Frequency of Cleft/bifurcation of the Sacrum 262 6.15Frequency of Cleft Atlas 267 6.16Frequency of Prechordal Cranial Base Defect
269
6.17Frequency of Numerous Lambdoidal Ossicles
273
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6.18Frequency of Fontanelle Bones 6.19Frequency of the Retention of the Mendosa Suture
273
6.20Frequency of Metopism
277
6.21Frequency of Sutural Agenesis Frequency of Partial Atresia of the External Auditory 6.22 Meatus 6.23Frequency of Tympanic Aperture Known Frequencies of Tympanic Aperture in Anasazi 6.24 Populations 6.25Frequency of Sternal Types From Puye
277
6.26Frequency of Manubrio-mesosternal Fusion
284
275
278 280 281 281
6.27Frequency of Xiphisternal Fusion 285 Frequency of Manubrio-mesosternal and Xiphisternal 6.28Fusion in the 287 Same individual 6.29Frequency of Type III Sterna 287 6.30Frequency of Sternal Aperture and Cleft 288 6.31Frequency of Xiphoid Aperture and Cleft Frequency of individuals Affected by One Or More 6.32 Caudal Cohesion Defects of the Sternum
288 291
Page xxv
Foreword Research in human skeletal paleopathology has undergone major changes during the past twenty-five years (for example, Ortner and Aufderheide 1991). During this period we have seen a much greater emphasis on population dynamics in disease and a greater focus on integrating research in paleopathology within an evolutionary theoretical context. Other developments include greater sophistication in differential diagnosis and, recently, the application of state-of-the-art biochemical technology to problems in skeletal paleopathology. Despite these changes, considerable room remains for further development of research in paleopathology. The story about past disease that can be extracted from archaeological human remains does have inherent limitations. However, the experience of the past twenty-five years clearly reveals again that much more can be learned if we approach the subject with a thorough understanding of all of the factors that contribute to abnormal change or development in skeletal tissue. This scholarly rigor must be combined with careful observation of abnormal features and an attempt to reconstruct the pathological processes that contributed to the abnormality. In other contexts (for example, Ortner 1991; Ortner 1992) I have appealed for greater attention to the methods, both descriptive and analytical, that we use in skeletal paleopathology. In the past too much emphasis has been placed on what is often superficial diagnostic methods that apply a name to an abnormality but leave unstated and perhaps unobserved all of the abnormal anatomical details associated with the case. I am indebted to many biomedical scientists who have shared their knowledge and insight with me. This, added to my own experience over the past thirty years, has taught me that careful attention to the details of abnormal anatomy is crucial to understanding the pathological process (pathogenesis) associated with a specific case of skeletal paleopathology. Diagnosis should be the end product of careful observation and description, not a shorthand for avoiding this basic element in paleopathological research. Descriptive rigor is essential in case studies of skeletal paleopathology. Is bone being added, destroyed, or both? What are the
Page xxvi
margins like that are adjacent to abnormal bone destruction? Is the bone tissue that results from abnormal bone formation well organized or poorly organized? Is the size or shape of the bone abnormal? What is the distribution pattern of abnormal bone? These and related questions need to be answered in detail to ensure that the diagnostic options are appropriate but also to give other scholars the information needed to arrive at an independent diagnostic opinion. Equally important are a thorough knowledge and understanding of the biology underlying and associated with a skeletal abnormality. Genetics and the phenotypic expression of our genetic heritage are important. Embryology and the factors that can affect the development of the embryo and fetus have obvious relevance, particularly for congenital diseases. Postnatal growth and development and the many factors, including infectious, nutritional, and metabolic variables, that can affect the developing embryo need to be understood. The way in which the size and shape of the skeleton are formed (morphogenesis) and the factors that adversely affect this process constitute another body of information that needs careful consideration in skeletal paleopathology. In the following pages, Dr. Ethne Barnes provides an excellent and instructive example of how a thorough understanding of embryology and developmental anatomy of the axial skeleton can be used in interpreting even rather subtle abnormalities in archaeological human skeletal remains. The focus of her research is the axial skeleton in samples of archaeological human remains from the American Southwest. In these remains Dr. Barnes looks for features that indicate developmental defects associated with embryological development in the first trimester of pregnancy. She argues that although these developmental defects rarely incur serious disease, they are correlated with congenital defects that are often lethal in utero or early in the postuterine period and that, because of early and high mortality, rarely appear in archaeological human skeletal samples. By the study of less severe developmental defects in the population, she can estimate the prevalence of the more serious congenital defects, even though direct evidence of such defects may be lacking. However, Dr. Barnes goes well beyond describing and counting these conditions. She provides a rich background on the embryological development of the axial skeleton, which is no mean task. The development of the axial skeleton, particularly the vertebral column, in utero through early childhood is probably the most complex in the entire skeletal system, seeming almost as if it were designed by a committee of middle-level government bureaucrats. However, it works most of the time, so this could not be the case.
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Indeed, it is remarkable, given this complex developmental process, that serious developmental defects of the axial skeleton do not occur more often. In the less serious defects that can be identified by careful observation of archaeological human skeletal remains lies the greatest potential for clarifying several historical and biomedical problems. Dr. Barnes stresses the importance of timing in the embryological development of the axial skeleton, particularly during the first trimester. A number of intrinsic and extrinsic factors can disrupt timing. Serious disruptions tend to be lethal to the embryo, and when they occur, they will typically be aborted early in fetal life. Some will permit complete fetal development but will cause death during the perinatal period. Many disruptions do not have serious effects and are fully compatible with normal adult life unless they are complicated by other factors, such as trauma. The approach Dr. Barnes takes of careful anatomical observation combined with substantial knowledge of embryological development has powerful explanatory power in interpreting abnormalities apparent in human skeletal remains. Biparietal thinning, for example, is a feature that is well-known but poorly understood in the literature on skeletal paleopathology. Dr. Barnes provides a review of this abnormality and attributes it to an embryological delay in the development of the diploe. She cites reports of this condition in infants and children, demonstrating clearly that the abnormality is not a senile change. This explanation of biparietal thinning was, somewhat to my embarrassment, new to me, because I had accepted without question the better-known and more traditional interpretations. However, it makes good sense and should relegate other explanations to the scientific dustbin. Dr. Barnes's book is richly endowed with similar insights that will undoubtedly enhance the ability of scholars to understand and interpret evidence of disease in archaeological human skeletal remains. She has done us all a great service. References Ortner DJ 1991. Theoretical and methodological issues in paleopathology. Pages 511 in Ortner, DJ and Aufderheide, AC, Human Paleopathology: Current Syntheses and Future Options. Washington, D.C.: Smithsonian Institution Press.
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Ortner DJ 1992. Skeletal paleopathology: Probabilities, possibilities, and impossibilities. Pages 513 in Verano, JW and Ubelaker, DH, Disease and Demography in the Americas Washington, D.C.: Smithsonian Institution Press. Ortner DJ and Aufderheide AC 1991. Human Paleopathology: Current Syntheses and Future Options. Washington, D.C.: Smithsonian Institution Press. DONALD ORTNER
Department of Anthropology National Museum of Natural History Smithsonian Institution
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Preface As an anthropologist, I am forever fascinated by the wide range of diversity in human culture and biology. Through my studies of human variation, I have learned to appreciate cultural and biological differences of human populations throughout the world, with an understanding of how important a role diversity plays in our lives. Without this diversity, evolutionary change, both cultural and biological, could not take place. Change is necessary. We are constantly shifting our demands on the environment, a process that has been ongoing since the dawn of humankind. As we make changes in our use of the world we live in, we change the way we are, both culturally and biologically. Most of the time the changes are subtle; cultural change proceeds on a different plane than biological change. We understand cultural change, but biological change is less understood and is much more complex. Life itself is a continuum of change. The embryo of all living things is a microcosm of evolution. As each individual embryo grows and develops, the evolutionary history of its species, along with the evolutionary tendencies for change, unfolds within its genetic background. This propensity for change within the evolutionary process makes the evolving embryo vulnerable to disruptions in its development. For every successfully developed embryo, countless others do not develop correctly. Sometimes the error is minor and causes little developmental disruption, and sometimes the error leads to total dysfunction of the embryo. In order for the possibility of needed biological change to occur, the microstructure of our genetic makeup must remain open-ended, able to rearrange itself to meet changing demands on the organism. Constant environmental pressures bombard all living organisms, causing them to shift their biological defenses accordingly. Most of these shifts go unnoticed; we are more likely to notice those that lead to dysfunction. Pathogens have been a constant threat to our well-being since life began on this planet. Our immune systems are always rearranging themselves to defend us against our everchanging microenvironment. During this process,
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many succumb, although enough of us survive to reproduce the next generation, which is equipped with a more adept immune system. Most of the environmental pressures on our bodies were met as we evolved, but our genes continue to carry the potential for change as needed. This is the living organism's strength as well as its weakness. The potential for change in order to survive in a changing environment makes the embryo vulnerable to errors in development, yet without it, we cannot survive. This vulnerability allows for biological change. Genetic mutation is ongoing and opportunistic, sometimes acting alone on a susceptible genetic background and at other times acting in tandem with an external factor. However, if the genetic background of the developing embryo does not accept the modifications offered by the mutant gene or its external agent, no change occurs. Although the potential for change in all aspects of our genetic being is constant, only when conditions for change are favorable will it take place. Most biological changes are miniscule and have a neutral effect on the living organism. Normal anatomy and physiology are actually represented by a range of acceptable variability that does not interfere with adequate functioning of the living organism. Most of us would not fit a cookie cutter pattern in our biological makeup. Human variation is necessary for the survival of our species. Population differences reflect genetic separation in time and space brought on by cultural and geographic barriers. The range of human variability differs from one population to another; some populations appear similar in genetic makeup, whereas other populations are very different. It all depends upon the selection and pooling of specific gene matrixes through time. Susceptivity to disturbances in embryonic development varies among different populations. Some populations are more prone to certain types of developmental disturbances than other populations. Every population has its own genetic pattern of developmental tendencies for producing particular defects. The range of expression of these defects can vary from minor, non-life-threatening expressions to major, lifethreatening outcomes. Environmental factors sometimes trigger the development of defects in susceptible individuals within a population. My research interests focus primarily on the skeletal biology and diseases of ancient populations (paleopathology). While searching for evidence of congenital defects in prehistoric skeletal collections for my dissertation research at Arizona State University, I realized that they only represent the tip of the iceberg in developmental defects. Concentrating on the axial
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skeleton, I soon discovered that each defect in development of a particular part or structure of the axial skeleton is represented by a range of expressions, varying from minor to major types. By studying the embryonic development of the axial skeleton, I was able to determine the process of development of these defects and devise a method for identifying and classifying them. This is known as the ''morphogenetic approach." Once I developed this method, I tested it on a large prehistoric skeletal collection in the National Museum of Natural History of the Smithsonian Institution in Washington, D.C. The collection comes from the Pueblo IV (A.D. 13001540) archaeological community of Puye on the Pajarito Plateau in north central New Mexico. The testing was a success; I applied this method to other Pajarito Plateau skeletal collections of the same time period (Otowi, Tsankawi, and Tsirege) for comparison, and I found that they all shared similar patterns of developmental disturbances, suggesting that they all came from the same population. The ranges of developmental defects in the axial skeleton can serve as genetic markers of a prehistoric skeletal collection, as well as tell us whether a population from the past was susceptible to severe congenital defects. This is only the beginning. I am now applying this approach to the study of other prehistoric skeletal collections from the Southwest in order to determine population patterns for trends in developmental disturbances. These data can then be used to determine genetic relationships between prehistoric populations and the movement of populations throughout the Southwest. I hope this text will serve other researchers in similar ventures in skeletal biology and that it will be of use to clinicians working with developmental defects. The methodology remains open-ended so that additional discoveries of developmental disturbances in the axial skeleton can be added. The next step is to devise a similar approach to the appendicular skeleton, then to other types of defects within the skeleton and to other parts of the body, as well as to multiple defects. My research would not have been possible without the support, advice, and constant encouragement of Arthur Rohn and Ethne Rhea. They stood by me through the long and difficult process of developing the morphogenetic approach. My dissertation adviser at Arizona State University, Chuck Merbs, initiated my interest in developmental defects and taught me the important aspects of cranial-caudal shifting of the vertebral borders. My dissertation committee members, Don Morris, Alfred Dittert, Mary Marszke, and Enrique Gerszten, provided valuable criticism, and the staff at the National
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Museum of Natural History of the Smithsonian Institution Don Ortner, Agnes Stix, David Hunt, Carol Butler, and Bob Mann provided much support for and interest in my research. My understanding of the archaeological context of the skeletal collections used to test the morphogenetic approach was helped by archaeologists Joan Mathien of the National Park Service in Santa Fe and Bev Larson of the Los Alamos Scientific Laboratories. Joan provided me with the early field notes on the burials from the Pajarito Plateau, and Bev shared her knowledge of the archaeology of the Pajarito Plateau. ETHNE BARNES
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Chapter 1 Introduction This text is intended as a guide for identifying and classifying developmental defects of the axial skeleton, focusing on skeletal remains of past populations. A morphogenetic approach is applied to the understanding of defects recognized at birth and other disturbances of development in the axial skeleton that go unrecognized at birth; these include minor expressions of major birth defects. This approach can be used to assess the epidemiology and familial links of birth defects affecting the axial skeleton and to assess the genetics of past populations. The morphogenetic method introduced here is the result of cumulative research over several years by many different investigators; I have only pulled it together into one comprehensive system. Researchers studying human skeletal remains from the past have been intrigued yet baffled by congenital defects. Achondroplasia, hydrocephaly, microcephaly, various forms of craniosynostosis, cleft palate, enlarged parietal foramina, Klippel-Feil syndrome, spina bifida, congenital scoliosis, and various fusion anomalies, as well as other types of congenital defects, have been recognized in prehistoric skeletal collections throughout the world. However, the actual number of specimens with known congenital defects reported in prehistoric skeletal collections has grown only slightly over the years (Brothwell and Powers 1968), and little has been done to investigate the complexities of these disorders. A call for papers to bring together research reports on congenital defects in prehistoric and early historic skeletal remains for the 1979 Paleopathology Association meeting was cancelled for lack of response. Few responded to another attempt in 1983. Until quite recently, paleopathologists have felt that congenital defects were rare and difficult to find in prehistoric skeletal material (Gregg 1983; Manchester 1983; Reyman 1983; Saul 1983; Zivanovic 1982). Part of the problem is definition (Turkel 1989). "Congenital defect" implies a severe developmental disorder identifiable in the newborn, but not
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all developmental defects are detectable at birth. The majority of such defects remain undetected until exacerbated by growth and development in childhood or adolescence or by functional stress or trauma in adulthood (Arey 1965; Goodman and Gorlin 1983; Saxen and Rapola 1969). Restricting research to the severe defects detectable at birth (which are also generally lethal) eliminates the bulk of defects that are not detected at birth (which are generally not lethal). Therefore, it is more appropriate to focus on developmental defects than on congenital defects. Shifting the focus from congenital to developmental defects changes our perspective, and attention can rightfully be placed on the frequent occurrence of minor variations of major defects, as well as those variations of less severe defects commonly referred to as "anomalies" (Brothwell 1967; Brothwell and Powers 1968; Morse 1969). Because most developmental defects have an underlying genetic basis (Bergsma and Lowry 1977; Brock 1981; Carter 1974; Fraser 1980; Green 1941; Gruneberg 1964; Leck 1984; McKusick 1974; Rimoin 1981; Sawin 1945; Saxen and Rapola 1969; Smith and Aase 1970; Williams et al. 1989), the wealth of information to be gained from being able to define and interpret these variations in an organized manner remains to be explored. Brothwell and Powers (1968) recognized the importance of minor variations of developmental defects commonly found in the vertebral column as they reviewed the literature in a search for data concerning known congenital defects in prehistoric populations. Finding the evidence for the major congenital abnormalities in earlier populations to be sparse, they suggested that concentrating on minor defects might be or more value. Gregg, Zimmerman, Clifford, and Gregg (1981) realized the potential behind the connection between minor and major expressions of known defects and postulated the possibility of estimating the nature and frequency of major defects in the prehistoric past based on the occurrence of minor expressions. Attempts to categorize congenital and developmental defects according to "errors" in development were made by Zimmerman and Kelley (1982). They hypothesized that most skeletal anomalies result from fusion abnormalities, additional ossification centers, accessory structures, underdeveloped structures, agenesis, or generalized skeletal abnormalities. However, they were unable to fit the various developmental defects they described into these categories. Manchester (1983) also classified congenital defects as abnormalities of developmenttotal failure of development, partial development, overdevelopment, and abnormal development. Attempts by Zimmerman and Kelley
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(1982) and Manchester (1983) to view congenital malformations as abnormalities of development failed to provide an alternative to the type classification system but did demonstrate the feasibility of a morphogenetic approach. During the 1983 Paleopathology Association meeting, Reyman (1983) called for efforts to concentrate less on the more dramatic developmental defectscongenital defectsand to direct attention to minor defects of development and "try to answer questions about consanguinity and the development of patterns of anomalies in a population, or questions concerning cultural patterns or environmental factors and their association with anomalies." This obvious need motivated me to pursue a morphogenetic approach to define, interpret, and organize into a comprehensive classification system the range of variations of developmental defects of the axial skeleton detectable in skeletal collections. The Morphogenetic Approach The processes governing disturbances in development of the axial skeleton skull, vertebral column, ribs, and sternum (Fig. 1.1) have not been emphasized enough. The blastemal (membranous) axial skeleton develops within the first eight weeks following conception. Most developmental disturbances occur during this crucial period of morphogenesis. Therefore, abnormalities affecting the axial skeleton can be traced and defined according to disturbances in morphogenesis occurring within specific embryonic developmental fields associated with the axial skeleton (Gruneberg 1964; Opitz, Jurgen, and Dieker 1969; Spranger et al. 1982). Clinical medicine recognizes that variable expressions of skeletal defects do occur within specific developmental fields during morphogenesis (Goodman and Gorlin 1983; Spranger et al. 1982; Tsou, Yau, and Hodgson 1980). The range of expression varies from minor to major, with two sets of factors affecting the type of expression presented. A susceptible underlying genetic template for the development of each skeletal unit appears to allow deviations to develop when other factors, either genetic (intrinsic) or environmental (extrinsic), interfere with the timing of developmental events (Gruneberg 1963; Opitz, Jurgen, and Dieker 1969; Saxen and Rapola 1969; Williams et al. 1989). This basic underlying genetic factor, allowing for the variable expression of certain types of defects within the different morphogenetic fields, is emphasized by this approach. Once the variable expressions for
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Fig. 1.1 The axial skeleton: skull, vertebral column, ribs, and sternum.
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specific disturbances within each field are identified, genetic patterns of developmental defects can be determined. Purpose Detecting patterns of developmental defects within a prehistoric skeletal population permits interpretive projections for the occurrence of major defects, biological affinities, and both cultural and environmental influences. Minor expressions of major defects can be used to extrapolate the occurrence of severe defects within a skeletal population. Prehistoric examples of severe developmental defects are rare, because most individuals born with them would not have survived infancy. If the defect alone did not cause death, its gross abnormal appearance would probably have caused the infant to be destroyed. The fragile immature bones of these unfortunate newborns would probably not survive through time, leaving little evidence of such defects. Even if they do survive the ravages of time, the incomplete ossification of immature bones does not allow identification of many defects. Infants born with related minor defects, undetectable at birth, would survive beyond infancy and often into adulthood, allowing these defects to survive in the skeletal record. Similar patterns of developmental defects among skeletal populations from different sites reflect population homogeneity, whereas different patterns reflect separate populations with different gene pools. Frequency variations of defects among closely related populations sharing similar patterns of developmental defects and similar environments provide a strong argument for cultural influences, such as marriage and residence patterns. Frequency variations occurring in closely related populations occupying different environments may reflect environmental (extrinsic) influences as well as cultural influences. Major defects are usually identified by clinicians at birth or shortly afterward. Minor variations of developmental defects generally go undetected by clinicians, because they are usually asymptomatic unless other factors precipitate symptoms. This has made it difficult for clinicians to study the full spectrum of expressivity of the more serious defects within the epidemiological context in order to determine heritability and environmental interaction. Anthropologists are not hampered by the lack of symptoms in recognizing these minor variations in skeletal collections, and they can assess heritability
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or risk of occurrence of the more severe forms of skeletal defects within specific population groups. Methodology In order to construct a morphogenetic approach to assess developmental disturbances in the axial skeleton, I had to expand my knowledge of embryology and combine my clinical and anthropological expertise. An extensive review of the medical literature and laboratory analyses of archaeologically derived skeletal collections provided the database for the development of this approach. The embryonic developmental fields associated with the axial skeletal structures were studied to determine the origin of known bony defects and the type of disturbances producing these defects. Only localized structural defects were studied. These malformations are related to disturbances of one or more bones occurring in specific developmental fields, as opposed to systematic disturbances (dysplasias) affecting specific tissue such as cartilage or bone (Gruneberg 1963, 1964; Patton 1987; Rubin 1964; Spranger et al. 1982). A "developmental field" is defined as the close embryonic interaction of select developing tissues involved in the complex composition of a specific structure or set of closely related structures (Gruneberg 1963; Spranger et al. 1982:161; Turkel 1989:112). The primary embryonic developmental field associated with the vertebral column is composed of two columns of mesoderm known as the paraxial mesoderm. The ribs and portions of the occipital bone of the skull, the exoccipitals and supraoccipital, also develop from this tissue. Development of the paraxial mesoderm is dependent on the normal development of its supportive structure, the primordial notochord. Secondary influences on the developing vertebral column and cranium come from the neural tube, forerunner of the spinal cord and the brain. The base of the skull develops from the prechordal cranial base, whereas the cranial vault evolves from the blastemal desmocranium. The mandible, maxilla, zygomatics, and palatine bones come from the first branchial arch of the developing embryo. The ectodermal groove of this arch provides the external auditory meatus, whereas the closing membrane between the groove and the endodermal pouch produces the tympanic plate. The second branchial arch gives rise to the styloid process, stylohyoid ligament, and lesser horn of the hyoid. The rest of the facial bones (the nasal bones, premaxilla, perpendicular
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plates of the ethmoid, vomer, lacrimals, and frontal process of the maxilla) evolve from the frontonasal process. The sternum evolves from three different sources of mesenchymal tissue coming together in the upper-central portion of the thorax. These include the bilateral sternal plates (source of the sternebrae, the xiphoid process, and part of the manubrium), the precostal element (part of the manubrium), and the bilateral suprasternal structures that form the interface between the manubrium and the clavicles. Variability in the expression of a field defect is determined by the timing of the disturbance in relation to a critical threshold event of development (Spranger et al. 1982; Opitz, Jurgen, and Dieker 1969). The most common type of disturbances results from a delay in development. How the disturbance is expressed depends on the timing. Several disturbances found in the vertebral column relate to errors in segmentation, and again, timing of the disturbance determines the expression of the defect. I have organized, defined, and illustrated the variable expressions of known defects of the axial skeleton according to their developmental field of origin in this text. This provides a guide to understanding and identifying the range of expressions of developmental disturbances in the axial skeleton and allows interpretation of underlying genetic patterns of developmental defects as they emerge in skeletal analyses. Disturbances in development of the axial skeleton can only be understood within the context of embryology. Therefore, morphogenesis of the axial skeleton is reviewed in Chapter 2, following a discussion of how defects in development can happen. This prepares the reader for the following chapters, which define and illustrate the developmental field defects of the axial skeleton according to their embryonic origin. Examples of the various defects in prehistoric skeletal material found in a literature search that focuses primarily on reports from the U.S. Southwest are included in each section. I also include some examples from skeletal collections I have studied at the National Museum of Natural History of the Smithsonian Institution. Chapter 3 covers the developmental field defects of the vertebral column, ribs, and associated parts of the cranium, the exoccipitals and supraoccipital. Developmental field defects of the rest of the skull are discussed in Chapter 4, and the sternum is covered in Chapter 5. In Chapter 6 I illustrate how the criteria developed for defining and interpreting the field defects of the axial skeleton can be used. A skeletal sample of 230 closely related individuals from a late prehistoric (fourteenth and fifteenth centuries) Anasazi population from Puye, New Mexico, was
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selected for testing. Three additional, smaller skeletal collections from the same region and time period as Puye Otowi, Tsankawi, and Tsirege were also examined for developmental defects. The test results show significant and similar patterns of developmental defects within these prehistoric skeletal populations, providing valuable empirical data that reflect genetic relationships and cultural influences. The information gathered from the skeletal collections is meaningless without the historical data. In Chapter 7 I provide this information and explain how culture can influence genetic patterns. In the final chapter I summarize the results of this research and interpret the test data.
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Chapter 2 The Development of Defects Developmental defects can range from a very minor disturbance in development to a major abnormality. For example, a small notch (dorsal notch) on the edge of the palate is a very minor defect compared to the major defect of a bilateral cleft palate. About 50% of developmental defects are severe enough to be detected in the neonate and are referred to as birth defects or congenital defects (Saxen and Rapola 1969). This leaves another 50% of developmental defects not apparent until laterin childhood, adolescence, or adulthood, depending upon the type of defect and its location (Arey 1965; Goodman and Gorlin 1983). Certain minor structural defects may only become symptomatic when traumatized. The incidence of severe developmental defects is much higher in still-births (about 20%) and spontaneous abortions (20% to 40%) than in new-borns. About 20% of fertilized human zygotes are lost in early pregnancy to severe defects in development (Saxen and Rapola 1969). Developmental defects can occur in any body tissue, and severe structural defects affect from 1% to 5% of all live births in any population (Kennedy 1967; Patton 1987). As infant mortality rates decrease in developing countries, the frequency of deaths related to severe defects is more noticeable. Today, birth defects are the leading cause of death in the United States, accounting for 21.3% of infant deaths reported in 1982 (Oakley 1986). Neural tube defects are the most common major defects of the axial skeleton (Brock 1981; Myrianthopoulos and Melnick 1987; Oakley 1981). Some populations are more at risk for certain specific malformations than others. The highest incidences of spina bifida and anencephaly occur in northwestern Europeans. The Japanese have the highest incidence of cleft lip and palate, with North American Indians close behind in frequency. Polydactyly is more common in Black populations than in others (Adams and Niswander 1968; Carter 1964; Leck 1984). Pedigree studies have shown that a number of developmental defects follow kinship lines, indicating genetic origin (Kelikian 1974; Young 1987).
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What causes developmental defects? Darwin suggested that defects in development are the cost of population variability (Edwards 1964), which is necessary to preserve the potential for evolutionary change. Most changes are minimal, reflecting normal variation. However, with evolutional variability comes the risk of abnormal development (Brothwell and Powers 1968; Hauser and DeStefano 1989; Zivanovic 1982). The majority (90%) of developmental defects are affected by genetic influences (Patton 1987). Experimental studies of laboratory animals have shown that three categories of factors affect development: single gene disorders, chromosomal disorders, and multifactorial disorders. Single gene disorders account for about one-third of congenital defects, and around one-twelfth are caused by chromosomal errors. The majority of defects are multifactorial, with a fraction of these being polygenic (Bergsma and Lowry 1977; Carter 1974; McKusick 1974; Rimoin 1981; Smith and Aase 1970; Williams et al. 1989). Multifactorial disorders are the result of interaction among genetic (intrinsic) factors or between genetic and environmental (extrinsic) factors. The combined effects of genetic and environmental factors are known as epigenetic interaction (Brock 1981; Fraser 1980; Green 1941; Gruneberg 1964; Leck 1984; Sawin 1945; Saxen and Rapola 1969). Environmental (extrinsic) factors can be mechanical, chemical, nutritional, maternal hormonal imbalances, variations in oxygen pressure, radiation, or infection (Adams and Niswander 1967; Carter 1974; Fraser 1959; Gruenwald 1956; Gruneberg 1963; Moghissi 1974; Seller 1987; Sever 1975; Warkany and Nelson 1940; Yates et al. 1987). Most multifactorial disorders occur when a certain basic genetically determined developmental threshold is reached during morphogenesis. This occurs at a time of rapid change, usually when newly formed cells are proliferating, migrating, differentiating, or regressing. The most common disturbance relates to delay in the timing of a threshold event. This leads to varying degrees of underdevelopment (hypoplasia) or absence (aplasia) of the developing element or structure. Rarely is timing speeded up to cause overdevelopment (hyperplasia). Hyperplasia generally results from unrestrained cell growth when controlling factors are missing. When two parts of a structure come together and converge, the absence of one part prevents the normal part from breaking its growth, and it overlaps its normal boundary (Gruneberg 1964). A threshold event can be altered by variant genes or nongenetic factors, upsetting normal development at this crucial time of vulnerability. At other
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times, the same upsetting agent cannot cause interference. Only when the critical threshold stages of development are reached can upsets occur. Some individuals have more sensitive genetic backgrounds than others, making them more vulnerable to epigenetic or other genetic upsets than those individuals with less sensitive genetic backgrounds. This may explain why some developmental defects are familial and some populations are more susceptible to certain defects (Falconer 1965; Fraser 1981; Gruneberg 1964; Saxen and Rapola 1969; Smith and Aase 1970). Certain genes modify certain developmental actions in the presence of a specific gene but not in its absence. Gruneberg (1963) calls them ''modifying genes." He has shown that the development of the transverse foramina of the cervical vertebrae of laboratory mice varies according to the genetic control of a modifying gene. Similarly, a recessive modifying gene affects the size of the spinous process of the second thoracic vertebra. Modifying genes can influence the effects of mutant genes. Extrinsic factors can also act as "modifiers" on certain genetic backgrounds or act synergistically with a mutant gene (Saxen and Rapola 1969). This explains why certain defects such as neural tube defect appear in epidemic proportions (Fraser 1959; Leck 1972) when environmental factors are favorable for their development in developing embryos with sensitive genetic backgrounds. Variation in the expression of a defect resulting from autosomal dominant gene disorders is thought to result from the degree of penetrance (Rimoin 1981), which may actually be under the control of modifying genes in the genetic background in which the dominant gene finds itself. The genetic background controls the position of a variant gene relative to the critical threshold in development that allows its expressivity, perhaps allowing the homozygote to cross the threshold but not the heterozygote. The modifying genes in the genetic background can also enhance or diminish the effects of a variant gene (Gruneberg 1963; Opitz, Jurgen, and Dieker 1969). Expressivity of a particular defect, occurring in a specific region or part of the body, reflects disturbance in a particular developmental field during morphogenesis. Select developing tissues involved in the complex composition of a specific structure or set of related structures during morphogenesis constitute a developmental field. Variability of a defect from minor to major is determined by the timing of the disturbance in relation to a critical threshold (Spranger et al. 1982; Opitz et al. 1969). Many times, multiple defects occur in the same or related developmental fields polytropic defects as a result of the same disturbance at a time when their anlage (precursor) structures are equally vulnerable (Spranger et
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al. 1982; Opitz, Jurgen, and Dieter 1969). Most polytropic field defects known by clinicians are classified by the pattern of anomalies expressed in the phenotype and are designated as syndromes. Clinicians are aware that the presence of minor anomalies in a population can often indicate the occurrence of related major defects (Opitz, Jurgen, and Dieter 1969). This is of great importance to anthropology, because major, life-threatening, or culturally nonviable developmental defects are rarely found in archaeological skeletal populations. By tracking down the spectrum of minor defects occurring in specific developmental fields detectable within a skeletal population, patterns of certain types of structural developmental defects can be determined and the probable incidence of major defects for that population can be formulated (Brothwell and Powers 1968). It is important to distinguish between developmental defects of morphogenesis malformations and deformations. Malformation results from disruption in the process of normal embryonic development, whereas deformation is the alteration of normally developing structures by mechanical forces in utero, or postnatally, as with the effects of rickets (Spranger et al. 1982). Malformations resulting from disturbances at threshold events as the embryo develops can occur as localized structural defects in one or more developmental fields or as systemic tissue defects. Systemic disturbances are due to enzymatic upsets in embryonic development occurring at the cellular level, producing defects in specific tissues known as dysplasias. Most of these are genetic. Systemic defects affect all of the structures that incorporate the defective tissue into their development. Many types of skeletal dysplasias affect the skeletal cells themselves. Skeletal dysplasias can evolve from enzymatic defects in the mesenchyme cells that form the embryonic blastemal skeleton, the following chondroblasts that form the cartilaginous skeleton, related fibrous cells that form connective tissue, or metabolic disturbances in the final bone cells. Dysplasias are generalized defects affecting a phase of skeletal development as a whole. This generalized cellular defect does not necessarily affect all parts of the skeleton to the same degree at the same time, because different skeletal parts develop at different times and some cells are more sensitive than others. Thus a spectrum of clinical manifestations of varying degrees is produced for each type of defect (Gruneberg 1963; 1964; Rubin 1964; Spranger et al. 1982). There are many types of skeletal dysplasias. Abnormalities of cartilage development the chondrodysplasias include those detectable at birth but incompatible with life, such as the thanatophoric dysplastic dwarfs. Those that
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are detectable at birth and compatible with life include the achondroplastic dwarfs. Some latent types of chondrodysplasias, such as hypochondroplasia, are not identified until later in life. Skeletal defects caused by disorganized development of cartilage and fibrous components include a range of disorders, such as fibrous dysplasia and neurofibromatosis. Abnormalities in the density of the cortical diaphyses and metaphyseal modeling of bone can cause numerous defects, including the differing forms of osteogenesis imperfecta and osteopetrosis. Of the metabolic disturbances affecting the skeleton, those that affect the complex carbohydrates the mucopolysaccharidoses and mucolipidosesare the most common. Many of these disorders are lethal (International nomenclature of constitutional diseases of bone 1978; Meschan 1985). A study of the skeletal dysplasias is a separate study and is not addressed in this text. Most of the dysplasias are not found in prehistoric skeletal populations because of their severity. The achondroplasias and latent forms of chondroplasias are the most likely forms to survive in archaeological remains, and some reported cases of achondroplastic dwarfism are found in the paleopathology literature (Bleyer 1940; Brothwell 1967; Frayer, Macchiarelli, and Mussi 1988; Gladykowska-Rzeczycka 1980; Hoffman 1976b; Hrdlicka 1943; Johnston 1963; Manchester 1983; Ortner and Putschar 1985; Rogers 1986; Snow 1943; Watrous and Richards 1992). Two prehistoric cases of osteogenesis imperfecta are known (Gray 1970; Wells 1965), as are two cases of a mucopolysaccharidosis (Campillo and Malgosa 1991; Ortner and Putschar 1985). Localized developmental defects of the skeleton are confined to structural disturbances of one or more bones occurring in specific developmental fields (Gruneberg 1964). These will be referred to as field defects, and those involving the axial skeleton (Table 2.1) are the focus of this research. Table 2.1. Developmental Fields of the Axial Skeleton Developmental Skeletal structures field provides scaffolding for developing vertebral column and Notochord basioccipital brain and spinal cord (defects affect developing vertebral column and Neural tube cranium) Paraxial vertebral column, ribs, exoccipitals, and supraoccipital mesoderm Prechordal basioccipital, sphenoid body, lesser sphenoid wings and roots of cranial base greater wings, ethmoid, and petromastoid of temporals
Page 14 Developmental Skeletal structures field Blastemal frontal, parietals, occipital interparietal, squamosa of temporals, desmocranium greater wings of sphenoid, and lamina of pterygoid processes Branchial arch I maxilla, zygomatics, palatine bones, and mandible Ectodermal groove external auditory meatus of branchial arch I Closing membrane tympanic plate of branchial arch I stylohyoid chain: styloid process, stylohyoid ligament, and lesser Branchial arch II horns of hyoid Frontonasal nasal bones, premaxilla, perpendicular plates of ethmoid, vomer, process lacrimals, and frontal process of maxilla Sternal plates part of manubrium, sternebrae, and xiphoid process Bilateral suprasternal manubrium interface with clavicles structures Precostal process part of manubrium
Morphogenesis of the Axial Skeleton In order to understand the development of field defects in the axial skeleton, it is necessary to review the early stages of development affecting skeletal morphogenesis: the embryonic blastemal (mesenchymal) or membranous, stage; the chondrification stage; and the primary ossification stage (Fig. 2.1). The blastemal stage plays the most important role in the development of field defects. The precursors of the cartilaginous and membranous skeletal structures are formed during this beginning stage of development; they in turn ossify into bone. Any disturbance affecting the developmental fields of the blastemal skeletal structures will alter the next phase of bone development. If the cartilaginous or membranous model for a bone structure is altered because of disturbance in the blastemal model, the final osseous structure is also affected. Normal development during morphogenesis depends upon timing of events. Delay in any single aspect of growth in any particular part will cause varying degrees of hypoplasia (underdevelopment) or aplasia (absence of development), depending upon the timing of the interference. Chondrification or ossification does not take place until the blastemal anlage reaches a certain critical size. If it does not reach that size in time, chondrification or
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Fig. 2.1 Stages of development of the axial skeleton.
ossification is delayed, thus reducing the size of the prospective structure or part (hypoplasia). Too small an anlage or failure of the blastema to mature fast enough can prevent a part or a structure from forming (aplasia), especially where they are thinnest. If one or both parts of a structure that are supposed to come together and fuse are underdeveloped or absent, fusion will not take place. Developmental defects caused by developmental delay are the most common of all defects, especially in the axial skeleton (Gruneberg 1954, 1963; Hauser and DeStafano 1989; Meschan 1985; Potter 1963; Williams et al. 1989). A. Blastemal Stage On the sixteenth day following conception, the formation of the axial skeleton starts with a series of complex migrations of cells from the primitive streak, a dense band of primordial cells at the caudal end of the embryonic disc. Some cells diverge to form the neural plate that will eventually form the neural tube, from which most of the central nervous system develops. Some of the primordial cells differentiate into the neural crest, a band of ectomesenchymal cells along the length of the neural tube, giving rise to peripheral neurons and connective tissue in the cephalic region. Some graduate into ectodermal cells to produce the sense organs, specialized glands, teeth, and skin tissue. Some become mesenchymal mesoderm cells with the capacity to
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move when triggered to do so, developing into a wide variety of tissues in the skeletal system when stimulated (Arey 1965; Noden 1986; Williams et al. 1989). Although some cells in certain predetermined regions develop into specific tissue on their own, other cells depend on the stepwise restrictions of the expanding specialized cells to determine their fate. These dependent cells, known as pluripotent tissue, can only react to the inductive influence of the usurping specialized tissue for a limited time to form specific adjacent tissue. This is known as embryonic induction and remains an ongoing process until all of the structures are developed. Embryonic induction represents a critical threshold event in development, occurring with constant rearrangement of cell clusters by synchronized movements to form tissue components. If the inductor tissue makes insufficient contact with the pluripotent tissue or loses its capacity for induction, a defect will develop. Any upset in the movement and differentiation of cells at this critical time can lead to a series of subsequent distortions, most of them lethal (Arey 1965; Saxen and Rapola 1969; Williams et al. 1989). 1. Notochord The primitive streak is stretched, forming a seamlike groove down the middle and a knob (Hensen's node) at its head end by the eighteenth day. Primordial cells grow downward and forward from this knob in the midline to form a rodlike column of cells known as the notochord (chorda dorsalis) that acts as a supporting framework for the developing blastemal axial skeleton (Fig. 2.2). The notochord provides the framework around which the blastemal vertebral column, basioccipital, and basisphenoid are preformed from paraxial mesodermal cells that build up quickly along its sides. The rodlike notochord begins to regress from the developing vertebral column as the seventh week of embryonic development begins. Remnants of notochordal tissue ultimately become the nucleus pulposus of the intervertebral discs and the apical and alar ligaments of the axis vertebra as they are surrounded by the developing vertebral column (Arey 1965; Bailey 1974; Williams et al. 1989). 2. Neural Tube The portion of the embryo ahead of the knob end elongates and a grooved median strip of ectoderm thickens to allow for the formation of the
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Fig. 2.2 Blastemal stage of development. a: primitive streak; b: Hensen's node; c: notochord; d: neural groove; e: somites; f: neural plate; g: branchial arch I; h: branchial arch II (redrawn from Arey 1965).
neural plate, which initially corresponds to the length of the notochord underlying it. As the neural plate grows, its margins raise up to form the neural folds, the first sign of brain formation (Fig. 2.2). The neural plate groove deepens, forming a slitlike canal the submerged neural tube (ultimately the spinal cord) extending both craniao- and caudalward. The ends are left open until the fourth week (Fig. 2.2). Before
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they close, the neural tube is dependent upon the amniotic fluid for nourishment. Closure coincides with the development of vascular circulation for the neural tube and the formation of embryonic cerebrospinal fluid (Arey 1965; Gruneberg 1963; Williams et al. 1989). Faulty development of adequate vascular circulation to the neural tube can interfere with its nutrition. This could prevent normal closure from occurring, leading to a neural tube defect (Stevenson et al. 1987). Other factors yet to be identified may also hinder normal closure and lead to a defect in neural tube development (Saxen and Rapola 1969). 3. Paraxial Mesoderm Mesenchymal cells are drawn to the notochord, forming two columns of mesenchymal tissue, known as the paraxial mesoderm, on either side of the notochord. Beginning at twenty-one days, the columns segment into hemimetameric pairs to form blocklike, symmetrical tissue components known as somites (Fig. 2.2), first appearing at the cephalic end and progressing caudalward. By the end of the fifth week, they increase in number to a total of forty-two to forty-five pairs, separated by intersegmental septae (membranes). The most cranial four of these pairs (maybe more), the occipital somite derivities, will form the exoccipitals (lateral portions of the base of the occipital containing the major portion of the occipital condyles) and the supraoccipital. The remainder establish the vertebral column. Usually, eight pairs flank the cervical region, twelve pairs flank the thoracic region, five pairs flank the lumbar region, and five pairs flank the sacral region. Eight to ten pairs are contained in the caudal end the tail which constitutes one-sixth of the total length of the embryo at the end of the somite phase of development. Within four weeks the tail regresses to a vestigial stump to form the coccyx. Sometimes additional or, rarely, fewer somites are formed, generally in the thoracic, lumbar, or sacral regions, leading to the development of additional or fewer vertebrae (Arey 1965; Bailey 1974; Epstein 1976; Gruneberg 1963, 1964; Ruge and Wiltse 1977; Walmsley 1959; Williams et al. 1989). The hemimetameric pair of somite derivities, positioned opposite each other adjacent to the notochord, eventually unite. They develop simultaneously but independently of each other prior to union, approaching each other in the same stage of development before uniting (Tsou, Yau, and Hodgson 1980).
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Once the somites have united, they differentiate into three types of cells. Some of the cells form the dermatome, spreading out to form dermis. The dorsolateral somite cells form a muscle plate, the myotome, that produces striated muscle. The ventromedial cells, the sclerotome, become mesenchymal, multiply rapidly, and migrate in a ventromedian direction, sorrounding the notocord with a continuous mesenchymal sheath. Sclerotome cells continue to migrate in a dorsal direction to surround the neural tube and ultimately form the vertebral column. The sclerotome segments around the notochord divide equally into cranial and caudal parts as the caudal portions grow more dense than the cranial halves. This is achieved by a transitory splitting along a fissure that appears between the two halves as they shift away from each other. The fissure quickly fills with loose mesenchymal cells from the cranial portion; and by the third month, these cells surround the notochord remnants and eventually form the intervertebral disc. The more dense caudal half combines with the separated cranial half of the adjacent sclerotome to form the anlage of the vertebral centrum (Fig. 2.3), the body of the vertebra. Cells from the denser caudal portion grow into spaces between the myotomes, extending dorsally to form the neural arches and ventrolaterally to form the transverse and costal processes. The costal processes in the thoracic spine continue to grow into primordial ribs (Arey 1965; Bailey 1974; Epstein 1976; Ruge and Wiltse 1977; Williams et al. 1989). Following segmentation, differentiation occurs as the newly united sclerotome halves develop into the anlages of the respective vertebrae in each region of the spine they represent. The first and second vertebral segments develop differently from the others. The anterior and posterior arches and lateral masses of the atlas and body of the dens are thought to be derived from the caudal half of the first cervical sclerotome. The cranial half (proatlas) becomes assimilated into the exocciptals and also forms the tip of the dens (Fig. 2.4). The body, posterior arch, and transverse processes of the axis are derived from the second cervical sclerotome (Shapiro and Robinson 1976). 4. Prechordal Cranial Base The notochord, extending into the head area, terminates in the caudal border of the fossa for the hypophysis of the sphenoid. Dense mesenchymal concentrations begin to congregate around it above the cervical somites by the end of the first month. Bilateral mesenchymal masses appear alongside the cranial end of the notochord and envelope it; bilateral concentrations
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Fig. 2.3 Schematic drawing of the development of the vertebral anlage. A: sclerotomes before separation. B: separation of dense and less dense halves of sclerotome. C: recombined halves forming vertebral anlage. d: notochord; e: sclerotome; f: intersegmental artery (redrawn from Arey 1965).
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Fig. 2.4 Schematic drawing of the development of the exoccipitals, atlas, and axis from the first and second cervical sclerotomes. A: original first and second cervical somites. B: recombined first and second cervical somites. C: exoccipitals. D: apical tip of odontoid. E: atlas vertebra. F: body of odontoid. G: axis vertebra. H: occipitocervical border.
appear in the interorbitonasal region, and similar concentrations encapsulate the developing otocysts. They soon chondrify separately into what are known as the parachordal, trabecular, and otic capsule cartilages (Fig. 2.5), growing together to create an indistinguishable cartilaginous mass the prechordal cranial base (Williams et al. 1989). 5. Blastemal Desmocranium The embryonic brain grows rapidly in size early on, developing from the thick ectodermal neural plate. Before the brain begins to develop, neural crest cells at the junction between the neural plate folds and surface ectoderm leave and become mesenchymal, migrating from each side of the neural plate into specific cranial regions. They are transformed into seven incomplete segments known as somitomeres. They first appear in the region of the forebrain (prosencephalon), progressing to the midbrain (mesencephalon)
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Fig. 2.5 Development of the blastemal prechordal cranial base. A: Development of the prechordal cartilages. B: Coalescence of the prechordal cartilages into the prechordal cranial base. c: nasal capsule; d: eye; e: trabecular cartilage; f: otic capsule; g: parachordal cartilage; h: occipital somites; i: cervical somites; j: notochord (redrawn from Arey 1965).
region, then to the hindbrain (rhombencephalon) region. Each somitomere is associated with a particular segment (neuromeres) of the brain anlage. They produce the antecedents of the bones enclosing the brain (Sulik 1990). By the thirtieth day, curved plates of condensed mesenchymal tissue from the somitomeres appear on the sides of the growing brain, leading to the development of the membranous cranial vault. By the end of the first month, the interparietal portion of the occipital bone, the frontal and parietal, and temporal squamosa precursers are recognizable (Arey 1965; Williams et al. 1989).
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Fig. 2.6 Stages of embryonic development, twenty-four days to four weeks. a: anterior neuropore; b: branchial arch I; c: branchial arch II; d: somites (redrawn from Arey 1965).
6. Branchial Arches Some of the neural crest cell migrations contribute to the development of the branchial arches and facial structures. Other neural crest cell invade other tissues to form neurons and other sensory cells (Arey 1965; Noden 1986; Williams et al. 1989). As the blastemal desmocranium begins to form, neural crest cells and mesodermal cells aggregate into five barlike ridges, the branchial arches, which are separated by ectodermal grooves and endodermal pouches, on each ventrolateral surface of the embryonic head (Figs. 2.6 and 2.7). Each side of the first branchial arch branches into a maxillary and a mandibular process. The maxillary processes develop primarily from neural crest cells from the midbrain upper hindbrain regions. The mandibular process are initially formed from mesodermal cells and are joined by neural crests cells from the lower midbrain and upper hindbrain regions (Sulik 1990). The palate, malleus, incus, dentine, cementum, and the antimalleolar and spheno-mandibular ligaments are also derived from the first branchial arch. The external auditory meatus is created from the dorsal end of the ectodermal groove of the first branchial arch (Fig. 2.7). The tympanic plate evolves from the closing membrane that separates the ectodermal groove of the first branchial arch from its endodermal pouch. The stapes, styloid process, stylohyoid ligament, and
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Fig. 2.7 Stages of embryonic development, five weeks to nine weeks. A: embryo at five weeks; B: embryo at eight weeks; C: embryo at nine weeks. a: notochord; b: branchial arch I (maxilla and mandible); c: ectodermal groove from branchial arch I (external auditory meatus); d: branchial arch II (stylohyoid chain); e: paraxial mesoderm (exoccipitals, vertebral column, and ribs); f: prechordal cranial base; g: beginning ossification of blastemal desmocranium (skull vault).
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lesser horns of the hyoid develop from the second branchial arch (Fig. 2.7), whereas the body and greater horns of the hyoid are derived from the third branchial arch (Arey 1965; Sulik 1990; Williams et al. 1989). 7. Frontonasal Process The ectodermal mouth invagination determines the development of the first branchial arch and, subsequently, the maxilla and mandible. Between the fifth and eighth weeks, the face and premaxilla develop between the first branchial arch and the bulging forebrain. Neural crest cells from the forebrain and upper midbrain regions converge to form the frontonassal process (Sulik 1990). Shallow pits for the eyes and nares are drawn toward each other from the sides (Fig. 2.8). For a short time, a groove from each of the developing nasal pits opens to the mouth cavity (Arey 1965; Williams et al. 1989). 8. Sternal Precursors The sternum consists of three parts: the manubrium, the mesosternum, and the xiphoid process. The precursors of the mesosternum appear during the sixth week as sternal plates, developing from a pair of mesenchymal bands originating in the venrolateral parts of the body wall (Fig. 2.9). Chondrification begins almost immediately, before the sternal bands reach the thoracic midline. As the primordial ribs reach these sternal bands, they progressively lenghten, chondrify, and unite in a craniocaudal direction, developing a caudal extensionthe xiphoid process. Once the sternal bands have united, they are influenced by the ribs to segment into four sections known as the sternebrae (Ashley 1956; Williams et al. 1989). The manubrium evolves during the ninth week from the fusion of the upper portions of the sternal bands and a mesenchymal condensation known as the precostal process, which localizes between a pair of mesenchymal condensations that form between the ventral ends of the primordial clavicles and line up with the cranial ends of the sternal bands. These are known as the suprasternal structures, fusing with the manubrium anlage to serve as the interface between the sternum and the clavicles (Arey 1965; Eijgelaar and Bijtel 1970; Williams et al. 1989).
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Fig. 2.8 Embryonic development of the face. a: maxillary prominence; b: triangular area; c: mandibular prominence; d: median nasal prominence; e: lateral nasal prominence; f: branchial arch I ectodermal groove (redrawn from Arey 1965).
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Fig. 2.9 Development of the sternum. From left to right; sixth week of embryonic development, ninth week of embryonic development, and child's sternum. A: precostal process. B: suprasternal structures. C: sternal bands or plates (redrawn from Arey 1965).
B. Cartilaginous Stage Cartilage begins to replace the primitive blastemal vertebral column by the sixth week. Disturbances in the developing blastemal skeleton can lead to a delay in or absence of cartilaginous replacement, producing hypoplasia, aplasia, abnormal separation, or anomalous union as the cartilage cells follow the pattern laid down by the blastemal cells. Chondrification will not begin until the blastemal antecedent reaches a critical size within a particular time frame. If too small, the blastema will not reach critical size in time, leading to a delay in chondrification; if too small or where it is thinnest, chondrification will occur. Failure of some cartilages to fuse normally (such as the neural arches) is also due to reduction in size of the blastemal precursor, leading to failure of the parts to make contact in time (Gruneberg 1963; Williams et al. 1989). 1. Vertebral Column Chondrification in each blastemal vertebra stems from two paired centers: one pair splits off into each growing arch rudiment, and the other pair quickly coalesces to form the centrum. Failure of these two to coalesce could lead to a defect in ossification in the vertebral body, in the form of hypoplasia or aplasia. Chondrification proceeds in a craniocaudal direction. The cartilaginous vertebral arches unite and enclose the spinal cord during
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the third month (Arey 1965; Bailey 1974; Epstein 1976; Ruge and Wiltse 1977; Williams et al. 1989). 2. Ribs The precartilaginous ribs chondrify from a single center, separated from the thoracic vertebrae by zones of remaining mesenchyme that eventually form the costovertebral ligaments and joints. The more cranial ones curve toward each other, coming into contact with the sternal plates. 3. Chondrocranium During the seventh week, the chondrification of the base of the skull begins in the parachordal mesenchyme, spreding laterally into the otic capsules and dorsally into the interorbitaonasal region, forming the trabecular cartilages. By the third fetal month, these unify to establish the primitive chondrocranium. C. Osteogenic Stage The third step in morphogenesis of the axial skeleton primary ossification, is dependent upon the pattern preset during chondrification for the derivatives of the paraxial mesoderm and prechordal cranial base, whereas those portions of the skull derived from neural crest cells ossify directly from membranous tissue formed during the blastemal stage. Developmental defects in ossification result from faulty fabrication in the preceding cartilaginous or membranous stage of development. 1. Vertebral Column Ossification commences at eight to nine weeks in the vertebral column. The ossification centers of the centra do not correspond with the previous chondrification centers. Ossification generally commences from just one center in the centrum. Bilateral ossification centers sometimes appear because of an upset in chondrification. They may completely fail to coalesce or may do so partially. Ossification begins in the centra of the lower thoracic-upper lumbar region during the ninth to tenth week, spreading in cranial and caudal
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directions, reaching the second cervical level in the twelfth week (Arey 1965; Epstein 1976; Williams et al. 1989). Each lateral half of the vertebral arch has a single center of ossification located in the region known as the pars interarticularis. Ossification centers first appear in the lower cervical-upper thoracic region about the eighth week, followed by the upper cervical region. After a short interval, the lower thoracic-lumbar region begins to ossify in cranial and caudal directions (Arey 1965; Epstein 1976; Walmsley 1959; Williams et al. 1989). The seventh cervical vertebra usually has a single ossification center for each costal process, appearing at about the sixth fetal month and fusing with the body of the transverse process at about the fifth or sixth year. With cranial shifting of the border between the cervical and thoracic vertebral segments during the blastemal stage, they may remain separate and form cervical ribs. Rarely, a small, separate center of ossification for each costal process can appear for the fourth, fifth, and sixth cervical vertebrae (Bailey 1974). The atlas vertebra ossifies from three separate centers. Lateral centers appear about the seventh week, and the third center for the anterior arch generally shows up during the first year after birth. The axis vertebra ossifies from five primary centers. The body and each half of the neural arch follow the ossification pattern of the other vertebrae. Ossification centers appear for each neural arch during the seventh to eighth week, and the ossification center for the body appears laterabout the fourth or fifth fetal month. During the sixth month, bilateral ossification centers appear in the erect cartilaginous projection, the dens (odontoid). They unite at birth into a single column, forming an apical cleft to allow for the development of secondary ossification at a later time (Bailey 1974; Epstein 1976). The mammillary processes of the lumbar vertebrae develop from separate ossification centers. The lumbar transverse processes will also occasionally develop from separate ossification centers, but they usually unite with the vertebrae. Caudal shifting of the border between the thoracic and lumbar vertebral segments during the blastemal stage will cause the transverse processes of the first lumbar vertebra to ossify from separate centers and form lumbar ribs (Epstein 1976; Williams et al. 1989). During the ninth week, ossification centers appear in the central part of the upper three sacral vertebral bodies. Much later, between the sixth and eighth fetal months, the other two bodies develop ossification centers as the vertebral arches begin to ossify from their centers. The costal centers for the lateral parts of the sacral vertebrae also appear at this time. The rudimentary
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coccygeal vertebral segments do not ossify until after birth (Epstein 1976; Ruge and Wiltse 1977). 2. Ribs The shafts of the sixth and seventh ribs begin ossification during the ninth week near their primordial angle, followed by the other ribs. The anterior ends of the ribs remain cartilaginous, developing into the costal cartilages. The costal cartilages of the first through seventh ribs connect with the sternum, those for the eighth through tenth ribs join with each other, and the last two remain unattached (Williams et al. 1989). 3. Chondrocranium The parachordal cartilages begin to ossify during the third fetal month into the basioccipital, which contains a small portion of the ventral aspect of the future occipital condyles. The lateral portions of the cranial base are formed from the exoccipitals furnished by the occipital sclerotomes and contain the major portion of the occipital condyles. The trabecular cartilages ossify into the body of the sphenoid, the lesser wings and roots of the greater wings, and the ethmoid, whereas the otic capsules become the petromastoid of the temporals (Arey 1965; Williams et al. 1989). 4. Membranous Skull The interparietal portion of the occipital, along with the frontal, parietals, and squamosa of the temporals, ossify directly from mesenchymal (membranous) tissue. The parietals are the first to begin ossification during the seventh week, followed by the temporal squamosa, frontal, and occipital interparietal by the ninth week. Ossification begins with the spreading out of fiber bone spicules that unite into a meshwork of trabeculae, forming a fan shape spreading in all directions. The frontal, developing from two ossification centers, presents as two halves at birth (Arey 1965; Williams et al. 1989). 5. Mandible and Maxilla The maxilla and mandible, derivatives, of the first branchial arch, undergo ossification directly from mesenchymal tissue, begining during the sixth
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week. The premaxilla, bearing the source material for the incisor teeth, fuses with the maxilla as they come together (Arey 1965; Williams et al. 1989). The mesenchymal core of the mandibular process transforms into a cartilaginous bar, Meckel's cartilage. It begins at the otic capsule, where it becomes surrounded by temporal bone, is eventually replaced by the incus and malleus, and extends to the ventral (symphyseal) end of each mandibular half. This cartilaginous structure acts as a support for the development of the blastemal mandible. The intermediate part disappears, but its sheath becomes the anterior malleolar and spheno-mandibular ligaments. The ventral part becomes enveloped in the symphyseal portion of the mandible (Arey 1965; Williams et al. 1989). 6. Styloid Process The styloid process, derived from cartilage, ossifies from two separate ossifying centers. The proximal portion, the tympanohyal, begins to ossify before birth. The distal portion, the stylohyal, does not ossify until after birth. It remains separate from the tympanohyal until after puberty (Williams et al. 1989). 7. Sternum Ossification of the sternum begins about the fifth fetal month, with the number and location of ossification centers varying according to the developmental timing of the fusion of the sternal bands. Ossification begins with the manubrium, generally from one to three centers. The first and second sternebrae begin to ossify commonly from single centers at about the same time, followed by the development of paired ossification centers in the last two sternebrae, usually by the sixth fetal month. The xiphoid process does not begin to ossify until after the third year and is extremely variable in form. Sternal form depends upon the timing of the cohesion of the sternal bands in the blastemal stage of development, which is genetically determined (Arey 1965; Ashley 1956; Williams et al. 1989). Summary This brief review of morphogenesis of the axial skeleton, as outlined in Table 2.2 at the end of this chapter, provides the background for understanding
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the development of structural defects within specific developmental fields. As the review points out, most of these defects occur during the initial stage of developmentthe blastemal stagein the first eight weeks of life, when the developmental fields are initiated. At the beginning of its development, the axial skeleton is most vulnerable to genetic or epigenetic interference. Timing is the key factor in development, and developmental delay during morphogenesis is a major cause of developmental field defects in the axial skeleton, regardless of the contributing agent. The delay is sometimes so great that the intended anlage does not develop at all, resulting in aplasia (absence) of that part. Developmental delay can lead to hypoplasia (abnormally small) or failure of two parts to join together properly. Chondrification will not take place until the blastema reaches a certain critical size, and if there is a delay, hypoplasia or aplasia results in the cartilaginous or membranous prototype of bone (Gruneberg 1963; Potter 1963). As the various structures of the axial skeleton develop within the boundaries of the developmental fields, disturbances (genetic and environmental) at critical threshold times within a field will alter normal developmental procedures. Disturbances in one field can also affect development in another field. For example, defects in the neural tube (such as meningomyelocele) can cause associated defects in the developing vertebral column (spina bifida). Field defects are classified according to the primary field disturbance. Spina bifida cystica is thus referred to as a neural tube defect. Expressivity depends upon the timing of the anomaly in relation to the critical threshold event, producing a range of variability from minor to major disturbances. There will be moments when not all structures or parts of a structure will be at a critical threshold at the same time within a developmental field. Critical thresholds across developmental fields will sometimes appear at the same time during an upset in the embryo, producing polytropic defects. For example, dysostosis cleidocranialis is a polytropic defect affecting the developing membranous skull and clavicles, which also ossify from membranous tissue. My primary concern in this investigation is to determine the developmental field of origin for those defects most likely to be recognized in prehistoric skeletal populations.
Page 33 Table 2.2 Morphogenesis of the Axial Skeleton Time Developmental events period 1618 primitive streak develops; notochord begins days 1820 Hensen's node appears; notochord develops; neural plate groove appears days neural plate groove deepens to form slitlike canalthe neural tubeand folds develop 2022 on cranial end (spinal cord and brain precursors); paraxial mesoderm forms and days first somites appear (vertebrae and rib precursors) notochord becomes a cellular rod, as somites continue to develop around it; sclerotomes begin to develop from the earlier somites; closure of anterior end of 2226 neural tube; branchial arches begin to appear (branchial arch I provides days precursors of mandible, maxilla, zygomatics, and palatine bones; groove provides precursor of external auditory meatus; and closing membrane provides precursor of tympanic plate; branchial arch II provides precursor of stylohyoid chain) closure of posterior end of neural tube; notochord in final position and somite formation complete; branchial arches developed, branchial arch I fuses, maxillary 2630 and mandibular processes prominent; mesenchymal elements of desmocranium days appear (precursors to membranous skull); prechordal mesenchyme masses appear (precursors to chondrocranium) 5 frontonasal prominence swells (precursor of premaxilla, nasal bones, weeks perpendicular plates of ethmoid, vomer, lacrimals, and frontal process of maxilla) facial region growing and differentiating; maxillary palatal processes appear 6 (palate precursors); membranous bone ossification begines in maxilla and weeks desmocranium; chondrification begins in prechordal structures; sternal plates appear (sternum precursors) notochord begins to regress; embryonic tail regresses (precursor of coccyx); 7 maxilla and premaxilla join through ossification; mandible ossifies; weeks chondrification begins to spread throughout prechordal structures; lateral ossification centers form in atlas and axis 8 lateral ossification centers form in vertebral arches of lower cervical-upper weeks thoracic vertebrae ribs begin to ossify; ossification centers appear in centra of lower thoracic-upper 9 lumbar vertebrae; ossification centers appear in centra of upper sacral vertebrae; weeks union of sternal plates, suprosternal structures, and precostal process 10 fusion of maxillary palatal processes; vetrebral ossification centers continue to weeks develop Table 2.2 continued on the next page
Page 34 Table 2.2 (continued) Time period Developmental events chondrocranium completely formed and begins to ossify; notochord 12 weeks degenerating rapidly; vertebral ossification centers complete palate complete; most bone structures complete; joint cavities appear; body 16 weeks of axis begins to ossify 20 weeks manubrium, first and second sternebrae of mesosternum begin to ossify bilateral ossification centers begin to appear in dens; third and fourth 24 weeks sternebrae of mesosternum begin to ossify 2432 weeks lower two sacral segments and vertebral arches of sacrum begin to ossify
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Chapter 3 Developmental Field Defects of the Vertebral Column, Ribs, and Associated Parts of the Cranium Developmental disturbances of the vertebral column are more complex than those affecting other parts of the axial skeleton. The major developmental fields affecting the developing structures are the notochord, neural tube, and paraxial mesoderm. Delay in reaching critical threshold events in any of these fields can lead to disturbances in the developing vertebral column, ribs, and basioccipital. Rarely, the outer ectodermal developmental field contributes to a benign bone defect in the cranium as the neural tube closes, causing some slow-moving ectodermal cells to be trapped in or near the outer surface of the skull. Although most developmental field defects occur during morphogenesis of the blastemal skeleton in the first eight weeks of embryonic life, a large number do not become obvious until ossification is completed or when functional stress or trauma induces symptoms, particularly in the vertebral column. This explains why many minor defects are found in prehistoric adult skeletal material. Part I: Notochord Field Defects The notochord provides the structural frame and inductive tissue for the development of the vertebral column, basioccipital, basisphenoid, and neural tube. Disturbances in the notochord affect the development of these associated structures. Without a notochord, the vertebral column would be a disorganized cartilaginous mass incompatible with life (Gruneberg 1963; Schmorl and Junghanns 1971; Tsou, Yau, and Hodgson 1980).
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The notochord, a flexible rod of cells, is enclosed by a thick, membranous sheath. The precursors of the centra develop around the notochord. As the chondrification centers for the centra begin to appear during the seventh week, the notochord begins to regress, disappearing by the twelfth week. Parts of the notochord are entrapped within the sclerotomic fissures of the developing vertebral segments and become the nucleus pulposi of the vertebral discs. This notochordal tissue begins to degenerate by the sixth fetal month, to be replaced by cells from the internal zone of the annulas fibrosus. This process continues after birth until all of the notochord cells are gone, by the second decade of life. Normally, vestiges of the notochord are absent in the adult (Arey 1965; Williams et al. 1989). A. Failure of the Notochord to Regress 1. Coronal Cleft Centrum Entrapment of notochordal tissue within the developing centra can interfere with normal chondrification between the anterior and posterior halves. This is followed in the ossification stage with a division between the two, producing a coronal cleft centrum. The cleft is usually filled with cartilage containing a core of notochordal cells. These clefts primarily appear in the lumbar area and sometimes in the lower thoracic area but not in the cervical area. The cleft appears as an irregular or ovoid depression. The posterior portion of the vertebral body tends to be smaller than the anterior portion. With normal growth the cleft eventually disappears as it ossifies, and it rarely appears in adults. For this reason, most clinicians do not consider it significantly abnormal. Coronal cleft centra occur predominantly in male neonates (Epstein 1976; Schmorl and Junghanns 1971; Warkany 1971). 2. Sagittal Cleft Centrum Failure of the notochord to recede from a developing vertebral segment can result in a bifid centrum, producing what is known as a ''butterfly" vertebra (Fig. 3.1). This rare defect usually involves only one vertebra. The apices of each half may be rounded or pointed. They tend to spread laterally, with a reduction in height that is compensated with vertebral disc tissue. The neural arches are not affected by this defect (Epstein 1976; Schmorl and Junghanns 1971; Tsou, Yau, and Hodgson 1980).
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Fig. 3.1 Failure of the notochord to regress sagittal cleft centrum (butterfly vertebra). a: narrow bifurcation; b: complete cleft; c: connecting bony bridge; d: connecting bony strands.
The sagittal cleft centrum usually occurs in the lumbar and thoracic spine, and it is found more often in males than in females. It may be associated with visceral defects in the gastrointestinal tract or central nervous system, as well as with other vertebral or rib defects. The cleft is filled with cartilaginous tissue in life, which explains why minor variants may remain asymptomatic. The two halves are generally symmetrically divided, separated by a wide or narrow cleft. They may be connected by a bony bridge or strands of bone. The two halves are generally of equal size and may be displaced laterally or wedged anteriorly. Hypoplasia of one or both halves sometimes occurs with
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the notochord disturbance. The surfaces of the divided vertebral body are usually indented as the upper and lower intervertebral discs connect through the cleft. The adjacent intervertebral spaces may be narrowed, and compensatory changes of adjacent vertebral segments are common, sometimes resulting in scoliosis or kyphosis. Heavy lifting or carrying can cause severe back pain (Epstein 1976; Fischer and Vandemark 1945; Ruge and Wiltse 1977; Schlitt, Dempsey, and Robinson 1989; Schmorl and Junghanns 1971). There have been a few reports of sagittal cleft vertebrae in prehistoric skeletal material. A sagittal cleft centrum was identified in an adult Tanoan burial from the Henderson site in the Pecos Valley, New Mexico. The sixth thoracic vertebra is affected, with bilateral hypoplasia of the vertebral body. There are compensatory changes in the adjacent vertebrae. The corresponding sixth ribs are fused at their vertebral ends as a result of this defect (Rocek and Speth 1986). Merbs and Wilson (1962:158159) discovered five cases of sagittal cleft vertebrae in Sadlermiut skeletal material from Canada, two of eleven children and three of sixty-one adults (5/72 = 7%). This is an unusually high frequency for such a rare defect, indicating strong familial undertones that may reflect genetic isolation. Both of the children (six and seven years of age) had involvement of two vertebral segments the eighth and tenth thoracic centra with a cleft in the eleventh thoracic vertebral arch. An adult male had involvement of the fifth and eighth thoracic centra. Only the eighth thoracic centrum of another adult male was affected, and the seventh thoracic centrum was affected in an adult female. Hypoplasia and aplasia of the separated parts of the centra appear to have accompanied the clefting caused by the delay in the notochord's regression, based on reported portions of the centra missing or much smaller than normal. A sagittal cleft vertebra was found in a prehistoric adult female from Pacatmu, Peru (Mann and Verano 1990). It appears in the eighth thoracic vertebra, with compensatory overgrowth of adjacent vertebral bodies. The fourth, fifth, and sixth vertebral neural arches are united into a block vertebra that is asymmetrical, because the left neural arch in T5 did not develop. The eleventh thoracic vertebra of an adult (National Museum of Natural History [NMNH] 385152) from the Trigg site in Virginia (A.D. 16101620) displays a sagittal cleft vertebra with hypoplasia of the left half. All of the other vertebrae are normal except for the adjacent tenth and twelfth thoracic vertebral segments. The tenth thoracic vertebral body has compensated with increased anterior height, and the twelfth vertebral body has raised its superior surface and broadened its anterior width as well as its height (Fig. 3.2).
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Fig. 3.2 Failure of the notochord to regress sagittal cleft T11 vertebra from the Trigg site in Virginia; adult (NMNH 385152) from early historic period. T11 also has hypoplasia of the right side, and the adjacent articulating surfaces of T10 and T12 have compensatory growth. A: superior view of T11. B: right lateral view of T10, T11, T12. C: anterior view of T10, T11, and T12.
3. Mesenchymal Diastematomyelia A very rare notochord defect mesenchymal diastematomyelia occurs when notochordal cells stray from their normal migratory path as they originate from the primitive node, usually in the thoracolumbar area. These wayward notochordal cells become trapped in the primordial neuroectodermal tissue forming the spinal cord, but they remain loosely connected by a
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pedicle to the rest of the notochord imbedded in the developing centrum. The inductive nature of the notochord cells in the pedicle attracts mesenchymal cells to it. These cells develop into a fibrocartilaginous or osseous spike along the pedicle, attaching to the posterior surface of the associated centrum in the midline (Tsou, Yau, and Hodgson 1980). The developing spinal cord, or cauda equina, will become bifurcated. Mild cases remain asymptomatic. Tethering (restraining) of the cord can take place with this defect. Symptoms appear between the ages of two and ten years of age, when growth and development place traction on the tethered cord. This can produce changes in gait, other lower extremity motor disturbances, and incontinence. When the spicule is osseous, it is usually ovoid, varying in length from 1 to 1½ centimeters. The vertebral canal is generally widened at the point of disturbance, and there is frequently an associated spina bifida (Epstein 1976; Meschan 1985; Ruge and Wiltse 1977; Schmorl and Junghanns 1971). Summary Outline: Notochord Field Defects Failure of Notochord to Regress Coronal cleft centrum irregular or ovoid depression, dorsal portion 1.smaller than anterior portion; primarily found in lumbar spine or lower thoracic spine Sagittal cleft centrum (butterfly vertebra) usually only one vertebra affected; rounded or pointed apices, tendency to spread laterally with decrease in height. Neural arches not affected; hourglass contour, 2. narrow in the middle, funneling toward both end plates with indented surfaces; may have unilateral or bilateral hypoplasia, scoliosis, or kyphosis. Four basic types: a. narrow bifurcation b. complete cleft c. connecting bony bridge d. connecting bony strands Mesenchymal diastematomyelia osseous spike, usually ovoid, 1 cm1½ cm long, attached to posterior surface of centrum in midline 3. projecting into neural canal; more than one vertebra can be affected, especially T3 to sacrum.
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Part II. Neural Tube Field Defects The neural tube develops into the structures of the central nervous system the brain and spinal cord closely aligned with the cranium and vertebral column. Disorders in the development of the neural tube, particularly anencephaly and meningomyelocele, are the most common major neural tube developmental defects known. A wide range of variation exists in the incidence of neural tube defects around the world and through time, with sporadic epidemics occurring in some regions. There appears to be an East-West gradient, highest in the British Isles (especially Northern Ireland, Wales, and Scotland) to a low in Japan, with North America in between (higher on the East Coast than on the West Coast). Exceptions occur in isolated pockets, such as in Egypt and Iran, where the frequency of anencephaly is unusually high. This could be a result of nutritional factors related to the zinc-poor soil. Most Black populations have a low frequency of neural tube defects. Females tend to be more affected than males. Studies of immigrants and their descendants show an underlying genetic component to neural tube defects, with a major environmental impact that appears to be nutritional, because these groups tend to maintain an incidence rate that is intermediate between their homeland and their resident country (Brock 1981; Carter 1974; Fraser, Frecker, and Allderdice 1986; Hoffman 1965; James 1985; Janerich and Piper 1978; Leck 1972, 1984; Lemire 1988; Myrianthopoulos and Melnick 1987; Oakley 1981; Sever 1975). There is a strong familial tendency for the development of neural tube defects. Apparently, a genetic predisposition to produce such defects requires some exogenous factor or factors for manifestation. The strongest evidence points to maternal nutritional deficits, particularly of zinc (zinc deficiency in Egypt and Iran is endemic), folic acid, and selenium. This would explain seasonal epidemics in some parts of the world (Breslin and McCormack 1979; Carter 1974; Kolata 1989; Leck 1984; Lorber 1965; Moghissi 1974; Myrianthopoulos and Melnick 1987; Seller 1987; Sever 1975). Individuals with neural tube defects frequently have other field defects (Hoffman 1965; Wynne-Davies 1975), which are probably also caused by maternal malnutrition. Yates and colleagues (1987) point out that an inherited faulty maternal folate metabolism may cause depressed folate levels, leading to neural tube defects in the embryo. This can be corrected with maternal folic acid supplements before conception, drastically reducing the incidence of neural tube defects (Shelby 1992). Folic acid enhances zinc absorption.
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Selenium also plays a key role in zinc absorption, priming the cells for growth and longterm zinc uptake. A diet low in selenium can also produce neural tube defects, and selenium supplements in areas where the soil is poor in this mineral decrease the incidence of such defects. As with zinc, the amount of selenium in soil varies around the world, following a cline similar to that of neural tube defects (Zimmerman and Lozzio 1989). All three nutrients are needed to regulate genetic control and cellular growth during morphogenesis. Normally, even diets marginal in one or more of these nutrients will provide what the embryo needs for proper growth and development. Genetics determine that need, and individual requirements for cellular uptake and utilization vary (Zimmerman and Carmen 1989). An embryo that requires more than what the mother's diet and metabolism can supply for any one of these essential nutrients is at risk for disturbances in the development of the neural tube. The greater the imbalance, the greater the risk for the more sever defects. The neural tube is produced by the folding of the neural plate into an epithelial tube, beginning about the twentieth day in the developing embryo (Fig. 3.3). Closure of the neural tube begins in the middle at the sixth somite stage of development in the paraxial mesoderm, with progression in both directions as the embryo grows. The cranial end of the neural plates enlarges to form the brain, closing over at the anterior neuropore when embryonic development reaches twenty somites (between twenty-two and twenty-six days). The caudal end (the posterior neuropore) closes at about the twenty-fifth somite stage of development (between twenty-six and thirty days) at the lower thoracic level. The rest of the neural tube below this level differentiates quickly in a progressive manner by canalization, as the caudal end of the body develops from the end bud. Early on, the developing spinal cord fills the entire vertebral canal. After the third fetal month, growth of the spinal cord lags behind the vertebral column, eventually ending at the level of the third lumbar vertebra at birth. Terminal connections from the tip end of the spinal cord are maintained during the growth of the vertebral column, ending up as the filum terminale surrounded by the spinal nerves of the cauda equina. At birth, traces of the original neural tube make up the coccygeal vestige near the tip of the coccyx (Arey 1965; Hall et al. 1988; Lemire 1988; Williams et al. 1989).
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Fig. 3.3 The human embryo at twenty-three days. a: anterior neuropore; b: neural plate; c: branchial arch I; d: closing neural plates; e: somites; f: closed neural tube; g: posterior neuropore (redrawn from Arey 1965).
A. Neurulation Defects Development of the neural tube from the neural plates is referred to as neurulation or primary neurulation. Defects developing during this time will occur as open lesions (not covered with normal skin tissue). If the neural folds fail to fuse, craniorachischisis (brain and spinal cord fissure) occurs, with concomitant failure of cranial and vertebral structures to develop normally, leading to death, usually early in the embryonic or early fetal stage of development.
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Fig. 3.4 Neurulation neural tube defect: craniorachischisis (brain and spinal cord fissure) with anencephaly. Prehistoric mummy from Hermopolis Catacombs (redrawn from DR Brothwell 1968).
1. Cranium: Anencephaly Anencephaly (absence of brain development) is the result of nonclosure of the anterior (rostral) neuropore (Fig. 3.3a) and is also lethal, usually prior to birth (Hall et al. 1988; Lemire 1988; Warkany 1971). Only one case of anencephaly is known from the prehistoric record: this was an Egyptian mummy described and illustrated by Saint-Hilaire in 1826 (Brothwell and Powers 1968), with rachischisis (spinal cord fissure) of the upper spine (Fig. 3.4). 2. Vertebral Column: Meningomyelocele Failure of the posterior neuropore (Fig. 3.3g) to close results in a meningomyelocele (Lemire 1988) displacement of a portion of the spinal cord and nerve roots outside the vertebral canal. Because the neural tube is closely interlocked with the developing paraxial mesoderm, the developing vertebral column is affected by defects in the spinal cord, and a spina bifida (failure of the vertebral neural arches to fuse) accompanies this defect (Gruneberg 1954).
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Fig. 3.5 Different types of neural arch defects. a: spina bifida of L5 and sacrum resulting from neural tube defect; b: normal L5; c: cleft neural arch of L5 resulting from developmental delay defect in the paraxial mesoderm; d: postneurulation neural tube defect spina bifida occulta; e: postneurulation neural tube defect spina bifida cystica (meningocele); f: neurulation spina bifida (meningomyelocele) (adapted from EP Hoffman 1965).
Spina bifida associated with a defect in the spinal cord (myelodysplasia) is known as spina bifida cystica and usually involves several vertebrae. The impinging cystic spinal cord defect interferes with the normal pace of development of the associated neural arches, leaving a gap between the two halves. Without fusion, the pedicles are thin, the laminae are deformed or absent, and the spinous process does not develop (Fig. 3.5e). The edges of the bony defect are raised by the cystic growth (Brailsford 1948; Epstein 1976; Hoffman 1965; Warkany 1971). Meningomyelocele (myelomeningocele) is the most common spinal cord defect associated with spina bifida cystica, occurring most frequently in the lumbosacral region. It always produces neurologic disability. The spina bifida is usually wide with stunted pedicles, in accordance with the protruding broad and rounded sac of the meningomyelocele. Symptoms vary with the
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level of involvement. Most infants born with severe involvement die very quickly. Paraplegia results from a meningomyelocele above the level of the third lumbar vertebra. If it occurs below this level, from the fourth lumbar vertebra on down, the hip extensors and knee flexors are paralyzed, with flail feet, and incontinence results. With a meningomyelocele occurring at the level of the first sacral vertebra on down, the hip extensors and knee flexors are not paralyzed, but they are weak, and the plantar flexors of the feet are paralyzed. Incontinence remains a problem. Involvement limited to the third sacral vertebral level and below leaves the lower limbs normal, but incontinence is still a problem (Epstein 1976; Goodman and Gorlin 1983; Hoffman 1965; Lemire 1988; Warkany 1971). About 65% to 75% of babies born with meningomyelocele develop progressive hydrocephalus, usually within six weeks following birth. This is generally associated with protrusion of brain tissue through the foramen magnum Arnold-Chiari malformation which obstructs the normal flow of cerebral-spinal fluid (Goodman and Gorlin 1983; Hoffman 1965; Lemire 1988). B. Postneurulation Defects Closure of the neuropores at the end of the first thirty days does not prevent the development of neural tube defects. The neural tube continues to grow in a caudal direction by canalization until the embryonic tail begins to regress during the seventh week. Disturbances can still occur along the length of the neural tube, particularly at the caudal end. Ectodermal tissue now covers the growing embronyic neural tube, and the resulting neural tube defects are closed lesions (covered with normal skin tissue). Some postneurulation defects affect the developing vertebral column and cranium. 1. Vertebral Column a. Spinal Meningocele with Spina Bifida Cystica Spinal meningocele consists of a portion of the meninges the three membranes surrounding the spinal cord and brain herniating outward through an opening in the vertebral column (spina bifida cystica). The meningocele develops after neurulation occurs, so the resulting cyst formation is covered with skin tissue, as opposed to the more commonly occurring spinal
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defect meningomyelocele without normal skin covering (Hall et al. 1988; Lemire 1988; Warkany 1971). The spina bifida is often smaller than the one associated with meningomyelocele and is usually narrow if located above the lumbar area, corresponding to a pedunculated meningocele. The pedicles spread, and the affected vertebrae appear broader than normal. When several vertebrae are affected, the defect will appear fusiform (tapering at both ends), with the widest portion in the middle. Symptoms vary according to the size and involvement of the defect, ranging from minimal to major neurological deficit. Meningoceles with spina bifida cystica, as with meningomyeloceles, most commonly occur in the lumbosacral region. An individual born with a meningocele will likely survive into adulthood. If the defect is small, few, if any, noticeable symptoms will appear until the lesion is aggravated by trauma (Arey 1965; Brailsford 1948; Epstein 1976; Goodman and Gorlin 1983; Hoffman 1965; Lemire 1988; Ruge and Wiltse 1977; Warkany 1971). b. Spinal Meningocele with Spina Bifida Occulta Occasionally, an occult meningocele or myelodysplasia involving the lumbosacral spine will not be visible as a protruding skin-covered sac. It will sometimes be hidden by an extra layer of fat (lipoma). The lipoma may contain elements of the cauda equina or a thick tuft of hair, or it may appear as a cutaneous dimple communicating with a deeper cyst or as unusual pigmentation caused by disorganized retrogression of the tail bud. Motor function is usually impaired, with diminished pain perception and disturbances of sphincter control. The spinal canal is widened, pushing the edges of the bony cleft defect (Figs. 3.5c and 3.6a) of the associated vertebral segments outward (Lemire 1988; Ruge and Wiltse 1977). Mild forms of occult neural tube defect involving fibrolipomatous tissue masses constrict the dura of the filum terminale. Recurrent or continuous low back pain radiates to the hips and sometimes to one or both legs. The neural tube defect sometimes causes the filum terminale to be tight, with tethering of the conus medullaris (conical portion of the lower end of the spinal cord). This produces disturbances in gait, such as limping or stumbling, or foot deformities, such as high arches and clawing of the toes, and progressive neurological involvement of the legs and bladder (Epstein 1976; Meschan 1985). Cleft vertebral segments that do not involve neural tube defect (often referred to as spina bifida without neural tube defect) are much more common
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Fig. 3.6 Neural arch defects of the sacrum: neural tube defect (spina bifida) versus developmental delay in the paraxial mesoderm (cleft neural arch). A: neural tube defect (spina bifida) in young adult female from the Federal Pathologic Anatomy Museum in Vienna, Austria (courtesy of Don Ortner). Cleft neural arch defect from developmental delay in the paraxial mesoderm in B: a young adult female (NMNH 308616) from Hawikku, New Mexico, and in C: an adult male (NMNH 228941) from Otowi, New Mexico.
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than cleft vertebrae with neural tube defect as high as 25% in a given population. Most clinicians do not consider them abnormal, because they are usually clinically insignificant (Hoffman 1965; Laurence, Bligh, and Evans 1968; Saluja 1988). Clefting of vertebrae without neural tube defect (Fig. 3.5b) generally involves only one or two vertebral segments at the borders between the differing types of vertebrae. Sometimes the entire dorsal plate of the sacrum fails to fuse (Fig. 3.6b). The resulting neural arch defect commonly appears as a bifid or cleft spinous process (Epstein 1976). Because there is no myelodysplasia, this type of cleft vertebra is most likely a neural arch developmental defect (Hoffman 1965) within the paraxial mesoderm developmental field. Studies trying to prove that spina bifida occulta is a minor manifestation of spina bifida cystica have led to some confusion (Bennett 1972; Laurence 1967; Miller, Fraser, and MacEwan 1962; Saluja 1988; Wynne-Davies 1975). If one can differentiate the appropriate developmental field of origin for the cleft neural arch, the confusion can be dispelled. Spina bifida occulta resulting from neural tube defect is definitely related to spina bifida cystica, whereas cleft neural arch resulting from neural arch defect is not. Laurence, Bligh, and Evans (1968) found a definite correlation between the more severe spina bifida occulta and spina bifida cystica but not with spina bifida with neural arch defect only. This presents a problem for paleopathology how to distinguish between the two types in order to determine the incidence of neural tube defects in prehistoric populations. Both neural tube defects and cleft neural arch without neural tube defect commonly occur in the lumbosacral region, and both can produce a complete cleft sacrum (Fig. 3.6). The spinal canal is widened with neural tube defect, pushing the edges of the bony cleft outward. In contrast, the spinal canal remains normal and the edges of the bony cleft are not raised when no neural tube defect is present (Fig. 3.5). Clefting without neural tube defect also occurs in presacral vertebral segments, usually at the border areas. If the difference can be determined, reference should be made to spina bifida occulta resulting from neural tube defect versus cleft neural arch defect instead of calling both spina bifida occulta. This would help to determine the true incidence of neural tube defects. Spina bifida has long been reported in prehistoric skeletal populations (Dickel and Doran 1989; Ortner and Putschar 1985). Most of these occurences have been described as spina bifida occulta, usually of the sacrum.
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We do not know how many of these are related to neural tube defects, but most are probably not related. The sacral hiatus, which normally terminates at the level of the third or fourth sacral vertebra, is sometimes confused with a spina bifida occulta (Devor and Cordell 1981). There are a few reports of individuals with spina bifida cystica in the prehistoric past, and chances are they were associated with meningoceles. An individual with spina bifida cystica formed from a meningocele, a skin-covered defect, would have had a better chance of surviving than someone born with the more serious meningomyelocele. Dickel and Doran (1989) describe a case of spina bifida cystica (probably meningocele) extending from the level of the third lumbar to the second sacral vertebra in a fourteen to sixteen year old in an early Archaic site (Windover) on the east coast of Florida. Disuse atrophy, noted in the bones representing the extremities, probably reflects a partial paralysis resulting from the location and extent of the myelodysplasia. A six-year-old child from an archaeological site from the north-central Peruvian coast, dating to five thousand years ago, was reported by De La Mata and Bonavia (1980) to have a spina bifida cystica. The fifth lumbar vertebra, an additional sixth lumbar vertebra, and the entire sacrum are affected. c. Sacral Agenesis Following closure of the posterior neuropore, the neural tube continues to develop in a caudal direction by canalization. Failure of this part of the neural tube to develop can affect development of the lumbosacral spine, causing missing lumbar vertebral segments or agenesis of the sacrum (Lemire 1988). Varying degrees of sacral agenesis can occur, from complete absence of the sacrum to incomplete formation (Fig. 3.7). Complete agenesis makes standing and walking impossible; however, if the first sacral segment is present or the fifth lumbar is sacralized, a bony ring forms with the pelvis, allowing normal stance and gait. In other instances, the sacral elements can be absent on one side with normal or defective development on the other side. Neurological problems and incontinence are associated with the milder forms that manage to survive infancy. Sacral agenesis is frequently associated with spina bifida cystica and other axial skeleton defects (Hotston and Carty 1982; Stanley, Owen, and Koff 1979; Warkany 1971). Rarely, meningoceles can occur in the anterior region of the sacrum with incomplete sacral agenesis. Symptoms do not usually appear until adolescence. Then the individual is bothered by low back pain, constipation, and
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Fig. 3.7 Neural tube defect: sacral agenesis. a: partial agenesis with first sacral segment present; b: unilateral agenesis with first and second sacral elements absent and hypoplasia of remaining sacral segments; c: unilateral hypoplasia.
urinary frequency, because cerebrospinal fluid collects in the sac of the meningocele. This defect can interfere with labor and delivery in the female. The intrasacral meningocele can also occur when the distal end of the dural sac widens instead of narrowing in the sacral canal, with or without bony involvement (Epstein 1976; Warkany 1971). Sacral agenesis, with or without anterior meningocele, has not been reported in the paleopathology literature to date.
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2. Cranium: Encephalocele and Meningocele Skin-covered meningoceles can also occur at the cranial end of the neural tube following neurulation. Brain tissue sometimes herniates outside the confines of the cranium within a skin-covered sac known as an encephalocele. Both of these defects are associated with a bony defect (Hoffman 1965; Lemire 1988). The intruding meningocele or encephalocele or both (meningoencephalocele) interfere with normal bony closure. They are usually located in the sagittal plane, in the occipital, and in the floor of the anterior and middle fossae. They can localize in the roof of the angle of the orbit, in the root of the nasion, or in the region of the sella turcica. They can also occur in the parietals at the vertex of the cranium and in the frontal bone near the anterior fontanelle (Brailsford 1948; Currarino 1976; Lodge 1975; Meschan 1985). Meningoceles are more likely to locate near the calvaria. The resulting cyst produces a smooth, rounded depression in the outer surface of the cranium as it protrudes from its stem through a small opening in the base of the depression (Fig. 3.8). The borders of the depression are sharply defined, surrounded by an outer flange of built-up bone. When the defect is located in the base of the skull, it appears as an ovoid opening in the bone without the built-up bony flange, but it will have an imprint of the smooth-surfaced cystic meningocele. With encephalocele, the opening is larger, and the cranium appears to be bifid. Most of these defects show up in the occipital region and are slightly more common in females than in males. Most infants born with an encephalocele die within the neonatal period, but individuals born with cranial meningoceles can survive into adulthood (Brailsford 1948; Currarino 1976; Lodge 1975; Meschan 1984). Clinical cases of cranial meningoceles are rare except in Burma, Thailand, and India, where the frequency is one in every thirty-five hundred births (Lemire 1988). A few cases of cranial meningocele have been identified in prehistoric populations in recent years. A cranial meningocele was erroneously reported as a trephination in a Woodland Tradition adult male cranium from the Spruce Swamp site near Norwalk, Connecticut (Powell 1970). Gass (1971), a neurosurgeon, correctly identified the cranial lesion as a cranial meningocele from the photographs accompanying the article, bringing to light the first prehistoric case reported in the literature. Stewart (1975) agreed with Gass and reported a similar case in an adult female (NMNH 264629) from Chicama (Fig. 3.8), found in the Smithsonian's National Museum of Natural History's Peruvian collection of crania Ales
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Fig. 3.8 Neural tube defect: postneurulation cranial meningocele at bregma. Adult female (NMNH 264629) from Chicama, Peru.
Hrdlicka gathered in 1910. Another case was mentioned by Saul (1983) in an adult male from Chichen Itza in Yucatan (dated A.D. 9001200). This lesion had previously been listed as an old, healed depression fracture. Webb and Thorne (1985) described a late prehistoric/early postcontact-period young adult Aboriginal female from New South Wales, Australia, with a similar lesion. Ortner and Putschar (1985:351) identified another case in the cranium of a six- to eight-year-old child from Ancon, Peru, in the skeletal collections of the Field Museum of Natural History. All of these cases are similar, because they all occur at bregma, extending into the sagittal or metopic suture. They all appear as ''saucer-like" depressions, with an irregular opening through the bone in the floor of this depression that connects to the sagittal suture. They all have some elevation of the borders around the depression. The Australian Aborigine has the largest lesion, whereas the Chicama cranium has the smallest one. The buildup of bone around the edges of the depression developed in response to the pulsations coming from the soft tissue lesion. The saucer-like shape of the depression occurs in response to the pressure of the soft tissue cyst. The
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irregular opening occurs when the sutures are prevented from closing normally by the extending peduncle (stem) of the meningocele. The soft lesion was covered by protective membrane and skin but must have been very tender and would have been vulnerable to irritation. When studying the skeletal collection from the Pueblo IV Zuni village of Heshotauthla, New Mexico, I found an adult male (NMNH 239539) with evidence of a small meningocele in the occipital bone. It is located just above and to the left of the inion as an oval depression with a thin, bony floor containing a small, irregular opening. A raised bony ridge forms the inferior and medial borders of the depression. Summary Outline: Neural Tube Field Defects A. Neurulation defects 1. Cranial anencephaly; absence of most of calvaria (unable to survive perinatal period) 2. Vertebral column meningomyelocele with spina bifida cystica, usually lumbosacral region; several vertebrae; wide, stunted pedicles; with or without hydrocephalus (not likely to survive perinatal period) B. Postneurulation defects 1. Vertebral column a. spinal meningocele (1) with spinal bifida cystica usually smaller than with neurulation defect; narrow (pedunculated defect) if above lumbar region; pedicles spread and vertebral body abnormally broad; with several vertebrae involved, fusiform bony defect with widest part in the middle; imprint of cyst on affected vertebrae. (2) with spina bifida occulta widened spinal canal, pedicles thin and pushed outward; commonly occurs in lumbosacral region b. sacral agenesis (1) complete absence of sacrum unable to walk (2) partial absence S1 present or L5 sacralized to form bony ring with pelvis, allows normal stance and gait (3) unilateral sacral segments missing on one side, neurological problems (4) unilateral hypoplasia one side abnormally small or deformed,
neurological problems.
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Part III. Developmental Ectodermal Inclusion Cysts Ectodermal inclusion cysts develop from the entrapment of ectodermal cells by other underlying developing embryonic tissues during morphogenesis. Similar to cranial neural tube defects, they also tend to form in the midline or sagittal plane of the skull, from the frontonasal region to the base of the occiptal, with the anterior fontanelle as the most favored location on the skull (Chaudhari et al. 1982; Chaudhari, Rosenthal, and Lipper 1984; Pannell et al. 1982; Parizek et al. 1989; Rubin et al. 1989; Wiemer 1988). Ectodermal inclusion cysts are more common in the lumbosacral region of the spine, but the only bony defect may be widening of the bony canal by the growth of the ectodermal cyst (Boldrey and Elvidge 1939; Schijman, Monges, and Cragnaz 1986). These cysts will not likely be recognizable in prehistoric skeletal collections. Timing appears to be the problem with the entrapment of surface ectodermal cells within underlying tissue and the formation of inclusion cysts. The outer layer of ectodermal tissue of the developing embryo normally retreats from the threat of impingement by underlying tissue parts coming together. With any kind of delay in this retreat, the closing tissue parts can trap some of the ectodermal cells between them (Boldrey and Elvidge 1939). Ectodermal inclusion cysts vary in type and location according to the timing and place of the entrapment of ectodermal cells. They can be found within intracranial, cranial, or extracranial tissue (Chaudhari et al. 1982; Rubin et al. 1989). A. Epidermoid Cysts Following closure of the neural tube, the surface ectodermal cells differentiate into the various cell components of the skin. Epithelial cells that form the outer layer of the skin are sometimes trapped in rapidly expanding underlying neural tissue. The encased developing epithelial cells form a solid tumor containing keratohyalin within a capsule of squamosal epithelium. This is known as a epidermoid cyst, growing in size from epithelial desquamation (Rubin et al. 1989; Scheie and Albert 1977). Epidermoid cysts occur much more often than dermoid cysts, affecting females twice as often as males. Epidermoids usually affect intracranial tissues and are frequently found within the dura, the outermost covering of the brain.
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The slow-growing intracranial ectodermal inclusion cyst can produce symptoms of varying degrees as pressure is exerted on associated tissues (Rubin et al. 1989). B. Dermoid Cysts Some surface ectodermal cells become trapped in underlying mesenchymal tissue at the time the anterior neuropore closes, before the ectodermal cells differentiate. The resulting cyst will contain the various components of dermoid tissueepithelium, hair follicles, hair, sebaceous gland tissue, and sweat gland tissue. These tend to develop in the diploe of the skull wherever two or more cranial bones come together, favoring the midline of the skull, particularly the anterior fontanelle. They can grow to up to 5 cm in diameter, are covered by bald skin, and are painless. The associated bony lesion in the diploe consists of a rounded depression with a thin floor that eventually gives way to the growing dermoid cyst (Pannell et al. 1982; Rubin et al. 1989; Schijman, Monges, and Cragnaz 1986). A dermoid (or epidermoid) cyst can sometimes form between the periosteum and the scalp. The underlying bone surface may have a shallow indentation, flattening, or pitting as a result of pressure from the overlying ectodermal cyst (Chaudhari, Rosenthal, and Lipper 1984; Wiemer 1988). C. Dermoid Sinus Rarely, an abnormal channel or sinus is formed from entrapped ectodermal tissue between internal and external tissues. These are found most often in the lumbosacral region of the spine. Those associated with the cranium are usually found in the occipital region at the level of inion and sometimes just above or below this point. Generally, dermoid sinuses are connected with intracranial ectodermal cysts. Sometimes they also connect with extracranial cysts found above the periosteum. The bony opening is usually quite small, about .5 cm in diameter, with rounded edges. Bacterial infections introduced through the dermoid sinus into the brain are common (Schijman, Monges, and Cragnaz 1986). Bone lesions associated with dermoid sinuses can be confused with those produced by cranial meningocele, because both communicate with intracranial tissues. Dermoid sinuses have rounded openings in the skull, whereas
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cranial meningoceles connect with intracranial tissue through an irregular opening. Rounded depressions in the outer surface of the skull can be produced by both dermoid cysts and cranial meningoceles; neural tube defects tend to have a buildup of bone around the border in response to pulsations, whereas ectodermal inclusion cysts have no such buildup. The only ectodermal inclusion cyst I know of in prehistoric skeletal material is found in a skeletal collection from the Pueblo IV Towa ruin, Amoxiumqua, on Virgin Mesa near Jemez Springs, New Mexico. The skeletal collection is curated at the Smithsonian's National Museum of Natural History. An adult female (NMNH 271858), forty-five to fifty years of age, has a large bony lesion (3.7 × 2.6 cm) involving the diploe of the supramedial margin of the left eye orbit (Fig. 3.9). The central portion of the thin, bony floor of the lesion has eroded away because of the pressure of a dermoid cyst. There is no sign of infection, and the margins of the lesion are well defined by the imprint of the cyst. Dermoid cysts that involve the eye orbit produce a progressive, painless exophthalmos (outward protrusion of the eyeball), which can cause blurred, double (diplopia) vision. Most periorbital dermoid cysts locate in the superolateral or medial borders of the eye orbit, sometimes in the lateral orbital wall or greater wing of the sphenoid, and rarely in the inferior portion of the orbit (Rubin et al. 1989; Scheie and Albert 1977). Summary Outline: Developmental Ectodermal Inclusion Cysts Epidermoid cyst frequently intracranial, usually within the dura; 1.midline from frontonasal region to base of occipital 2.Dermoid cyst diploe of skull, anywhere two or more cranial bones meet; a. frequently found in anterior fontanelle; rounded depression up to 5 cm diameter with thin or disappearing floor periorbital, usually supralateral or median borders; bony lesion same b. as above supraperiosteal, usually midline; shallow indentation, flattening, or c. pitting Dermoid sinus connection between intracranial and extracranial tissue; frequently found in occipital at level of inion, or just above or below 3. it; .5 cm rounded, bony opening with smooth edges; may be associated with bone defect of supraperiosteal dermoid cyst
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Fig. 3.9 Dermoid cyst from Amoxiumqua, New Mexico. Adult female (NMNH 271858) with large 2.6 cm × 3.7 cm oval lesion from dermoid cyst in the supramedial margin of the left eye orbit (unfortunately, the face is missing). A: frontal view with re-created face. B: left lateral view of cranial vault. C: top of cranial vault view.
Part IV. Paraxial Mesoderm Field Defects The paraxial mesoderm columns produce the vertebral column, ribs, and exoccipitals. Genetic influences on this developmental field are strong, according to the evidence produced by experimental embryonic studies in laboratory animals, studies of monozygotic twins, and pedigree studies (Gruneberg 1963; Potter 1963; Warkany 1971).
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The repertoire of structural developmental field defects is limited, but these defects can result from a variety of genetic and epigenetic determinants Most field defects arise from disturbances caused by temporal delays in segmentation, differentiation, and development. The underlying genetic disturbance probably results from alteration of the structural or enzymatic proteins, with the end result dependent upon the threshold stage reached. Some disturbances can be potentiated or depressed by exogenous factors, providing a spectrum of variation for certain defects (Gruneberg 1963; Potter 1963; Warkany 1971). Many defects may not be detected at birth, going unnoticed until symptoms appear with growth and development in childhood or adolescence and often not until trauma strikes the affected area in adulthood (Nassim and Burrows 1959). The expression of field defects within the paraxial mesoderm varies in different populations. The paraxial mesoderm columns, developing from mesenchyme along both sides of the notochord, straddle the developing neural tube. Transverse clefts begin to appear in the columns by the twentieth day, subdividing the paraxial mesoderm into paired symmetrical hemimetameric blocklike masses the somites. This process begins toward the cephalic end and progresses in a caudal direction until the thirtieth day. Each of these segments contains three types of cell clusters dermatome, myotome, and sclerotome. The dermatome forms skin tissue, and the myotome produces muscle tissue. The sclerotome, located next to the notochord, quickly surrounds the notochord and neural tube with a continuous mesodermal sheath the blastemal analog of the vertebral column and exoccipitals (Arey 1965; Epstein 1976; Williams et al. 1989). A. Segmentation Errors 1. Asynchronous Development of Hemimetamere Pairs The matching somite pairs develop simultaneously but independently of each other along the paraxial mesoderm columns. When they reach a certain threshold in their development, the paired somites fuse along the midline.
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a. Hemimetamere Shifts: Hemivertebra Delay in development of one of the somite hemimetameres slows its movement to the midline at the critical threshold time of fusion. The tardy side misses its connection with the other half of its somite complement. It shifts down one segment to pair up with the next available hemimetameric segment as it approaches its threshold time for fusion. This leaves the remaining hemimetameric segment unpaired, to form a lateral wedge-shaped hemivertebra (Fig. 3.10a). This is known as a hemimetameric shift or displacement, or asynchronous development of the hemimetamere pair (Tsou, Yau, Hodgson 1980). Sometimes extra somites contribute to the formation of extra vertebral segments in hemivertebra form. Hemimetamere shifts usually lead to congenital scoliosis. The adjacent vertebral segments compensate with corresponding deformation or fusion with the hemivertebral segment. Sometimes a normal rib projects from the thoracic hemivertebra, and the contralateral side will not have a rib (Epstein 1976; Schmorl and Junghanns 1971; Tsou, Yau, and Hodgson 1980). Solitary hemivertebral segments resulting from hemimetamere shifting (Fig. 3.10a) are rare and probably result from the lack of development of a counterpart hemimetameric segment. Hemimetamere shifts generally produce multiple hemivertebrae, unilateral (Fig. 3.10c) on one side, contralateral (Fig. 3.10b) on opposite sides, or, rarely, bilateral. Bilateral hemivertebrae are produced when two opposing hemimetameres shift downward to the same level. These can be confused with sagittal cleft vertebra (butterfly vertebra) because of the lateral wedge shape of each half, but they clearly differ in form as fully developed vertebral halves, totally separate from each other. The most frequently occurring hemimetameric defect is the double-balanced hemivertebrae, involving two opposing out-of-phase pairs of somites, resulting in two contralateral hemivertebrae separated by normal vertebral segments (Fig. 3.10b). They are balanced enough to offset spinal deformity (Schmorl and Junghanns 1971; Tsou, Yau, and Hodgson 1980). Brothwell (1967:430) describes a double-balanced set of hemivertebrae fused to the fourth and fifth lumbar vertebral segments in an adult male from the Beaker (Bronze Age) culture at Crichel Down, Dorset, England. Hemivertebrae are often fused to adjacent vertebrae. MacCurdy (1923:261; plate XLIV) discovered two unilateral hemivertebrae producing scoliosis in an adult male from Paucarcancha in the highlands of Peru near Cuzco. They represent an extra thoracic vertebral segment located between the third and fourth thoracic and fourth and fifth thoracic
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Fig. 3.10 Variations of hemimetamere shift defects. a: solitary shift; b: contralateral double shift (balanced). c: unilateral double shift (unbalanced). Note that the apices of the hemivertebrae do not cross the midline.
vertebrae on the right side with curvature toward the left side. The last two cervical vertebrae are partially fused on the right side, and the first thoracic vertebra and the first four ribs on the left side are fused at their vertebral junctions into one solid mass (Fig. 3.11). I discovered a solitary hemivertebra on the right side of the fifth lumbar vertebral segment in a young adult female (NMNH 381243) from the Pueblo IV Southern Tiwa site of Quarai, New Mexico. This specimen is in the Smithsonian's National Museum of Natural History's skeletal collections.
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With the shifting of the hemimetamere of L5, the lumbosacral border has also shifted somewhat upward on the right side as represented by the incomplete sacralization of the L5 hemivertebra. The first and second lumbar vertebrae are normal in shape, and the third and fourth lumbar vertebrae have compensated growth. The third lumbar vertebral body is wedged laterally on the right side, and the fourth lumbar vertebra has an ovoidshaped inferior aspect. The first and second sacral segments have hemimetamere hypoplasia of the left side of S1 and the right side of S2. The left side of the lumbosacral border has shifted downward slightly, with an apophyseal articulation between the first and second sacral segments (Fig. 3.12). b. Hemimetamere Hypoplasia-Aplasia A solitary hemivertebra can result from simple aplasia of one of the hemimetameres without shifting. This leaves the remaining somite to develop without its partner. It reaches the midline on time, developing an irregular medial border that crosses the midline (Fig. 3.13a), and a scoliosis develops. Hemivertebra resulting from hemimetamere shift do not cross the midline, and the missing half of the evolving centrum is sometimes marked by a rudimentary rib. Individuals can be born with multiple solitary hemivertebrae. They generally have other severe abnormalities and do not survive beyond birth (Epstein 1976; Schmorl and Junghanns 1971; Tsou, Yau, and Hodgson 1980). Minimal hypoplasia of one or more of the hemimetameres on one side produces laterally wedged vertebral segments (Figs. 3.13b and 3.14). This leads to a congenital scoliosis of the affected spine. With multiple unilateral hemimetameric hypoplasia, the resulting vertebral segments are frequently joined together. The apophyseal joints are absent, and the laminae are fused into a bony mass known as a postlateral bar. The ribs on the affected side tend to fuse together near their vertebral junctions (Fig. 3.13c). Sometimes the costovertebral joints also fail to develop. Complete coalescence of the affected vertebral segments (no markings of segmentation of the centra present) with coalition of the affected ribs occurs with severe forms of multiple hemimetameric hypoplasia (Fig. 3.13d). The resulting congenital scoliosis is quite severe, and usually there are other associated severe defects found in the paraxial mesoderm (Epstein 1976; Keim and Hensinger 1989; Schmorl and Junghanns 1971; Tsou, Yau, and Hodgson 1980; Warkany 1971).
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Fig. 3.11 Hemimetameric unilateral double shift in adult male from Paucarcancha, in the highlands of Peru. Hemivertebrae between T3 and T4, T4 and T5 on the right side with scoliosis and fusion of first four ribs on the left side (drawn from photograph in MacCurdy 1923; plate XLIV).
2. Failure of Segmentation a. Block Vertebra The sclerotome mesenchyme in each of the united somite pairs separates into cranial and caudal portions as the caudal portion grows more rapidly than the cranial portion, forming a much denser condensation of mesenchyme
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Fig. 3.12 Hemimetameric shift with solitary hemivertebra of the fifth lumbar vertebral segment from Quarai, New Mexico. Adult female (NMNH 381243) with solitary right L5 hemivertebra incompletely sacralized to the sacrum (transverse process articulates with right side of sacrum) and unilateral hypoplasia of the left side of the first sacral segment and the right side of the second sacral segment; the last sacral segment is missing. A: superior view of L5 hemivertebra. B: anterior view of L3, L4, L5 hemivertebra and sacrum. C: dorsal view of L4, L5 hemivertebra and sacrum.
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Fig. 3.13 Variations of hemimetamere hypoplasia-aplasia. a: solitary aplasia; b: unilateral multiple hypoplasia; c: unilateral multiple hypoplasia with coalescence into postlateral bar; d: severe multiple unilateral hypoplasia with coalescence into postlateral bar. Note that the apices of the hemivertebrae cross the midline.
The two become separated as the growth of intersegmental arteries forms a temporary transverse fissure between them. As they separate, they recombine with adjacent sclerotomes. The dense portions shift in a caudal direction, combining with less dense neighboring cranial portions to form the precursors of the vertebral segments (Fig. 2.3). The denser sclerotome mesenchyme forms the compact posterior portion of each vertebra, whereas the more loosely arranged mesenchyme cells form the anterior portion. After the sclerotome portions separate and recombine,
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Fig. 3.14 Mild unilateral multiple hemimetamere hypoplasia in Chinese cannery worker from Alaska. Adult male (NMNH 364426) with scoliosis of the upper thoracic spine caused by hemimetamere hypoplasia of T3, T4, and T5 on the left side. From left to right, anterior view of T1 through T6; anterior and dorsal views of T3, T4, and T5.
the transverse fissure develops into a dense band the anlage of the intervertebral disc. The intersegmental arteries now cross the middle of the vertebral segments. The intervertebral disc space and adjacent vertebral segments constitute a single developmental unit (Arey 1965; Epstein 1976; Walmsley 1959; Williams et al. 1989). Failure of the sclerotomic fissure to appear within the developmental unit produces a continuous block of blastemal tissue. The developmental unit fails to separate into all or some of its different parts, and a block vertebra results (Fig. 3.15). This is not fusion of two vertebral segments, because they never separated or only partially separated. The degree of failure of separation depends upon the timing of the delay in the critical threshold event triggering the development of the sclerotome transverse fissure. There is usually complete unity between the centra with complete or incomplete cohesion of the neural arches (Fig. 3.16).
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Radiographic examination will show either complete ossification throughout the affected segments or discrete lines of partial demarcation. Sometimes only the centra are united, completely or incompletely; at other times, only the neural arches are united (Fig. 3.15c). Developmental block vertebrae can be confused with vertebrae fused by disease, but the degenerative changes and ossification of ligaments associated with pathological fusion tell the difference (Epstein 1976; Gunderson et al. 1967; Jarcho and Levin 1938; Schmorl and Junghanns 1971; Warkany 1971). More than two vertebral segments can be involved, with the cervical and lumbar vertebral segments more often affected than the thoracic segments. When block vertebra does occur in the thoracic area, it is most likely to show up in the midthoracic region (Epstein 1976; Schmorl and Junghanns 1971). b. Klippel-Feil Syndrome Classic Klippel-Feil syndrome refers to ''congenital fusion" of cervical vertebrae, producing a short neck, low posterior hair line, and limited movement of the neck. Klippel and Feil described the first case of cervical block vertebrae with these attributes in 1912, based on a case with four cervical vertebral segments involved. The term "KlippelFeil syndrome" has since been used to denote any type of segmental failure in the cervical spine (Jarcho and Levin 1938; Spillane, Pallis, and Jones 1957). Block vertebra in the cervical region is quite variable, with differing etiology and clinical symptoms. The different expressions follow different genetic paths, which is seen with familial tendencies favoring one type of expression over another. Three types of cervical block vertebra have been defined (Bailey 1974; Gunderson et al. 1967): Type I the classic Klippel-Feil syndrome of several cervical and upper thoracic vertebrae incorporated into one osseous block of grossly abnormal appearance and nearly always associated with other major defects. Type II only two or three vertebral segments are involved, with the second and third cervical segments the most commonly affected (Fig. 3.16), and there is evidence of autosomal dominant transmission; the fifth and sixth cervical segments are the next most common, usually expressed as an autosomal recessive trait. (Type II is also found in the gorilla, orangutan, armadillo, porcupine, and dog.) Type III cervical block vertebrae, with coexisting vertebral segmental errors in the thoracic and lumbar regions.
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Fig. 3.15 Failure of segmentation of the sclerotomes. a: schematic drawing of sclerotomes, with failure of segmentation of the less dense half for C2 and the high-density half for C3. b: C2C3 block vertebra (type II); c: T6T7 block vertebra (type II), with failure to segment between the neural arches only.
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Fig. 3.16 Type II block vertebra from Hawikku, New Mexico. C2C3 block vertebra from adult female (NMNH 308655); anterior, dorsal, and right lateral views.
The type II category is applicable to block vertebra found in the thoracic and lumbar spines as well as the cervical spine. Type II defects are the most commonly occurring block vertebrae, and they generally produce no symptoms. Infants born with either type I or type III defects usually suffer from multiple defects that severely compromise their ability to survive (Bailey 1974; Brown, Templeton, and Hodges 1964; Goodman and Gorlin 1983; Gorlin, Cervenka, and Pruzansky 1971; Gunderson et al. 1967). Block vertebrae are occasionally mentioned in the paleopathology literature, and there are a number of cases in Southwest skeletal collections. Wade (1981) applied the Klippel-Feil syndrome classification system to his analysis of an unusually high frequency of block vertebra in a group of Kayenta Anasazi skeletal collections from closely related sites in northeastern Arizona. He identified five cases of C2C3 block vertebrae from twenty-nine cervical spines (5/29 = 17%), all males. None of the female cervical vertebrae were affected. However, two of the females represented have block vertebrae in the thoracic spine.
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One of the males also had cranial shifting at the lumbosacral border, with sacralization of the last lumbar vertebra, which in this case is described as a sixth lumbar vertebra. Three other males without block vertebrae also had this defect, either complete or incomplete, and another male and a female had sacralization of the fifth lumbar vertebra. Thirteen thoracic vertebrae occurred in one adult female. Clefting of the neural arches was found in sacral vertebrae in one of the adult males with block vertebra and in other individuals without it. Based on these data, Wade defines all of the vertebral defects as part of the type III Klippel-Feil syndrome. However, this type represents coexisting cervical, thoracic, and lumbar vertebral segmentation errors in the same individual, and it is generally accompanied by major defects that can be life threatening. The block vertebrae represented in the Kayenta population are type II, which generally follows a familial trend along autosomal dominant genes. The high frequency suggests genetic isolation. Type I and type III may have existed in infants who failed to survive. The morphogenetic evidence indicates that the defects Wade mentioned as part of the Klippel-Feil syndrome are actually separate genetic entities that may appear together in the same individual or alone. As Don Ortner is fond of saying, "A dog can have ticks and fleas at the same time." Block vertebrae are also found in other Anasazi populations. Reed (1981:83) reported one case of type II cervical block vertebra in a Tompiro adult male from Mound 7, Las Humanas, at Gran Quivira National Monument (Pueblo IVV). Two other individuals from this site had thoracic block vertebrae. Akins (1986) mentioned a C2C3 block vertebra in one individual from Chaco Canyon (Pueblo IIII). Miles (1975) noted two cases of block vertebrae in Northern San Juan Anasazi from Wetherill Mesa, Mesa Verde skeletal material (Pueblo IIII), with coalescence only between the vertebral arches. Palkovich (1980) identified fused neural arches of the second-third cervical vertebrae in a young Tanoan adult male, a ten- to eleven-month-old infant, and a neonate from Arroyo Hondo, New Mexico (Pueblo IV). Anderson (1989) described a neonate and five-and-one-half-month-old fetus from the Homol'ovi Ruins (Pueblo IV) in northern Arizona, with unilateral cohesion of adjacent neural arches in the cervical and thoracic spines. The neonate also had fused ribs on the left side and a bifid rib on the right side. Type III Klippel-Feil syndrome is indicated. There must have been other defects in soft tissue that did not allow them to survive. These individuals were probably genetically related. Anderson (1989) described a third individual, a one-year-old child, with asymmetry of the mandible and maxillary palate that he suggested was part of
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the genetic complex affecting the other two subjects. This individual's defect derived from another developmental field (branchial arch I) and thus is unlikely to be related to the defects of the other two individuals. Matthews (1891) found two type II cervical block vertebrae (C2-C3) and one individual with united thoracic vertebrae in Hohokam skeletal material collected by the Hemenway expedition to Los Muertos in the Salt River Valley in the Phoenix, Arizona, area. Two C2C3 block vertebrae are found in the Pueblo IV-V Towa skeletal collection from Giusewa, and one C3-C4 block vertebra is from Amoxiumqua (Pueblo IV Towa); both are near Jemez Springs, New Mexico. The large Pueblo IV-V Zuni skeletal collection from Hawikku, New Mexico, contains three C3-C4 block vertebrae, one C2-C3 block vertebra (Fig. 3.16), and one T2-T3 block vertebra. The skeletal collection from the neighboring Zuni site of Heshotauthla (Pueblo IV) contains one C2-C3 block vertebra and one T4-T5 block vertebra. The National Museum of Natural History skeletal collection from Elden Pueblo (Pueblo III Sinagua) near Flagstaff, Arizona, contains an adult female with a C2C3 block vertebra. I found a classic type I block of vertebral segments in a Northern San Juan Anasazi adult from a site related to the Pueblo III Yellow Jacket ruin near Cortez in southwest Colorado. This individual has C7-T4 consolidated into one osseous block (Fig. 3.17). The third and sixth cervical vertebrae and the first lumbar are the only other vertebral segments present, and they are normal. Unfortunately, the vertebral bodies and most of T4 have been damaged, and the area for the rib facets for T2-T4 on the right side are damaged; the left side shows the rib facets very close to one another, indicating they were probably fused together. Gregg and Gregg (1987) reported six cases of type II cervical block vertebrae and twelve thoracic block vertebrae in their study of four thousand proto-Arikara from the Upper Missouri River Basin in the northern plains. 3. Irregular Segmentation of Ribs The same sclerotomic tissue that forms the posterior portion of the vertebral bodies and neural arches grows ventrolaterally to form the costal processes that eventually form the ribs along the thoracic spine. Irregular segmentation can produce a wide variety of expressivity that includes bifurcation, flaring, abnormal wideness, merging (fusion), bridging, and partial bridging with articulations between ribs (Figs. 3.18 and 3.19). Developmental
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defects affecting the ribs only primarily affect the anterior ends. Bridging can sometimes be found near the vertebral ends. With bifurcation, the anterior end of the ribusually the third, fourth, or fifthis affected, more so on the right side. Rib spurs look like incomplete attempts at bifurcation and can vary in size. Flaring is an unusually wide anterior rib end. When the width of a rib is equal to or exceeds the combined widths of two adjacent ribs, it is considered abnormally wide; this is closely aligned with flaring ribs. Bridging is closely linked to the merging of ribs. An osseous bridge of bone connects adjacent ribs. Merging is sometimes incomplete and results in articulation between two ribs rather than osseous bridge formation. Merging occurs most frequently between the first two ribs (Fig. 3.20) (Martin 1960; Sycamore 1944). Segmental disturbance is sometimes caused by malformed or absent vertebrae. Then the associated ribs arise irregularly from the vertebral column, merging together near their dorsal ends. If the sternum is deformed, the ventral ends of associated ribs will also be affected (Warkany 1971). Shifting of the cervicothoracic vertebral border can also influence rib size, shape, and segmentation. Cervical ribs can be produced by the shifting of the border downward, and they can articulate or unite with the first thoracic rib (Fig. 3.21b). Shortened and deformed first thoracic ribs result from the border shifting upward, and these defective ribs often articulate or join with the second thoracic rib (Fig. 3.21a) (White, Poppel, and Adams 1945). Martin (1960) emphasized the genetic component of rib segmental defects with his study of one thousand Samoan chest radiographic films. Samoans showed a high incidence of bifid ribs, rib spurs, and wide ribs, with twice as many males affected as females, providing strong evidence for genetic links among the various expressions of rib segmentation errors. Few reports of rib segmentation errors appear in the paleopathology literature, probably because they are considered unimportant. Brues (1946) found three Northern San Juan Anasazi individuals, two adults and one child, with rib defects out of twenty-two individuals (3/22 = 14%) from Anasazi burials on Alkali Ridge, Utah (Pueblo I-III). The child has a bifurcated rib, and the adults display bridging between two adjacent ribs. The child and one adult were from the same site, and the other adult came from a site three and one-half miles away. Even though one of the individuals was buried some distance from the other two, Brues suggests that the high frequency of rib defects reflects inbreeding. Rib segmentation errors have also been identified in another Northern San Juan Anasazi
population. Miles (1975) found one case of fused ribs and
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Fig. 3.17 Type I block vertebra from Yellow Jacket outlying village in southwest Colorado. Gracile adult (probably female) with failure of segmentation of vertebral segments C7, T1, T2, T3, and T4 (dorsal view); C6 in picture not affected.
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Fig. 3.18 Variations of irregular segmentation of the ribs. A: merging (fusion). B: partial bridging or articulation. C: flaring. D: wide. E: bridging. F: bifurcation. G: bridging at vertebral end. H: rib spur.
one case of bifurcated ribs in the Wetherill Mesa (Pueblo II-III), Mesa Verde skeletal material. There is a fused right cervical and a first thoracic rib (NMNH 327128) from Pueblo Bonito (Pueblo II-III) in Chaco Canyon. Fused first and second thoracic ribs are present in a Towa adult (NMNH 271822) from Pueblo IV Amoxiumqua near Jemez Springs, New Mexico, and in an adult (NMNH 239259) from Pueblo IV Heshotauthla (Fig. 3.20) near Zuni, New Mexico.
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Fig. 3.19 Examples of irregular segmentation of the ribs. A: flared rib. B: large rib spur. C and D: bifid ribs (from the NMNH study collection).
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Fig. 3.20 Unilateral (L) merging of the first and second ribs from Heshotauthla, New Mexico. Superior view of first and second ribs from adult male (NMNH 239259).
Another individual (NMNH 239453) from Heshotauthla has bridging of one pair of ribs near the vertebral ends. The associated vertebrae are normal. Flared ribs are present in two adult females from Pueblo IV-V Hawikku (Zuni). One of these (NMNH 308632) also has a bifurcated rib. Merbs (1985) discovered a bifurcated rib in Hohokam skeletal material from the Broadway and McClintock site in Tempe, Arizona. 4. Neural Arch Joint Failure of Segmentation Disturbance in segmentation of the mesenchymal tissue at the junctions for the development of the apophyseal and costovertebral joints of the neural arch does not allow the intended joint to develop. Cohesion of affected apophyseal joints can limit movement, and if several vertebrae are involved, a progressive kyphosis can develop. Unilateral apophyseal joint failure can result in an abnormal curvature of the vertebral column (lordoscoliosis). Failure of the costovertebral joints to develop does not allow the rib to separate, and it becomes a true extension of the vertebra. This is usually asymptomatic when it occurs by itself (Tsou, Yau, and Hodgson 1980).
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Fig. 3.21 Merged first and second ribs, and cervical rib merged with first rib. A: first and second rib, with first rib slightly underdeveloped from caudal shifting of the cervicothoracic border. B: cervical rib from C7 and first rib; cervical rib developed from cranial shifting of the cervicothoracic border (from NMNH study collection).
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5. Numerical Errors of Segmentation Many studies of numerical variation in the presacral vertebrae show a variation between twenty-three and twenty-five presacral segments (Allbrook 1955; Bornstein and Peterson 1966; Merbs 1974; Shore 1930; Stewart 1932; Willis 1929). The normal number of presacral segments is twenty-four, with seven cervical, twelve thoracic, and five lumbar vertebrae. With the five sacral and four caudal segments added, the entire vertebral column has a total of thirty-three vertebral segments. Most of the numerical variations in one part of the vertebral column derive from segmental border shifts as vertebrae in transitional zones assume the characteristics of the region either above or below the border, thus increasing or decreasing the number of that particular type of vertebra. If the sacral region were included in analyses, a compensatory alteration in the number of sacral vertebrae corresponding to the presacral variation would also be seen in a majority of cases. Occasionally, an extra or missing vertebra relates to an abnormal number of somites rather than to a segmental border shift (Allbrook 1955; Schmorl and Junghanns 1971; Shore 1930). A reduction in the normal number of vertebral segments is rare, although extra vertebral segments are not unusual. It is often difficult to determine the exact number of vertebrae in the vertebral column of prehistoric skeletal material, especially with abnormal reduction. Any incompleteness of recovered human remains makes an exact count impossible. Prehistoric skeletal collections housed in museums carry no guarantee that the entire vertebral column of an individual is present. Extra vertebral segments can generally be identified at the borders between the different kinds of vertebrae. Most extra vertebral segments show up at the thoracolumbar or lumbosacral borders, taking on transitional characteristics of one or the other sides of the border. Extra transitional vertebrae at the thoracolumbar border usually take on thoracic characteristics. Those at the lumbosacral border can appear as complete extra lumbar vertebrae or be incorporated to some degree into the sacrum. Occasionally, an extra segment appears at the sacrocaudal border as an extra sacral segment. Extra vertebral segments at the cervicothoracic border taking on cervical characteristics are rare. Stewart (1932) examined a number of Eskimo skeletons and was able to identify twelve cases with a sixth lumbar vertebra and twelve normal thoracic vertebrae and thirteen cases with an extra thoracic vertebra and five normal lumbar vertebrae. Allbrook (1955) studied the numerical variation of vertebral segments in an East African skeletal collection and found 11.6% of 206
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individuals with twenty-five presacral vertebrae. An extra lumbar vertebral segment was more common than an extra thoracic segment in this collection. Reduction to twenty-three segments was noted in 3.4% of individuals, and all but one (a missing cervical) were seen in the lumbar area. Bornstein and Peterson (1966) examined 1,239 individuals from North America, most of them autopsy specimens from the Terry Collection. They tried to infer differences among Caucasian, Black, and Mongoloid populations, but they skewed their data by disregarding sacralized lumbar vertebrae and occipitalized atlases and by counting vertebrae with cervical or lumbar ribs as thoracic vertebrae. Reports of extra vertebral segments are found in Southwest skeletal collections. Reed (1981:85) reported six lumbar vertebrae in six Tompiro adults from Mound 7, Las Humanas, Gran Quivira, New Mexico (Pueblo IVV). Wade (1981) reported the presence of a sixth lumbar vertebra in four adult males and an extra thoracic vertebra in an adult female from the Kayenta Anasazi in northeastern Arizona (Pueblo IIIII). One adult female (NMNH 327077) from Pueblo Bonito (Pueblo IIIII) has an extra sacral segment and fused first caudal segment in the sacrum. An extra sacral segment at the sacrocaudal border is present in an adult male from Quarai (Pueblo IVV Southern Tiwa). The ancestral Zuni pueblo of Hawikku (Pueblo IVV) skeletal collection shows a frequency of 15.0% (9/60 complete vertebral columns) of extra vertebra. Four of these are represented as thoracic vertebrae, with three females having an extra vertebral segment at the thoracolumbar border and one female with an extra vertebral segment at the cervicothoracic border. The other five are represented as extra lumbar vertebral segments at the lumbosacral border in three females, one male, and one child. B. Cranial-Caudal Border Shifting Variations in the numbers of regional vertebrae caused by the shifting of differentiating characteristics in border vertebrae are not rare. Shifts occur primarily at the less stable lumbosacral and occipitocervical borders. Border shifting can also be found at the cervicothoracic, thoracolumbar, and sacrocaudal borders. The affected vertebra is referred to as a transitional vertebra. It takes on the characteristics of the adjacent vertebra in the neighboring region, either cranial or caudal depending upon the direction of the border shift. The reason
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behind this shift in characteristics during morphogenesis is not clear, but delay in the formation of the vertebral developmental unit (intervertebral disc space and adjacent vertebral segments) that borders two regions of the vertebral column likely triggers it. The neural arches are primarily affected, indicating the denser portion of the sclerotome is at fault for this delay. Changes involve the transverse processes and apophyseal joints, with minor changes, if any, to the vertebral body. The transition can occur as either a unilateral or a bilateral shift. It can be symmetrical or asymmetrical, complete or incomplete. A wide range of expressions are related to shifting, depending upon the timing of the delayed response to the critical threshold event of border demarcation. Cranial shifts usually involve only one or two border areas; caudal shifts frequently involve three or four border areas (Köhler and Zimmer 1968; Schmorl and Junghanns 1971). There is a strong genetic tendency for shifting of these characteristics to occur at specific vertebral borders in either a cranial or a caudal direction (Kühne 1932, 1934, 1936). This phenomenon occurs in all mammal species. In general, caudal border shifting is found more often in humans than is cranial border shifting. When cranial border shifting occurs, it is found more often in females than in males. Vertebral border shifting patterns vary significantly from one population to another (Allbrook 1955; Shore 1930; Stewart 1932). Shifting at different borders can occur in both directions in the same individual (Allbrook 1955; Bornstein and Peterson 1966; Green 1941; Merbs 1974; Schmorl and Junghanns 1971; Searle 1954; Shore 1930). This is possible because the precursors of the different parts of the vertebral column appear and develop at different times. The occipitocervical border can be very unstable, with either cranial or caudal shifting involving the occipital and first cervical sclerotomic units. Some confusion exists regarding how the exoccipitals differentiate from the atlas during morphogenesis. Both Hadley (1948) and McRae and Barnum (1953) stated that there is no exchange between occipital and cervical sclerotomes, defining the border between the cranial half of the first cervical sclerotome and the caudal half of the last occipital sclerotome. This would leave the atlas to form from both halves of the first cervical sclerotome and the cranial half of the second sclerotome. Epstein (1976) agreed with them, calling the last occipital sclerotome the ''spondylocranium," which in birds and reptiles occurs as a separate bone, the proatlas. In humans the last occipital sclerotome is normally retained in the exoccipitals, which form the lateral portions of the base of the cranium and contain the major portion of the occipital condyles. A small portion of
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the ventral aspect of the condyles develops from the basioccipital that evolves from the parachordal cartilages in another developmental field. Harris (1959) described the atlas and dens as both forming from the caudal half of the last occipital sclerotome and the cranial half of the first cervical sclerotome. More recent research points to the contribution of the cranial half of the first cervical sclerotome to the formation of the proatlas area of the base of the occipital the exoccipitals and the tip of the dens, whereas the caudal half forms the atlas and the body of the dens (Bailey 1974; Shapiro and Robinson 1976). In any event, the occipitocervical border is considered highly unstable as a result of an evolutionary trend in humans for the proatlas to be incorporated into the base of the occipital. The evolutionary evidence points to an overall trend toward a normal caudal shifting in humans, both at the cranial junction and at the lumbosacral border another highly unstable region. Failure of this normal caudal shifting to stabilize at the upper end of the vertebral column allows the border to move upward, resulting in the manifestation of vertebral characteristics at the base of the occipital; failure to stabilize at the lower end of the vertebral column results in the last lumbar vertebral segment joining the sacrum (sacralization of the last lumbar vertebra). This is referred to as cranial shifting of the vertebral border. When the normal evolutionary caudal shifting is not held in check, the border moves down another segment (caudal shifting of the border). This is represented at the occipitocervical border by incorporation of the atlas into the occipital (occipitalization of the atlas) and at the lumbosacral border by separation of the first sacral vertebral segment (lumbarization) from the sacrum (Bailey 1974; Epstein 1976; Lombardi 1961; O'Rahilly, Muller, and Meyer 1983; Peyton and Peterson 1942; Schmorl and Junghanns 1971; Shapiro and Robinson 1976). 1. Occipitocervical Border Abnormal caudal shifting of the occipitocervical border leading to occipitalization of the atlas is more common than cranial shifting that produces a manifestation of an occipital vertebra. Wide variation exists in the expression of both types of shifting, ranging from very minor to major upsets (Fig. 3.22). Occipitalization of the atlas (sometimes referred to as atlanto-occipital fusion) can be expressed as complete, partial, symmetrical, or asymmetrical
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incorporation into the occipital. The greater the shift, the greater the portion of the atlas incorporated. The occipital vertebra manifests itself as varying forms of osseous protuberances around the foramen magnum, never completely separated from the base of the occipital. It may be symmetrical or asymmetrical in expression. Asymmetrical formation from either cranial or caudal border shifting can produce a kyphosis or scoliosis in the cervical spine (Köhler and Zimmer 1968; Peyton and Peterson 1942). Cranial and caudal border shifting can produce similar expressions, but certain differences distinguish one from the other. The main difference lies in the expression of the articulating condyles. The occipital vertebral expression will have normal-appearing condyles, oval and convex, converging in a caudal direction, whereas the assimilated atlas will have flattened (rarely convex) condyles, converging in a cranial direction. The assimilated atlas will have a foramen, or an attempt to develop a foramen, on each transverse side, which is generally lacking in the expression of the occipital vertebra. Both can affect the size and shape of the foramen magnum, with accessory bony elements known as paracondylar processes (Hadley 1948; Peyton and Peterson 1942). a. Cranial Shift With complete cranial shifting of the occipitocervical border, the occipital vertebra is expressed (Fig. 3.22a). It invariably lacks a complete posterior arch, and a complete anterior arch is rare (about 15% of cases). Generally, there is some expression of a portion of the anterior arch around the foramen magnum (Peyton and Peterson 1942). Bony processes produced by incomplete regression of the lateral parts of the occipital vertebra may be present (Figs. 3.22b and 3.23), distorting the shape of the foramen magnum (Epstein 1976; Lombardi 1961; Shapiro and Robinson 1976). A blunt, rounded bony extension from the inferior side of the anterior rim of the foramen magnum, referred to as a precondylar tubercle (Figs. 3.22c and 3.24), represents a minor expression of cranial shifting at the occipitocervical border. It varies in size but is usually quite small (Lombardi 1961; Shapiro and Robinson 1976). Other variations of minor, incomplete cranial border shifting include basioccipital horizontal clefts or fissures (Figs. 3.22e and 3.25), bipartite condylar facets (Fig. 3.22d), and defects of the odontoid (Fig. 3.22g). Bipartite hypoglossal canals (Fig. 3.22f) are also thought to be associated with mild cranial shifting at the occipitocervical border (Epstein 1976; Kruyff 1967;
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Fig. 3.22 Occipitocervical border shifting. 1. Cranial shifting: A: expression of occipital vertebra (condylar facets converge caudally). B: precondylar process. C: precondylar tubercle. D: bipartite condylar facets. E: transverse basilar cleft. F: bipartite hypoglossal canals. G: odontoid displacements. 2. Caudal shifting: H: atlas occipitalized (condylar facets converge cranially). I: paracondylar process. J: hypoplasia of condylar facets. K: epitransverse process. L: precondylar facets.
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Shapiro and Robinson 1976). The divided hypoglossal canals reflect the original segmentation of the occipital sclerotomes that usually fuse together with the parachordal condensations into one solid mass of mesenchyme (Hamilton, Boyd, and Mossman 1952). Basioccipital clefts are rare, usually occurring with bipartite condylar facets (see Fig. 3.25) or bipartite hypoglossal canals. The blastemal precursors of the basioccipital are apparently influenced by mild cranial border shifting of the occipital sclerotomes. Transverse clefts form along one or both sides of the basioccipital. The clefts are usually incompletely formed, narrow slits with smooth edges. They vary from 3 mm to 5 mm in length and cause no clinical problems (Johnson and Israel 1979; Kruyff 1967; Lombardi 1961; Shapiro and Robinson 1976). Most manifestations of the occipital vertebra are asymptomatic. However, asymmetry can create an abnormal tilting of the head, causing compensatory changes in the cervical spine in the form of scoliosis or lordosis. Major Manifestations of the occipital vertebra were not found in the paleopathology literature. Minor expressions appear in a few reports. El-Najjar (1974) identified mild forms of cranial border shifting in the form of the precondylar tubercle in high frequencies among the Canyon de Chelly Anasazi. Individuals from the Pueblo III phase of occupation had a lower frequency (2/16 = 12.5%) of this trait than the Pueblo I-II individuals (4/13 = 30.7%) and earlier Basket Maker individuals (12/56 = 21.4%). MacCurdy (1923:270) reported fifteen prehistoric crania with bipartite hypoglossal canals in highland Peruvian skeletal material from eight locations around Cuzco. Minor cranial border shifting represented by a bony precondylar protuberance was noted in one adult female (NMNH 157687) from Chavez Pass (Pueblo II-III), Arizona, in the National Museum of Natural History skeletal collection from that site (Fig. 3.23b). Other Southwest collections in the museum also have examples of mild cranial shifting at the occipitocervical border. Amoxiumqua (Pueblo IV Towa) has one female (NMNH 271804) with a paracondylar bony protuberance. Bilateral precondylar protuberances are present in two females and one male from Hawikku (Pueblo IV-V Zuni). Other signs of mild cranial border shifting in the Hawikku skeletal collection include paracondylar protuberances in two males, one female with two post-condylar protuberances, a very small precondylar tubercle in one male and one female, a larger precondylar tubercle in one female, and bilateral transverse basilar clefts in one female. One female in the Pueblo Bonito (Pueblo II-III) collection has a very small precondylar tubercle, and one is present in a female from Amoxiumqua.
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Fig. 3.23 Partial expressions of the occipital vertebra resulting from cranial shifting of the occipitocervical border. A: occipital of adult male (NMNH 266531) from Pachacamac, Peru. B: occipital of adult female (NMNH 157687) from Chavez Pass, Arizona.
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Fig. 3.24 Precondylar tubercle resulting from cranial shifting at the occipitocervical border. Occipital of adult female (NMNH 266497) from Pachacamac, Peru.
Defects in the odontoid (Fig. 3.22g) can result from cranial border shifting, but they are rare (Epstein 1976; Shapiro and Robinson 1976). Defects of the odontoid have been classified by Dawson and Smith (1979) as follows: TypeOs odontoideumoccurs when the dens remains separate from the body of the axis as the cranial shifting of segmentation takes place. I Ossiculum terminalethe tip, or apical, segment of the dens is formed from the same sclerotome as the occipital condyles. With Typecranial shifting, it may be separated from the body of the dens to II form a separate ossicle. It usually attaches to the anterior aspect of the atlas, but it may attach to the anterior rim of the foramen magnum (Fig. 3.26) or remain a separate entity. TypeAgenesis of the densleaves the apical segment without a base to III which to attach.
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Fig. 3.25 Basilar transverse clefts and bifid condylar facets resulting from cranial shifting at the occipitocervical border. Base of occipital of adult female (NMNH 342790) from Czechoslovakia.
Type IV Type V
Agenesis of the apical segment with a hypoplastic base; the dens appears short and blunt. Complete agenesis of the odontoid; both the base and the apical segment fail to develop (Fig. 3.27).
Agenesis can lead to subluxation of the atlanto-axial junction, particularly when trauma occurs. Neurological symptoms will develop if the diameter of the cervical canal is reduced to less than 10 mm. This can produce headache, neck pain, disturbed muscular coordination, intermittent loss of consciousness, transient vertigo, and numbness in the extremities (Dawson and Smith 1979). Type I and type II usually remain asymptomatic, with mild episodes of transient numbness caused by subluxation of the atlanto-axial junction whenever the neck is placed in full flexion (Bailey 1974; Dawson and Smith 1979; Epstein 1976; Scannell 1945). The paleopathology literature is lacking in reports of developmental disturbances in the odontoid. Miles (1975) reported a "persistent" acessory
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ossification center for the odontoid in an individual from Wetherill Mesa, Mesa Verde, Colorado. The accompanying photo shows the apical segment missing. This could be a type II defect of the odontoid related to cranial shifting at the occipitocervical border. Palkovich (1980) described a similar case in an adult Pueblo IV Tanoan female from Arroyo Hondo, New Mexico. There is one adult male (NMNH 271905) from Amoxiumqua (Pueblo IV Towa) with a type II defect of the dens. The tip of the dens has separated and attached to the anterior rim of the foramen magnum (Fig. 3.26). Anderson (19861987) reported a missing dens in an adult male from a medieval cemetery in Trondheim, Norway. This proved to be an acquired case rather than a developmental defect, because there was an articulating facet for the dens on the atlas. Anderson excavated the skeleton and noticed immediately that the dens was missing but was unable to find it in situ, despite careful excavation practices. However, because Anderson recognized the articulating facet on the atlas, the dens had to have been fractured from its base as opposed to having experienced developmental misplacement. There are reports in the clinical literature of the dens fractured from its base. b. Caudal Shift Occipitalization of the atlas caused by caudal border shifting is more common than the reverse phenomenon, manifestation of the occipital vertebra. The atlas is incorporated either completely or partially into the base of the occipital (Figs. 3.22h and 3.28). About half of the cases are associated with block vertebrae. Either caudal border shifting within the occipital and first cervical sclerotomes has some effect on the separation of the developmental unit between the first and third vertebral segments, or the timing of both events is equally vulnerable in some individuals (Bailey 1974; McRae 1960; McRae and Barnum 1953; Schmorl and Junghanns 1971). Paracondylar bony processes can sometimes appear bilaterally or unilaterally, symmetrically or asymmetrically, along with assimilation of the atlas, or they can appear alone. They generally have a broad base and can be quite large, assuming the shape of a cone (Fig. 3.22i). They are sometimes confused with paramastoid processes that can develop at the posterior border of the jugular foramen, yet they are completely unrelated to this phenomenon (Lombardi 1961; Meschan 1985; Peyton and Peterson 1942; Shapiro and Robinson 1976). Gregg and Steele (1969) reported that the frequency of caudal shifting at the occipitocervical border in the form of paracondylar processes and atlas assimilation ranges from .15% to 1.67% in any given population.
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A thin ridge of bone may arise from the transverse process of the atlas, projecting upward toward the occipital condylesthe epitransverse process (Fig. 3.22k). It too can occur unilaterally as well as bilaterally, and it sometimes assimilates into the occipital (Lombardi 1961; Shapiro and Robinson 1976). The posterior bridge occasionally found on the atlas may be a part of this phenomenon. The bridge arches over the sulcus for the vertebral artery and first cervical nerve behind the superior articular facet. The posterior bridge can appear unilaterally or bilaterally, complete or incomplete, and is known to be under genetic control (Selby, Garn, and Kanareff 1955). Hypoplasia of the occipital condyles (Fig. 3.22j), either unilaterally or bilaterally, represents mild caudal shifting at the occipitocervical border. It sometimes occurs with the assimilation of the atlas (Epstein 1976; Shapiro and Robinson 1976). The condyles appear abnormally small. The exoccipital portion of the condyles fails to develop because of the caudal shift, leaving only the portions created by the basioccipital. During morphogenesis, the blastemal odontoid lies close to the base of the occipital, sometimes entering the foramen magnum. During the fetal period, it normally descends to a position below the foramen magnum (Bailey 1974; Epstein 1976; O'Rahilly, Muller, and Meyer 1983; Spillane, Pallis, and Jones 1957). Caudal shifting at the occipitocervical border can sometimes prevent the normal descent of the odontoid, and it may continue to protrude onto or into the foramen magnum. This can take place with or without assimilation of the atlas into the occipital. When it does occur without assimilation of the atlas, the dens and the anterior arch of the atlas vertebra remain close to the foramen magnum, and one or both may articulate directly with its rim. The articulating facet, known as the precondylar facet (Figs. 3.221 and 3.29), that forms on the rim of the foramen magnum of the occipital is often referred to as a third condyle. Occipitalization of the atlas has been identified in Southwestern Anasazi populations. Merbs and Euler (1985) describe occipitalization of the atlas with an associated C2-C3 block vertebra in an Anasazi Western Pueblo II-III adult female from Bright Angel ruin in the Grand Canyon, Arizona. Reed (1981:113) mentions one case from the Pueblo IV-V Tompiro Las Humanas site at Gran Quivira, New Mexico, and two from a Tanoan site, Pueblo Largo (Pueblo IV), in the Galisteo basin, New Mexico (also one from the Fremont culture at Lapoint, Utah). Akins (1986) discovered a case from Chaco Canyon (Pueblo IIII). A case was also found at another Tanoan Pueblo IV site, Arroyo Hondo, New Mexico (Palkovich 1980).
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Fig. 3.26 Type II odontoid defect resulting from cranial shifting at the occipitocervical border, with the separated apical tip attached to the anterior rim of the foramen magnum. Occipital of adult male (NMNH 271905) from Amoxiumqua, New Mexico.
I found only one case of complete occipitalization of the atlas in the Anasazi Southwest skeletal collections I examined in the Smithsonian's National Museum of Natural History. There is one adult male (NMNH 239208) from Heshotauthla (Pueblo IV Zuni) with the first, second, and third cervical vertebrae fused to the occipital. The atlas was assimilated into the occipital asymmetrically; the right side is completely formed, but the left side is part of the occipital and is associated with a basilar depression. The second and third vertebrae are a block vertebra that fused secondary to the atlas, with the dens forced to the right of its atlas articulation (Fig. 3.30). There is a marked cervical scoliosis. This unfortunate individual must have suffered from neurological
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Fig. 3.27 Type V odontoid defect resulting from cranial shifting at the occipitocervical border. C1 has no articulating facet for the missing dens of C2; from Caucasian male (778 Terry Collection), fifty-six years old, died in 1928 from pulmonary tuberculosis.
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symptoms. The space between the dens and the dorsal internal border of the atlas is 46 mm in diameter. With less than 10 mm diameter of the cervical canal, headache, neck pain, disturbed muscular coordination, intermittent loss of consciousness, transient vertigo, and numbness of the extremities occur (Dawson and Smith 1979). Unfortunately, the rest of the vertebral column is missing. Precondylar facets, representing caudal shifting at the occipitocervical border, were found in two females and one male (see Fig. 3.29) in the Hawikku (Pueblo IVV Zuni) collection, and in one female from Elden Pueblo (Pueblo III Sinagua). Occipitalization of the atlas has been identified in southern Southwest Hohokam populations. Matthews (1891) reported two cases from Los Muertos in the Phoenix area. Another Hohokam case was discovered at Casa Buena (Barnes 1988). Merbs (1985) described an adult male Hohokam cranium from the Cashion site west of Phoenix, with a ''hemi-proatlas" accompanying an occipitalized atlas. This defect was caused by a rare hemimetameric segmental shift or displacement of the last occipital somite before caudal border shifting took place during morphogenesis and may have been a contributing factor to the shift. Gregg and Gregg (1987:140142) found a high frequency of caudal shifting at the occipitocervical border in the Proto-Arikara Upper Missouri River Basin skeletal collections. Large paracondylar processes were common, followed by the full expression of caudal border shifting the assimilation of the atlas into the occipital. MacCurdy (1923:268270) found a frequent tendency for caudal shifting at the occipitocervical border, expressed as paracondylar processes, in a highland Peruvian skeletal collection from Paucarcancha. One adult female from Torontou, another highland location nearby, displayed very large paracondyloid processes that articulated with the atlas. Complete occipitalization of the atlas appears frequently among crania collected by Hrdlicka from Pachacamac and Chicama on the coast of Peru (Fig. 3.28). c. Basilar Impression Indentation of the base of the occipital basilar impression (basilar invagination) may be found with occipitalization of the atlas. Conditions that soften bone, especially Paget's disease and osteogenesis imperfecta, usually cause basilar impression. Osteomalacia, rickets, senile osteoporosis, cleidocranial dysostosis, and osteitis deformans can also produce basilar impression (Bailey 1974; Hadley 1948; Spillane, Pallis and Jones 1957).
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Fig. 3.28 Variations of occipitalization of the atlas resulting from caudal shifting of the occipitocervical border, from Peru. A: adult female (NMNH 264612) from Chicama. B: adult female (NMNH 293804) from Cinco Cerros. C: adult female (NMNH 264644) from Chicama. D: adult female (NMNH 264614) from Chicama. E: adult female (NMNH 264615) from Chicama. F: adult male (NMNH 266360) from Pachacamac.
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Depending upon the degree of assimilation of the atlas into the basioccipital, the region associated with assimilated parts of the atlas can appear depressed. Severe cases can make the upper cervical spine look as though it has been pushed up into the skull, distorting the foramen magnum and making it smaller than usual, with upturned margins. The petrous portions of the temporal bones can be pushed upward instead of normally sloping slightly downward. Severe basilar impression forces the structures near the posterior portion of the foramen magnum upward, including the dens. The displaced dens can impinge upon parts of the central nervous system, causing a variety of symptoms that generally do not appear until the second or third decade of life. These symptoms are usually progressive, and the defect is frequently fatal. Death is caused by compression of the brain stem, increased intracranial pressure, adhesions, or ischemia from reduced blood supply. The most common symptoms are weakness and motor incoordination of the lower extremities or numbness and pain in the upper extremities. Other symptoms include dizziness, pain in the nape of the neck, headaches and a stiffening sensation, limited movement of the neck, blurred vision, diplopia, mirror image movements of the hands, frequent buzzing sensation in the ears, or earache. Bulbar involvement, such as difficulty swallowing or regurgitation of fluids through the nose, can also occur. Trauma affecting the atlantooccipital region will aggravate or precipitate the neurological symptoms (Bailey 1974; Hadley 1948; McRae and Barnum 1953; Peyton and Peterson 1942; Shapiro and Robinson 1976; Spillane, Pallis, and Jones 1957; Vakili, Aquilar, and Muller 1985; Warkany 1971). Clinicians use a variety of craniometric procedures to measure on radiographs the location of the dens relative to the foramen magnum in order to determine the presence and extent of basilar impression (Bailey 1974; Shapiro and Robinson 1976; Spillane, Pallis, and Jones 1957). Normally, the structures at the base of the occipital incline downward, with the basion slightly higher than the opisthion and the dens below the foramen magnum. Basilar impression is not difficult to spot in dry bone material, giving the anthropologist an advantage over clinicians, who must rely on radiographs. Any indentation around the foramen magnum indicates a basilar impression. The problem is how to determine whether it represents part of a developmental defect or whether it is acquired. If it is associated with assimilation of the atlas, it is probably developmental, particularly if it is localized adjacent to areas where portions of the atlas have been completely assimilated. This seems to be the case with the individual from Heshotauthla (NMNH
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Fig. 3.29 Precondylar facet resulting from caudal shifting at the occipitocervical border. Occipital of young adult male, eighteen to twenty years of age (NMNH 308638) from Hawikku, New Mexico; C1 and C2 missing.
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Fig. 3.30 Occipitalization of the atlas resulting from caudal shifting of the occipitocervical border, with pathological fusion of C2-C3 block vertebra to the atlas. Cranium of adult male (NMNH 239208) from Heshotauthla. A: left lateral view of skull. B: anterior view of C1-C3 fused to skull. C: dorsal view of C1-C3 fused to skull.
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239208) with the occipitalized atlas with fusion of the C2-C3 block vertebra to C1 mentioned earlier. The small, localized basilar impression is associated with the underdeveloped side of the assimilated atlas (Fig. 3.30). Gregg and Gregg (1987:141142>) describe a Sioux male cranium that formerly was located in the Smithsonian's National Museum of Natural History, with unilateral basilar impression with no evidence of occipitocervical border shifting. It is not known whether this was acquired or whether it formed as a defect of development. Further research is needed for other possible developmental causes of basilar impression. Disfigurement of the base of the occipital around the foramen magnum associated with caudal border shifting can produce symptoms similar to those caused by basilar impression. This can be caused by the constriction of the foramen magnum or the displacement of the dens, and it is more pronounced with greater degrees of shifting and asymmetry. Symptoms appear when pressure is placed upon the lower part of the medulla oblongata by the misplaced dens or by the posterior arch of the assimilated or partially assimilated atlas, by the posterior border of the foramen magnum, or sometimes by a thick band of dura at the junction of the cranial and spinal dura. These structural aberrations narrow the foramen magnum and the spinal canal, especially when the head is flexed. Flexion further decreases the diameter of the foramen magnum, squeezing the spinal cord and brain stem even more. Compression can cause sudden death (McRae 1960; Vakili, Aquilar, and Muller 1985). Whatever the cause, when the foramen magnum is too small, neurological deficit results. The size of the functional opening through the foramen magnum is reflected by the shortest distance measured from the dens to either the posterior arch of the atlas or the posterior rim of the foramen magnum. This anterior-posterior diameter should not be less than 19 mm (McRae 1960; Vakili, Aquilar, and Muller 1985). Meschan (1985) says that if the anterior-posterior diameter anywhere in the cervical spinal canal is 10 mm or less, cord compression is likely. 2. Cervicothoracic Border Shifting of the cervicothoracic border is identified by the developing costal processes. The costal processes of the thoracic vertebrae develop into ribs, whereas the costal processes of the cervical vertebrae generally do not. The seventh cervical vertebral costal processes have separate ossification centers that have the potential to grow into ribs. Separate ossification centers
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may also appear in other cervical vertebral costal processes with the same potential, although this is rare (Williams et al. 1989). Cranial border shifting causes the costal processes of the seventh cervical vertebra to develop into a rib or riblike structure, whereas caudal border shifting affects the rib development of the first thoracic vertebra, which then becomes rudimentary. Cervical ribs were first described by Hunauld (1744), and rudimentary first ribs were first described by Bellamy (18741875) (Dow 1925; Gladstone and Wakeley 1932; Schmorl and Junghanns 1971). a. Cranial Shift Cranial shifting of the cervicothoracic border is represented by the transformation of the costal processes of the last cervical vertebral segment into bony extensions known as cervical ribs. There is wide variation in the expressivity of cervical ribs, ranging from tubercles (small, bony nodules) on the ends of the transverse processes to blunt, bony projections extending from the transverse process to complete, separate articulating ribs with costal cartilages (Fig. 3.31a). The true cervical rib has a head, neck, and body much like a thoracic rib. The body shape differs from the first rib, with a narrow, constricted shape. The length and width of the cervical rib are quite variable, ranging from about 20 mm to 85 mm. Jointed ribs are more common than those without a joint (Steiner 1943). When cervical riblike extensions develop without the formation of a costal joint, they usually occur bilaterally. Cervical ribs with costal joints happen more often unilaterally than bilaterally. Cranial shifting is more common than caudal shifting of the cervicothoracic border, occurring in .5% to 1.0% of human populations (Gladstone and Wakeley 1932; Honeij 1920; Steiner 1943; Warkany 1971). Cervical ribs have been described in the sixth cervical vertebral segment, as well as the seventh, and rarely up to the third cervical level (Bailey 1974; Schmorl and Junghanns 1971). Cervical ribs rarely reach the sternum and may articulate or fuse with the first rib. Often the second thoracic rib moves upward in its attachment to the manubrium (Fig. 3.31b), attaching to the lateral edge instead of the manubriosternal junction (Gladstone and Wakeley 1932). Variants in the expression of cranial shifting of the cervicothoracic border can be classified according to Gruber (Honeij 1920) as follows: Class I small tubercle that does not extend beyond the normal lateral dimensions of the transverse processes (Fig. 3.31I).
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Class II blunt, bony extension 40 mm to 50 mm long (Fig. 3.31II). Class III riblike extension (Fig. 3.31III) that articulates with first rib or attaches to sternum via a ligamentous band. Class IV complete, separate rib (Fig. 3.31IV) with costosternal cartilage that may or may not articulate or fuse with the first rib. About 50% to 75% of individuals with cervical ribs remain asymptomatic, but symptoms may appear with trauma, occupational stress, or progessive ossification. Symptoms are usually unilateral, affecting the left side more than the right. Shorter cervical ribs (class II) usually have a free anterior end. Occasionally, they may be connected to the first rib by a fibrous band. The class II cervical rib is more likely to exert pressure on the brachial plexus, causing pain in the back of the neck, shoulder, or supraclavicular region, tingling or loss of feeling, or sensation in the hand and fingers on the affected side. Class III and class IV cervical ribs can cause pressure on the subclavian artery, interfering with circulation to the affected arm. Pressure can be exerted on the eighth cervical and first thoracic spinal nerves, producing motor and sensory disturbances. Muscle weakness with motor loss of power in the arm can result from neurological and circulatory disturbances, and the muscles in the hand and arm may atrophy (Gladstone and Wakeley 1932; Honeij 1920; Schmorl and Junghanns 1971; Warkany 1971; White, Poppel, and Adams 1945; Williams et al. 1989). There are a few reports of cervical ribs in prehistoric skeletal material. Denninger (1931) was the first to report such an occurrence. He described an adult male from a cemetery site in Lewistown, Illinois, with a right cervical rib (class IV) and a projection of bone extending from the transverse process on the other side (class II). Brues (1946) discovered an abnormally long costal process that she identified correctly as a cervical rib (class III) in a Northern San Juan Anasazi adult male from Alkali Ridge (Pueblo IIII) in Utah. Reed (1981:85) identified two cases of cervical ribs from Mound 7, Las Humanas (Pueblo IVV Tompiro), Gran Quivira, New Mexico. Two adults with cervical ribs from Arroyo Hondo (Pueblo IV Tanoan), New Mexico, were reported by Palkovich (1980). Finnegan (1978) identified cervical ribs in an adult male from the Bradford House III site (SJ52) in Jefferson County, Colorado, with associated disuse atrophy of the left humerus. Finnegan suggested that the left arm was partially impaired from pressure exerted on the brachial plexus by the left cervical rib.
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The skeletal collection from Amoxiumqua, a Pueblo IV Towa site near Jemez Springs, New Mexico, contains what appears to be a seventh, or extra, transitional vertebra at the cervicothoracic border, with class III cervical ribs (NMNH 271896). This is an isolated specimen, with no other associated skeletal material. The body of this vertebra has more of a thoracic shape than a cervical shape. Blunt, bony costal extensions reach out on both sides, for a length of 47 mm (Fig. 3.32). The class I expression of cervical rib in the form of a bony nodule on the end of the transverse process was found in another individual, a female (NMNH 271801), from Amoxiumqua. Another class I expression of cervical rib was identified in one adult female from Hawikku (Pueblo IVV Zuni). The right side of the seventh cervical vertebra has a small, rounded bony tubercle extending anteriolaterally from the transverse process. Both of these cases are similar to those depicted in Figure 3.31I. Completely formed class IV bilateral cervical ribs are manifest in an adult female (NMNH 327049) from Pueblo Bonito (Pueblo IIIII) from Chaco Canyon. The entire vertebral column and most of the thoracic ribs are present. Cranial shifting at the lumbosacral border has also occurred, with the last lumbar incompletely sacralized. The left cervical rib is 31 mm in length much smaller than the right side, which is 55 mm long (Fig. 3.33). The longer, right cervical rib extends downward, articulating with the middle portion of the first thoracic rib, whereas the shorter rib segment extends slightly upward. This was an aging individual, with degenerative joint disease in the vertebral column, and in both knee and elbow joints, making it difficult to determine if the cervical ribs contributed to disability. Another individual (from group burial NMNH 327128) in the Pueblo Bonito skeletal collection has a right cervical rib fused to the first thoracic rib. Four other individuals from Pueblo Bonito display rib facets on the seventh cervical vertebrae, two on the left and two on the right side. Unfortunately, the skeletons are incomplete, and the cervical ribs are missing. b. Caudal Shift The first thoracic vertebra takes on the characteristics of the last cervical vertebral segment with caudal shifting of the cervicothoracic border. The transverse processes are reduced, and transverse foramina may be present. The first thoracic ribs are underdeveloped (Fig. 3.31d). The transverse processes of the adjacent last cervical vertebral segment may be shorter than those above it.
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Fig. 3.31 Cervicothoracic border shifting. 1. Cranial shifting: A: variation of expression of cervical rib I. bony tubercle. II. blunt, bony projection. III. rib extension without costal joint. IV. true rib with costal joint. B: second rib attaches to manubrium only. 2. Caudal shifting: C: stunted transverse process on C7. D: rudimentary first rib articulating with second rib. E: second rib attaches to mesosternum only.
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The rudimentary first thoracic ribs can be quite small less than 30 mm long and abnormal in shape, yet they are wider than cervical ribs. They frequently articulate or fuse to the second ribs near the scalene tubercle or are connected to the manubrium by a ligamentous band. In some cases the second thoracic rib cartilage moves downward with caudal shifting and attaches to the side of the mesosternum instead of to the manubriosternal joint (Fig. 3.31e) (Gladstone and Wakeley 1932; Honeij 1920; Schmorl and Junghanns 1971; Steiner 1943; White, Poppel, and Adams 1945). Rudimentary first thoracic ribs are found unilaterally more often than bilaterally. They are more common in males than in females and do not usually become symptomatic before age 20. Unlike most cases of cervical ribs that remain asymptomatic, most cases of rudimentary first thoracic ribs do cause problems. They are more likely to produce irritation or pressure on the brachial plexus and compress subclavian blood vessels than are cervical ribs. The symptoms are similar to those described for cervical ribs but are usually more severe (White, Poppel, and Adams 1945). 3. Thoracolumbar Border The transition between the thoracic and lumbar spines is most obvious in the articulating processes between the last thoracic vertebra and the first lumbar vertebra. Normally, the superior facets of the twelfth thoracic vertebra are flat-thoracic types, and the inferior facets are cupped-lumbar types. Cranial shifting at this border moves the transitional set of facets up to the next thoracic vertebra the eleventh (Fig. 3.34c). Caudal border shifting moves the set of facets down to the first lumbar vertebra (Fig. 3.34f). Unilateral expression is not uncommon (Merbs 1974; Schmorl and Junghanns 1971). a. Cranial Shift Cranial shifting of the thoracolumbar border can also reduce the size of the last thoracic rib (Fig. 3.34a), as well as move the transitional apophyseal facets up to the eleventh thoracic vertebral segment. The last thoracic ribs frequently appear rudimentary without cranial border shifting; therefore it is difficult to determine cranial shifting effects on the ribs alone. The rudimentary thoracic ribs are slender and tapered obliquely in an upward direction, in contrast to the blunt, thick, or wide lumbar ribs that occur with caudal shifting at the thoracolumbar border (Schmorl and Junghanns 1971).
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Sometimes an extra, transitional vertebral segment at the thoracolumbar border takes on the appearance of the last thoracic vertebra with transitional facets and a small pair of thoracic-shaped ribs. Reed (1981:82) reported a number of individuals from Mound 7, Las Humanas (Pueblo IVV Tompiro), Gran Quivira, New Mexico, as having ''exceptionally small" twelfth ribs, at least on one side. This probably represents cranial shifting at the thoracolumbar border. b. Caudal Shift Whereas mild caudal shifting of the thoracolumbar border places the transitional apophyseal facets on the first lumbar vertebra, complete shifts cause the costal portion of the transverse processes to produce lumbar ribs (Fig. 3.34d and e) on the first lumbar vertebral segment (Williams et al. 1989). They are usually bilateral, varying in length from small, tuberclelike articulating processes to true articulating ribs up to 70 mm long. Lumbar ribs usually appear with well-formed costal joints with the transverse processes. In most clinical studies, lumbar ribs are less common than cervical ribs, and they occur more often in females than in males (Epstein 1976; Steiner 1943; Warkany 1971). Asymmetry of bilateral lumbar ribs is common. Lumbar ribs are more horizontally directed and wider than thoracic ribs, and they have rounded blunt or oval ends (Fig. 3.35). Thoracic ribs are slender and have tapered ends (Schmorl and Junghanns 1971). The majority of individuals having lumbar ribs will experience some soreness and tenderness or even severe pain in the affected region of the back. Lumbar ribs are rarely reported in the paleopathology literature. Mac-Curdy (1923:282) described five cases of lumbar ribs in highland Peruvian skeletal material. One of these also had lumbarization of the first sacral segment. Five other individuals had very small or rudimentary transverse processes on the first lumbar vertebra. This may indicate lumbar rib formation. One adult male (NMNH 271823) from Amoxiumqua (Pueblo IV Towa) near Jemez Springs, New Mexico, has a lumbar rib 53 mm long (Fig. 3.35b) on the left side of the first lumbar vertebra. The right side has a normal transverse process. One pair of adult lumbar ribs associated with NMNH 269207 burial from Giusewa (Pueblo IVV Towa) near Jemez Springs, New Mexico, resembles the one from Amoxiumqua. The left side is 45 mm long, and the right side is 51 mm long. The first lumbar vertebra of one adult male (NMNH 381249) from Quarai (Pueblo IVV Southern Tiwa) has a shortened left transverse process with a rib facet on it, whereas the right side has a long transverse process
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Fig. 3.32 Class III cervical ribs resulting from cranial shifting of the cervicothoracic border. C7 (or possibly supernumerary vertebra at this border) in adult (NMNH 271896) from Amoxiumqua, New Mexico; this is the only vertebra present. A: superior view. B: dorsal view. C: left lateral view.
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Fig. 3.33 Class IV cervical ribs resulting from cranial shifting of the cervicothoracic border. Photograph of C7 with asymmetrical cervical ribs and T1 with first ribs (note facet on right first rib for articulation with the right cervical rib), adult female (NMNH 327049) from Pueblo Bonito, New Mexico. A: superior view of C7 with cervical ribs articulated. B: anterior view of C7 and cervical ribs; right rib extends downward, and the shorter left rib extends upward. C: right lateral view of C7 showing articulating facets for cervical rib. D: superior view of cervical ribs.
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angled upward. Two adult males from Heshotauthla (Pueblo IV Zuni) have rib facets on one side of the first lumbar vertebra, one on the right and one on the left. 4. Lumbosacral Border The lumbosacral border is the most frequent and most variable site of border shifting in the presacral vertebral column. Marked differences in frequencies of cranial and caudal border shifting have been noted in various populations. It is sometimes difficult to determine what kind of shift has taken place without an exact count of sacral and lumbar vertebrae. The presence of an extra lumbar or sacral segment only adds to the difficulty. Incorporation of the first caudal segment into the sacrum further compounds the problem (Brailsford 1948; Schmorl and Junghanns 1971). Schmorl and Junghanns (1971) recommend more research on large anatomical collections to determine exact differences between the two. This would help clarify distinguishing markers. When it is difficult to determine what kind of shift is taking place, it is best to refer to the aberrant vertebral segment at the lumbosacral border as a transitional vertebra. a. Cranial Shift Cranial border shifting creates varying degrees of assimilation, or sacralization, of the last lumbar vertebra into the sacrum. The pedicles and transverse processes are transformed into sacral alalike processes, with some degree of incorporation or articulation with the sacrum. They can also articulate with the ilium if they are very long and directed laterally. Whenever the last lumbar vertebral transverse processes articulate with the sacrum (Fig. 3.36b) or ilium, incomplete cranial shifting has taken place. A complete cranial shift causes complete assimilation of the last lumbar vertebral segment into the sacrum (Fig. 3.36c). Occasionally, the completely sacralized L5 will retain some form of apophyseal facets, and there may be a narrow space between L5 and the first sacral vertebral segment. Sometimes mild cranial shifting at the lumbosacral border causes the transverse processes of the last lumbar vertebra to develop into wide, alalike transitional transverse processes that do not articulate with the sacrum (Fig. 3.36a), and sometimes one or both of the transverse processes are also bifurcated. Cranial shifting can occur unilaterally or bilaterally, symmetrically or asymmetrically. Bilateral symmetrical assimilation into the sacrum is asymptomatic and is the least common type of cranial shifting at the lumbosacral
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Fig. 3.34 Thoracolumbar border shifting. 1. Cranial shifting: A: rudimentary twelfth rib. B: absent twelfth rib, no rib facet on T12. C: transitional facets on T11. 2. Caudal shifting: D: lumbar rib and rib facet on L1. E: small, blunt lumbar rib on L1. F: transitional facets on L1.
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Fig. 3.35 Lumbar rib resulting from caudal shifting of the thoracolumbar border. A: normal twelfth rib (L). B: lumbar rib (L) of adult male (NMNH 271823) from Amoxiumqua, New Mexico.
border. Some have suggested that sacralization of the last lumbar vertebra gives the sacrum more height and strength (Brailsford 1948; Shore 1930); however, this sacralization is more likely to occur unilaterally (more common on the right side) or asymmetrically. This causes curvature and rotation of the lumbar spine and can lead to a progressive scoliosis. Symptoms are low back pain and sciatica; these appear most frequently and most severely on the unaffected side, which is more susceptible to injury (Brailsford 1948; Harris 1959; Schmorl and Junghanns 1971; Searle 1954). b. Caudal Shift When caudal shifting takes place at the lumbosacral border, the first sacral vertebral segment attempts to move up into the presacral vertebral column. It becomes partially or completely independent from the sacral body (Figs. 3.36f-g and 3.38) as it takes on the characteristics of the lumbar spine. This is known as lumbarization of the first sacral vertebral segment. Frequently, the apophyseal articulating processes of the lumbarized sacral vertebra are rudimentary, and the disc space below it is greater in height than normal. The sacral body of the lumbarized sacral vertebra is short and wide, and the alae of the sacral body are generally higher than the level of the uppermost sacral body. Asymmetry caused by unilateral, incomplete lumbarization can create symptoms similar to those caused by unilateral sacralization of the lumbar vertebra (Brailsford 1948; Schmorl and Junghanns 1971). A mild caudal shift will sometimes produce an anterior cleft between the vertebral borders of the first and second sacral segments (Fig. 3.36e). Mild caudal shifting can also create rudimentary apophyseal joints between the first and second sacral vertebral segments (Fig. 3.36d) (Shore 1930).
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Transitional vertebra at the lumbosacral border have been reported in the paleopathology literature. Cases of both cranial and caudal shifts have been found in a number of Southwestern Anasazi skeletal collections. Coyne (1981:151) identified four cases of transitional lumbosacral vertebrae in eightyfour adult and twenty-four juvenile vertebral columns (4/108 =4%) in Pueblo IVV Tompiro skeletal collections from Gran Quivira, New Mexico. Three (2.7%) were unilateral caudal shifts, incomplete lumbarizations of the first sacral segment; and one (.09%) was a unilateral cranial shift, incomplete sacralization of the fifth lumbar vertebra. Akins (1986) identified incomplete caudal shifts (lumbarizations) of the first sacral segment in three Pueblo IIII adults from a skeletal collection of 135 individuals (3/135 = 2%) from Chaco Canyon (Pueblo IIII). Miles (1975) mentions one Northern San Juan individual from Wetherill Mesa (Pueblo IIIII), Mesa Verde, Colorado, with a unilateral cranial shift (sacralization of the fifth lumbar vertebra). Three adults from Quarai (Pueblo IVV Southern Tiwa) have cranial shifts at the lumbosacral border one male with incomplete sacralization of L5, one female and one male with complete sacralization of L5. The Smithsonian's National Museum of Natural History's Elden Pueblo skeletal collection (Pueblo III Sinagua) contains one male with incomplete sacralization of the last lumbar vertebra. Giusewa (Pueblo IVV Towa) has one female with incomplete sacralization of L5, and neighboring Amoxiumqua (Pueblo IV Towa) has six individuals with sacralized L5. Three of these are incomplete (one is unilateral), and three are unilateral complete sacralizations. One Amoxiumqua female has unilateral lumbarization (caudal shift) of the first sacral segment. Hawikku (Pueblo IVV Zuni) shows seven individuals with cranial shifts in the form of three complete and four incomplete sacralizations (one unilateral) of the last lumbar vertebra. Neighboring Heshotauthla (Pueblo IV Zuni) has one adult female with unilateral lumbarization (caudal shifting) of the first sacral vertebral segment. Minor variations of shifting are also present in these collections. Bennett (1972) found nine individuals out of a minimum of thirty-three (9/33 = 27%) from a proto-historic Modoc site in northern California with transitional lumbosacral vertebrae. He felt this indicated inbreeding within this small population. He did not specify the type of segmental border shifting that was taking place. MacCurdy (1923:280) found that highland Peruvians around Cuzco had a tendency for caudal shifting, with lumbarization of the first sacral vertebra, predominantly in females.
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Fig. 3.36 Lumbosacral border shifting. 1. Cranial shifting: A: nonarticulating bifid, alalike transverse process of L5. B: articulating alalike transverse process of L5 (incomplete sacralization). C: complete sacralization of L5. 2. Caudal shifting: D: apophyseal joints between S1 and S2. E: anterior cleft between S1 and S2. F: incomplete (unilateral) lumbarization of S1. G: complete lumbarization of S1.
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Fig. 3.37 Incomplete sacralization of L5 resulting from cranial shifting of the lumbosacral border. A: unilateral (R) articulation of transverse process of L5 with sacrum of child (NMNH 308686) from Hawikku, New Mexico. B: bilateral articulation of transverse processes of L5 with sacrum of adult female (NMNH 327049) from Pueblo Bonito, New Mexico.
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5. Sacrocaudal Border Much variation is found in the configuration and position of the coccyx, which normally articulates with the apex of the sacrum. Segmental border shifting is generally not noticed by clinicians or anthropologists because of this variation in this area, which is almost always asymptomatic. It is also difficult to tell the difference between cranial and caudal shifting at this border (Epstein 1976; Schmorl and Junghanns 1971). Extra vertebral segments appearing at this border can also cause confusion. a. Cranial Shift Cranial shifting of the sacrocaudal border affects the last sacral vertebral segment, which disengages from the rest of the sacrum, either partially or completely (Fig. 3.39a-d). Partial separation is more common than complete separation. The lateral circumferences of the foramen formed between the last two sacral segments are incomplete or absent with partial detachment. This can happen either bilaterally or unilaterally (Merbs 1974; Schmorl and Junghanns 1971). b. Caudal Shift The first caudal segment assimilates either completely or partially to the sacrum when the border moves down (Fig. 3.39e-h). The caudal cornua generally remain separate from the dorsal protrusions of the last sacral segment. Complete assimilation of the caudal segment into the sacrum produces extra sacral foramina. With incomplete assimilation, only one foramen may appear, or there may be none when just the caudal body joins the sacrum. Sometimes the caudal segment is asymmetrically fused to the sacrum (Schmorl and Junghanns 1971). Shifting of the sacrocaudal border is rarely mentioned in the paleopathology literature. MacCurdy (1923:281) noticed a marked tendency toward caudal shifting of the sacrocaudal border in the adult males from skeletal collections gathered in the highlands of Peru around Cuzco. He reported 50% of the males had the caudal vertebrae fused to the sacrum, but none of the females had this. Assimilation of the first caudal segment into the sacrum (caudal shifting), either completely or partially, is common in the Southwest skeletal collections I have studied. Only a few examples of partial separation of the last sacral vertebral segment (cranial shifting) were noted.
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Fig. 3.38 Incomplete and complete lumbarization of first sacral segment resulting from caudal shifting of the lumbosacral border. A: unilateral separation of S1 from sacrum of adult female from Heshotauthla, New Mexico. B: bilateral separation of S1 from sacrum in adult female from Hawikku, New Mexico.
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6. Patterns of Border Shifting Although some of the defects caused by shifting have been recognized in prehistoric skeletal material, patterns of border shifting have been recognized in only one published report. Merbs (1974) studied border shifting patterns in Sadlermiut Eskimo and Northwest Coast Haida, Kwakiutl, and Nootka. He concluded from the combined data of all four groups that there was a strong tendency toward caudal border shifting, with much more occurring in males than in females. The frequency of caudal shifting increased in a cranial-caudal direction, going down the vertebral column. The data collected by Merbs further reveal some differences in the patterns of border shifting between the Sadlermiut and Northwest Coast Indians. Cranial shifting occurred rarely in the cervicothoracic and sacro-caudal borders of the Northwest Coast Indians, but it was nonexistent in the Sadlermiut. Cranial shifting in the thoracolumbar border was much more frequent among the Northwest Coast Indians than among the Sadlermiut. Cranial shifting of the lumbosacral border was slightly more common among the Sadlermiut. Caudal shifting was present much more often than cranial shifting in both populations. The frequency of caudal shifting of the lumbosacral border was about equal between the two populations. Caudal shifting of the thoracolumbar and sacrocaudal borders, however, occurred much more often in the Sadlermiut than in the Northwest Coast Indians. Caudal shifting of the cervicothoracic border appeared in only one individual, a Sadlermiut. Caudal shifting of the occiptocervical border appeared in only one individual, a Kwakiutl of the Northwest Coast Indian population. A case description of multiple defects caused by border shifting is described by Brothwell (1967:431). In a young adult female from Sakkara reported in detail by Barclay-Smith, shifting apparently happened with every border except the sacrocaudal border. The description of eight cervical vertebrae with the atlas fused to the occipital and the eighth with a cervical rib may well represent seven cervical vertebrae with an expression of the occipital vertebra (cranial occipitocervical border shift) and a cranial shift of the cervicothoracic border. Transitional apophyseal joint facets on the eleventh thoracic vertebra indicate a mild cranial shift in the thoracolumbar border. Caudal shifting is apparent on the lumbosacral border, with partial lumbarization of the first sacral segment. Other developmental defects involving the paraxial mesoderm include clefts in the lower three lumbar and first sacral neural arches and a C2-C3 block vertebra.
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C. Developmental Delay of Vertebral Elements Delay in any single aspect of growth in any one particular vertebral element will cause varying degrees of hypoplasia or aplasia of that part, depending upon the timing of the interference. Chondrification will not begin until the blastemal anlage reaches a certain critical size. If it does not reach that size in time, chondrification is delayed, thus reducing the size of the developing part. Too small an anlage or failure of the blastema to mature fast enough can prevent the part from developing, especially where it is thinnest. If this incomplete formation occurs where two parts are supposed to come together and fuse, fusion will not take place (Gruneberg 1954, 1963; Meschan 1985; Potter 1963; Williams et al. 1989). 1. Hypoplasia-Aplasia of the Neural Arch Complex During early morphogenesis of the vertebral column, sclerotome cells from the rapidly proliferating caudal part of the somite precursor of the vertebra migrate dorsally. There they flank the neural tube to form the anlage of the neural arch and its processes. Chondrification centers appear at the base of each neural arch half during the sixth embryonic week. Chondrification then proceeds ventrally into the pedicles that penetrate the centrum and dorsally into the laminae and spinous process, which fuse during the fourth fetal month. The transverse and articular processes chondrify from the neural arches (Williams et al. 1989). Ossification centers for each arch half of the neural arch complex begin to appear at the ninth week in the lower cervical-upper thoracic vertebrae, progressing in a cranial direction, then in a caudal direction. Primary ossification begins in the region of the pars interarticularis, spreading dorsally into the laminae, forward into the pedicles, and laterally into the transverse processes. The newly ossified neural arch halves remain separate from each other and the centrum, yet they are united by cartilage until ossification is completed after birth. Developmental delay of any part of the neural arch complex during the blastemal stage can result in developmental defect in chondrification and ossification (Shore 1930; Walmsley 1959; Warkany 1971). a. Cleft Neural Arch Developmental delay resulting in hypoplasia or aplasia of one or both parts of the precursors of the pedicles, laminae, or spinous process can lead
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Fig. 3.39 Sacrocaudal border shifting. 1. Cranial shifting: A: unilateral (incomplete) separation of S5, anterior view. B: dorsal view of A. C: complete separation of S5, anterior view. D: dorsal view of C. 2. Caudal shifting: E: unilateral (incomplete) sacralization of first caudal segment, anterior view. F: dorsal view of E. G: complete sacralization of first caudal segment, anterior view. H: dorsal view of G.
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to failure of the two halves to coalesce and result in a bifid or cleft neural arch (Fig. 3.40). This is the most commonly known developmental defect of the vertebral column; it is usually referred to as spina bifida. I prefer to not use this term, because it confuses this developmental defect of the neural arch with the defect associated with the neural tube defect, spina bifida occulta. I prefer the term ''cleft neural arch." With a minor delay in development of the neural arches, the two halves come together but do not coalesce, forming a bifid neural arch (Fig. 3.40a and c). When there is a major delay in the development of the neural arches, the two halves do not come together at all, leaving a cleft in the neural arch (Figs. 3.40b and 3.41). Variations in cleft formation correlate with the underlying part or parts of the neural arch that are affected by either hypoplasia or aplasia. Minor delay in the development of the neural arches results in a small midline cleft or bifurcation of the spinous process (Fig. 3.40c), the most common type of developmental defect of the neural arch. Clefting with an absent spinous process can also occur with a greater degree of delay in development (Figs. 3.40f and 3.42). Asymmetrical clefting is less common than symmetrical clefting. It happens when there is unilateral hypoplasia or aplasia of one or more elements. The unaffected side often grows beyond its boundaries when the hypoplastic or aplastic side fails to meet with it at the proper time (Fig. 3.40d and h). The separated halves sometimes become displaced and may override adjacent spinous processes (Epstein 1976; Meschan 1985; Schmorl and Junghanns 1971; Shore 1930; Warkany 1971). Clefting from developmental delay of the neural arches is quite common, with frequencies as high as 25%. The cleft is covered with tough fibrous tissue, protecting the underlying tissues the same way the missing bony part would, and therefore is clinically insignificant (Hoffman 1965; Laurence, Bligh, and Evans 1968; Saluja 1988). Clefting generally occurs in the border regions of the vertebral column, particularly at the lumbosacral border (Fig. 3.43). Usually, only one or two vertebrae are affected, but occasionally more can be, particularly in the highly unstable sacral neural arches forming the dorsal plate of the sacrum. The neural arches of the last two sacral segments normally remain underdeveloped, creating what is known as the sacral hiatus. The normal sacral hiatus is sometimes mistaken for a cleft defect (Brailsford 19281929; Epstein 1976; Schmorl and Junghanns 1971). Cleft defects in the first sacral segment are fairly common. Clefting and bifurcation can be found in more than one sacral segment. Occasionally,
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clefting occurs in all of the sacral segments, extending into the sacral hiatus and creating a complete cleft sacrum. The bony opening is covered with tough fibrous tissue, leaving little chance for disturbance of underlying soft tissue components (Meschan 1985; Schmorl and Junghanns 1971). Complete clefting caused by aplasia or hypoplasia (or both) of the sacral neural arches can be confused with sacral clefting resulting from neural tube defect (see Fig. 3.6b and c). With neural tube defect, the spinal canal is wider, and the edges of the bony defect are pushed outward. With clefting from developmental delay, the spinal canal remains normal, and the edges of the bony defect are not pushed outward (see Fig. 3.5). Clefting of the posterior arch of the atlas (Fig. 3.41) is found in about 5% of adults. Occasionally, clefting of the anterior arch occurs. Both are usually asymptomatic, because a tough fibrous band takes the place of the missing bone. The lower cervical border is not affected as commonly as the upper border. Clefting in the thoracic spine is rare, occurring mostly at the lower border (Fig. 3.42). The lower lumbar border is affected much more often than the upper border (Bailey 1974; McRae 1960; Schmorl and Junghanns 1971). Cleft neural arches are frequently reported in prehistoric skeletal collections, but they are often mistakenly referred to as spina bifida occulta. Ferembach (1963) examined twenty-one adult sacra from different time periods found in Taforalt Cave in northeast Morocco and noted variable types of clefting in ten of them. She also noticed that the frequency of clefting increased through time. Thus she hypothesized that endogamy was practiced and that the gene influencing the development of clefting spread in a relatively short time. Bennett (1972) described eight individuals from a proto-historic Modoc site in California with variable clefting in the lumbosacral region, indicating that they were genetically related. Merbs and Wilson (1962:156158) identified neural arch clefting in three of the eleven children present in the Sadlermiut Eskimo skeletal collection. Of the sixty-one adults in this collection, one male and one female also exhibited clefting (5/72 = 7%). The clefts occurred in the spinous processes of the eleventh thoracic and fifth lumbar vertebrae. One case was accompanied by aplasia of the spinous process. Another individual simply lacked the spinous process because of aplasia of its precursor. Bradtmiller (1984) was able to determine differing patterns of sacral clefting between two proto-historic Arikara groups from South Dakota, showing that developmental defects can be very useful as genetic markers. Various expressions of neural arch clefting occur in the Southwest skeletal collections I examined. The only clefting I found in the collection
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Fig. 3.40 Variations of developmental delay defects of the vertebral elements. a: bifurcated posterior arch of atlas; b: cleft posterior arch of atlas; c: bifurcated neural arch of T6; d: aplasia of lamina of T6; e: aplasia of transverse process of T6; f: aplasia of spinous process of T6; g: aplasia of apophyseal facet of T6; h: aplasia of pedicle of C7.
from Quarai (Pueblo IV Southern Tiwa) was a bifid atlas in one male (NMNH 381266). Another atlas from a Pueblo Bonito adult (NMNH 327128 Pueblo IIIII) is cleft (Fig. 3.41), and twelve other individuals from Pueblo Bonito have clefting at the lumbosacral border. Small clefts appear in one or two sacral vertebral segments in eleven of these; two also have a bifid L5. One individual has a complete cleft sacrum with a bifid L5 neural arch. Two individuals from the Elden Pueblo (Pueblo III Sinagua) collection at the Smithsonian's Natural History Museum have small clefts in one sacral vertebral segment, and one individual has a cleft through the first three sacral vertebral segments. Giusewa (Pueblo IVV Towa) has four individuals with
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Fig. 3.41 Cleft atlas resulting from developmental delay of the neural arch. Adult (NMNH 327128) from Pueblo Bonito, New Mexico.
cleft sacra; two have a cleft S1, one has bifid and cleft S2S4, and one has a complete cleft sacrum. Neighboring Amoxiumqua (Pueblo IV Towa) has two individuals with cleft S1S2, and one of these also has a bifid neural arch in L5. There are sixteen individuals with clefts at the lumbosacral border in the Hawikku (Pueblo IVV Zuni) skeletal collection. Clefting or bifurcation of only the first sacral vertebral segment appears in eight of these individuals two have involvement of two sacral segments, and six individuals have a complete sacral cleft. Bifid neural arches of the last lumbar vertebra accompany two of the complete cleft sacra. Neighboring Heshotauthla (Pueblo IV Zuni) has five individuals with clefting at the lumbosacral border one with cleft S2, and four with cleft or bifurcated S1S2; one of these also has a bifurcated L5 (Fig. 3.43). b. Other Neural Arch Defects Hypoplasia of the neural arch without cleft formation can occur. It can be unilateral, bilateral, symmetrical, or asymmetrical. Unilateral or asymmetrical hypoplasia generally produces clinical symptoms. Bilateral hypoplasia of the atlas sometimes occurs, producing a small atlas that usually remains asymptomatic (Epstein 1976). The spinous process alone is sometimes affected by hypoplasia or aplasia. The spinous process may be absent, rudimentary, or shortened (Schmorl and Junghanns 1971; Shore 1930).
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Fig. 3.42 Bifurcated neural arch of T11 and T12 resulting from developmental delay of the neural arch. Adult of indeterminate age and sex from Haley's Point, southern Oklahoma. T11 also has bilateral symmetrical aplasia of spinous process, and T12 has unilateral aplasia of the spinous process, with the left side developing without resistance from the missing right side.
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Fig. 3.43 Bifurcated neural arch of L5 with cleft first and second sacral segments resulting from developmental delay of the neural arches. Adult female (NMNH 239293) from Heshotauthla, New Mexico; right side of neural arch of L5 affected by hypoplasia, left side overcompensated in its unrestricted development.
Aplasia of the pedicles is rare (Fig. 3.40h). When it does occur, it is usually in the cervical spine between the fourth and seventh cervical vertebrae. Missing lumbar pedicles are even rarer than cervical cases, and they are unheard of in the thoracic spine. Missing pedicles generally occur unilaterally and remain asymptomatic until traumatized. Without the pedicle, the superior articular facet is absent, and the lateral mass is malformed, with the
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inferior articular facet dorsal to the superior facet of the adjacent vertebra. The transverse process does not develop normally but is often elongated and malaligned (Bailey 1974; Epstein 1976; Mizutani, Yamamuro, and Shikata 1989; Oestreich and Young 1969; Sakov and Morizono 1983; Wilson and Norrell 1966). Soft tissue damage can occur with a missing pedicle when the cervical spine is injured. Symptoms vary with the cervical level of involvement. The left side of the fifth cervical vertebra is most often affected, with symptoms ranging from slight neck pain, stiff neck with flexion, and numbness of the fourth and fifth fingers of the right hand to numbness of the entire arm. The sixth cervical vertebra is the next most often affected. Symptoms may be expressed equally on both sides but more often on the right side. They include neck and scapula pain, numbness of the upper right arm, and difficulty in writing. These symptoms also appear when the fourth cervical vertebra is affected. When the seventh cervical vertebra is missing a pedicle, the symptom is numbness of the third and fourth fingers (Bailey 1974; Epstein 1976; Mizutani, Yamamuro, and Shikata 1989; Oestreich and Young 1969; Sakov and Morizono 1983; Wilson and Norrell 1966). The articular facets of the apophyseal joint sometimes vary in size and shape and occasionally are missing (Fig. 3.40g). If unilateral hypoplasia or aplasia occurs, the joint becomes mechanically unstable and is susceptible to injury (Shore 1930). Asymmetry of the articulating facets between the atlas and axis is common (McRae 1960). Asymmetry of the articular facets between the last lumbar and first sacral segments is also common, but complete absence of one of these articular facets is rare. Asymmetry of the articulating facets causes low back pain and leg pain, with intermittent numbness and weakness, with functional stress in the adult (Brailsford 1948; Epstein 1976; Meschan 1985; Pellegrini and Hardy 1983; Schmorl and Junghanns 1971; Warkany 1971). c. Transverse Elements Developmental delay involving the transverse process can result in hypoplasia or aplasia of any of its elements. When the costal portion of the cervical vertebra is affected, the transverse foramen is either cleft or absent. Aplasia or hypoplasia of the entire transverse process causes it to be rudimentary or absent (Fig. 3.40e).
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2. Hypoplasia-Aplasia of the Centrum The blastemal centra chondrify from a pair of cartilaginous centers that begin to appear during the sixth embryonic week. They quickly coalesce into one. Ossification centers, usually one for each centrum, begin to appear during the ninth week. Interference in the development of the blastemal centrum can result in a variety of hypoplastic or aplastic cartilaginous models that in turn develop into osseous dorsal or ventral hypoplasia, or hemivertebrae. Dorsal or ventral hemivertebrae are rare (Epstein 1976). Schmorl and Junghanns (1971) theorize that the underlying cause may be the absence of vascularization into the centrum, which proceeds posteriorly-anteriorly. This vascularization is necessary for osteogenesis to take place. Tsou, Yau and Hodgson (1980) support this view. Delay in the development of the blastemal anlage may interfere with the timing for the normal growth of the blood vessels into the developing centrum. a. Hypoplasia Hypoplasia of either the dorsal or ventral portion of the centrum can happen when there is a delay in the blastemal stage. This can lead to a delay in the development of one of the chondrification centers. The result is slowed chondrification of the half that is affected. Ossification probably comes from two centers in this case, with the retarded half containing less ossification potential. This leads to hypoplasia of that half, and the result is a wedge-shaped vertebral body (Fig. 3.44). The wedged end is directed anteriorly or posteriorly (Fig. 3.45a and c), according to the affected half of the centrum. Hypoplasia of both halves leads to an unusually small vertebral body. b. Aplasia When only the dorsal part of the centrum develops, the anterior portion is filled by intervertebral disc tissue. With age, this soft tissue may disappear and allow the anterior aspects of the adjacent vertebrae to touch. To compensate for the loss of the anterior portion of the dorsal hemivertebra (Fig. 3.45b), the anterior aspects of the adjacent vertebrae increase in height during growth and development. The original cuboid-shaped dorsal hemivertebra fuses with the pedicles and progressively becomes wedge-shaped from structural stress, leading to kyposis abnormal convex curvature of the spine (Schmorl and Junghanns 1971; Tsou, Yau, and Hodgson 1980). Ventral hemivertebra is extremely rare. The dorsal portion of the centrum fails to develop, and intervertebral cartilaginous tissue fills the void.
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Fig. 3.44 Mild ventral hypoplasia of T11 and T12 vertebrae resulting from developmental delay of the centra. Right lateral view of T10 to L4 of adult male (NMNH 314280) from Hawikku, New Mexico; compensatory osteophytes on L1 and L2 from forward curvature of the spine caused by the ventral hypoplasia of T11 and T12.
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Fig. 3.45 Developmental delay defects of the centrum. A: ventral hypoplasia. B: ventral aplasia producing dorsal hemicentrum. C: dorsal hypoplasia. D: dorsal aplasia producing ventral hemicentrum.
The pedicles may fuse with both sides of the ventral hemivertebra (Fig. 3.45d). No curvature of the spine will occur as long as the height of the anterior portion remains normal (Schmorl and Junghanns 1971; Tsou, Yau, and Hodgson 1980). Complete absence of the centrum is the most severe and rare form of this defect. The pedicle roots, normally developing separately from the neural arches, enlarge and fuse in front of the spinal cord. This leads to congenital kyphosis (Schmorl and Junghanns 1971; Tsou, Yau, and Hodgson 1980).
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Summary Outline: Paraxial Mesoderm Field Defects A.Segmentation errors 1.Asynchronous development of hemimetamere pairs a.hemimetamere shifts solitary lateral wedge-shaped hemivertebra; thoracic (1) hemivertebra may have normal rib; does not cross midline (2)multiple lateral wedge-shaped hemivertebrae contralateral shift bilateral balanced; usually separated by (a) one or more normal vertebrae; can be multiple pairing defects (b)unilateral shift one side, unbalanced (c) bilateral shift opposing, same level b.hemimetamere hypoplasia-aplasia (1)hypoplasia unilateral lateral wedge-shaped hemivertebra(e) with (a) irregular medial border, crosses midline; scoliosis may be present unilateral coalescence of multiple neural arches; absent apophyseal joints and fused laminae form postlateral (b) osseous bar; costovertebral joints may also coalesce; scoliosis unilateral conjoined neural arches and centra; complete (c) coalescence of vertebral segments into solid postlateral bar; no segmentation markings on affected side; severe scoliosis (2)aplasia solitary lateral wedged-shaped hemivertebra, crosses (a) midline; irregular border; rudimentary rib may mark absent thoracic hemimetamere multiple lateral wedged-shaped hemivertebrae; frequently (b) associated with other severe abnormalities (lethal) 2.Failure of segmentation of vertebral segments Type I several cervical and upper thoracic vertebrae appear as one a. block vertebra; usually associated with other defects Type II two or three vertebral segments as one block vertebra, b. usually C2-C3, then C5-C6 Type III coexisting cervical, thoracic, and lumbar block vertebrae; c. associated with multiple defects and usually lethal
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Irregular segmentation of ribs (more common on right side, rarely 3.below R5) combined (fused) adjacent ribs usually incomplete, rarely below a. R3, mostly R1 and R2 bridging osseous bridge connecting adjacent ribs, complete or b. partial wide or double equal to or greater in width than two adjacent c. ribs d.flared ventral rib ends wide e.bifurcated anterior rib ends bifid f. rib spurs Neural arch joint failure of segmentation absence of apophyseal 4. joints 5.Numerical errors in segmentation supernumerary vertebral segment, usually in thoracic or lumbar a. spine b.reduction in number of segments, usually lumbosacral region Cranial-caudal border shifts (unilateral, bilateral, symmetrical, B. asymmetrical, mild, complete, or incomplete) 1.Occipitocervical border a.cranial shift complete or incomplete expression of occipital vertebra articulating occipital condyles appear normal, oval and (1)convex, converging in caudal direction; lacks complete posterior arch; some expression of anterior arch around foramen magnum as bony protuberances (2)mild expressions (a) precondylar tubercle (b)transverse basilar cleft (c) bipartite occipital condylar facets (d)bipartite hypoglossal canal (3)odontoid displacements (a) Type I os odontoidem dens separated from body of C2 Type II ossiculum terminale (most common type) apical tip separated, attaches to anterior aspects of C1 or anterior (b) rim of foramen magnum; odontoid appears short and blunt
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Type III agenesis of dens apical tip present, base of odontoid (c) missing Type IV agenesis of apical segment hypoplastic base, absent (d) apical segment Type V agenesis of odontoid absence of both base and apical (e) tip b.caudal shift complete or incomplete occipitalization of atlas articulating (1)occipital condyles are flat, converging in a cranial direction; usually have or attempt to have transverse foramen (2)mild expressions paracondylar processes, usually broad based, often cone(a) shaped epitransverse process; thin, bony ridge arising from transverse (b) process of C1, projecting upward (c) hypoplasia of occipital condyles (d)precondylar articulating facet 2.Cervicothoracic border a.cranial shift (1)complete or incomplete cervical rib expression (a) Class I bony tubercle (b)Class II blunt 4050-mm bony projection Class III rib extension without costal joint, articulates or (c) attaches to R1 or sternum via ligament (d)Class IV complete rib with costal joint mild expression T2 rib attaches to lateral edge of manubrium (2) instead of manubriosternal junction b.caudal shift complete or incomplete expression first thoracic rib rudimentary (less than 30 mm long); frequently attaches to R2; reduced T1 (1) transverse processes; may have transverse foramen; C7 transverse processes shorter than C6 mild expression T2 rib attaches to side of mesosternum instead of (2) manubriosternal joint 3.Thoracolumbar border a.cranial shift complete expression T12 rudimentary ribs smaller than normal or (1) absent (slender, tapered tips)
(2)mild expression transitional facets at T11 instead of T12
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b.caudal shift complete expression lumbar ribs usually bilateral; broad with (1) rounded, blunt, or oval tips (2)mild expression transitional facets at L1 instead of T12 4.Lumbosacral border a.cranial shift complete expression incorporation (sacralization) of L5 into (1)sacrum with narrow space between L5 and S1; small transverse processes on L4 incomplete expression transverse processes of L5 wide, alalike, (2) articulate with sacrum, sometimes articulate with illium mild expression transverse processes of L5 wide, alalike, (3) sometimes bifurcated, do not articulate with sacrum b.Caudal shift complete expression separation (lumbarization) of S1 from sacrum; short, wide body; frequently apophyseal facets are (1)rudimentary; sacral alae appear higher than normal; inferior disc space greater than normal; transverse processes on L4 larger than normal (2)incomplete expression partial separation of S1 from sacrum mild expression rudimentary apophyseal joints between S1 and (3) S2; small anterior cleft between S1 and S2 5.Sacrocaudal border a.cranial shift complete expression last sacral segment separated from sacral (1) body incomplete expression last sacral segment partially separated (2)from sacral body, lateral circumference of last sacral foramen not closed b.caudal shift complete expression incorporation (sacralization) of first (1)caudal segment into sacrum; caudal cornua usually separate; five sacral foramina incomplete expression partial incorporation of first caudal (2) segment into sacrum C.Developmental delay of vertebral elements 1.Neural arch
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cleft neural arch hypoplasia or aplasia of any neural arch element(s); unilateral or bilateral, asymmetrical or symmetrical; common in atlas a. and lumbosacral region; neural canal normal, and affected neural arch alignment usually normal (1)major delay cleft (2)mild delay bifurcation other neural arch defects hypoplasia or aplasia of pedicle, lamina, b.transverse process, spinous process, or apophyseal joint; unilateral or bilateral, symmetrical or asymmetrical 2.Centrum aplasia of centrum absent vertebral body, pedicles enlarged and may a. fuse in front of spinal cord; congenital kyphosis b.hypoplasia-aplasia of ventral portion of centrum hypoplasia dorsal-ventral wedge-shaped vertebral body, leading (1) to kyposis aplasia dorsal hemivertebra, originally cuboid, progressively becomes wedge-shaped, producing kyposis; anterior aspects of (2) adjacent vertebral bodies increase in anterior height and may touch c.hypoplasia-aplasia of dorsal portion of centrum hypoplasia ventral-dorsal wedge-shaped vertebral body, may lead (1) to lordosis aplasia ventral hemivertebra; pedicles may fuse with ventral half; (2)may maintain normal height or become wedge-shaped under functional stress, producing lordosis
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Chapter 4 Developmental Field Defects of the Skull Whereas the exoccipitals are created from the occipital somites of the paraxial mesoderm, most of the base of the cranium the chondrocranium is derived from another developmental field, the prechordal cranial base. The calvarium, the superior portion of the cranium, develops from the blastemal desmocranium. Most of the facial bones develop from the blastemal frontonasal process, and the first branchial arch produces the maxilla and the mandible. The external auditory meatus is created from the ectodermal groove of the first branchial arch, and the tympanic plate comes from the closing membrane of the first branchial arch. The second branchial arch supplies the stylohyoid chain. Part I. Prechordal Cranial Base Field Defects The prechordal cranial base first becomes apparent by the end of the first embryonic month. A pair of dense mesenchymal masses appears above the occipital somites and parallel to the cranial end of the notochord. These masses envelop the cranial portion of the notochord by the sixth embryonic week. By the seventh week, they begin to chondrify into the parachordal cartilages, the precursors of the basioccipital (Fig. 4.1c). Immediately following the appearance of the parachordal mesenchyme, bilateral condensations appear in the interorbitonasal region and chondrify into the trabecular cartilages. Similar condensations encapsulate the developing otocysts (Fig. 4.1a and b). Chondrification spreads out from the cartilaginous centers to unite the prechordal cranial base into one cartilaginous mass by the beginning of the third month, spreading into the supraoccipital region between the superior
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Fig. 4.1 Elements of the prechordal cranial base. a: otic capsules: (1) petromastoid of temporal bone, external surface; (2) petromastoid, internal surface. b: trabecular cartilages: (1) ethmoid (excluding perpendicular plates); (2) sphenoid body, lesser wings, and roots of greater wings. c: parachordal cartilages: basioccipital and anterior portion of occipital condyles.
nuchal line and the foramen magnum. Ossification begins as soon as chondrification has been completed, starting in the parachordal region, which ossifies into the basioccipital (Fig. 4.1c). The basioccipital contains the anterior portion of the occipital condyles, whereas the major portion of the condyles is contained in the exoccipitals formed from the occipital sclerotomes associated with the paraxial mesoderm. The basioccipital, exoccipitals, and supraoccipital remain separate at birth. The exoccipitals unite with the supraoccipital by the third year and with the basioccipital by the sixth year. The trabecular cartilages ossify into the body, lesser wings, and roots of the greater wings of the sphenoid and into the ethmoid (except for the perpendicular plates that ossify directly from
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membrane) (Fig. 4.1b). The otic capsule ossifies into the petromastoid portion of the temporal (Fig. 4.1a) (Arey 1965; Williams et al. 1989). Delay in development of any of the primordial condensations of mesenchyme can lead to hypoplasia or aplasia of any or all parts of the sequel (Fig. 4.2). Seligmann (1912:17) described an adult cranium from eighteenth dynasty Egypt as a ''cretin" skull because of the "characteristic lack of development (hypoplasia) of the bones laid down in cartilage." The base of the cranium, the superior portion of the maxillae, and the nasal bones were extremely small. The lambdoidal suture had closed prematurely, and frontal bossing was extreme. The accompanying photograph of the base of the cranium shows the absence of the basioccipital. The basisphenoid was described as hypoplastic. This can be interpreted to mean that the parachordal cartilages were aplastic and the trabecular cartilages hypoplastic. Brothwell (1958) identified a similar aplasia of the basioccipital in an adult male cranium from a Roman-British burial in York, England. The sphenoid was not affected. Extreme basilar impression was present, along with caudal shifting of the occipitocervical border, in the form of partial occipitalization of the atlas. The reduced basion-bregma height and basion-nasal length were compensated for by an increase in breadth, giving the cranium a globular appearance. This field defect can be classified as developmental delay of the parachordal cartilages resulting in aplasia of the basioccipital. Ortner and Putschar (1985:331334) suggested that the cretin skull Seligmann (1912) described is actually the cranium of an achondroplastic dwarf. The shortened skull base is typical of achondroplasia, which creates the classic midfacial depression of this cartilaginous defect. Hypoplasia of the basioccipital does appear to be associated with achondroplasia. Ortner and Putschar (1985) analyzed five prehistoric crania identified as achondroplastic dwarfs and found all had hypoplastic basioccipitals. Their sample included one of the two achondroplastic dwarfs from fourth dynasty Egypt that Brothwell (1967:433) reported (the other dwarf was represented by postcranial skeletal material only); the two dwarfs from Moundville, Alabama, reported by Snow (1943); the dwarf from Sacramento, California, that Hoffman (1976b) found; and a dwarf from a site near Waverly, Ohio, that Fowke (1902) discovered. They also found an isolated skull from an ossuary at Ferguson Farm in Accokeek, Maryland, with hypoplasia of the basilar occipital, suggestive of achondroplasia. Although the evidence supports the association of hypoplasia of the basioccipital with achondroplasia, it is not limited to this defect of the
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Fig. 4.2. Defects of the basioccipital resulting from developmental disturbance of the parachordal cartilages. a: bilateral symmetrical hypoplasia; b: unilateral asymmetrical aplasia; c: unilateral hypoplasia; d: bilateral aplasia.
cartilaginous cells. It can occur as an isolated field defect. When the postcranial skeleton is missing and hypoplasia of the basioccipital occurs in association with hypoplasia or aplasia of other prechordal structures, achondroplasia is suggested. In his analysis of prehistoric Hawaiians from Mokapu, Oahu, Snow (1974:6167) discovered twenty individuals (eleven females and nine males)
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with a peculiar deformity of the cranial base. The foramen magnum is markedly twisted to one side. The basioccipital appears to be shortened on one side in the photographs, giving the impression that the other side is abnormally enlarged, with the condyle on that side elevated. This phenomenon probably results from unilateral delayed development of one of the parachordal cartilages, leading to a unilateral hypoplasia of the basioccipital, which forces the foramen magnum into an unusually lopsided shape. Such a large frequency of an unusual defect must have been genetically determined. Summary Outline: Prechordal Cranial Base Field Defects Developmental delay leading to hypoplasia-aplasia, unilateral or bilateral, symmetrical or asymmetrical A. Parachordal cartilages 1.basioccipital 2.anterior portion of occipital condyles B. Trabecular cartilages 1.body, lesser wings, and roots of greater wings of sphenoid 2.ethmoid (excluding perpendicular plates) C. Otic capsule 1.petromastoid of temporal bone Part II. Blastermal Desmocranium Field Defects Ossification centers for the membranous cranial vault begin to appear at well-vascularized points in the dense mesenchymal (membranous) desmocranium during the seventh embryonic week. Each parietal squamosa generally forms from two ossification centers that appear one above the other near the centralized membranous tuberosity. These ossification centers quickly coalesce, producing needlelike spicules of bone that radiate into a meshwork of fiber bone, spreading radially in all directions. The frontal bone ossifies from two separate centers in a similar manner. These centers form bilaterally equal halves divided by a temporary suture, the metopic suture, that normally fuses and is obliterated by age two. The squamosal and tympanic portions of the temporal bone also ossify directly from mesenchymal tissue (Arey 1965; Williams et al. 1989).
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The squamosal part of the occipital bone, the interparietal, ossifies directly from mesenchymal tissue. This portion of the occipital bone above the superior nuchal line is part of the membranous calvarium, and the portion below the superior nuchal line the supraoccipital is part of the chondrocranium and is transformed into cartilage before ossifying. As the two types of bony tissue grow toward each other, they unite to form the occipital plate. The interparietal ossifies from a complex of ossification centers that vary genetically. It was once thought that the interparietal ossified from two centers that quickly coalesced. More recently, Srivastava (1977) has shown that is not that simple. Srivastava divides the interparietal into three areas: two lateral plates with two ossification centers each, a central section with two ossification centers, and a preinterparietal part with two ossification centers. Delay in the development of one or more of these areas can lead to delayed ossification and failure of that part to fuse with the other areas. This explains the range of variation we see in ossicle bones forming within the interparietal of the occipital. Sutural growth varies among different sutures and within the same suture. Growth can be equal or unequal. Equal growth produces an even suture line, whereas unequal growth leads to an irregular suture line. Suture type appears to be genetically programmed in the blastemal stage (Furtwangler et al. 1985; Sarnat 1986). The cranial bones remain separated at birth, with six membranous fontanelles at major junctions (Fig. 4.3). The largest is the anterior rhomboid-shaped fontanelle, in which the frontal halves and parietals meet at the junction known as bregma. A posterior triangularshaped fontanelle is located at the junction of the parietals and the occipital at lambda. Small, irregular anterolateral (sphenoid) fontanelles occur at the junction of the sphenoid, frontal, temporal, and parietal, in the region known as the epipterion. Small posterolateral (mastoid) fontanelles occur at the junction of the temporal, occipital, and parietal at asterion. The anterior fontanelle is filled in with the growing bone ends of the parietals and the frontal after birth by the middle of the second year. The posterolateral (mastoid) fontanelles are obliterated by the end of the first year, and the posterior and anterolateral (sphenoid) fontanelles disappear by the third postnatal month (Williams et al. 1989). A seventh fontanelle, the fetal sagittal fontanelle, closes in before birth. This fontanelle is usually located toward the posterior one-third of the sagittal suture region near obelion (Fig. 4.3e). It closes as the parietals grow toward the sagittal suture line. Sometimes
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Fig. 4.3 Failure to coalesce defects in the blastemal desmocranium. A: extra lambdoidal suture ossicles. B: retention of the mendosa suture. C: multiple inter-parietal bones. D: ossicle at lambda posterior fontanelle. E: obelion ossicle sagittal fontanelle. F: bregma ossicle anterior fontanelle. G: epipterion ossicle anterolateral fontanelle. H: asterion ossicle posterolateral fontanelle. I: parietal notch bone superior extension of posterolateral fontanelle. J: petromastoid ossicle inferior extension of posterolateral fontanelle.
a fontanelle develops into an independent bone; this is known to be hereditary (Hess 1946). A. Failure to Coalesce Extra ossicles within the cranial sutures can result from the delayed approach of a portion of a cranial bone's blastemal precursor to a designated meeting with another cranial bone's blastemal precursor. For some reason this triggers the development of an extra ossification center in the tardy tissue that fails to coalesce with the rest of the cranial bone. Extra ossicles (wormian bones) within the cranial sutures are generally referred to as "anomalies" and are generally of no clinical concern. The heritability of developmental ossicles
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in the cranial sutures (El-Najjar and Dawson 1977; Torgersen 1951) is of value for genetic studies in anthropology, and these ossicles have been used in nonmetric population comparison studies. 1. Primary Suture Ossicles a. Patterned Extra Sutural Ossicles Extra ossicles (wormian bones) are commonly found within the lambdoidal suture (Fig. 4.3a) and occasionally within other cranial sutures. Suture ossicles generally develop in response to genetic programming, but they can also form within the suture membranes after the formation of the blastemal cranial bones. This happens secondarily as ossification centers are fragmented by metabolic upsets disturbing the membranous tissue. Secondary suture bones are often associated with polytropic defects affecting the cranium, such as cleidocranial dysotosis, or metabolic defects affecting several systems of the body. Secondary ossicles can appear late, even after birth, wit exogenous disturbances affecting the suture membranes that connect the cranial bones (El-Najjar and Dawson 1977; O'Rahilly and Twohig 1952). Some researchers have studied the association between extra ossicles in the lambdoidal suture and cultural deformation of the skull (Bennett 1965; El-Najjar and Dawson 1977; Finkel 1971; Gottlieb 1978; Ossenberg 1970). There appears to be no significant difference in the frequency of exta lambdoidal ossicles and cultural deformation within the same population. The ossicles found with cranial deformation are under the same genetic programming as undeformed crania (El-Najjar and Dawson 1977). Primary ossicles correspond to the aberrant ossification center in the blastemal cranial segment. They may appear as ossified fontanelle bones, or they may represent ossification centers that failed to coalesce, or they may form true suture bones. Secondary ossicles usually form numerous complexes of extra sutural bones. Primary ossicles can also appear in this manner, particularly with complex or irregular lambdoidal sutures. Specific patterns in their appearance and frequency within a population would suggest a genetic disposition, whereas sporadic incidences may have an associated metabolic disturbance. Extra ossicles in the lambdoidal suture can be found in most populations. They appear in high frequencies in Southwest skeletal collections and are often associated with complex sutures. Hooton (1930) reported a high frequency of extra lambdoidal ossicles at Pecos. Bennett (1965) also found a high frequency of lambdoidal ossicles in the Mesa Verde and Point of Pines
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collections, and El-Najjar and Dawson (1977) reported high frequencies in the Southwest Pueblo skulls they studied. b. Fontanelle Bones Fontanelle bones are created when the fontanelle maintains its separation from adjacent cranial elements; these bones include the following: bregma anterior fontanelle (Fig. 4.3f). lambda posterior fontanelle (Fig. 4.3d). epipterion anterolateral fontanelle (bilateral) (Fig. 4.3g). asterion posterolateral fontanelle (bilateral) (Fig. 4.3h). obelion fetal sagittal fontanelle (Fig. 4.3e). The size of the fontanelle bones depends upon the timing of the delay in development leading to the separate manifestation of the bones into an ossicle. Fontanelle bones are frequently identified in prehistoric skeletal collections. Bregma and obelion bones are rare. Only one individual from the large Hawikku (Pueblo IV-V Zuni) skeletal collection, an adult male (NMNH 308601), and one female (NMNH 239202) from neighboring Heshotauthla (Pueblo IV Zuni) have bregma bones. There is a large bregma bone in one adult female (NMNH 327115) from Pueblo Bonito (Pueblo III). Obelion bones are present in two males and one female from Hawikku, in one male from Heshotauthla, and in one female from Pueblo Bonito. c. Retention of the Mendosa Suture Occasionally, the interparietal and supraoccipital portions of the occipital do not unite at the primordial (mendosa) suture that separates them at the superior nuchal line. The mendosa suture remains intact, and the interparietal becomes a separate bone (Fig. 4.3b). This is usually referred to as the inca phenomenon, because it was found to be fairly common in South American Indians (O'Rahilly and Twohig 1952). Retention of the mendosa suture is frequently mentioned in the paleopathology literature. El-Najjar (1974) noted a steady increase in this defect through time within the Anasazi population of Canyon de Chelly. The frequency of this defect increased from 4.8% in Basket Maker crania to 10.5% in Pueblo III crania, which could indicate inbreeding. Matthews (1891:187) reported a "high frequency" of retention of the mendosa suture in eighty-eight Hohokam crania in the Hemenway skeletal collection from the Los Muertos
site near Phoenix, Arizona. He reported that
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5.68% of the crania displayed this phenomenon, compared with 5.46% frequency of crania from an unknown Peruvian skeletal collection. Failure of the mendosa suture to fuse was found in three females in the large skeletal collection from Hawikku (Pueblo IVV Zuni) and in two females from the small collection from neighboring Heshotauthla (Pueblo IV Zuni). d. Multiple Interparietal Bones of the Occipital The interparietal bone can subdivide along the borders of one or more of its separately developing elements as they fail to coalesce (Fig. 4.3c). The resulting sutural division can be complete or incomplete, bipartite or multi-partite, and it can be divided in any direction. This may be associated with retention of the mendosa suture. When it does occur, it is more commonly found in males and usually appears unilaterally (O'Rahilly and Twohig 1952; Shapiro 1972). Multiple interparietal bones are not uncommon in Southwest skeletal collections and often appear with lambdoidal ossicles. 2. Enlarged Parietal Foramina As the blastemal parietals ossify outward from their centers, bone growth normally slows as they approach the sagittal suture near the posterior part of the vault. This leaves a lozenge-shaped area of the membranous cranium unossified until the seventh fetal month. Sometimes development of the parietal blastemal precursors is slightly delayed, and ossification is slower than normal as it reaches the posterior edges of the sagittal fontanelle. This allows bilateral emissary veins to develop and pass through the lateral angles of the fontanelle before the osseous border is closed. These small veins are known as Santorini's emissary veins, and they connect with the occipital veins and the superior sagittal veins. As the sagittal fontanelle eventually closes by extension and fusion of the anterior and posterior parietal borders, small parietal foramina form for Santorini's emissary vessels. They are generally quite small, 1 mm to 2 mm in diameter, occurring unilaterally or bilaterally in about 60% of a given population. They appear more often on one parietal rather than on both, and a single foramen sometimes forms in the sagittal suture. Multiple parietal foramina for multiple emissary veins have been reported but are rare (Currarino 1976; Irvine and Taylor 1936; O'Rahilly and Twohig 1952). Bone growth into the sagittal fontanelle is sometimes delayed until a few months after birth because of delayed development of the parietal mesenchyme. This bone growth delay gives the sagittal suture in the region of
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the sagittal fontanelle a cruciform shape, with the vertical limb as the pars obelica the portion of the sagittal suture between the parietal foramina (O'Rahilly and Twohig 1952). Longer periods of delay in the development of the blastemal parietals can interfere with normal ossification of their posterior portions. This leaves a single, large posterior parietal defect confluent with the posterior fontanelle at birth. Ossification slowly progresses parasagittally in both parietals, ending by the second or third year. Two very large bony openings in the parietals remain (Fig. 4.4). Known as enlarged parietal foramina (foramina parietalia permagna), they can be as large as 50 mm in diameter and are covered by thick, membranous tissue. The edges of these bony defects become markedly beveled as ossification progresses within the inner table ahead of the outer table. The developmental delay affecting the closing of these aberrations also affects the development of the sagittal and lambdoidal sutures, with complete or partial absence. A remmant of the sagittal suture in cruciform will sometimes appear between the enlarged parietal foramina. The enlarged parietal foramina are sometimes accompanied by normal-sized parietal foramina (Currarino 1976; O'Rahilly and Twohig 1952; Pepper and Pendergrass 1936). Enlarged parietal foramina occur more frequently in males than in females. They are known to be familial and probably result from autosomal dominant genes. This defect has been referred to as the "Catlin" mark by Goldsmith (1922), who discovered several members of the Catlin family with it. Enlarged parietal foramina are rare, but they have been reported in many different populations (Hollender 1967; Irvine and Taylor 1936; Lodge 1975; Murphy and Gooding 1970; Pepper and Pendergrass 1936; Warkany and Weaver 1940). Enlarged parietal foramina are as rare in prehistoric skeletal populations as they are in modern populations. However, Hoffman (1976a) was able to identify this defect in thirteen Late Horizon crania from two sites in northern California, and he realized the genetic significance of this find (Fig. 4.4a-c). Eleven of the crania five adult males, four adult females, and two children came from Ponce Mound near Palo Alto. Two adult female crania came from Contra Costa County, fifty miles away. Hoffman suggested that marriage exchange occurred between the two groups. The enlarged parietal foramina ranged in diameter from 2.4 mm to 37.4 mm. They also varied in shape from oval, round, rectangular, slitlike, and irregular-shaped to dimpled depressions. Two crania displayed metopism. The sagittal suture is absent in six of the crania, with part or all of the lambdoidal and coronal sutures
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Fig. 4.4 Enlarged parietal foramina. Occipital view of crania from Late Horizon sites in northern California. a: adult male (NMNH 276981) with agenesis of sagittal and lambdoidal sutures (superior view in photograph); b: adult female (LMA 12-5575) with partial agenesis of sagittal and lambdoidal sutures (from Hoffman 1976a); c: four-year-old child with plagiocephaly resulting from agenesis of coronal, sagittal, and right side of lambdoidal sutures; d: clinical case of seventy-five-year-old man with cruciform suture connecting foramina (drawing from photograph in O'Rahilly and Twohig 1952).
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(Hoffman 1976a). Knowing that it is familial, this concentration of such a rare genetic defect in one area offers strong evidence for close biological ties between the two sites. Two of the crania with enlarged parietal foramina are housed in the Smithsonian's National Museum of Natural History. An adult male (NMNH 276981), twenty-four years old, also has absence of the sagittal and lambdoidal sutures. The other cranium belongs to a four-year-old child (NMNH 276982), and this cranium also has plagiocephaly associated with the absence of the coronal, sagittal, and right upper lambdoidal sutures. Travers and Wormley (1938) reported a case of enlarged parietal foramina in an Egyptian mummy, but no details are given. Perizonius, Brooks, and Brooks (1991) reported enlarged parietal foramina in an adult skull from the Netherlands. The defects appeared as irregular ovals with beveled rims with a connecting suture. Enlarged parietal foramina have been reported in an Eskimo skull and a skull from the Viking period (A.D. 8001050) from Langeland, Denmark. The Viking period skull displays a suture connecting the defects, but the Eskimo skull does not (Bennike 1992). 3. Developmental Thinness of the Parietals This defect is as rare as enlarged parietal foramina, and it occurs in the same posterior region of the parietals. It has been referred to as ''senile" atrophy of the parietals, because most clinical cases have been noted in the elderly, leading to an assumed association with senile osteoporosis. Sampling error may contribute to this, because the defect has not been noticed until postmortem examination. Cases are known in individuals younger than thirty, with one case occurring in a fouryear-old child. Developmental thinness of the parietals has also been described in a nineweek-old infant. Parietal thinness has been found more frequently in males than in females (Camp and Nash 1944). The defect occurs when there is a delay in the development of the diploe, resulting in hypoplasia or aplasia of the anlage of this spongy bone layer sandwiched between the inner and outer tables of the calvarium. The defect usually appears as bilateral, symmetrical, shallow depressions (Fig. 4.5a) up to 75 × 25 mm across, flat and quadrangular. It sometimes takes the form of shallow grooves (sulci) (Fig. 4.5b). The inner and outer tables appear normal, and the degree of thinness relates to the amount of hypoplasia or aplasia of the diploe between them (Camp and Nash 1944). Developmental defect of the diploe was first postulated as the etiology by Greig (1926).
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Fig. 4.5 Developmental thinness of the parietals. Superior and occipital views of crania with a: bilateral shallow quadrangular depressions; b: bilateral sulci (shallow grooves).
Developmental thinness of the parietals is generally known as "bilateral symmetrical thinning of the parietals," but it does not always occur bilaterally. Unilateral expressions have been identified in a small percentage of cases. Occasionally, it can appear asymmetrically in bilateral cases, with more emphasis on the right side (Camp and Nash 1944; Wilson 1947).
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About 80% of all known clinical cases occur as bilateral, shallow, flat depressions. A small number have bilateral, shallow grooves (sulci). The shallow-grooved form apparently involves less of the anlage tissue than the flat-depression form. Both types have smooth borders, with progressive thinning toward the center (Camp and Nash 1944; Wilson 1947). Parietal foramina sometimes accompany this defect, and there is frequently a small depression in the posterior end of the sagittal suture (Lodge 1967, 1975). In dry bone material, the thinned areas sometimes become brittle and readily broken. This could easily be mistaken for traumatic pathology or possibly trephination. Symmetrical parietal thinning has been identified in five ancient Egyptians by Lodge (1967). Brothwell (1967) found three cases in England, all middle-aged females. Two of these came from two different Saxon cemeteries, and one came from a Roman-British cemetery. Ortner and Putschar (1985:292293) identified symmetrical parietal thinning in another ancient Egyptian, an old adult male (NMNH 256186) from the twelfth Dynasty near List in Upper Egypt, located in the National Museum of Natural History. There is one adult female from this same site and time period in Egypt (NMNH 256087)(Fig. 4.6) with symmetrical parietal thinning. Ortner and Putschar (1985:292293) also described another adult male (NMNH 294027) with this defect from a prehistoric site near Santa Lucia on the coast of Peru (Fig. 4.7). 4. Metopism Developmental delay of the precursors of the frontal bone in the blastemal stage can prevent the metopic suture (Fig. 4.8) from fusing either completely or partially. This can be accompanied by facial asymmetry, usually mild, and in most cases it is continuous with the sagittal suture. Metopism can occur alone as a field defect or as part of a polytropic syndrome of other defects. Metopism appears to be associated with increased frontal curvature. Evidence argues that some cases are familial, whereas others occur sporadically (Hess 1945; Sjovold 1984; Torgersen 1951, 1963). Metopism generally appears sporadically and infrequently in North American Indian and Eskimo, African, and Australian skeletal populations. Some of the highest frequencies (11.3% to 13.7%) are found in some Chinese and Mongolian populations in eastern Asia and among Europeans (8% to 12%). Despite the high frequencies in Europeans, Lapps infrequently have metopism; Japanese populations have a slightly lower frequency (7.8%) than the Chinese; and Canary Islanders have a frequency rate (11%) similar to that of Europeans. Melanesians in the western Pacific have a low frequency (3.4%)
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Fig. 4.6 Developmental thinness of the parietals from Egypt. Cranium of twelfth Dynasty adult female (NMNH 256087). A: top view. B: right lateral view.
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Fig. 4.7 Developmental thinness of the parietals from Peru. Artificially deformed cranium of adult male (NMNH 294027) from Santa Lucia. A: left lateral view. B: occipital view. C: dorsal view of parietals. D: superior view.
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Fig. 4.8 Metopism. a: newborn cranium with normal metopic suture; b: adult cranium with abnormal retention of the metopic suture.
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of metopism, whereas Easter Islanders in the eastern Pacific have a high frequency rate of 11% (Reed 1981:109111). South American Indians appear to have a high frequency of metopism. MacCurdy (1923:268) found that approximately 9% of the prehistoric crania he examined from the highlands of Peru near Cuzco had metopism. Reed (1981:109111) found the occurrence of metopism in the Southwest United States to be much like that in other parts of North America sporadic and infrequent. The most cases found in one region came from Point of Pines in Arizona (Mogollon), where 5 out of 208 (2%) individuals showed metopism. Metopism appears to be rare in Anasazi collections. There is one case of metopism in an adult female (NMNH 308711) from Hawikku (Pueblo IVV Zuni). B. Failure to Differentiate: Sutural Agenesis Failure of differentiation between opposing cranial bone precursors leads to coalescence into one bone, either partially or completely. The suture that would normally appear between them never develops. This phenomenon is usually referred to as craniosynostosis, but because the suture never forms, it is best to refer to this developmental disturbance as sutural agenesis (Cohen 1988; Furtwangler et al. 1985; Muakkassa et al. 1984). Sutural agenesis can be recognized in the newborn. Usually, only two opposing bones are involved, either completely or partially. It can occur as an isolated field defect, with enlarged parietal foramina, or as part of a polytropic syndrome. There are instances of familial trends of sutural agenesis, indicating a genetic base (Cohen et al. 1971). Some researchers believe that certain external factors can cause a suture to close prematurely (craniosynostosis). These factors include endocrine dysfunction, anoxia, intrauterine infection, birth trauma, and metabolic disorders such as rickets, hyperthyroidism, and hypophosphatasia (Cohen 1988; Herrmann, Pallister, and Opitz 1969; Muakkassa et al. 1984). Absense of one or more sutures can produce various types of cranial deformity, because the growing brain is displaced (Fig. 4.9). The cranial deformity can be asymmetrical or symmetrical, depending upon the extent of coalescence and the suture or sutures involved. The sagittal suture is most commonly affected, significantly more often among males than among females. Absence of the sagittal suture generally produces a long, narrow cranium known as scaphocephaly (Fig. 4.9a).
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Fig. 4.9 Variations of sutural agenesis. Agenesis of a: sagittal suture with scaphocephaly; b: coronal suture: (1) unilateral with plagiocephaly, (2) bilateral with brachycephaly; c: coronal and lambdoidal sutures with oxycephaly; d: coronal and sagittal sutures (usually part of Crouzon's syndrome); e: lambdoidal suture: (1) unilateral with plagiocephaly, (2) bilateral with brachycephaly; f: metopic with trigonocephaly.
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Absence of the coronal suture is more common in females. With complete absence of the coronal suture, the cranium usually takes on a rounded (brachycephalic) appearance (Fig. 4.9b2), and an aysmmetrical shape (plagiocephaly) can occur with partial coalescence (Fig. 4.9b1). Absence of the lambdoidal suture is rare and is found more often in males than in females. Complete absence of the lambdoidal suture can also create a brachycephalic cranium (Fig. 4.9e2), with a flat, high occiput and externally indented lambdoidal suture line with a complementary bulging internal suture line (Herrmann, Pallister, and Opitz 1969; Meschan 1985; Muakkassa et al. 1984). When the lambdoidal and coronal sutures are both affected (Fig. 4.9c), the growing brain causes the cranium to increase dramatically in height and width (oxycephaly). Absence of both the coronal and sagittal sutures can produce a variety of shapes (Fig. 4.9d). This is usually seen as a pointed, tower-shaped cranium known as oxycephaly, acrocephaly, or turricephaly. The occiput is flat, and the calvarium is short, with a steep frontal bossing (Brothwell 1981; Meschan 1985; Morse 1969). The metopic suture separating the frontal halves normally closes by the second postnatal year. Absence of the metopic suture at birth can produce a cranium with a triangular, pointed frontal (Fig. 4.9f), known as trigonocephaly (Brothwell 1981; Meschan 1985; Morse 1969). Sutural agenesis of the coronal and sagittal sutures (Fig. 4.9d) usually associates with Crouzon's syndrome, a group of disorders caused by developmental delay of the cranium and face. The lambdoidal suture is usually absent in most of these cases, the eye orbits are abnormally far apart, the maxilla is hypoplastic with mandibular prognathism, and the nose is short and "stubby." Crouzon's syndrome results from an autosomal dominant gene in about half the cases, with the remainder attributed to mutation (Goodman and Gorlin 1983; Herrmann, Pallister, and Opitz 1969; Kolar, Munro, and Farkas 1988). Prokopec (1984: 111) reported a prehistoric case of a five-year-old Australian aboriginal child with what appears to be Crouzon's syndrome from his description of "widespread premature closure, with a 'clown's cap' and pentathoid shape." Sutural agenesis of the lambdoidal and coronal sutures produced an oxycephalic-shaped skull in an adolescent from the western Andean region of Venezuela (Berrizbeitia 1992). Trigonocephaly caused by sutural agenesis of the metopic suture was identified in a child's skull from Santa Rosa Island off the coast of California (Richards 1992). Sutural agenesis is occasionally found in prehistoric Southwest populations, with scaphocephaly the most common type reported. Bennett (1967)
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discovered only twelve cases of prehistoric sutural agenesis in over one thousand individuals (1%) collected from all over the state of Arizona. Nine of these, mostly children, involved the sagittal suture. Hooton (1930:320, plates X-19 and X-20) observed three cases of scaphocephaly one adult male, a female, and one child in the Pecos skeletal collection Pueblo IV-V Towa) from New Mexico. Reed (1981:112) described an unusual sutural agenesis in an adult male cranium from Mound 7, Las Humanas, Gran Quivira, New Mexico (Pueblo IV-V Tompiro). The left squamosal suture is absent, and the parietal and temporal are completely coalesced into one bone. Reed also mentioned two other types of sutural agenesis from this site, another one from Frijoles Canyon at Bandelier National Monument (Pueblo IV Keres) with metopism, and still another from Mustang Mesa. Another unusual form of sutural agenesis was found in a neonate (probably Basket Maker) from Site Na7145 in the lower Glen Canyon region in southeastern Utah. All of the cranial sutures are partially coalesced (Bennett 1967). Matthews (1891:187) mentioned four cases of absent sagittal sutures in the Hohokam skeletal material collected by the Hemenway expedition from Los Muertos near Phoenix. Miles (1975) cited one case of partial coronal sutural agenesis in a cranium from Wetherill Mesa (Pueblo I-III) in the Mesa Verde skeletal collections. Akins (1986) reported absence of the sagittal suture in one adult and one child from Chaco Canyon (Pueblo II-III). Sutural genesis appears in three individuals from Pueblo Bonito (Pueblo II-III) in Chaco Canyon. One female (NMNH 327067) is missing the left side of the coronal suture, and one male (NMNH 327094) and one child (NMNH 327127) are each missing the right squamosal suture. Agenesis of the squamosal suture is present in three individuals from the Pueblo IV-V ancestral Zuni village of Hawikku. It is absent on the left side in one female (NMNH 308727) and on the right side in another female (NMNH 308750). Only the posterior portion of the left squamosal suture is absent in a male (NMNH 314276) who also has agenesis of the sagittal and lambdoidal sutures producing scaphocephaly. One Hawikku female (NMNH 314331) has agenesis of the lambdoidal suture and the posterior portion of the sagittal suture. Scaphocephaly is present in one female (NMNH 239530) with agenesis of the sagittal suture from Heshotauthla (Pueblo IV Zuni), and another female (NMNH 239203) is missing the right coronal suture (Fig. 4.10). Scaphocephaly is present in one child (NMNH 271948) from Amoxiumqua (Pueblo IV Towa); the sagittal suture is absent (Fig. 4.11). A similar
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Fig. 4.10 Agenesis of right side of coronal suture without plagiocephaly. Superior view of cranium of adult female (NMNH 239203) from Heshotauthla, New Mexico.
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Fig. 4.11 Agenesis of the sagittal suture with scaphocephaly in a child. Superior view of affected cranium (NMNH 271948) compared with another child's cranium with normal shape; both are from Amoxiumqua, New Mexico.
case of scaphocephaly is present in one female (NMNH 381243) from Quarai (Pueblo IV Southern Tiwa). The Elden Pueblo (Pueblo III Sinagua) skeletal collection at the Smithsonian's National Museum of Natural History has one female (NMNH 339716) with scaphocephaly resulting from the absence of the sagittal and lambdoidal sutures (Fig. 4.12). C. Microcephaly Complete absence of all or most of the cranial sutures would produce an abnormally small cranium (microcephaly), but this has yet to be encountered. Microcephaly primarily results from microencephaly reduced brain size accompanied by severe mental retardation. The forebrain and occipital lobes are primarily affected, placing this defect outside the field defects of the axial skeleton. The cranial sutures are not obliterated as in developmental sutural agenesis. Head circumference in older children and adults falls below 46 cm, and brain weights are less than 900 gr. The cranium has a conoidal
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Fig. 4.12 Agenesis of the sagittal and lambdoidal sutures with scaphocephaly and bulging occipital. Left lateral view of cranium of adult female (NMNH 339716) from Elden Pueblo, Arizona.
shape (''pinhead") because of a narrow, receding frontal and flat occipital, with a large face (Warkany 1971). Brain growth can be disturbed by several types of environmental disturbances and genetic factors. Familial cases suggesting autosomal recessive inheritance have been reported. The frequency for microcephaly can reach one in two thousand births with inbreeding in isolated populations. Some microcephalics who survive into adulthood can perform simple chores and acrobatic stunts (Goodman and Gorlin 1983; Warkany 1971). A few cases of microcephaly have been identified in prehistoric skeletal material. Brothwell (1981) mentioned microcephalic crania from Japan, Egypt, Ireland, and England. Morse (1969) reported two microcephalics from a late Woodland Mound, the Riviera aux Vase site in Macomb county, Michigan. Hrdlicka (1943) identified a "midget" skull of a 1617-year-old female (NMNH 379510) from the Chilca burial mound south of Lima on the coast of Peru and concluded that the small size was caused by a decrease in brain size (490 cc). He also found other small crania from this site but of larger brain capacity 910 cc. Ortner and Putschar (1985:304) described this
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cranium as a "congenital idiot." This specimen is a classical example of microencephaly. Richards (1985) identified a microcephalic child, three years of age, from a site from A.D. 11001700 near San Jose, California, with cranial capacity of 630 cc. Metric comparisons with other three year olds from the same area, and studies of endocasts of this individual suggesting frontal, parietal, and temporal lobe abnormalities, led Richards to his conclusion of microcephaly. The occipital lobe did not appear to be affected. Summary Outline: Blastemal Desmocranium Field Defects A.Failure to coalesce 1.Primary suture ossicles patterned extra sutural ossicles usually associated with complex a. lambdoidal suture b.fontanelle bones (1) bregma anterior fontnelle (2) lambda posterior fontanelle (3) epipterion anterolateral fontanelle (4) asterion posterolateral fontanelle (5) obelion fetal sagittal fontanelle c.retention of mendosa suture complete or incomplete multiple interparietal bones single to multiple, unilateral or d. bilateral, complete or incomplete Enlarged parietal foramina bilateral large parietal openings, 2.5 mm to 50 mm, beveled edges, usually accompanied by agenesis of part or all of sagittal and lambdoidal sutures; may have connecting 2. cruciform-shaped suture; normal parietal foramina may also be present; shapes can be oval or round, rectangular, slitlike, irregular, or dimpled depressions Developmental thinness of the parietals shallow depressions on 3. outer surface, bilateral or unilateral a.flat and quadrangular b.shallow grooves (sulci) Metopism retention of the metopic suture, frequently associated 4.with increased frontal bossing; may be associated with mild asymmetry (unilateral hypoplasia) of the face and frontal B.Failure to differentiate sutural agenesis
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Sagittal suture scaphocephaly with complete agenesis; long, narrow 1.skull with median ridge in adult 2.Sagittal and lambdoidal sutures complete agenesis produces scaphocephaly, long and narrow low a. skull with prominent occipital region partial agenesis produces asymmetrically shaped posterior of skull b. (plagiocephaly) 3.Coronal suture partial, unilateral agenesis may produce asymmetrically shaped a. frontal (plagiocephaly) complete, bilateral agenesis produces rounded cranium b. (brachycephaly) Coronal and lambdoidal sutures increases cranial height and width, 4. produces pointed tower skull (oxycephaly) Coronal and sagittal sutures part of Crouzon's syndrome; frontal 5. bossing with steep forehead, short calvarium, and flat occipital 6.Lambdoidal suture partial, unilateral agenesis produces asymmetrical rhomboid shape a. (plagiocephaly) complete, bilateral agenesis produces high, flat occiput; external b.indented suture markings with internal bony buildup for suture markings Squamosal suture partial or complete, may alter dimensions of 7. cranial width Metopic suture complete agenesis produces triangular, pointed 8. forehead (trigonocephaly) Microcephaly cranial circumference in older children and adults is C.less than 46 cm; conoidal ("pinhead") shape, narrow frontal, flat occipital, and large face Part III. Branchial Arch I Field Defects The first branchial arch produces the mandible, maxilla, zygomatics, and palatine bones. Most of the developmental field defects found are associated with the maxilla and the mandible. The zygomatics and palatine bones can be affected by developmental delay, resulting in hypoplasia or aplasia, but this is rare.
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A. Field Defects of the Mandible The two halves of the mesenchymal mandibular precursor grow in a ventromedial direction, meeting in the midline of the floor of the pharynx. Ossification centers appear near the mental foramina during the sixth embryonic week. Meckel's cartilage, previously formed and present throughout the mesenchymal mandibular anlage, becomes surrounded and infiltrated by osseous tissue by the tenth week. The two mandibular halves are united by fibrous tissue at birth, and final osseous fusion takes place by the third year (Arey 1965; Williams et al. 1989). 1. Developmental Delay Delay in development of the mandibular anlage can interfere with normal growth of the mandible. Developmental delay can also cause delayed or absent fusion of the mandibular halves. a. Cleft Mandible Developmental delay of mesenchymal growth into the ventral portion of the mandible interferes with normal fusion of the two mandibular processes. This rare defect can be a full separation of the mandibular halves, a partial cleft, or an indentation with a space, known as a diastema (Fig. 4.13) (Weinberg, Moncarz, and Van de Mak 1972). b. Hypoplasia-Aplasia of the Mandible Hypoplasia or aplasia of the ascending ramus and portions of the mandibular body results from delay in the development of the mandibular precursor. The severe forms are frequently associated with asymmetry of the face hemifacial microsomia. As the name of this disorder implies, it is usually a unilateral defect. However, 20% to 30% of cases are bilateral and often go undetected if the hypoplasia is mild, unless asymmetry with more severe involvement on one side occurs. Hemifacial microsomia can involve developmental disturbance of the maxilla, nose, orbit, zygomatic, and external auditory meatus, as well as the mandible. The affected side of the mandible becomes progessively distorted as the normal side grows, restricting the vertical growth of the maxilla on that side. This can decrease the distance between the orbital floor and the alveolus and cause the zygomatic to be hypoplastic (Kaban, Mulliken, and Murray 1981; Stewart and Poole 1982).
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Fig. 4.13 Cleft mandible resulting from developmental delay. a: complete cleft; b: minor cleft, indentation with diastema.
Type I hemifacial microsomia is the mildest form of this disorder, resulting in mild hypoplasia of one or both sides of the mandible (Fig. 4.14b) and temporomandibular joints. This does not allow the posterior teeth of the affected mandibular half to occlude normally with the upper teeth. Facial nerve palsy may be present, because the seventh nerve is affected (Bixler and Christian 1971; Caldarelli et al. 1980; Kaban, Mulliken, and Murray 1981). Type II hemifacial microsomia involves a greater degree of mandibular hypoplasia. The ramus is small and abnormally shaped (Fig. 4.14c), with an underdeveloped temporomandibular joint. The mandibular arch is narrow and nonoccluding on the affected side (Bixler and Christian 1971; Caldarelli et al. 1980; Kaban, Mulliken, and Murray 1981).
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Type III hemifacial microsomia signifies aplasia of one half of the mandibular anlage (Fig. 4.14d). The ramus and temporomandibular joint are absent (Bixler and Christian 1971; Caldarelli et al. 1980; Kaban, Mulliken, and Murray 1981). A hypoplastic mandible is sometimes associated with other developmental defects such as Pierre Robin syndrome (Bixler and Christian 1971; Kaban, Mulliken, and Murray 1981; Shafner, Hine, and Levy 1983). Gregg and Gregg (1987:143144) described a case of unilateral mandibular hypoplasia in their study of the pathology of the Upper Missouri River Basin skeletal series. The affected male adult mandible from the proto-Arikara Crow Creek collection appears to have a type II hemifacial microsomia, affecting the left side. An adult female (NMNH 242146) from California in the Smithsonian's National Museum of Natural History skeletal collections is a good example of type II hemifacial microsomia (Fig. 4.15). The left half of the mandible is affected, with a narrow ramus and slight asymmetry of the face. The right side is normal. Anderson (1989) reported a one-year-old Pueblo IV child from Homol'ovi in northern Arizona with marked asymmetry of the mandible and palate. This can be classified as hemifacial microsomia type I. One adult female (NMNH 308754) from Hawikku (Pueblo IV-V Zuni) has a mild unilateral left side type I hypoplasia, with severe temporomandibular joint dysfunction. Bilateral hypoplasia of the mandibular condyles with short rami in a twenty-year-old medieval Polish male is described by Alexandersen, Szlachetko, and Wiecinska (1979). This appears to be a type I bilaterally symmetrical facial microsomia. 2. Bifid (Double-Headed) Condyles The mandibular condyle is formed from secondary cartilage that extends from the mandibular head into a narrow portion of the ramus. All but the proximal end is infiltrated by membranous ossification extending up into the ramus during fetal life. The proximal end remains cartilaginous to ensure growth of the condyles. Well-vascularized partitions (septa) are programmed to extend into the growing cartilage from the overlying fibrous articular tissue by the twentieth fetal week. The fibrous tissue septa increase in number within the growing cartilage until the head of the condyles form by the nineteenth month after birth. They act as scaffolding for the calcifying cartilage, and once the head of the condyle is formed, they recede. Retention of one or more of
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Fig. 4.14 Variations of mandibular hypoplasia-aplasia associated with hemifacial microsomia. a: normal mandible; b: type I, mild hypoplasia (can be bilateral); c: type II, abnormally shaped ramus; d: type III, aplasia of the ramus.
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Fig. 4.15 Unilateral mandibular hypoplasia associated with type II hemifacial microsomia. Adult female (NMNH 242146) from California. A: right side normal. B: left side deformed from hypoplasia; slight asymmetry of the face and agenesis of left squamosal suture present in the cranium.
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these fibrous septa beyond the time they should regress results in a bifurcation of the head of the mandibular condyle (Blackwood 1957; Moffett 1966). Postnatal development of bifurcated mandibular condyles can occur with injury. Trauma to the condylar heads in the postnatal period can interfere with normal vascularization and ossification in the growing cartilage and produce bifurcated condyles (Blackwood 1957; McCormick et al. 1989). The bifid condyles associated with injury are oriented anteroposteriorly, whereas those resulting from developmental defect are positioned mediolaterally (Szentpetery, Kocsis, and Marcsik 1990). Bifurcated condyles associated with injury have only been recorded in a few clinical cases. Bifid condyles can appear as two complete, distinct articular facets separated by a depression or groove or as partially separated double condylar heads. Bifid condyles will have corresponding bifid articular grooves in the temporal joint space. Bilateral expression is rare, and it is found more often in females than in males. Bifid condyles are generally asymptomatic, but with age they can lead to temporomandibular joint dysfunction (Blackwood 1957; McCormick et al. 1989). Bifid condyles resulting from developmental defect were first reported by Hrdlicka (1941). He described twenty-one cases of complete and partial bifurcation among the National Museum of Natural History skeletal collections (Fig. 4.16). Only three of these cases were bilateral. Twenty-nine additional cases have been reported since Hrdlicka's discovery; nineteen of these were clinical cases, and four were bilateral (McCormick et al. 1989; Szentpetery, Kocsis, and Marcsik 1990). Hrdlicka's (1941) sample included six Caucasians, three Eskimo, two Kodiak Islanders, four North American Indians, three Peruvians, two Chinese, and one Mongol. One of the North American Indians was an adult female (NMNH 239457) from Heshotauthla (Pueblo IV Zuni). The right condyle has two distinct articulations with corresponding bifid articular depressions in the temporal bone. The height and width of the right ramus are smaller than on the left side, and dental wear is uneven and more pronounced on the right side (Fig. 4.17). Partially bifurcated condyles were identified in one Iron Age mandible, one seventheighth-century (Avar period) mandible (both sides), and four mandibles from the eleventh-thirteenth centuries (Arpadian Age) in Hungary (Szentpetery, Kocsis, and Marcsik 1990). Gregg and Gregg (1987:136) mentioned three cases of bifid mandibular condyles in their report on the pathology of the Upper Missouri River Basin skeletal series.
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Fig. 4.16 Variations of bifid (double) mandibular condyles from Hrdlicka (1941).
3. Developmental Excess: Hyperplasia Hyperplasia of any part of the mandible can be stimulated by injury or infection. Hyperplasia caused by developmental disturbances is rare. a. Condylar Hyperplasia Excessive chondrification of the condyles can extend into the condylar neck within the boundaries of the secondary cartilage, producing a larger than normal condyle. This may be caused by morphogenetic disturbance within the precursor of the condylar cartilage. Condylar hyperplasia is generally unilateral, leading to an asymmetrical mandible (Bruce and Hayward 1968).
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Fig. 4.17 Unilateral bifid mandibular condyle from Heshotauthla, New Mexico. Mandible of adult female (NMNH 239457) with only the left side affected. A: comparison of left and right condyles, anterior view. B: dorsal view of condyles. C: lateral view of rami and condyles; D: mandibular fossae on temporal bones of skull; right side has double impressions, whereas left side is singular.
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Fig. 4.18 Hyperplasia of the coronoid processes. a: normal; b: abnormally large, usually bilateral and familial (from Schultz and Theisen 1989).
b. Coronoid Hyperplasia This rare defect usually develops bilaterally and prevents the mandible from fully opening, because the coronoid processes impinge upon the posterior aspects of the zygomatic bones. The coronoid processes progressively elongate (Fig. 4.18) until they limit opening of the mouth during adolescence. The majority of cases reported have occurred in males, and there appears to be a familial tendency, supporting a genetic etiology (Schultz and Theisen 1989).
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Fig. 4.19 Solitary developmental cyst (Stafne defect) in the mandible from developmental delay defect of the mucosa. Inner aspect of left side of mandible of adult male (NMNH 271851) from Amoxiumqua, New Mexico; right side missing.
4. Devlopmental Inclusion Cyst (Stafne Defect) The sublingual salivary gland can develop prematurely within the region of the submandibular fossa of the embryonic mandible. This can create a deep cavity within the developing mandibular structure, progressively enlarging as the gland enlarges (Stafne 1969). The defect generally appears as a shallow, oval depression with a corrugated floor (Figs. 4.19 and 4.23a). It is found below the mylohyoid line near the inferior border of the posterior region of the mandible, generally in the region of the third molar, or retromolar region. Some cases are known to appear past middle age, indicating that not all of these defects are morphogenetic developmental defects (Stafne 1969). Finnegan and Marcisk (1980) found a high frequency of this defect in Plains Archaic and Middle Mississippian skeletal populations. Ten cases were found among 295 mandibles from the Arar period in Hungary, and ten additional cases were identified from fifteen different populations in the skeletal collections at the Smithsonian's National Museum of Natural History
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Males outnumbered females, as is true in clinical cases as well. The left side of the mandible was affected more than the right side. The defect had an average range of 6.87 mm to 10.09 mm in diameter. Some defects were found in the region of the second molar, to an area below the second premolar (Finnegan and Marcsik 1980). One of the cases of developmental inclusion cyst of the mandible in the Smithsonian's National Museum of Natural History skeletal collections comes from an adult male (NMNH 271851) from Amoxiumqua (Pueblo IV Towa). The oval lesion is 14 mm by 5.5 mm, situated along the inferior border below the second and third molars of the left side of the mandible (Fig. 4.19). B. Field Defects of the Maxilla Development of the maxilla is more complex. It depends upon the emerging premaxilla and nasal portions of the frontonasal process. As modeling of the face takes place between the fifth and eighth weeks, with the merging of the frontonasal prominences and the lateral maxillary processes, the various parts of the upper jaw take form. Proliferating mesenchymal cells unite the maxillary processes with the lateral nasal prominences and the median nasal prominences (premaxilla) as they come into contact with each other. Ridges form along the inferior borders of the maxillary processes and project vertically downward alongside the developing tongue that lies in the back part of the nasal area. As these ridges develop into the palatal processes, the tongue and the floor of the mouth descend, allowing the palatal processes to quickly assume a horizontal position, grow toward each other, and unite. This closes off the oral cavity from the nasal cavities. Ossification for each maxillary process proceeds from a center above the canine fossa begining during the sixth embryonic week (Arey 1965; Fraser 1963; Williams et al. 1989). 1. Developmental Delay a. Cleft Palate Developmental delay in the descent of the primitive tongue from the nasal region slows the change in direction of the palatal processes (Fig. 4.20). This upsets the timing of their development and their approach to one another. Hypoplasia or aplasia of one or both sides can result, and fusion is abnormal. This can cause a defect ranging from a minor cleft (dorsal notch)
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Fig. 4.20 Normal development of the palate. A: sixth embryonic week. B: seven to eight embryonic weeks. C: palate at ninth embryonic week. D: newborn palate. 1: palatal process; 2: maxillary process; 3: premaxilla; 4: uvula (redrawn from Arey 1965).
in the posterior edge of the palate (Fig. 4.21b) to a large, U-shaped cleft resulting from aplasia of both palatal processes (Fig. 4.21d). The affected palate is usually shorter and broader than normal. Cleft palate occurs more frequently in females than in males (Fraser 1980; Gorlin, Cervenka, Pruzansky 1971; Shafner, Hine, and Levy 1983). Because fusion begins at the ventral edges of the two palatal processes as they merge with the premaxilla and nasal septum of the frontonasal
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Fig. 4.21 Variations of cleft palate resulting from developmental delay of the palatal processes of the maxilla. a: normal; b: bilateral dorsal notch; c: bilateral partial clef; d: bilateral full cleft (vomer not attached); e: unilateral dorsal notch; f: unilateral partial cleft; g: unilateral full cleft.
prominence, the time lag primarily interferes with fusion directed toward the dorsal edge. The extent of the clefting depends upon the timing of the developmental delay and whether both palatal processes (bilateral) or only one (unilateral) is affected (Fig. 4.21). The most severe form of cleft palate happens when both palatal processes are absent (Fig. 4.21d) because of a long delay in development. The resulting wide bilateral cleft leaves a small palatal rim at the base of the alveolar ridge on both sides, up to the premaxillary border. Bilateral hypoplasia allows
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some development of the palate, creating a symmetrical cleft of varying size (Fig. 4.21), depending upon the amount of developmental delay. Bilateral clefting does not allow either palatal plate to unite properly with the vomer (Fraser 1980; Gorlin, Cervenka, Pruzansky 1971; Shafner, Hine, and Levy 1983; Williams et al. 1989). The most common form of cleft palate results from unilateral hypoplasia or aplasia of one palatal process (Fig. 4.21 e-g). Only one side of the palate is affected. The cleft appears asymmetrical and varies in size, depending upon the amount of delay in development. Unilateral cleft palate leaves one side united with the vomer (Fraser 1980; Gorlin, Cervenka, Pruzansky 1971; Shafner, Hine, and Levy 1983; Williams et al. 1989). The smaller bony clefts (dorsal notches) result from mild delays in development and fusion. The dorsal notch can be asymmetrical from unilateral developmental delay (Fig. 4.21e) or symmetrical from bilateral developmental delay (Fig. 4.21b). It is usually hidden by mucosa as ectoderm continues to develop toward completion, forming what is known as a submucous cleft palate. Middle ear infections are frequently found in a high percentage of cases with submucous cleft palate, with substantial hearing loss if left untreated (Thaler and Smith 1968). Infants born with open cleft palate are not able to suckle well, and part of the feeding may be expelled through the nose. The cleft interferes with normal breathing, and these infants are very susceptible to upper respiratory infections. Speech develops in a guttural tone. Mild delay in development of the palate can interfere with the normal development of the uvula the small, soft tissue mass extending from the palate leading to an unusually broad or bifid structure. This is considered a microform of cleft palate (Burdi and Faist 1967; Shapiro et al. 1971; Thaler and Smith 1968). Some populations tend to have a high frequency of cleft uvula and a coexisting low frequency of cleft palate. This is found in Navajo and Chippewa Indians and some Inuit (Gorlin, Cervenka, Pruzansky 1971; Jaffe and DeBlanc 1970; Jarvis and Gorlin 1972; Lowry and Renwick 1969; Shapiro et al. 1971). Other Inuit populations have extremely low frequencies of cleft uvula and cleft palate (Heathcote 1974), suggesting that cleft uvula follows a more familial trend than an overall population trend. The amount of developmental delay of the palatal processes is held to the minimum in some family lineages and is expressed as cleft uvula. The frequency of cleft palate varies less among population groups than does the frequency of cleft lip, which is a completely different entity developing
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from disturbance associated with another morphogenetic field, the frontonasal process. Cleft palate appears to be a multifactorial response, with strong genetic involvement that seems to vary among family groups more than among population groups (Leck 1984), similar to cleft uvula. Cleft palate tends to appear more frequently in females than in males. Five isolated family groups have been identified with an X-linked form of cleft palate four Caucasian families from Iceland, Denmark, and the United States, and one North American Indian family from British Columbia (Bjornsson, Anason, and Tippet 1989; Lowry 1971). Ferguson (1978) has made a plea to paleopathologists to watch for the less conspicuous signs of cleft palate in the form of dorsal notching associated with submucous clefting. This minor form of cleft palate should be fairly easy to see in prehistoric palates that are free of damage, and it should provide significant data for the incidence of cleft palate. Despite his appeal, reports of dorsal notching of the palate have not appeared in the subsequent paleopathology literature. Cleft palate appears to have been an uncommon phenomenon in prehistoric populations, according to the paucity of reports in the paleopathology literature. Ferguson (1978) claimed to have identified about twenty cases from Europe and North America. Sandison (1980) reported two cases of cleft palate in Australian Aborigine skeletal material. Alexandersen (1967) mentioned some cases of cleft palate from reports and included an illustration of a cleft palate in an adult female Eskimo in his review. Brothwell (1981:170) described a cleft palate in a Saxon child from Burwell, Cambridgeshire, England. MacCurdy (1923:272; plate XIV) discovered a small cleft in a very broad palate of an adult male from Huispang in the highlands of Peru near Cuzco. Ortner and Putschar (1985:348351) identified a large, bilateral cleft palate in an adult female from the Nubian skeletal collection located in the British Museum of Natural History. They identified another large, bilateral cleft palate in an incomplete adult male cranium (NMNH 243208), with aplasia of the vomer and conchae, from an archaeological site in Kentucky (Fig. 4.22). There is hypoplasia of the left premaxilla, with distortion of the left nares, and the left central and lateral incisors never developed. 2. Developmental Fissural (Inclusion) Cysts The development of the ectodermal tissue overlying the mesenchymal palatal processes and premaxilla parallels their development. As the underlying mesenchymal tissues approach each other at the shallow ectodermal
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Fig. 4.22 Bilateral cleft palate from Kentucky. Cranium and palate of adult male (NMNH 243208); also has unilateral hypoplasia, left side, of the premaxilla, creating asymmetry of the nares and congenital absence of the left central and left lateral incisors; the vomer and conchae are also absent.
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Fig. 4.23 Developmental cysts of the mandibular and maxillary mucosa. a: solitary Stafne defect of the mandible; b: median anterior maxillary fissural (inclusion) cyst; c: median palatal fissural (inclusion) cyst; d: globulomaxillary fissural (inclusion) cyst.
grooves that separate them, the overlying ectodermal tissue is retracted. Delay in this retraction can lead to entrapment of epithelial tissue in the grooves between any of these structures as they unite. This leads to the formation of a true cyst, lined with epithelium and containing fluid or a semisolid substance (Little and Jakobsen 1973; Patten 1961; Shafner, Hine, and Levy 1983; Stafne 1969). a. Median Anterior Maxillary Cyst The most common type of maxillary developmental cyst, the median anterior maxillary cyst, occurs in or near the incisive canal. This cyst forms when epithelial tissue is caught between the palatal processes and the premaxilla as they unite. It usually localizes in the midline as a rounded or oval-shaped cavity overlapping the palatal halves on both sides (Fig. 4.23b). It sometimes
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extends to just one side, developing out of one of the major lateral canals within the incisive canal. More than one cyst can develop as epithelial tissue is trapped between the various canals that can be found in the incisive canal. They are generally limited in size and remain asymptomatic, but occasionally they can expand upward (Shafner, Hine, Levy 1983; Stafne 1969). b. Median Palatal Cyst A less common maxillary developmental cyst, the median palatal cyst, arises from epithelial tissue trapped between the two palatal processes as they come together and fuse. They usually localize midline opposite the retromolar-molar region (Fig. 4.23c) and frequently display a sclerotic border (Shafner, Hine, and Levy 1983). c. Globulomaxillary Cyst Another type of maxillary developmental cyst, known as the globulomaxillary type, occurs at the lateral junction of the premaxilla and maxilla, usually between the lateral incisor and canine (Fig. 4.23d). This defect extends down into the crest of the alveolus, where it may cause the tooth roots to diverge. There is some doubt concerning the proper origin of this cyst. It may not be caused by the entrapment of epithelial tissue, but instead it may be derived from later odontogenic tissue (Little and Jakobsen 1973; Shafner, Hine, and Levy 1983; Stafne 1969). Gregg and associates (1983) believe the maxillary developmental cysts are ''abortive" forms of facial clefting. They also feel the presence of the fissural cysts in a prehistoric population indicates the presence of facial clefting in the form of cleft lip and palate. Their view is based on the similarities in development and anatomy. From a morphogenetic standpoint, maxillary fissural cysts and facial clefting appear to be two different kinds of events. Cleft lip with or without secondary cleft palate results from failure of the premaxilla and maxilla anlages to merge or the precursors of the premaxilla halves to merge on time. Maxillary developmental fissural cysts evolve when epithelial cells from the overlying ectodermal tissue of the palate fail to retreat ahead of the underlying mesodermal components as they merge within the ectodermal grooves. Gregg and Gregg (1987) report several cases of maxillary developmental cysts in the Upper Missouri River Basin series of over four thousand proto-Arikara skeletons. Over 50% (N = 147) of the cases involve the most common type the median anterior maxillary fissural cyst followed by globulomaxillary
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fissural cysts (N = 46), and the less common type, the median palatine fissural cyst (N = 20). One adult female (NMNH 271914) from Amoxiumqua (Pueblo IV Towa) has an oval median anterior fissural cyst involving the left side of the incisive canal. The border is smooth and even, with a sclerotic edge. Summary Outline: Branchial Arch I Field Defects A.Mandible 1. Cleft mandible a.complete separation of mandibular halves incomplete (mild expression) indentation or cleft between central b. incisors with dental diastema 2.Hypoplasia-aplasia usually associated with hemifacial microsomia type I mild hypoplasia, abnormally small ascending ramus, a. unilateral or bilateral type II severe hypoplasia; small, abnormally shaped ascending b.ramus; narrow mandibular arch with nonocclusion; hypoplastic temporomandibular joint; usually unilateral type III aplasia, absent ascending ramus and temporomandibular c. joint; usually unilateral Bifid (double-headed) condyles mediolateral with bifid 3. temporomandibular joint; usually unilateral a.bifid heads completely separated b.bifid heads not separated 4.Developmental excess hyperplasia a.condylar enlarged condylar head, usually unilateral coronoid process bilateral progressive enlargement; by b.adolescence impinges upon zygomatics, limiting opening of mouth; familial Developmental inclusion cyst (Stafne defect) oval depression with corrugated floor, below mylohoid line near inferior border of 5. posterior region, generally located below third molar or retromolar region B.Maxilla 1.Cleft palate mild hypoplasia unilateral or bilateral dorsal notch (submucous a. cleft)
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unilateral severe hypoplasia or aplasia asymmetrical or unilateral b.cleft, unaffected side attached to vomer bilateral severe hypoplasia or aplasia complete cleft, vomer not c. attached to palate 2.Developmental fissural (inclusion) cysts median anterior maxillary cyst rounded or oval, single or more, in or a. near incisive canal, usually midline median palatal cyst rounded or oval, midline, usually opposite b. molar-retromolar region globulomaxillary cyst rounded, oval, or irregular; usually between c. lateral incisor and canine, extending into alveolar crest at junction of premaxilla Part IV. Blastemal Frontonasal Process Field Defects The blastemal frontonasal process forms from the ventral swelling of the cranial end of the developing embryo. Axial skeletal tissues produced by the frontonasal mesenchyme include the nasal bones, premaxilla, perpendicular plates of the ethmoid, vomer, lacrimals, and frontal process of the maxilla. Hypoplasia or aplasia of any of the blastemal precursors of these bony elements will result in defect. A. Facial Clefts The midface region develops from the frontonasal process as its median and lateral prominences develop and grow toward each other, uniting with each other and with the maxillary prominences (Fig. 4.24). Ectodermal tissue overlies all of the developing mesenchymal midfacial prominences, including the maxillary prominences. Grooves form in this ectodermal tissue between the midfacial prominences and the maxillary prominences as they are growing toward one another. When the prominences encounter the grooves, their mesenchymal tissue penetrates the ectodermal grooves and unites the prominences. Should the mesenchyme fail to penetrate the ectodermal grooves at the critical threshold time of union, the parts involved will not unite properly. The groove is maintained, and a facial cleft results (Burdi, Lawton, and
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Fig. 4.24 Developmental components of the face. A: embryonic face at seven weeks. B: adult cranium. a: maxillary prominence of branchial arch I; b: lateral nasal prominence of blastemal frontonasal process; c: median nasal prominence of the blastemal frontonasal process.
Grosslight 1988; Mladlick et al. 1974; Monasterio, Fuente del Campo, and Dimopulos 1987; Shafner, Hine and Levy 1983; Williams et al. 1989). Developmental delay of one or more of the prominences prevents the mesenchymal invasion into the ectodermal groove(s) at the appropriate time (Burdi, Lawton, and Grosslight 1988; Noden 1986). This leaves a hypoplastic or aplastic part trying to meet an opposing part on time in order to fuse properly. The resulting cleft formation reflects the degree of developmental delay of the affected part. Thus the cleft formation can be unilateral or bilateral, symmetrical or asymmetrical, complete or incomplete. Severe forms of facial clefting are often associated with polytropic developmental defects known clinically as syndromes (DeMyer 1967). Severe facial clefting between the inferior nasal border and the eye orbit generally
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involves malformation of the brain and is therefore incompatible with life outside the uterus. Milder forms of clefting in this region often do not involve brain malformation, and neonates are thus viable, often reaching adulthood with only minor problems (Mladick et al. 1974). 1. Nasomaxillary Cleft Facial clefting resulting from failure of the maxillary prominence(s) and the lateral nasal prominence(s) to unite is very rare. The underlying cause is bilateral or unilateral hypoplasia or aplasia of the lateral or maxillary prominences, producing a nasomaxillary cleft (Fig. 4.25a). The cleft formation follows the border between the maxillary and lateral nasal prominences, from the oral cavity to the eye orbit. The direction of the cleft depends upon the developmental disturbance of the affected parts (Mladick et al. 1974). 2. Naso-Ocular Cleft The naso-ocular groove separates the lateral nasal prominence from the median nasal prominence as they approach each other. Normally, this groove becomes the nasolacrimal duct, but it remains open when the two prominences fail to unite properly. Developmental delay of the lateral nasal prominence causes the affected part to be hypoplastic or aplastic, creating a cleft formation between the eye orbit and the oral cavity (Fig. 4.25b). The median nasal prominence generally develops normally, producing normal nares and premaxilla. Sometimes the median nasal prominence is hypoplastic, and the premaxilla is small. This produces a bilateral cleft from the oral cavity to the inner aspect of the eye orbit (Mladick et al. 1974). 3. Median Cleft Median facial clefting, resulting from developmental delay of the two halves of the median nasal prominence, affects the final location of the eye orbits. Failure of these two halves to coalesce can be so severe as to threaten life, or it can be very mild, with little to moderate deformity (DeMyer 1967). Aplasia of the median nasal prominence brings the eye orbits too close together (hypotelorism), and there is generally severe brain malformation as well, with poor chance for survival. The nasal bones, vomer, perpendicular plates of the ethmoid, and premaxilla are absent (Mladick et al. 1974).
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Fig. 4.25 Variations of facial clefting resulting from developmental delay defects involving the frontonasal process. A: embryonic face at seven weeks. B: newborn face. a: nasomaxillary facial cleft; b: naso-ocular facial cleft; c: median facial cleft with hypertelorism; d: bilateral cleft lip; e: unilateral cleft lip; f: midline cleft lip.
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Hypoplasia of one or both parts of the median nasal prominence may not allow them to come together and unite at the proper time, leaving a wide gap between them (Fig. 4.25c). This prevents the eye orbits from coming together at a normal distance (hypertelorism). In mild cases the nares are widely spaced and flat, with a broad nasal root. The nasal bones attach at unusual angles, and there may be notching of the alae. The frontal sinuses are atypical or absent, the vomer and perpendicular plates of the ethmoid may be hypoplastic, and the premaxillary alveolus may be notched or cleft. Most of the individuals with mild forms of medial nasal clefting do not suffer from brain malformation and have normal mentalities (Goodman and Gorlin 1983; Mladick et al. 1974). It is interesting that the clinical picture of the face presented by these individuals strongly resembles a feline motif. The broad, flat nose and wide-set eyes give the impression of a cat's face (Fig. 4.26), which could have had an affect on prehistoric peoples who revered feline deities or spirits. It is fairly easy to imagine individuals suffering from this developmental defect of the face being called "cat people." 4. Bilateral/Unilateral Cleft Lip Cleft lip is the most common type of facial clefting. It is also the second most common severe developmental defect in humans and in all other mammals (Fraser 1963). Cleft lip develops when one or both of the maxillary prominences fail to unite with the premaxillary prominence (Fig. 4.25d and e). One or both of the maxillary prominences are delayed in arrival at the ectodermal groove(s) separating them from the premaxillary prominence. The maxillary prominence(s) does not get there at the critical threshold time for release of mesenchymal tissue into the groove for union with the premaxilla. Sometimes only part of the maxillary prominence is tardy, which leads to partial fusion and a variety of forms of cleft lip. Unilateral clefting (Fig. 4.25e) is much more common (80%) than bilateral clefting (Fig. 4.25d), and cleft lip is more common in males than in females (Bixler 1981; Fraser 1970; Gorlin, Cervenka, and Pruzansky 1971; Sayetta et al. 1989). Unilateral clefting occurs more often on the left side than on the right side (Goodman and Gorlin 1983). The more severe the clefting between the maxilla and the premaxilla (particularly with bilateral clefting), the more likely it is for there to be a secondary cleft in the palate as well (Fig. 4.27a-c). The delay in fusion between the maxillary prominence(s) and the premaxillary prominence interferes with the timing of the fusion of the maxillary palatal plates. The maxillary prominence
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Fig. 4.26 Median cleft face with hypertelorism. a: face with "catlike" appearance, broad nose; b: nasal bones attached at odd angles; c: hypoplastic perpendicular plates and vomer; d: notched premaxilla.
normally unites with the premaxillary prominence before its palatal processes unite. Mild clefting at the maxilla-premaxilla border does not generally interfere with the later fusion of the palatal processes, but greater clefting at that border does interfere with the later fusion of those processes. Various forms of cleft palate can result, depending upon the degree of cleft lip. With bilateral cleft lip, the premaxilla becomes rounded, almost balllike, because it is pushed forward by the unrestricted growth of the attached vomer (Fraser 1963; Mladlick et al. 1974). The expression of cleft lip varies from a complete gap between the nostril and the oral cavity to a simple cleft hidden by soft tissue in the alveolar ridge between the canine and lateral incisor teeth, the boundary between the
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Fig. 4.27 Variations of cleft palate secondary to cleft lip. a: unilateral small fissure cleft lip and palate; b: unilateral cleft lip and palate; c: bilateral cleft lip and palate; d: midline cleft lip and palate with agenesis of right central incisor; e: small fissure midline cleft lip and palate.
maxilla and premaxilla (Fraser 1963). The type of expression depends upon the degree of the developmental delay. The upper incisors are contained within the premaxilla. The border between the premaxilla and maxilla lies between the lateral incisor and canine. The dental precursors of the lateral incisors are prone to disturbances when fusion between the premaxilla and maxilla is upset. Defects of the lateral incisors are common. The teeth can be rotated, misplaced, hypoplastic, peg-shaped, or absent; or they may remain unerupted, with retention of the deciduous teeth. Supernumery lateral incisors can develop, remaining imbedded in bone or erupting in the floor of the nares (Cosman and Crikelair 1966; Gorlin, Cervenka, and Pruzansky 1971; Mills et al. 1968; Stafne 1969). Cleft lip, with or without secondary formation of cleft palate, can occur alone or with other field defects as part of a syndrome (Goodman and Gorlin 1983; Gorlin, Cervenka, and Pruzansky 1971). The genetics behind cleft lip
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are complex and variable, and they form part of a multifactorial response (Fraser 1970). Metabolic disorders, such as the inability to metabolize folic acid, may predispose a developing embryo to manifest a cleft defect (McComb 1989). Nutritional deficiency, starvation, excessive amounts of vitamin A, and oxygen deficiency have all been explored as possible environmental factors that interact with a susceptible genetic background to produce clefting (Fraser 1963). Significant seasonal peaks in the occurrence of cleft lip high in December and January, low in May and June may reflect seasonal nutritional deficiencies (Coupland, Orth, and Coupland 1988). Infants born with a major cleft lip, with or without cleft palate, suffer from overt facial disfigurement as well as feeding, breathing, and, later, speech problems. They cannot create a sufficient vacuum in the mouth to suckle properly. They are highly susceptible to upper respiratory problems and middle ear infections leading to loss of hearing. Minor expressions of small alveolar clefts or fissures hidden by soft tissue, along with dental defects, are far less threatening. The frequency of cleft lip, with or without secondary cleft palate formation, varies among population groups. American Indians have the highest frequency, followed by Asians. Blacks have the lowest frequency. The frequency for Caucasians falls between those of Blacks and Asians (Fraser 1970; Gorlin, Cervenka, and Pruzansky 1971; Marazita et al. 1986; Niswander and Adams 1967; Sayetta et al. 1989; Vanderas 1987). Because a high frequency of cleft lip (with or without secondary cleft palate formation) tends to be associated with a lower frequency of cleft palate (Lowry and Renwick 1969), the two defects almost certainly represent different entities (Fraser 1970), developing in different morphogenetic fields from different causes. Cleft lip, with or without associated cleft palate, is uncommon in prehistoric skeletal material, according to reports in the literature. This defect, as with so many other defects, may be difficult to identify, because the bones involved are often damaged because of the fragility of the osseous material containing the defect. Two very astute researchers, Brooks and Hohenthal (1963), were able to identify three cases of cleft lip-cleft palate in badly damaged crania from two prehistoric California sites. All three individuals are adults, two females and one male. The adult male appears to have a unilateral cleft lip and associated cleft palate. One of the females has a bilateral cleft lip, probably with an associated cleft palate. The other female, from a different site, has a unilateral cleft lip only.
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Fig. 4.28 Unilateral cleft lip and palate from Nazca, Peru. Face and palate of child (NMNH 293252), eight to ten years of age, with the left side and palate affected; the left central and left lateral incisors are congenitally absent, and the left conchae are absent; the incisive canal is present on the unaffected right side, and the vomer is attached to the unaffected right side.
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Ortner and Putschar (1985) identified a large, unilateral cleft lip and palate in the cranium of a South Pacific Islander (Wellcombe Museum, London). The left side of the premaxilla and palate is affected. They describe another unilateral cleft lip and palate in the cranium of an eight- to ten-year-old child (NMNH 293252) from Nazca on the south coast of Peru (Fig. 4.28). The left side of the premaxilla and palate is affected, and the left central and lateral incisors never developed. 5. Midline Cleft Lip On occasion, the two halves of the premaxillary prominence fail to coalesce properly because of developmental delay in one or both halves. This can cause hypoplasa or aplasia in one or both parts, and a midline cleft can develop (Fig. 4.25f). Hypoplasia is more common than aplasia and generally produces a midline cleft that is quite small (Burdi and Faist 1967; Shafner, Hine, and Levy 1983; Stafne 1969). The two halves border between the central incisors. Failure of the premaxillae to unite affects the development of the central incisors, and disunity sometimes affects the lateral incisors. The central incisors may be absent, rotated, misplaced, hypoplastic, or malformed. Sometimes the palatal plates are also affected, disturbed by the delay in the cohesion of the premaxillae, and a secondary cleft palate evolves (Fig. 4.27d and e). Minute forms of midline cleft lip may be represented by an indentation or notch in the alveolar space between the central incisors (Fig. 4.27e). Infants born with severe midline cleft lip have similar cosmetic, feeding, breathing, and speech problems as those born with bilateral/unilateral cleft lip. However, minor degrees of this defect are less noticeable and cause fewer problems. Prehistoric examples of midline cleft lip are uncommon. Sandison (1980) described a ''hare-lip and cleft palate" in a twelve-year-old Australian Aborigine from the MurrayBlack collection. The photograph in his report shows an obvious midline cleft derived from hypoplasia of the premaxilla, predominantly on the right side. A midline cleft lip caused by total aplasia of the premaxilla was noted by Derry (1938) in an adult female found in a grave south of Assiut, Egypt, and dating to the twenty-fifth dynasty (700 B.C.). Derry described a different case with a similar defect in another Egyptian female cranium of unknown provenance. The upper incisors are obviously absent, with a missing premaxilla, and the palate appears to be very short. The missing premaxilla leaves a wide cleft from the nares to the canine teeth.
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Fig. 4.29 Unilateral hypoplasia of the premaxilla with mild midline cleft lip and associated unilateral cleft palate from southwestern Colorado. Face and palate of young adult female (NMNH 316482) from unknown Puebloan site; right side of premaxilla and palate affected; congenital absence of both central incisors and right lateral incisor, and vomer attached to unaffected left side of palate; conchae missing.
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Fig. 4.30 Unilateral hypoplasia of the premaxilla, creating cleft nares and associated unilateral cleft palate, from Pachacamac, Peru. Face and palate of adult male (NMNH 266052) with left side of premaxilla and palate affected; incisive canal present on unaffected right side of palate, vomer attached to unaffected side, and all incisors and conchae present.
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Ortner and Putschar (1985) described a prehistoric eighteen- to twenty-year-old female cranium (NMNH 316482) from an unknown archaeological site in southwestern Colorado (probably Anasazi) with a cleft lip and palate. The right premaxilla is hypoplastic, and the palate is cleft by hypoplasia on the right side. The central and right lateral incisors never formed, and the alveolar ridge where they should have been located is marked by a thin sheet of bone and a small midline cleft that communicates with the cleft palate (Fig. 4.29). Hypoplasia of the left premaxilla, with an associated unilateral cleft palate on the left side, was noted in an adult male cranium (NMNH 266052) from Pachacamac, Peru, located in the Smithsonian's National Museum of Natural History. The defect in the premaxilla is most noticeable at the nasal border, which is much lower on the left side than on the right, giving the nares an uneven appearance (Fig. 4.30). The dentition of the premaxilla does not appear to have been disturbed, and there is no obvious cleft in the alveolar ridge. Berndorfer (1962) reported a hypoplastic premaxilla with a very narrow, incomplete cleft just right of the midline in an adult female from a five-hundred-year-old site in southern Hungary. The right side of the premaxilla is smaller than the left side, and the incisor teeth are absent, with only a thin alveolar ridge present. 6. Hypoplasia of the Median Nasal Prominence: Binder's Syndrome Binder's syndrome represents a mild hypoplasia of the median nasal prominence (Fig. 4.31). The glabella is flat, with a short, flat nose missing the anterior nasal spine. The frontal sinuses are hypoplastic, the nares are typically semilunar or crescent-shaped, and the premaxilla is smaller than normal. This makes the normally developed mandible appear prognathic. Sometimes there are associated cervical vertebral defects. This form of hypoplasia of the median nasal prominence appears to be fairly common, and there is some evidence for it being familial (Horswell et al. 1987). B. Nasal Bone Hypoplasia-Aplasia The nasal bones are products of the triangular area of the frontonasal process. They develop from mesenchyme after the triangular area grows downward and elevates to form the bridge and apex of the nose. Single centers
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Fig. 4.31 Mild hypoplasia of the median nasal prominence, producing midface hypoplasia (Binder's syndrome).
of ossification appear in the mesenchymal precursors for each nasal bone. Developmental delay of the anlages can result in hypoplasia or aplasia of the nasal bones. This can be unilateral or bilateral, symmetrical or asymmetrical (Fig. 4.32). Rudimentary or absent nasal bones are relatively common and are often associated with premaxillary hypoplasiaaplasia (Brothwell 1981; Wahby 19031905). Snow (1974) identified bilateral and unilateral aplasia, as well as hypoplasia of nasal bones, in several prehistoric Hawaiians. Two of these individuals were previously housed in the Smithsonian's National Museum of Natural History. One (NMNH 225468), an adult female, had aplasia of the
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Fig. 4.32 Variations of developmental delay defects of the nasal bones. a: unilateral hypoplasia; b: bilateral hypoplasia; c: unilateral aplasia; d: severe bilateral hypoplasia; e: bilateral aplasia.
right nasal bone and hypoplasia of the left nasal bone. There is also asymmetry of the nares due to mild hypoplasia of the left premaxilla (Fig. 4.33a). The other individual (NMNH 225465), an adult male, showed aplasia of the left nasal bone (Fig. 4.33b). C. Lacrimal Bone Hypoplasia-Aplasia The lacrimal bones are thought to arise from mesenchyme condensations out of the lateral nasal prominences, ossifying from single centers (Arey 1965). Hypoplasia or aplasia of the mesenchyme anlages can result in rudimentary or missing lacrimal bones, unilaterally or bilaterally. MacCurdy
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Fig. 4.33 Nasal bone hypoplasia and aplasia from Hawaii. A: face of adult female with unilateral (left) nasal bone hypoplasia. B: face of adult male with unilateral (left) nasal bone aplasia (both individuals have been repatriated).
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(1923:265) reported several incidences of aplasia of lacrimal bones in his analysis of prehistoric skeletal material from eight localities in the highlands northwest of Cuzco, Peru. Summary Outline: Blastemal Frontonasal Process Field Defects A.Facial clefts Nasomaxillary cleft nonunion of maxillary prominence and 1. lateral nasal prominence, from eye orbit to oral cavity Naso-ocular cleft nonunion between lateral nasal prominence 2.and medial nasal prominence along nasal groove, from eye orbit to oral cavity Median cleft nonunion of two halves of medial nasal 3. prominence aplasia of one or both parts brings eye orbits too close a. together (hypotelorism); lethal hypoplasia of one or both parts keeps eye orbits far apart (hypertelorism); mild form survives with eye orbits far apart, widely spaced flat nares with broad nasal root, nasal bones attached at unusual angles, nasal alae may be notched, b. frontal sinuses atypical or absent, vomer and perpendicular plates may be hypoplastic, notched or cleft premaxillary alveolus may be present, frequently associated with oxycephaly 4.Bilateral/unilateral cleft lip mild expression small fissure or notch between canine and a. lateral incisor (border between maxilla and premaxilla) severe expression complete cleft between canine and lateral b. incisor (maxilla and premaxilla fail to unite) c.associated defects (1) deviated nasal septum (2) disruption of nasal floor (3) dental disturbances of lateral incisor(s) (4) secondary cleft palate 5.Midline cleft palate mild expression small fissure, indentation, or notch between a. central incisors, with dental diastema (border between two halves of premaxilla)
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severe expression complete or incomplete midline cleft, usually small, symmetrical or asymmetrical (unilateral or b.bilateral hypoplasia or aplasia of the two halves of premaxilla) c.associated defects (1)deviated septum (2)disruption of nasal floor dental disturbances of central incisor(s) and sometimes (3) lateral incisor(s) (4)secondary cleft palate 6.Hypoplasia of the median nasal prominence Binder's syndrome flat, short glabella; absent anterior nasal a. spine; small frontal sinuses; semilunar or crescent-shaped nares; small, flat premaxilla; mandible appears prognathic Nasal bone hypoplasia-aplasia unilateral or bilateral, symmetrical B. or asymmetrical Lacrimal bone hypoplasia-aplasia unilateral or bilateral, C. symmetrical or asymmetrical Part V. Branchial Archiectodermal Groove Field Defects Developmental Delay of the External Auditory Meatus The outer ear opening, the external auditory meatus, is formed from the dorsal end of the ectodermal groove of the first branchial arch (Fig. 4.34) as it projects inward to form a funnel-shaped tube filled with a solid epidermal plug. The inner part of the meatus and the tympanic membrane are formed when the central cells of this plug break down (Williams et al. 1989). The branchial arch ectodermal grooves form when the external ectodermal tissue layer meets the developing internal endodermal pouches. As the ectodermal grooves of the first branchial arch disappear with continued growth, dorsal remnants of the grooves remain and form the external auditory meattus. Delay in the development of this portion of the groove can result in hypoplasia or aplasia and leads to complete or partial atresia (absence of the normal opening) of the external auditory meatus (Fig. 4.35). This can be found unilaterally or bilaterally. Usually, only one external auditory meatus is
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Fig. 4.34 Normal development of the external auditory meatus from the branchial arch I ectodermal groove. a: fifth embryonic week; b: seventh embryonic week (redrawn from Arey 1965); c: newborn.
affected, and the right side is affected more often than the left side. Sometimes one side may be absent and the other side hypoplastic (Hrdlicka 1933). This defect also affects the development of the tympanic plate that borders the inferior aspect of the external auditory meatus and, in turn, the styloid process that is positioned medially to the external auditory meatus within its tympanic sheath. When the external auditory meatus is completely absent, the tympanic plate does not develop from the closing membrane that normally separates the ectodermal groove from its counterpart, the endodermal pouch. The sheath for the styloid that forms from the tympanic plate cannot form, and the styloid process usually is missing or rudimentary. The petrotympanic (Glaserian) fissure, a narrow groove posterior to the mandibular fossa for the chorda tympani nerve, is usually distorted or missing.
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Fig. 4.35 Hypoplasia and aplasia of the external auditory meatus. a: partial atresia (hypoplasia of ectodermal groove); b: complete atresia (aplasia of ectodermal groove).
The petrous portion of the temporal may be smaller than normal (Hrdlicka 1933). The inner part of the meatus, the inner ear canal, is also affected by delay in the development of the dorsal end of the ectodermal groove of the first branchial arch. With aplasia, the external auditory meatus fails to develop and, consequently, so does the inner part of the meatus. There is no communication with the tympanic cavity. Hypoplasia of the external auditory meatus extends into the inner part of the meatus and creates a shortened inner ear canal that may or may not reach the tympanic cavity, depending upon the severity of the disturbance. Partial or complete hearing disability will result. Developmental delay of the external auditory meatus, with resulting hypoplasia or aplasia, can affect the timing of the development of the auricle (external ear). The auricle is derived from six hillocks of tissue that appear during the sixth embryonic week and that form around the dorsal end of the ectodermal groove of the first branchial arch. Three of these hillocks extend from the dorsal edge of the first branchial arch, and three appear from the
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Fig. 4.36 Unilateral atresia (aplasia of the ectodermal groove) from Chicama, Peru. Lateral view of both temporal bones of adult female (NMNH 265201). A: right side with complete absence of the external auditory meatus, styloid sheath, and styloid. B: normal left side.
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cranial border of the second branchial arch. Ectodermal tissue from the first branchial arch forms the tragus (cartilaginous projection) of the auricle, and mesenchyme from the second branchial arch forms the rest of the auricle (Arey 1965; Williams et al. 1989). With atresia (absence) of the external auditory meatus, the timing of the development of portions or all of the embryonic hillocks may be disturbed. This can result in deformity or microtia (unusually small size) of the external ear. Clinical cases of atresia of the external auditory meatus are frequently associated with hypoplasia of the first branchial arch derivatives, the maxilla and mandible, and with middle ear malformations (Caldarelli et al. 1980). Although this defect is rare, when it does occur it is found more often among North American Indians (9.67/10,000) than among other ethnic groups (Hodges, Harker, and Schermer 1990). Hrdlička (1933) recognized five cases of unilateral atresia of the external auditory meatus among the prehistoric crania he collected from the coast of Peru in 19101913 and two additional cases from prehistoric North American Indians. The Peruvian examples include an adult male (NMNH 264542) and an adult female (NMNH 265201) from Chicama (Fig. 4.36), a child (NMNH 266024), and two adult females (NMNH 266029 and NMNH 266026) from Pachacamac. One adult female came from Arkansas, and another adult female was from Carlsbad, New Mexico. Hrdlicka * noted that a number of crania from the same Peruvian cemetery sites as some of the affected individuals had unusually small external auditory meattus. We should expect this, because the underlying genetic basis for this defect tends to follow a hypoplastic-aplastic gradient, from partial expression to complete expression. Brothwell (1981) described atresia of the external auditory meatus in an Iron Age cranium from Lachish, Palestine, and Hodges, Harker, and Schermer (1990) describe a late Woodland (A.D. 4001000) adult female burial with unilateral incomplete atresia of the external auditory meatus on the left side. The opening is small, and the inner canal is shortened (as shown on tomograph). The right external auditory meatus and inner canal are normal. Summary Outline: Branchial Arch I Ectodermal Groove Field Defects A. Hypoplasia-aplasia of the external auditory meatus
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Complete atresia (aplasia) no external auditory meatus, tympanic plate, or tympanic sheath for the styloid process; absent or rudimentary 1.styloid process; petrotympanic (Glaserian) fissure absent; inner canal absent; temporal petrous portion may be small Partial atresia (hypoplasia) very small external auditory meatus, 2.reduced tympanic plate and tympanic sheath for styloid process; inner canal may be short or may not reach tympanic cavity Part VI. Branchial Arch I Closing Membrane Field Defects The thin membrane separating the ectodermal groove from the endodermal pouch of the first branchial arch produces the anlage of the tympanic plate. Four ossification centers appear around the edges of the tympanic membrane by the ninth embryonic week. By the tenth week they coalesce to form the U-shaped tympanic ring that eventually fuses to the squamous portion of the temporal bone by the thirty-fifth fetal week. It is still present at birth (Fig. 4.37a), and grows posterolaterally into a cylindrical fibrocartilaginous tympanic plate. The anterior and posterior ends of the newly formed tympanic plate ossify rapidly (Fig. 4.37b-c). Ossification of the anterior portion of the inferior aspect of the tympanic plate membrane does not occur until the fifth year. This leaves a temporary opening in the floor of the bony tympanic plate known as Huschke's foramen (Herzog and Fiese 1989; Williams et al. 1989). A. Developmental Delay of the Tympanic Plate: Tympanic Aperture/Cleft Delay in the development of the closing membrane between the ectodermal groove and the endodermal pouch of the first branchial arch can result in hypoplasia or aplasia of the antecedent of the tympanic plate. Aplasia (absence of the tympanic plate) is rare. If there is no tympanic plate, there is no tympanic sheath for the styloid, and the styloid may be missing or rudimentary. Aplasia of the tympanic plate is generally associated with complete atresia of the external auditory meatus. Hypoplasia of the closing membrane interferes with normal ossification of the tympanic plate. Severe hypoplasia prevents ossification of the anterior
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Fig. 4.37 Development of tympanic plate defects. a: newborn with normal tympanic bony ring; b: normal tympanic opening in one year old; c: closure of tympanic aperture begins during second year; d: normal absence of tympanic aperture in adult; e: tympanic aperture retained in adult (hypoplasia of closing membrane); f: tympanic cleft in adult (severe hypoplasia of closing membrane).
portion of the inferior aspect of the tympanic plate. This defect creates a complete cleft from the inferior aspect of the tympanic plate to the external auditory meatus (Fig. 4.37f). Less severe hypoplasia of the closing membrane slows ossification of the anterior portion of the inferior aspect of the tympanic plate, and the aperture (Huschke's foramen) that normally closes in early childhood persists into adulthood (Fig. 4.37e). This tympanic aperture varies in size, according to the degree of disturbance in the closing membrane. The
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bony opening remains covered by fibrocartilage that protects underlying soft tissue and generally has no clinical significance (Herzog and Fiese 1989). The tympanic aperture defect is often referred to as tympanic dehiscence, which is incorrect because no dehiscence takes place. The tympanic aperture defect is frequently found in prehistoric skeletal material. It has often been used as a nonmetric trait in biological distance studies. From the study of the morphogenesis of the tympanic plate, this defect appears to possess a strong genetic component. The defective tympanic aperture is quite common in both modern and prehistoric populations and varies in frequency from 5% to 45% (Williams et al. 1989). The defect is usually bilateral and can be symmetrical or asymmetrical in form. Sexual differences have been noted in the frequency of tympanic aperture in some adult populations, with higher frequencies for females than for males. The defect was found in 40% of Burmese females as opposed to 25% of Burmese males (Williams et al. 1989). Hooton (1930:107) discovered a similar sexual difference in frequency for the tympanic aperture in the Pecos, New Mexico (Pueblo IV-V Towa), skeletal collection. Tympanic aperture was found in 24% of the Pecos females and 16% of the males. El-Najjar (1974) detected an increase in the frequency of the tympanic aperture through time in the Canyon de Chelly Anasazi population. The frequency increased from 10% in the early Basket Maker residents to 36.6% in the later Pueblo III residents. Turner and Katich (1981:145) described a frequency of 33.3% in the Tompiro skeletal collections from Gran Quivira (Pueblo IV-V), New Mexico. They noted that Hopi (Pueblo IV-V) skeletal collections showed a higher frequency (44%), and Towa Pecos (Pueblo IV-V) skeletal material overall had a lower frequency (21.5%) of defect in the tympanic plate. MacCurdy (1923:270) reported a marked tendency for incomplete formation of the tympanic plate (over 30%) in Peruvian skeletal material from the highlands near Cuzco. Turner and Katich (1981:145) found twice that frequency (62.3%) in coastal Peruvians from Pachacamac and Chincha. B. Developmental Excess of the Styloid Sheath The sheath for the styloid process is created from an extension of the tympanic plate. Occasionally, the extension is excessive and produces a very large styloid sheath. The etiology for this defect is not known. It may be caused by developmental hyperplasia of the closing membrane.
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Snow (1974:23) reported seven cases of bilateral developmental excess of the tympanic sheath around the styloid processes in prehistoric Hawaiians. One measured 33 mm long. Summary Outline: Branchial Arch I Closing Membrane Field Defects A.Developmental delay of tympanic plate Aplasia absent tympanic plate and tympanic sheath; styloid process 1.rudimentary or absent; usually associated with atresia of the external auditory meatus 2.Hypoplasia mild expression tympanic aperture, small or large, unilateral or a. bilateral, asymmetrical or symmetrical severe expression cleft tympanic plate, unilateral or bilateral, b. asymmetrical or symmetrical Developmental excess of tympanic sheath enlarged tympanic sheath B. (hyperplasia) for styloid process Part VII. Branchial Arch II Field Defects The mesenchymal component of the second branchial arch develops into a cartilaginous band Reichert's cartilage on each side of the head near the otic capsule and below the first branchial arch and ectodermal groove. The two bands grow forward and meet in the midline at the hyoid. The dorsal end separates to evolve into the stapes, whereas the rest of the Reichert's cartilage develops into the stylohyoid chain (Fig. 4.38a). This consists of the styloid process, the stylohyoid ligament that connects the styloid process to the hyoid, the lesser cornu of the hyoid, and probably the cranial rim of the hyoid body. The third branchial arch supplies the greater cornu and the caudal portion of the hyoid body. Normally, the styloid process and hyoid portions of Reichert's cartilage ossify into their respective bony components, and the remaining intervening portion of Reichert's cartilage is converted into the stylohyoid ligament (Arey 1965; Williams et al. 1989). The segments of Reichert's cartilage that form the stylohyoid chain and their respective derivatives include the tympanohyal, the base of the styloid process (Fig. 4.38a1); the stylohyal, the tip of the styloid process (with a separate ossification center from the tympanohyal segment)
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Fig. 4.38 Variations of failure of portions of Reichert's cartilage to differentiate. a: normal stylohyoid chain: (1) tympanohyal, (2) stylohyal, (3) epihyal, (4) hypohyal (lesser cornu of hyoid), (5) greater cornu of hyoid; b: ossification of stylohyal (tip of styloid process) absent; c: ossification of styloid process absent; d: ossification of epihyal (styloid ligament); e: complete ossification of stylohyoid chain; f: normally ossified styloid process (tympanohyal and stylohyal).
(Fig. 4.38a2); the epihyal (ceratohyal), the stylohyoid ligament (Fig. 4.38a3); and the hypohyal, the lesser cornu of the hyoid (Fig. 4.38a4). The tympanohyal and stylohyal ossify from separate ossification centers. The tympanohyal ossification center is present before birth, whereas the stylohyal ossification center appears after birth. The two eventually unite after puberty (Fig. 4.38f).
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A. Failure of Bony Elements of Stylohyoid Chain to Ossify Sometimes delay in the development of the stylohyal segment that forms the tip of the styloid process does not allow it to chondrify and then ossify, thus shortening the bony styloid process (Fig. 4.38b). Delay at a different point on the critical threshold of development can slow chondrification and delay ossification so as to prevent fusion with the tympanohyal segment. This forms a separate bony stylohyal and shortens the styloid process. Rarely, the tympanohyal segment fails to develop properly, because of developmental delay, and produces a shorter or missing styloid process (Fig. 4.38c). The normal length of the styloid process does not exceed 25 mm, with an average length of 10 mm (Camarda, Deschamps, and Forest 1989b; Eagle 1958). Hrdlicka * (1933, 1943) stated that ''rudimentary" styloid processes are common among American Indians. I have found that hypoplasia-aplasia of the styloid process is common in Southwest Anasazi skeletal collections. B. Failure of Reichert's Cartilage to Differentiate It is not unusual for portions or all of the epihyal segment (the stylohyoid ligament) of the stylohyoid chain to retain their cartilaginous potential. This happens when the epihyal fails to differentiate into fibrous tissue during the embryonic period because of delay in development of its precursor. The epihyal cartilage ossifies along with the stylohyal and tympanohyal, giving the impression that the styloid process is elongated (Fig. 4.38d). The normal styloid process may look different with the added ossification of the stylohyoid ligament. Often it is crooked, with a blunt tip. Ossification of the epihyal usually occurs unilaterally and incompletely, but it can be bilateral and asymmetrical. Styloid processes longer than 25 mm suggest ossification of all or part of the stylohyoid ligament. Ossification of the stylohyoid chain appears to be more common in males than in females (Camarda, Deschamps, and Forest 1989a; Eagle 1958; Freedman and Hooley 1968; Gossman and Tarsitano 1977). In rare cases all of the stylohyoid chain segments ossify but remain separate. They are held together by fibrous connective tissue. Complete ossification of the stylohyoid chain is rare. When this happens, the stylohyoid chain forms a complete bony unit with the hyoid (Fig. 4.38e). Cavenagh (1937) reported a clinical case in a fifty-six-year-old male, who also had ossification
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of the thyroid ligament and portions of the thyroid and cricoid cartilages derived from the third branchial arch. Ossification of the stylohyoid chain occurs in about 2% to 4% of the general population. It begins between ages five and eight, when the styloid process normally ossifies. Stylohyoid chain ossification generally remains asymptomatic in the young because of the elasticity of the soft tissues around it. When middle age is reached, the soft tissues lose elasticity and become more resistant to the impinging hard tissue defect. This is when symptoms are most likely to develop (Camarda, Deschamps, and Forest 1989b; Gossman and Tarsitano 1977). The most common symptoms caused by the ossification of the stylohyoid chain include difficulty in swallowing, the sensation of something stuck in the throat, constant dull ache in the throat, pain in the ear, headache, and pain associated with the pathways of the carotid arteries. The styloid process is normally situated between the external and internal carotid arteries behind the pharyngeal wall in the area of the palatine fossa. Three muscles are attached to it. Pressure on the external carotid artery produces facial pain above the level of the eye, and pressure on the internal carotid artery causes pain to radiate from the eye to the occipital region in the form of a persistent nagging headache (Camarda, Deschamps, and Forest 1989b; Christiansen, Meyerhoff, and Quick 1975; Eagle 1958; Gossman and Tarsitano 1977). Hooton (1930:103) mentions that males in the Pecos skeletal collection (Pueblo IV-V Towa) have larger styloid processes than females and that four males and four females have very large styloid processes that must have resulted from ossification of the epihyal segment of the stylohyoid chain. One male and five females have missing styloid processes, reflecting aplasia of the tympanohyal segment. Gregg and Gregg (1987) mention several cases of elongated styloid processes in the Upper Missouri River Basin skeletal series that must have resulted from ossification of the epihyal segment of the stylohyoid chain. Summary Outline: Branchial Arch II Field Defects A.Failure of stylohoid chain to ossify 1.Small styloid process (less than 10 mm in length) tip (stylohyal) fails to ossify or to unite with base of styloid a. process (tympanohyal) b.base of styloid process (tympanohyal) fails to ossify completely
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Absent styloid process tympanohyal, with or without the stylohyal, 2.fails to ossify 3.Absent lesser cornu of hyoid hypohyal fails to ossify B.Failure of Reichert's cartilage to differentiate Styloid ligament (epihyal) ossifies completely or partially and unites with styloid process; elongated styloid process, greater than 25 mm 1. in length, usually appears crooked and may have blunt or pointed tip 2.Complete ossification of stylohyoid chain complete, but separate, ossification of each element of the a. stylohyoid chain (rare) complete ossification and unification of stylohyoid chain to hyoid b. (rare)
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Chapter 5 Developmental Field Defects of the Sternum The sternal plates develop from mesenchymal bands located in the ventrolateral portions of the embryonic body wall. The bands move forward of the growing primordial ribs, meeting in the ventro-midsection. The suprasternal structures develop from a pair of mesenchymal condensations between the ventral ends of the evolving anlages of the clavicles, localizing in line with the cranial ends of the sternal bands as they approach one another. The precostal process evolves from another mesenchymal condensation that appears between the caudal ends of the suprasternal structures. This process is incorporated, along with the suprasternal structures, into the sternal bands as they begin to fuse at their cranial ends during the seventh embryonic week. Fusion continues from the cranial end toward the caudal end and is completed by the tenth week (Eijgelaar and Bijtel 1970; Jewett, Butsch, and Hug 1962; Williams et al. 1989). Chondrification of the sternal bands begins as they approach each other. Following unification and the attachment of the embryonic ribs, the primordial sternum subdivides into the four sternebrae of the mesosternum and the manubrium, leaving a remnant of united mesenchyme from each sternal band extending from the caudal border to form the future xiphoid process. The sternebrae segment along the opposing caudal ends of embryonic ribs two through five. Ossification centers begin to appear during the fifth fetal month. Usually, one or two centers appear, but the number can vary up to four or five. The location of the centers can also vary. The timing of the development and fusion of the sternal bands determines the number and location of ossification centers that will appear in the cartilaginous mesosternum. This phenomenon appears to be genetically determined (Ashley 1954). The manubrium ossifies from one to three centers, the first and second sternebrae generally ossify from single centers, and the last two usually ossify
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from paired centers. The cartilaginous xiphoid does not begin to ossify until after the third year. The sternebrae of the mesosternum (Fig. 5.1) begin to unite by puberty in a caudal-cranial direction until they are completely united by no later than age twenty-five (Jewett, Butsch, and Hug 1962; Williams et al. 1989). A thin layer of fibrous membrane (lamina) forms between the primitive manubrium and the first sternebra of the mesosternum at the level of the second costal cartilages. This is the precursor to the cartilaginous manubrio-mesosternal joint (Ashley 1954). A similar fibrous lamina usually develops between the last sternebra and the xiphoid process anlage, leading to a xiphisternal joint (Jit and Bakshi 1986). A. Failure to Differentiate 1. Manubrio-Mesosternal Joint Fusion Sometimes the fibrous lamina fails to develop completely or at all between the primitive manubrium and the first sternebra of the mesosternum. The cartilaginous manubriomesosternal joint does not develop where the lamina is missing as the sternum ossifies, and the manubrium becomes fused, either partially or completely, to the manubrium (Fig. 5.2b-c). This can interfere with optimum respiration and has been associated with lung infection, such as tuberculosis (Ashley 1954). Fusion of the manubrio-mesosternal joint commences around age twelve in males and about age sixteen in females. Fusion can be completed as young as age twenty-one (Jit and Bakshi 1986). On rare occasions, fusion of the manubrio-mesosternal joint is visible in the neonate. This happens when the ossification centers for the manubrium and first sternebra form close to each other, and the missing lamina cannot keep them from coalescing into one (Ashley 1954). Pathology, particularly degenerative joint disease, can cause fusion between the manubrium and the sternum, especially in older individuals. Care must be taken to differentiate between this type of fusion and fusion caused by developmental defect (Ashley 1954). Fusion caused by developmental defect has a smooth, even contour at the manubrio-sternal joint, whereas acquired fusion does not. Ashley (1954) and Warkany (1971) found fusion of the manubrio-mesosternal joint in approximately 10% of all the adult sterna they investigated.
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Fig. 5.1 Immature sternum (manubrium and sternebrae) from eighteen- to twenty-four-month-old child (NMNH 314342) from Hawikku, New Mexico, with unilateral hypoplasia (right) and caudal cleft of the last sternebra.
Paterson (1904) studied 236 fetal sterna and found that 23.6% lacked the fibrous lamina between the manubrium and mesosternum. Fusion of the manubrio-sternal joint (Fig. 5.3a) has been observed in prehistoric skeletal material, including Southwest skeletal collections. Reed (1981:81) mentioned cases from Mound 7 at Gran Quivira (Pueblo IVV). Zivanovic (1982) found it to be common in medieval European populations. MacCurdy (1923:278), however, noted only two cases of manubrio-mesosternal fusion in all of the skeletal populations he studied from the highlands of Peru around Cuzco. 2. Misplaced Manubrio-Mesosternal Joint Sometimes the fibrous lamina forms at the wrong level, between the first and second sternebrae at the third costal cartilage instead of between the manubrium and first sternebra. This leads to the formation of a cartilaginous
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Fig. 5.2 Failure of sternal precursors to differentiate. a: normal sternum (manubrium and xiphoid process separate); b: partial manubrio-mesosternal joint fusion; c: complete manubrio-mesosternal fusion; d: misplaced manubrio-mesosternal joint, between first and second sternebrae; e: complete xiphisternal joint fusion.
joint between the first sternebra and the remaining mesosternum, and the manubrium is coalesced with the first sternebra (Fig. 5.2d) (Ashley 1954). Brues (1946) identified a misplaced manubrio-mesosternal joint between the first and second sternebrae in a middle-aged male Anasazi (Pueblo IIII) from Alkali Ridge, Utah. Reed (1981:81) reported one case from Mound 7, Las Humanas (Pueblo IVV Tompiro) at Gran Quivira, New Mexico. 3. Xiphisternal Joint Fusion Not all xiphoids fuse to the sternum with old age as previously thought. The majority of fusions appear to be developmental rather than caused by aging. The fibrous lamina separating the xiphoid process from the sternum can fail to develop properly, much like the manubrio-mesosternal joint defect. This results in complete or partial fusion of the xiphoid process to the sternum (Fig. 5.2e). The xiphoid process is the last element of the sternum to ossify, so fusion of the xiphisternal joint does not usually appear until after age eighteen in the male, and after age twenty in the female (Jit and Bakshi 1986).
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Fig. 5.3 Manubrio-mesosternal joint fusion and xiphisternal joint fusion from Hawikku, New Mexico. A: type I sternum of adult female (NMNH 308624) with failure of the manubrio-mesosternal joint to develop. B: type I sternum from adult male (NMNH 308620) with failure of the xiphisternal joint to develop.
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Fused xiphoids are mentioned rarely in the paleopathology literature. Reed (1981) mentioned some from Mound 7 at Gran Quivira (Pueblo IV-V Tompiro). MacCurdy (1923:278) mentioned three cases in his analysis of skeletal material from the highlands of Peru around Cuzco. I found a number of fused xiphoids (Fig. 5.3b) in the Southwest skeletal collections at the Smithsonian Institution. B. Developmental Delay 1. Cranial Fusion Delay Defects a. Suprasternal Ossicles Delay in the fusion of the suprasternal structures into the developing embryonic sternum during the ninth week can prevent those structures from being incorporated into the manubrium anlage. They develop separately from the manubrium, ossify during puberty, and generally remain as separate ossicles. They can articulate posteriorly with the lateral border of the jugular notch of the manubrium, or they can unite with the manubrium during adolescence as they ossify, forming bony nodules on the manubrium (Fig. 5.4). Sometimes they unite with each other. Suprasternal ossicles range in diameter from 2 mm to 15 mm, with variable shape. They are more common in females than in males and can form unilaterally as well as bilaterally. Most cases are bilateral and separate from the manubrium. Sometimes one suprasternal ossicle can be fused to the manubrium, whereas the other one is not (Köhler and Zimmer 1968; Stark et al. 1987; Williams et al. 1989). Unilateral expression of a suprasternal ossicle fused to the manubrium was found in an adult male (NMNH 314279) from Hawikku (Pueblo IV-V Zuni). The ossicle is fused to the dorsal aspect of the manubrium on the left side, just below the clavicular notch (Fig. 5.5). b. Delayed Cranial Cohesion of Sternal Bands The cranial ends of the sternal bands fuse together with the suprasternal structures and precostal process by the seventh embryonic week. This is followed by fusion of the rest of the bands in a caudal direction. If the sternal bands are delayed in their approach and fusion at the cranial end, a defect can develop. Mild delay produces a small cleft or aperture in the manubrium anlage (Fig. 5.6a). Too long a delay prevents the bands from coming together at the critical threshold time and a bifid sternum is created (Fig. 5.6b) (Chang,
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Fig. 5.4 Development of suprasternal ossicles. a: early blastemal stage of developing sternum; b: normal sternum at nine embryonic weeks; c: normal sternum after birth; d: sternum at nine embryonic weeks with separate suprasternal structures; e: sternum after birth with separate suprasternal ossicles (redrawn from Arey 1965); f: adolescent manubrium with attaching suprasternal ossicles (redrawn from Köhler and Zimmer 1968).
Davis, and Clayton 1961; Eijgelaar and Bijtel 1970; Jewett, Butsch, and Hug 1962). Cranial fusion delay defects of the sternum are rare. The major defect, bifid sternum, is not necessarily life threatening, depending upon the degree of bifurcation. Usually, there is some fusion at the caudal end of the mesosternum, and the fissure is generally held together by fibrous tissue and covered by skin. Severe forms cause difficulty in breathing and attacks of cyanosis, with
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Fig. 5.5 Suprasternal ossicle from Hawikku. Dorsal aspect of manubrium from adult male (NMNH 314279) with suprasternal ossicle attached below the left suprascapular notch.
increased susceptibility to recurrent upper respiratory infections (Eijgelaar and Bijtel 1970; Jewett, Butsch, and Hug 1962; Warkany 1971). 2. Caudal Fusion Delay Defects Delay in caudal fusion of the mesosternum is common and variable. It varies from delayed cohesion, leading to a wide mesosternum, to incomplete cohesion, with the development of a sternal aperture or cleft, to lack of fusion, producing a fissure (rare). Hypoplasia or aplasia of the last segment of the mesosternum may also occur with delayed caudal fusion (Ashley 1956; Köhler and Zimmer 1968). The ultimate shape of the mesosternum, based upon the number and location of the ossification centers that develop within the sternebrae, is determined by the timing of the fusion of the sternal bands (Ashley 1956). Ideally, these bands meet and fuse in an orderly fashion, allowing for the development of single midline ossification centers that produce a definitive mesosternum. The sides are narrow, usually between 20 mm and 30 mm wide, and fairlu parallel. Ashley (1956) refers to this mesosternum form as type I (Fig. 5.7). Sometimes a mesosternum can appear abnormally narrow, less than 20 mm wide, as a result of hypoplasia of the sternal bands. Although the first two sternebrae generally develop from single midline ossification centers, the last two sternebrae most often develop from two ossification centers. This happens because the caudal portion of the sternal
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Fig. 5.6 Variations of delayed cranial cohesion defects of the sternal plates. A: manubrium with aperture. B: bifid sternum.
bands is usually slower to fuse than the cranial aspect. When the caudal portion finally fuses, a longitudinal groove, formed by the tardy medial borders of the sternal bands, interferes with the development of single midline ossification centers. Instead, bilateral ossification centers develop, in either a symmetrical or an asymmetrical relationship to one another. When the mesosternum appears narrow in the first segment (usually less than 30 mm wide) and wide in the caudal end, delayed fusion has created bilateral ossification centers in the lower sternebrae, particularly in the third sternebra, which is wider than the first sternal segment. Ashley (1956) called this mesosternum form type II (Fig. 5.7) and found that the majority of mesosterna are type II, followed by type I. a. Delayed Caudal Cohesion of Sternal Bands When a marked delay occurs in the fusion of the sternal bands, widely separated multiple ossification centers develop, and a broad mesosternum is the result (Figs. 5.8a and 5.9a). Ashley (1956) classifies this is a type III mesosternum. The mesosternum is greater than 30 mm wide throughout its
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Fig. 5.7 Variations of sternal types I, II, III, and IV based on Ashley's method (1956).
length, usually with nearly parallel sides from the first segment to the third segment (Fig. 5.7). Excessive delay in the fusion of the cranial portions of the sternal bands, with hypoplasia or aplasia of the caudal portions, results in the development of a very wide, short sternum with a tapered caudal end. The first and second sternebrae develop from widely spaced, multiple ossification centers (greater than 30 mm wide), and the caudal sternebra(e) ossifies from only one or two closely packed centers (less than 30 mm wide). Ashley (1956) named this a type IV mesosternum (Fig. 5.7). It is rare among humans but common in the gorilla.
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Fig. 5.8 Large type III sternum contrasted with a small type I sternum from Hawikku, New Mexico. A: manubrium is fused to mesosternum, which is 23 mm wide at the first segment and 55 mm wide at the last segment (adult male NMNH 308626). B: mesosternum has a very small xiphoid fused to it (manubrium is missing) and is only 23 mm wide at the first segment and 25 mm wide at the last segment (adult female NMNH 308625).
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Fig. 5.9 Sternal variations of types I, II, and III from Guisewa, New Mexico. A: type I. B: type II with manubrio-mesosternal and xiphisternal fusion. C: type III with manubrio-mesosternal fusion and sternal aperture (all are from adult males).
Abnormally wide type III and type IV sterna appear less frequently in human populations than do types I and II. Variations of the different types of sterna can occur, but the general shape of the sternum and width of the first segment compared to the width of the third segment reflect the four basic types described by Ashley (1956). The caudal end of the type II sternum can sometimes be abnormally wide as a result of excessive delay in the fusion of the caudal portion of the sternal bands. Delay in the development of one or both of the caudal ends of the sternal bands sometimes leads to hypoplasia (Fig. 5.10) or aplasia (Fig. 5.11 c-d) of one or both of the last sternebrae. The affected mesosternum can appear shorter than normal or can have an asymmetrical lower segment. b. Incomplete Caudal Cohesion of Sternal Bands Incomplete caudal cohesion generally occurs between the third and fourth sternebrae. This results in a sternal aperture (mistakenly referred to as a sternal foramen) at which the sternal bands fail to fuse together (Fig 5.12a). The size and shape of this defect depend upon the timing of the delay in fusion.
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Fig. 5.10 Immature and mature type I sterna with hypoplasia of last sternal segment (sternebra) from Hawikku, New Mexico. A: immature sternum of child (NMNH 308635) eleven to twelve years of age, with last hypoplastic sternebra fused to third sternebra; B: adult female sternum (NMNH 308636), with sternal aperture in third sternal segment.
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Fig. 5.11 Sternal variations of types I, II, and III from Amoxiumqua, New Mexico. A: type I, from adult male. B: type II with sternal aperture, from adult male. C: type III with aplasia of last sternebra, from adult female. D: type III with manubrio-mesosternal and xiphisternal fusion and aplasia of last sternebra, from adult male.
The aperture is usually oval shaped, with smooth, even edges, and can be quite small or very large and elongated (Ashley 1956; Cooper, Stewart, and McCormick 1988; McCormick 1981; Williams et al. 1989). There is evidence that the frequency in the occurrence of the sternal aperture appears to vary in different populations. Ashley (1956) found a higher frequency in 98 east Africans (13.2%) than in a sample of 573 Europeans (4%). McCormick (1981) noted that American Blacks in his sample of 324 cadaver sterna had a higher frequency of sternal aperture than the remainder of the sample population. Sternal apertures are frequently reported in prehistoric populations. Reed (1981:81) identified eight sternal apertures in the skeletal collection from Mound 7 at Gran Quivira (Pueblo IVV Tompiro). Two of his sternal illustrations show small clefts at the caudal end of the mesosternum. I found a number of sternal apertures in the Southwest collections at the Smithsonian Institution (Figs. 5.9c, 5.10b, 5.11b, 5.13b and d, and 5.14b).
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Fig. 5.12 Delayed caudal cohesion defects of the sternal plates. A: sternal aperture. B: sternal cleft or notch. C: sternal fissure. D: xiphoid aperture. E: xiphoid cleft.
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Fig. 5.13 Sternal variations of types I and II from Heshotauthla, New Mexico. A: type I sternum. B: type I sternum with partial manubrio-mesosternal fusion and oblong sternal aperture. C: type II sternum. D: type II mesosternum (manubrium missing) with sternal aperture and large, fused, cleft xiphoid (all of the sterna belong to adult females).
Incomplete fusion of the caudal end of the last segment results in a cleft formation (Fig. 5.12b). Usually, the cleft appears as a small notch in the inferior border of the last sternebra (see Fig. 5.1). Complete failure of fusion of the last segment produces a large caudal sternal fissure (Fig. 5.12c), which is rare (Ashley 1956). A delay sometimes occurs in the development of the xiphoid process from the mesenchymal condensations at the caudal ends of the sternal bands. This leads to hypoplasia or aplasia of part or all of the xyphoid process anlage, producing a variety of shapes and sizes (Gruneberg 1963). This is common with the xyphoid process. Delay in the fusion of the caudal end of the sternal bands can delay the fusion of the xiphoid anlages. This delay produces a cleft or aperture of varying size and shape in the xiphoid process (Fig. 5.12d-e) (Köhler and Zimmer 1968). Reed (1981:81) illustrates large and small clefts in the xiphoids of some of the sterna from Mound 7 at Gran Quivira (Pueblo IVV Tompiro) in New
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Fig. 5.14 Sternal variations of type II from Pueblo Bonito, New Mexico. A: narrow type with manubrio-mesosternal joint fusion. B: very wide caudal end with small sternal aperture (both sterna are from adult males).
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Mexico. The sternum from an adult male from Pueblo Bonito (Pueblo II-III) has a large aperture in the xiphoid process that is also fused to the mesosternum (Fig. 5.15). An unusually large mesosternum with a fused, large xiphoid process was found in the Smithsonian's National Museum of Natural History's Southwest skeletal collections. The adult male mesosternum (NMNH 315952) comes from an unknown ''Puebloan" site in New Mexico. Unfortunately, the manubrium is missing and the upper portion is damaged, as is the caudal end of the xiphoid process. Delay in the fusion of the sternal bands produced a very wide mesosternum, with a maximum width of 61 mm, and a very large sternal aperture, 13.5 mm wide and 25 mm long. The body of the xiphoid process is 26.5 mm wide (Fig. 5.16). C. Developmental Excess of Sternal Bands An unusually long mesosternum occasionally develops from extra-long sternal bands. Hyperplasia of the sternal bands produces an extra sternebra (Ashley 1956). Hyperplasia of the mesenchymal condensations at the caudal ends of the sternal plates sometimes produces a very large xiphoid process (Köhler and Zimmer 1968). Summary Outline: Developmental Field Defects of the Sternum A.Failure to differentiate 1.Manubrio-mesosternal joint fusioncomplete or incomplete Misplaced manubrio-mesosternal jointlocated between first and 2. second mesosternal segments 3.Xiphisternal joint fusioncomplete or incomplete B.Developmental delay 1.Cranial fusion delay defects suprasternal ossiclesunilateral or bilateral, asymmetrical or a. symmetrical, variable shape, 2 mm to 15 mm in diameter remain separate from manubrium, usually articulate with (1)manubrium at posterolateral border of jugular notch; may fuse to each other if bilateral fuse to manubrium during adolescence as bony nodules at (2) posterolateral border of clavicular or jugular notch
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Fig. 5.15 Large xiphoid aperture from Pueblo Bonito, New Mexico. Type II sternum of adult male (NMNH 327084) with xiphisternal fusion.
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Fig. 5.16 Unusually large mesosternum from unknown Puebloan site in New Mexico compared to normal type II sternum from Hawikku, New Mexico. This unusually large mesosternum (NMNH 315952) is 61 mm wide at the third sternal level, with a large sternal aperture (26 mm × 13.5 mm) and xiphisternal fusion; unfortunately, the sternum is damaged and the manubrium is missing (both sterna are from adult males).
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b.delayed cranial cohesion of sternal bands (rare) (1)mild small cleft or aperture in manubrium severe bifid sternum, complete or incomplete separation, (2) usually some fusion at caudal end 2.Caudal fusion delay defects a.delayed caudal cohesion of sternal bands type IV sternum first two segments wide (greater than 30 mm), (1)last segment less wide (less than 30 mm); may have only three segments (rare) type III sternum all segments wide (more than 30 mm), width (2)of first segment equals width of third segment; last segment may be narrower than third or may be absent MOST COMMON STERNAL VARIANTS type II sternum first segment always narrow (less than 30 mm), and third segment always wide (more than 30 mm), sometimes caudal end abnormally wide type I sternum all segments narrow (less than 30 mm) with parallel sides, can be abnormally narrow (less than 20 mm wide) hypoplasia-aplasia of caudal end(s) unilateral or bilateral, (3) symmetrical or asymmetrical; affects last sternebra b.incomplete caudal cohesion (1)mesosternum sternal aperture usually between last two sternebrae; small (a) or large; usually round or oval; smooth beveled edges (b)small cleft or notch inferior border of last segment (c) complete sternal fissure in last sternebra (2)xiphoid process (a) xiphoid aperture (b)cleft xiphoid process (c) hypoplasia-aplasia of xiphoid process Developmental excess of sternal bands hyperplasia of sternal bands C. with extra sternebra, extra-long mesosternum
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Chapter 6 Developmental Field Defects of the Axial Skeleton in the Puye and Central Pajarito Plateau Skeletal Populations The morphogenetic criteria outlined in the previous chapters for identifying the various expressions of developmental defects were tested on a large prehistoric skeletal collection from the Southwest United States. The collection selected was salvaged from the Pueblo IV prehistoric site of Puye on the northern part of the Pajarito Plateau of northern New Mexico. Additional analyses of three smaller skeletal collections from neighboring sites located in the central portion of the Pajarito Plateau, contemporary with Puye and sharing the same culture and environment, were added to the study, increasing the number of individuals in the test pool. A total of 354 individuals are represented in the Pajarito Plateau skeletal collections at the Smithsonian's National Museum of Natural History. Most of these are adults, and several of them have incomplete skeletons. They were acquired by the museum in the early part of this century from Edgar Hewett's archaeological excavations in northcentral New Mexico. Hewett (1905) did not salvage what he considered damaged or fragile skeletal material, especially the skeletons of infants and young children, which led to an underrepresentation of juvenile skeletal material from all of the sites he excavated. Although the skeletal collections are biased in this respect, this does not prevent us from analyzing developmental defects of the axial skeleton in these collections. Expressions of the majority of developmental field defects in the axial skeleton can be found in adult skeletal material. The axial skeletal material of each individual was inventoried and recorded, along with the presence or absence of developmental field defects,
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according to the specified fields of development. Each recorded defect was described in detail, with illustrations, to determine its form of expression. A total of 230 individuals from Puye were examined. Only 14 of these were juveniles, from 4.5 to 16.5 years of age. The collection contains 133 adult females and 74 adult males (9 adults are of indeterminate sex), and all ages are represented for both sexes. The majority of crania are brachycephalic with asymmetrical vertical occipital deformation. Crania from the neighboring Pajarito Plateau sites show the same pattern of cranial shape. Most of the skeletal material from Puye is in good condition, with good to fair representation of the axial skeleton in the majority of individuals represented. There are 124 individuals representing the neighboring central Pajarito Plateau sites excavated by Hewett. This group includes 86 individuals from Otowi (36 females, 28 males, 16 adults of indeterminate sex, and 6 children); 13 from Tsirege (8 females, 4 males, and 1 adult of indeterminate sex); and 25 from Tsankawi (15 females, 7 males, 2 adults of indeterminate sex, and 1 child). The skeletal material from these three sites is in very poor condition, and several individuals are represented by very little axial skeletal material. The individuals represented in the Tsirege collection lack vertebral columns, ribs, and sterna. However, developmental field defects associated with the cranium were identified and recorded (Table 6.1). Each Pajaritan community was treated separately for comparative purposes to determine any similarities or differences in its patterns of defects. Sharing the same culture and environment within the same time period, the communities are most likely part of a homogeneous population. The patterns of developmental defects should be similar, based upon underlying genetics. Table 6.1. Skeletal Collections Analyzed Site Puye Central plateau total Otowi Tsankawi Tsirege
N 230 124 86 25 13
Adults 216 117 80 24 13
Juveniles 14 7 6 1 0
Most of the developmental field defects detected in the Puye and central Pajarito Plateau skeletal collections are minor. The majority of defects consisted of disturbances in the paraxial mesoderm of the vertebral column.
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Segmentation errors (block vertebrae), segmental border shifting, and developmental delay of vertebral elements (clefting of the sacrum and atlas) are the most common paraxial mesoderm defects. Less common are numerical errors of vertebral segments, but the recorded numbers may be low because many of the vertebral columns are incomplete. Asymmetrical hemimetamere pairing and minor irregular segmentation of ribs do occur but are rare. Indications of notochord and neural tube field defects of the vertebral column are absent. Disturbances in the developmental fields of the cranium are very minor, with the majority occurring in the blastemal desmocranium (calvaria). Most of these take the form of anomalous extra ossicles. One defect is related to the prechordal cranial base developmental field, and another derives from the first branchial arch ectodermal groove (the external auditory meatus). No disturbances were detected in the developmental fields of the first branchial arch (the mandible and maxilla) and the blastemal frontonasal process (the face), which are rare in any population. The second branchial arch (stylohyoid chain) was not evaluated because most of the styloid processes were damaged. Defects from the developmental field of the closing membrane between the ectodermal groove and endodermal pouch (tympanic aperture) are well represented (Table 6.2). Table 6.2. Developmental Fields Affected by Disturbances in the Puye and Central Pajarito Plateau Skeletal Collections Developmental field Puye Otowi Tsankawi Tsirege Notochord 0 0 0 Neural tube 0 0 0 Paraxial mesoderm segmentation errors hemimetamere pairs s 0 0 failure to segment x x x numerical errors x u u segmental border shifts occipitocervical x x x 0 cervicothoracic 0 0 0 thoracolumbar 0 0 0 lumbosacral x x x sacrocaudal x x x developmental delay of vertebral elements x x x Prechordal cranial base s 0 0 0
Page 234 Table 6.2 (continued) Developmental field Puye Otowi Tsankawi Tsirege Blastemal desmocranium failure to coalesce primary suture ossicles x x x x metopism 0 0 0 s failure to differentiate 0 s 0 0 Branchial arch I 0 0 0 0 Blastemal frontonasal process 0 0 0 0 Branchial arch I ectodermal groove 0 0 0 s Branchial arch I closing membrane x x x x Branchial arch II Sternal plates failure to differentiate x x x misplaced manubrio-mesosternal joint s 0 0 delayed cranial fusion 0 0 0 delayed caudal fusion x x x x = present; 0 = absent; s = sporadic incidence; = unavailable; u = not enough data.
A large number of sterna are present in the skeletal collections, making it possible for the first time to determine the pattern of sternal types in a skeletal population, based upon the method developed by Ashley (1956). Defects resulting from developmental delay of the sternal plates occur as delayed caudal fusion defects and as delayed (wide sternum) and incomplete caudal cohesion (sternal and xiphoid apertures or clefts). Failure to differentiate between the manubrium and mesosternum and between the mesosternum and xiphoid is also present in some individuals. Developmental delay represented by cranial fusion (suprasternal ossicles) or delayed cranial cohesion (cleft or aperture in the manubrium) are not present. These are rare in any population. A. Paraxial Mesoderm Field Defects 1. Asynchronous Development of Hemimetamere Pairs One 2530-year-old female (NMNH 262939) from Puye has a paraxial mesoderm field defect resulting from asynchronous hemimetamere development
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Fig. 6.1 Asynchronous development of hemimetamere pairs for T4 and T5: contralateral balanced shifting with failure of segmentation (block vertebra) of T3, T4, and T5. From adult female (NMNH 262939) from Puye. A: anterior view. B: dorsal view. C: right lateral view.
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(Fig. 6.1). This has been described and illustrated by Ortner and Putschar (1985:357358). All of the vertebrae are present except the first and sixth cervical vertebral segments. The primary defect affects the fourth and fifth thoracic segments, with bilateral balanced shifting of the hemimetamere pairs, producing two contralateral hemivertebrae. Delay in reaching the midline on time for fusion forced displacement of the hemimetamere pairs of T4 and T5. This interfered with segmentation, resulting in a single block vertebra combining T3, T4, and T5. The transverse processes of all three vertebral segments are present, and only the left sides of T3 and T4 are fused. The spinous processes of all three segments are united as one. Rib facets for all three corresponding ribs are present, but the ribs themselves are missing postmortem. The rib facets are closely spaced, especially on the left side, suggesting that the ribs were probably joined together at their vertebral ends. Because the shifting is balanced, this individual probably developed no major clinical symptoms. This is the only case of this type of defect present in all of the skeletal material examined from Puye and the central Pajarito Plateau sites (Table 6.3). Sample sizes from Otowi (N = 16) and Tsankawi (N = 13) are too small to provide enough data to suggest its presence or absence, and no vertebrae are present to decipher in the Tsirege collection. Table 6.3. Frequency of Asynchronous Development of Hemimetamere Pairs Site N Occurrence Frequency (%) Puye 142 1 .07 Central plateau total 29 0 0 Otowi 16 0 0 Tsankawi 13 0 0 Tsirege 0
Hemimetamere defects usually appear sporadically in a population that has a tendency toward this type of disturbance of the paraxial mesoderm. The defects may appear when a particular genetic or external factor acts upon a sensitive genetic background to delay the timing of development or movement of certain hemimetameres, leading to the shifting phenomena or hypoplasia-aplasia. Severe forms of multiple hemimetamere defects can appear
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in individuals with very sensitive genetic backgrounds, leading to severe deformity of the vertebral column. Most of these individuals would probably not have survived the neonatal period in prehistoric populations. The presence of a less severe hemimetamere defect in the Puye population indicates that a tendency for asynchronous development of the hemimetamere pairs was present. 2. Errors in Segmentation: Block Vertebrae Errors in segmentation leading to the development of block vertebra are present in eight adult individuals (8/142 = 5.6%) from Puye. All of these can be considered type II block vertebrae (including upper thoracic block vertebrae), based upon the Klippel-Feil classification (Bailey 1974; Gunderson et al. 1967). The defect is represented equally in females and males, and most (6/8 = 75%) are located in the cervical spine. The C2-C3 vertebrae (3/8 = 37.5%) are affected the most (Fig. 6.2a and b) and make up 50% of the cervical block vertebrae in the Puye collection. This is the most commonly affected area of the cervical spine. Autosomal dominant transmission is suggested (Bailey 1974; Gunderson et al. 1967). Two of the C2-C3 block vertebrae have associated minor cranial border shifts, bipartite hypoglossal canals (male), and type II dens defect (adult of indeterminate sex) at the occipitocervical border. The second most common type of block vertebra in the Puye collection is the C5-C6 block vertebra, usually considered to be an autosomal recessive condition (Bailey 1974; Gunderson et al. 1967). It occurs in one adult male and one adult female, representing 25% of the affected cervical spines (2/8). The female also has mild cranial shifting at the occipitocervical border in the form of a small precondylar tubercle. One additional female has the C3-C4 vertebrae as a block vertebra. The representation of cervical block vertebra in the Puye skeletal collection follows the generally accepted frequency trend: C2-C3 is the most frequent, followed by C5-C6. Two of the eight individuals with block vertebrae have failure of segmentation within the upper thoracic spine. One of these (NMNH 262939) has been mentioned, with the hemimetamere defect and failure of segmentation of the T3-T4-T5 vertebral segments. The other individual, a male, has a block vertebra consisting of the T2-T3 vertebral segments (Fig. 6.2c), with signs of mild caudal segmental shifting at the occipitocervical border in the form of a precondylar facet. Generally, the thoracic spine is affected less often
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Fig. 6.2 Type II block vertebrae from Puye. A: anterior view of C2-C3 block vertebra. B: right lateral view, from adult female (NMNH 262934). C: left lateral view of T2-T3 block vertebra from adult male (NMNH 269289).
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than the cervical spine, but when it is, the defect usually occurs in the midthoracic region. One adult female from Otowi (1/16 = 6.2%) has a type II C2-C3 block vertebra with an associated mild caudal shift at the occipitocervical border in the form of a precondylar facet. This frequency is similar to that of Puye. Two of thirteen individuals from Tsankawi have type II cervical block vertebrae. An adult female has a C2-C3 block vertebra with an associated mild caudal shift at the occipitocervical border in the form of a precondylar facet. An adult of indeterminate sex (NMNH 228999) has a C6-C7 block vertebra with unilateral neural arch aplasia of the seventh cervical vertebral segment. Sample size from Otowi (N = 16) and Tsankawi (N = 13) may be a contributing factor to the estimated frequencies (Table 6.4). However, it seems relevant that the defect appears in both of these small samples. This suggests that the projected frequencies are not far off and that the frequency for Tsankawi appears to be more than twice that of Puye and Otowi. Table 6.4. Frequency of Block Vertebrae Site N Occurrence Puye 142 8 Central plateau total 29 3 Otowi 16 1 Tsankawi 13 2 Tsirege 0
Frequency (%) 5.6 10.3 6.2 15.4
Caudal segmental shifting in the form of occipitalization of the atlas is usually found in about half of all C2-C3 block vertebrae (Bailey 1974). Mild variations of cranial shifting are associated with 66.7% (2/3) of the C2-C3 block vertebrae and with one C5-C6 block vertebra (1/2 = 50%) in the Puye collection (Table 6.5). The Otowi and Tsankawi collections show a trend toward mild caudal shifting in the occipitocervical border associated with C2-C3 block vertebrae. These data suggest that Otowi and Tsankawi may be more closely related; they also imply some slight genetic differences between the northern community of Puye and the central communities (Otowi and Tsankawi) on the plateau.
Page 240 Table 6.5 Frequency of Minor Occipitocervical Border Shifting Associated with Failure of Segmentation (Block Vertebrae) Block Site vertebra type N Cranial shift Caudal shift No shift Puye C2-C3 3 2 0 1 C3-C4 1 0 0 1 C5-C6 2 1 0 1 T2-T3 1 0 1* 0 T3-T4-T5 1 0 0 1 Subtotal 8 3 1 4 Central 3 0 2 1 plateau total Otowi C2-C3 1 0 1* 0 Tsankawi C2-C3 1 0 1* 0 C6-C7 1 0 0 1 Tsirege 0 * = expressed as precondylar facet
Symptoms associated with type II block vertebrae are generally mild, if they are present at all. Most of the individuals with block vertebrae in these collections were probably unaware of anything being out of order. The presence of this type of block vertebra implies that more severe forms involving several vertebral segments (type I and type III) may have been present. Individuals born with them generally suffer other major defects as well, and most do not survive into adulthood. Type II block vertebrae have also been found in other Anasazi populations: Arroyo Hondo (Palkovich 1980), Chaco Canyon (Akins 1986), Mesa Verde (Miles 1975), Kayenta (Wade 1981), Gran Quivira (Reed 1981:83), Giusewa, Amoxiumqua, Hawikku, and Heshotauthla. Giusewa (Pueblo IV-V) and Amoxiumqua (Pueblo IV) are Towa sites southwest of the Pajarito Plateau on the southern slopes of the Jemez Mountains. Arroyo Hondo is a Pueblo IV Tanoan site located just east of Santa Fe. Gran Quivira, located in the Salinas area southeast of Albuquerque, was inhabited by the Tompiro during Pueblo IV and V. Mesa Verde, in the Northern San Juan region, was abandoned prior to the development of Pueblo IV on the Pajarito Plateau, and it may be ancestral to the Pajaritans. Chaco Canyon was also abandoned prior to the establishment of the Pajaritan Pueblo IV towns. Hawikku and Heshotauthla are ancestral Zuni. The Kayenta skeletal material dates to Pueblo II and Pueblo III and is considered ancestral to the Hopi.
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Type III block vertebrae were also identified in a neonate and in a fetus from the Pueblo IV site of Homol'ovi (Anderson 1989), also considered ancestral to the Hopi, and in an adult associated with the Pueblo III Yellow Jacket ruin in the Northern San Juan region. 3. Irregular Segmentation of Ribs The numbers of ribs are underrepresented and fragmented for many of the individuals in the skeletal collection from Puye. Very few ribs are present in the Otowi and Tsankawi collections. Only three individuals from Puye display mild developmental defects of the ribs. Two individualsone adult female twenty-seven to thirty years of age and a twelve-yearold childshare similar developmental rib defects known as rib spurs on the first and second ribs (Fig. 6.3a and c.). Rib spurs represent the mildest form of bifurcation. Without any provenance for the burials, it is difficult to judge familial ties, even though it is tempting to speculate that these two individuals were related. The sternal end of a midthoracic left rib in an adult male is flared (Fig. 6.3b). No other ribs were found with this particular defect. There is a strong genetic base for both minor and major expressions of this type of irregular segmentation of the ribs (Martin 1960). Brues (1946) found one bifurcated rib in Northern San Juan Anasazi skeletal material at Alkali Ridge. Bifurcation of a rib in one individual was also noted in Northern San Juan Anasazi skeletal material from Mesa Verde (Miles 1975) and in one ancestral Zuni from Hawikku. 4. Numerical Errors in Segmentation Numerical errors in segmentation pertain to extra vertebrae or too few vertebrae as a result of an irregular number of somites during development. An extra vertebra is more common than a missing vertebra, and extra vertebral segments usually appear at the thoracolumbar or lumbosacral borders (Allbrook 1955; Stewart 1932). The recognition of numerical errors in segmentation requires full preservation of the vertebral column in the skeletal material. Generally, few individuals within a prehistoric skeletal collection retain their original number of vertebrae. Puye is no exception. Only ten adults (six females and four males) have complete vertebral columns.
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Fig. 6.3 Irregular segmentation of ribs from Puye. a: small rib spurs on first ribs of twelve-year-old child (NMNH 262987); b: flared sternal rib end of adult male (NMNH 269292); c: small rib spur on right second rib of adult female (NMNH 262910).
Two adults (one female, one male) each posses an extra segment at the thoracolumbar border, plus the normal seven cervical, five lumbar, and five sacral segments (Table 6.6). The transitional apophyseal facets are present on the supernumeray thoracic segment. Both individuals had thirteen sets of ribs. Although all of her ribs are missing, the female (NMNH 262043) has thirteen sets of rib facets. The male (NMNH 269276) has a rudimentary (transitional) rib attached to one side of his supernumerary thoracic vertebra (Fig. 6.4). The rib on the other side is missing, but a small rib facet indicates that a rib was present. Signs of cranial shifting at the lumbosacral border are present in both of these individuals. The female has transitional transverse processes on L5, and the male has unilateral incomplete sacralization (transitional transverse process articulates with the sacrum) of L5 on the right side.
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Table 6.6. Frequency of Numerical Errors in Segmentation: Extra Vertebral Segments Found in Complete Vertebral Columns Fig. 6.4 Supernumerary vertebra at the thoracolumbar border with transitional rib from Puye. Superior view of T12, supernumerary vertebra, and L1 from adult male (NMNH 269276); transitional rib on left side has rounded, blunt tip. Site N Occurrence Frequency (%) Puye 10 2 20.0 Central plateau total
Comparisons of numerical errors from Puye with possible numerical errors from Otowi and Tsankawi could not be done because of the lack of complete vertebral columns in these collections. Extra vertebral segments have been found in a few other Anasazi populations. Reed (1981:85) discovered six supernumerary lumbar vertebrae in the Tompiro skeletal remains from Gran Quivira. Wade (1981) reported four extra lumbar vertebrae, all in males, plus one female with an extra thoracic vertebral segment in the western Anasazi population from Kayenta. Supernumerary thoracic and lumbar vertebrae appear in 15% (9/60) of the Pueblo IVV Zuni skeletal collection from Hawikkuall females, except for one male and one child.
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5. Border Shifting in the Vertebral Column a. Occipitocervical Border Shifting No major border shifts involving expression of the occipital vertebra or occipitalization of the atlas were found in any of the Pajarito Plateau skeletal collections. Minor variations of cranial and caudal border shifting, however, were noted in fifteen occipitals (15/128 = 11.7%) with intact bases in the Puye collection. Minor variations of caudal border shifting were found in 8/15 (53.3%) and minor variations of cranial border shifting in 7/15 (46.7%) of the occipitals. Generally, major shifting of the occipitocervical border takes place more commonly in a caudal direction than in a cranial direction (Epstein 1976). The most common form of shifting present at this border is the expression of a precondylar facet (Fig. 6.5a) on the anterior rim of the foramen magnum as a result of caudal border shifting. Six adults in the Puye collection four males and two females have this defect. The precondylar facet articulates with only the anterior arch of the atlas in one of the males and one of the females. It articulates with the dens and the atlas (Fig. 6.5b) in the other female and one other male and with the dens only in two males. Precondylar articulating facets are also present in the Otowi and Tsankawi collections. They are very similar to the ones found in the Puye collection and represent the only type of shifting found at the occipitocervical border in the central plateau collections. Two of the four individuals from Tsankawi with intact occipital bases (both adult females) have precondylar articulating facets. One of these articulates with the atlas alone, and the other articulates with both the atlas and the dens. One individual from Otowi, an adult female, has a precondylar articulating facet. It articulates with the atlas only. Despite the small sample size, the frequency ratio is similar to that for Puye (Table 6.7). Tsirege is represented by eight cranial bases, none of which expresses any type of shifting at the occipitocervical border. Although the sample sizes for Tsankawi and Tsirege are small, there is a dramatic difference between them in the frequency of this defect. It is ironic that two of the four individuals from Tsankawi are affected, whereas none of the eight individuals from Tsirege has the defect.
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Fig. 6.5 Precondylar facets resulting from caudal shifting at the occipitocervical border from Puye and Tsankawi. A: occipital of adult female (NMNH 269267) from Puye with precondylar facet and C1 with matching articulating facet. B: C1 articulated with C2 of adult female (NMNH 228967) from Tsankawi with articulating facets matching precondylar facet on occipital (not shown).
Page 246 Table 6.7. Frequency of Precondylar Facets (Minor Caudal Shifting at the Occipitocervical Border) Site N Occurrence Frequency (%) Puye 128 6 4.7 Central plateau total 29 3 10.3 Otowi 17 1 5.9 Tsankawi 4 2 50.0 Tsirege 8 0 0
Precondylar facets are rare in Southwest Anasazi skeletal collections. I have only been able to find three other cases, all from the large Hawikku (Pueblo IVV Zuni) collection. Paracondylar processes representing caudal shifting at the occipitocervical border are present in one adult male and one adult female in the Puye collection. The paracondylar process in the female is 78 mm wide and 2 mm high. It is located dorsal to the left occipital condyle, with a small postcondylar foramen also present. The adult male also has hypoplasia of the right occipital condyle, with the paracondylar process located on the right side and measuring 13 mm wide and 16 mm high (Fig. 6.6). The hypoplasia involves the right side of the lateral segment of the occipital, and it affects the size of the jugular foramen on the right, which is much larger than it is on the left side. There is a large posterior condylar foramen on the right and none on the left. The mastoid process is less pronounced on the right side than on the left. The most common minor expression of cranial shifting at the occipitocervical border in the Puye collection is the presence of bipartite (double) hypoglossal canals (4/7 = 57.1%) in four adults two males and two females. Two of these cases are unilateral (one on the left and one on the right), and one has only one side present. One has two small posterior condylar foramina and two very small foramina on the posterior edge of the foramen magnum. The male with bipartite hypoglossal canals also has a C2C3 block vertebra. Other minor expressions of cranial shifting in the Puye collection include the presence of precondylar tubercles in one adult male and one adult female and the displacement of the odontoid, type II (tip of dens missing), in an adult of indeterminate sex (Table 6.8). Miles (1975) noted a similar odontoid defect in a Northern San Juan Anasazi individual from Mesa Verde, and Palkovich (1980) reported one from the Tanoan pueblo of Arroyo Hondo. There is also one case of type II dens defect in the Amoxiumqua (Pueblo IV Towa) collection.
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Fig. 6.6 Paracondylar process resulting from caudal shifting at the occipitocervical border from Puye. Occipital of adult male (NMNH 26268).
El-Najjar (1974) found a high frequency of the precondylar tubercles in the Canyon de Chelly Basket Makers (12/56 = 21.4%), which decreased in frequency through Pueblos I, II, and III (2/16 = 12.5%). Precondylar tubercles are present in three individuals from Hawikku (Pueblo IV-V Zuni), one female from Pueblo Bonito (Pueblo II-III), and one female from Amoxiumqua (Pueblo IV Towa). Table 6.8. Frequency of Minor Occipitocervical Border Shifting Site N Cranial shift Caudal shift Puye 128 7 (5.5%) 8 (6.3%) females 85 3 (3.5%) 5 (5.9%) males 41 3 (7.3%) 3 (7.3%) indeterminate 2 1 0 Central plateau total 29 0 3 (10.3%) females 19 0 3 (15.8%) males 10 0 0
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Minor caudal border shifting appears to be more common than minor cranial border shifting in females, whereas males tend to have equal representation of both types of minor occipitocervical border shifting in the Puye collection. No indications of cranial shifting at this border were found in the Otowi and Tsankawi samples, and the minor expressions of caudal shifting were found only in females. Sample size for Otowi and Tsankawi may be a factor. The major form of caudal shifting at the occipitocervical border, occipitalization of the atlas, has been found in other Anasazi populations. Palkovich (1980) reported a case from the Pueblo IV Tanoan site of Arroyo Hondo. Another Pueblo IV Tanoan site, Pueblo Largo in the Galisteo Basin southeast of Santa Fe, had two cases, and one case was found in the Tompiro population at Gran Quivira (Reed 1981:113). Akins (1986) identified another case at Chaco Canyon. Merbs and Euler (1985) described a western Anasazi female from Bright Angel ruin (Pueblo II-III) in the Grand Canyon with occipitalization of the atlas associated with a C2-C3 block vertebra. A similar case of occipitalization of C1 with a C2-C3 block vertebra was found in an adult male from Heshotauthla (Pueblo IV Zuni). It is very significant that none of the 157 intact cranial bases from the Pajarito Plateau towns showed occipitalization of the atlas, despite the tendency toward minor expressions of caudal shifting at the occipitocervical border. The Anasazi residents of the northern and central portions of Pajarito Plateau differed markedly from other Anasazi populations in this respect. b. Thoracolumbar Border Shifting Expressions of shifting at this border were found in five of eighty-four adults (5.9%) in the Puye collection (Table 6.9). A trend toward caudal shifting at the thoracolumbar border is much more common than cranial shifting in this collection, with four of the five individuals (80%) affected. All of these are females. Major caudal border shifting in the form of lumbar ribs is present in one of the females. The other three have mild expressions of caudal shifting in the form of transitional facets on the first lumbar vertebral segment. The female with major caudal border shifting has a 15-mm-long tuber-clelike right lumbar rib articulating with a stunted transverse process of the first lumbar vertebral segment (Fig. 6.7). A small articulating facet on the left side indicates that a similar, companion left lumbar rib was present but has been lost during the collection process. Lumbar ribs can cause severe pain or soreness in the lumbar region.
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Fig. 6.7 Lumbar rib resulting from caudal shifting at the thoracolumbar border from Puye. Young adult female (NMNH 269299) with articulating right lumbar rib (left side missing). a: dorsal view; b: inferior view.
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The only expression of a cranial border shift (1/5 = 20%) occurs in an adult male. The twelfth thoracic vertebra has a small right costal facet and absent left costal facet. This reflects a rudimentary twelfth rib on the right side (missing postmortem) and the lack of a twelfth rib on the left side. No evidence of shifting at the thoracolumbar border could be found in the Otowi (N = 4) or the Tsankawi (N = 6) collections. Sample sizes are too small. Table 6.9. Frequency of Thoracolumbar Border Shifting Site N Cranial shift major Puye 84 1 (1.1%) females 54 0 males 29 1 (3.4%) indeterminate 1 0 Central plateau total 10 0
Caudal shift minor 3 (3.5%) 3 (5.5%) 0 0 0
major 1 (1.1%) 1 (1.8%) 0 0 0
Lumbar ribs (major caudal shifting at the thoracolumbar border) are not common in any population (Brailsford 1948), and they are much less common than cervical ribs (cranial shifting at the cervicothoracic border). Bilateral, asymmetrical lumbar ribs were found in one adult from Giusewa (Pueblo IV-V Towa), located southwest of the Pajarito Plateau on the other side of the Jemez Mountains. The neighboring Pueblo IV Towa town of Amoxiumqua has one individual (male) with unilateral expression of a lumbar rib. The southern Tiwa group from Quarai (Pueblo IV) also has one individual with unilateral expression of lumbar rib, and the Pueblo IV Zuni town of Heshotauthla has two males with unilateral lumbar rib. Reed (1981:82) reported a number of Tompiro individuals from Gran Quivira with cranial shifting at the thoracolumbar border in the form of unusually small twelfth ribs. c. Lumbosacral Border Shifting Expressions of cranial shifting (29/93 = 31.1%) are much more common than expressions of caudal shifting (7/93 = 7.5%) at the lumbosacral border in the Puye collection. Complete cranial border shifting in the form of bilateral sacralization of the last lumbar vertebral segment occurs in only one individual (1/29 = 3.4%). One female has unilateral sacralization of L5 on the
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left side, whereas the right side remains separate and articulates with the sacral ala (Fig. 6.8). Incomplete sacralization is represented by the transformation of the transverse processes of the last lumbar vertebral segment into wide, alalike processes that articulate with the sacrum (Fig. 6.9). This was found in eleven adultsseven females and four males (11/29 = 37.9%). Two are bilateral and nine are unilateral, five on the right side and four on the left side. The complete and incomplete sacralizations together represent 13.9% (13/93) of lumbosacral spines in the Puye collection. The remaining sixteen individuals ten females and six males have mild cranial border shifting represented by transitional transverse processes of the last lumbar vertebra. These are wide, alalike processes that do not articulate with the sacrum (16/29 = 55.1%). Two have unilateral expressions on the left side, whereas the other side appears normal. Sacralized lumbar vertebral segments (cranial shift), complete and incomplete (13/93 = 13.9%), are much more common than lumbarized sacral vertebral segments (caudal shift), complete and incomplete (3/93 = 3.2%), in the Puye collection. Only two adults one female and one male have complete lumbarization of the first sacral segment. One adult female has incomplete lumbarization in which S1 is not quite free of the sacrum. Four adults two males and two females have mild expressions of caudal border shifting in the form of transitional S1 inferior apophyseal facets articulating with the second sacral segment. This is the equivalent of the mild expression of cranial shifting, the nonarticulating transitional lumbar transverse processes (Table 6.10). Expressions of caudal shifting at the lumbosacral border were not found in the Otowi (N = 9) and Tsankawi (N = 7) skeletal collections. A mild expression of cranial shifting was noted in one adult of indeterminate sex from Tsankawi in the form of nonarticulating transitional transverse processes of the last lumbar vertebra (1/7 = 14.2%). Three adults two females and one male from Otowi (3/9 = 33.3%) have transitional transverse processes of the last lumbar vertebra. One of the females has unilateral expression of the transitional transverse process on the right side, articulating with the sacrum. Table 6.10. Frequency of Lumbosacral Border Shifting Site N Cranial shift Caudal shift minor major minor Puye 93 16 (17%) 13 (14%) 4 (4.3%)
major 3 (3.2%)
Page 252 Table 6.10 (continued) Site females males Central plateau total Otowi females males Tsankawi Tsirege
N Cranial shift minor 59 10 (17%) 34 6 (17.6%) 16 3 (18.7%) 9 2 (22.2%) 4 1 (25%) 5 1 (20%) 7 1 (14.2%) 0
major 8 (13.5%) 5 (14.7%) 1 (6.2%) 1 (11.1%) 1 (25%) 0 0
Caudal shift minor 2 (3.4%) 2 (5.9%) 0 0 0 0 0
major 2 (3.4%) 1 (2.9%) 0 0 0 0 0
Expressions of cranial shifting at the lumbosacral border are present in Puye, Tsankawi, and Otowi. Otowi (33.3%) appears to have a similar frequency of shifting at this border as Puye (38.7%). The frequency for shifting at Tsankawi (14.2%) appears to be far less. With this type of defect, Tsankawi appears to differ the most from the other sites in the expression of cranial shifting. In its lack of caudal shifting, Tsankawi is similar to Otowi (Table 6.10). Table 6.11. Frequency of Total Shifts at the Lumbosacral Border Site N Occurrence Frequency (%) Puye 93 36 38.7 Central plateau total 16 4 25.0 Otowi 9 3 33.3 Tsankawi 7 1 14.2 Tsirege
In contrast to Puye, the Tompiro of Gran Quivira exhibit a much lower frequency of cranial shifting in the form of sacralization (1/108 = .9%). Lumbosacral caudal border shifting in the form of lumbarization of S1 (3/108 = 2.7%) occurs more often than sacralization of L5 in the Gran Quivira population (Coyne 1981:151). This is just the opposite of Puye, where cranial shifting is much more common than caudal shifting. The Pajaritans have a
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Fig. 6.8 Sacralization of fifth lumbar vertebra resulting from cranial shifting at the lumbosacral border from Puye. Anterior view of adult female (NMNH 262941) sacrum with unilateral (left side) and incomplete (right side) sacralization of L5.
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Fig. 6.9 Unilateral incomplete sacralization of fifth lumbar vertebra resulting from unilateral cranial shifting at the lumbosacral border from Puye. Anterior view of adult female (NMNH 262953) sacrum and L5; right transverse process of L5 wide and articulating with the sacrum; left side normal.
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much higher frequency of major shifts at the lumbosacral border (14/109 = 12.8%) than the Gran Quivirans (4/108 = 3.7%) A few other cases of shifting at the lumbosacral border have been reported elsewhere in Southwest Anasazi skeletal collections. Incomplete lumbarization of S1 (caudal border shifting) was noted in three Anasazi adults (3/135 = 2.2%) from Chaco Canyon (Akins 1986). Miles (1975) mentions one Northern San Juan Anasazi from Mesa Verde with cranial shifting in the form of unilateral sacralization of L5. Sacralization of L5 is present in three adults from Quarai (Pueblo IV Southern Tiwa), one female from Giusewa (Pueblo IV-V Towa), six individuals from Amoxiumqua (Pueblo IV Towa), and seven individuals from Hawikku (Pueblo IV-V Zuni). Unilateral expression of lumbarized S1 is present in one female from Amoxiumqua and one female from Heshotauthla (Pueblo IV Zuni). d. Sacrocaudal Border Shifting Cranial border shifting affecting the last sacral vertebral segment was not found in any of the Pajarito Plateau skeletal collections. By contrast, caudal border shifting involving the incorporation of the first caudal segment into the sacrum is common. Twenty adult sacra in the Puye collection ten females, nine males, and one of indeterminate sex have this defect. Only four of these (4/20 = 20%) two females and two males have complete bilateral incorporation of the first caudal segment and the formation of extra sacral foramina. The remaining sixteen individuals (80%) show incomplete expressions of caudal shifting at the sacrocaudal border. Eight (six females and two males) have only the body of the first caudal segment incorporated into the sacrum. The other eight have formed an extra sacral foramen on one side, along with the incorporation of the body of the first caudal segment (Fig. 6.10). Two males (2/9 = 22.2%) in the Otowi skeletal collection exhibit caudal shifting of the sacrocaudal border. One of these has complete incorporation of the first caudal segment into the sacrum, except for a small space at the sacrocaudal border on the dorsal aspect. The other individual has incomplete incorporation of the first caudal segment, with only the body fused to the sacrum (Table 6.12). An adult female (1/7 = 14.3%) from Tsankawi has caudal shifting of the sacrocaudal border. The body of the first caudal segment is asymmetrical, with hypoplasia of the left side, and it has been incorporated into the sacrum (Fig. 6.11). The frequencies of caudal shifting at the sacrocaudal border appear to
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Fig. 6.10 Incomplete sacralization of first caudal segment resulting from caudal shifting at the sacrocaudal border from Puye. Anterior view of sacrum, with body and right side of first caudal segment incorporated into last sacral segment; adult female (NMNH 263086).
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Fig. 6.11. Incomplete sacralization of first caudal segment resulting from caudal shifting at the sacrocaudal border from Tsankawi. Anterior view of sacrum, with body of first caudal segment asymmetrically fused to last sacral segment; young adult female (NMNH 228991).
be similar for Puye (21.5%) and Otowi (22.2%) but are somewhat different for Tsankawi (14.2%). I have found that caudal shifting of the sacrocaudal border is common in many of the Southwest Anasazi skeletal collections. Table 6.12. Frequency of Sacrocaudal Border Shifting Site N Cranial Puye 93 0 Central plateau total 16 0 Otowi 9 0 Tsankawi 7 0 Tsirege
Caudal 20 (21.5%) 3 (18.7%) 2 (22.2%) 1 (14.2%)
There are significant shifting tendencies at the transitional borders of the vertebral column in the Puye collection. These tendencies do not follow the same direction. Tendencies toward more cranial shifting than caudal
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shifting occur at the lumbosacral border, and tendencies toward more caudal shifting are found at the occipitocervical, thoracolumbar, and sacrocaudal borders. In general, more females than males are affected by border shifting (Table 6.13). Table 6.13. Trends in Border Shifting of the Vertebral Column for Puye Cranial shift (%) Caudal shift (%) Segmental border N Occipitocervical 15 minor 46.7 minor 53.3 female 8 37.5 62.5 male 6 50.0 50.0 indeterminate 1 100.0 0 Cervicothoracic 0 minor 0 minor 0 female 0 0 0 male 0 0 0 Thoracolumbar 5 major 20.0 major and minor 80.0 female 4 0 80.0 male 1 20.0 0 Lumbosacral 36 major and minor 80.6 major and minor 19.4 female 22 50.0 50.0 male 14 30.6 69.4 Sacrocaudal 20 major and minor 0 major and minor 100.0 (no major difference between sexes)
Shifting can affect more than one border in the same individual. Such shifting may or may not be in the same direction. Shifting in different directions at different borders in the same individual is possible because of the way the somites develop during morphogenesis; they develop at different times and reach their critical thresholds at separate times. By the time the first somites have completed their transformation in the sclerotome stage, later somites are just forming. The different border segments also complete their formation at different times and apparently do not influence each other. Disturbance at one border, therefore, does not necessarily affect other borders. Seven adults (three females and four males) in the Puye collection display more than one border shift. All of these cases except one involve the sacrocaudal border. The majority (5/7 = 71.4%) affect both the lumbosacral and sacrocaudal borders. Three of these (3/5 = 60%) two females and one
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male show cranial shifting at the lumbosacral border with caudal shifting at the sacrocaudal border. Two males (2/5 = 40%) have caudal shifting at both the lumbosacral and sacrocaudal borders. One adult male has unilateral cranial shifting at the lumbosacral border and bilateral caudal shifting at the thoracolumbar border. One adult female has caudal shifting at the occipitocervical and sacrocaudal borders. Shifting at more than one border could only be detected in one individual from the other Pajarito Plateau sites, an adult female from Tsankawi. This individual has cranial shifting at the lumbosacral border with caudal shifting at the sacrocaudal border. 6. Developmental Delay of the Vertebral Elements a. Sacral Neural Arch Defects Developmental delay of the vertebral elements can be recognized in twenty-two individuals (22/183 = 12.0%) in the Puye collection. The majority of these defects (18/22) found in seven adult females, six adult males, one adolescent, and four children involve the sacral vertebral segments. This represents 6.5% of the female sacra (8/122), 13% of the male sacra (6/47), and 29% of the juvenile sacra (4/14). Males appear to be more prone to developmental delay defects in the sacrum than females. Defects resulting from developmental delay in the sacrum appear as either hypoplasia or aplasia of the neural arches, leading to bifurcation or varying degrees of clefting. Bifurcation occurs with moderate hypoplasia of one or both of the neural arches, allowing them to meet but not to fuse together. Varying degrees of clefting occur, with a greater degree of hypoplasia of one or both neural arches. Wide clefts of varying degrees are produced when there is aplasia of one or both neural arches. In the Puye collection, all but one of the sacra with neural arch segments affected by developmental delay have either a cleft or a bifid first sacral segment (Fig. 6.12). This one individual, an adult female (NMNH 269269), has a normal first sacral segment, then a wide cleft in the second sacral segment, ending in a narrow bifurcation at the border with the third sacral segment. The third segment has a jagged-appearing cleft that continues into the sacral hiatus. One adult male (NMNH 263024, Fig. 6.12) has only a small cleft in the upper border of the first sacral segment. The other sixteen individuals have disturbances affecting more than one sacral segment. In 50% (9/18), only the first and second sacral segments are affected (Fig. 6.13). There appears to be
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Fig. 6.12 Variations of sacral cleft neural arch from Puye.
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Fig. 6.13 Sacrum with cleft first and second sacral segments from Puye. Sacrum and L5 from adult male (NMNH 262942).
a trend toward bifurcation or clefting as a result of hypoplasia or aplasia at the first sacral level, followed by a cleft in the upper portion of the second sacral level. This can be seen in all stages of development in the juveniles represented in this sample. Sometimes the disturbance continues downward, in the form of bifurcations or clefting, to various degrees. In general, the sacra in the Pajarito Plateau skeletal collections have a minimal sacral hiatus that does not extend beyond the border of the fourth and fifth sacral segments. When developmental delay disturbances continue downward in the sacral segments to affect the third segment, the last two segments are also affected, and the hiatus is usually wider, extending into the cleft or bifurcation of the third segment (Fig. 6.14). There is no consistent pattern in the developmental delay defects of the sacrum below the first sacral segment. When clefts appear below the second sacral segment, they tend to be irregular in shape. Three adultstwo females (NMNH 263005 and NMNH 262949) and one male (NMNH 262947) have every sacral segment affected by either clefting or bifurcation (Fig. 6.12). Developmental delay defects of the sacrum affect approximately 10% (18/183) of the sacra in the Puye collection.
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Fig. 6.14 Cleft and bifurcated neural arches of sacrum from Puye. Adult female (NMNH 262949).
The sacralized last lumbar vertebra of an adult female (NMNH 262941, Fig. 6.12) has a bifid neural arch. A ten-year-old child has a small cleft neural arch in the last lumbar vertebra; unfortunately, the sacrum is missing. The trend toward developmental delay disturbances in the first sacral segment is similarly seen in the Otowi collection in the form of clefting as a result of hypoplasia or aplasia of the neural arches (Table 6.14). Clefting of the first sacral segment is common in many populations. Table 6.14. Frequency of Cleft/Bifurcation of the Sacrum Site N Occurrence Puye 183 18 Central plateau total 19 10 Otowi 12 8 Tsankawi 7 2
Frequency (%) 9.8 52.6 66.6 28.5
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Fig. 6.15 Variations of sacral cleft neural arch from Otowi (rows A and B) and Tsankawi (row C). Table 6.14 (continued) Site Tsirege
N Occurrence 0
Frequency (%)
Fifty percent (4/8) of the Otowi sacra with developmental delay disturbances involve only the first and second sacral segments (Fig. 6.15a). The same is true for Puye. One adult male (NMNH 228954, Fig. 6.15b) has a normal first sacral segment followed by a cleft in the second sacral segment. A young adult (NMNH 229003, Fig. 6.15b) has a wide cleft in the first sacral segment
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Fig. 6.16 Complete cleft sacra from Otowi and Tsankawi. A: bifid L5 and cleft sacrum of adult male (NMNH 228941) from Otowi. B: complete cleft sacrum of adult female (NMNH 228967) from Tsankawi.
extending into the upper portion of the second sacral segment and an irregular cleft in the third segment. Another Otowi adult male (NMNH 228990, Fig. 6.15b) has an unusually high and wide sacral hiatus for a Pajaritan; it extends into the lower portion of the third sacral segment. This is unlike any of the other sacra and may represent someone who originated outside the population. Another adult male (NMNH 228941, Fig. 6.15b) has a complete wide cleft through all sacral segments and a small cleft in the last lumbar vertebral segment (Fig. 6.16a). Only twelve sacra are present in the Otowi collection. Approximately 67% (8/12) are affected by developmental delay, all exhibiting some form of clefting and no bifurcation (Fig. 6.15a-b). The trend here is toward greater hypoplasia and more aplasia than in Puye, and there is an extremely high frequency despite the small sample size. Another complete wide sacral cleft was found in an adult female (NMNH 228967, Figs. 6.15c and 6.16b) in the Tsankawi collection. One adult female (NMNH 228937, Fig. 6.15c) in this collection has a small, oval cleft
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involving the lower border of the first sacral segment and the upper border of the second segment. Only seven sacra are present in the Tsankawi collection, with approximately 29% (2/7) affected by developmental delay. The completely clefted sacrum of the adult female is very much like that of the adult male in the Otowi collection (Fig. 6.16a), suggesting they were related. All of the sacral cleft defects would have been covered by protective, tough, fibrous tissue, and the affected individuals were probably unaware of any abnormality. Otowi has the highest frequency for developmental delay defects of the sacrum (66.6%), followed by Tsankawi (28.5%) and Puye (9.8%). The frequency of the involvement of the first and second sacral segments with developmental delay defects appears to be highest in Otowi (4/12 = 33.3%) and lowest in Puye (9/183 = 4.9%), with Tsankawi in between (1/7 = 14.2%). Clefting of the neural arches is not uncommon, with a frequency averaging up to 25% in any population. Otowi, however, has an unusually high frequency. To sum up, despite the variability in the number of sacral segments affected, the shapes of the clefting/bifurcation defects of the sacrum are similar in character for all three skeletal collections. This commonality indicates that Puye, Otowi, and Tsankawi all shared the same gene pool. The tendency for greater hypoplasia leading to aplasia of the sacral neural arches would most likely be an outgrowth of inbreeding, that would increase the risk of developing a full cleft. As already mentioned, there is a strong probability that the two individuals with full sacral clefting were genetically related, even though one came from Otowi and the other from Tsankawi. Similarly, I suspect that the three individuals from Puye with almost, but not quite, full clefting may have shared common familial ties. Other expressions of clefting/bifurcation of the sacrum were found in the ancestral Zuni collections from Hawikku and Heshotauthla, in the Towa collections from Giusewa and Amoxiumqua, and in the Pueblo Bonito collection. b. Atlas: Posterior Arch Defects Other defects of the vertebral elements caused by developmental delay found in the Puye collection include hypoplasia and aplasia of the posterior arch of the atlas. This defect is present in four adults (4/87 = 4.5%) three females and one male (Fig. 6.17). This is near the generally expected frequency of 5% for any population (Bailey 1974) (Table 6.15).
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Fig. 6.17 Posterior arch defects of the atlas from Puye. a: aplasia of right side with compensatory growth from left side in adult female (NMNH 262911), (1) inferior view, (2) superior view; b: cleft posterior arch in adult female (NMNH 262915), superior view; c: cleft posterior arch in adult female (NMNH 269252), superior view; d: bifurcated posterior arch in adult male (NMNH 262974), superior view.
Page 267 Table 6.15 Frequency of Cleft Atlas Site N Occurrence Puye 87 4 Central plateau total 2 Otowi 1 Tsankawi 1 Tsirege 0
Frequency (%) 4.5
Two of the females have a cleft posterior neural arch. One (NMNH 262915) also has hypoplasia of the right transverse process of the fifth lumbar vertebral segment. The other female (NMNH 262911) has an unusual aplasia of the right side of the posterior neural arch, with compensatory overgrowth of the left side, which extends toward the lateral mass on the right side in a very thin, tapered arch with a forked tip (Fig. 6.17a). The male (NMNH 262974) displays a bifurcated posterior arch (Fig. 6.17d). Only the female with the unilateral aplasia of the posterior neural arch would have suffered discomfort from some malalignment. The others were probably unaware of their defects, because the missing bony union is generally filled in with tough, fibrous tissue. Cleft atlas appears to be rare in other Southwest Anasazi skeletal collections. Only two other examples were found an adult male from Quarai (Pueblo IV Southern Tiwa) and one adult of unknown sex from Pueblo Bonito (Pueblo III) in Chaco Canyon. c. Other Vertebral Element Defects Minimal developmental delay disturbances affecting other vertebral elements appear to be sporadic in the Puye skeletal collection. The adult female with the extra thoracic vertebral segment also exhibits asymmetry of the transverse processes on the third lumbar vertebral segment. Another adult female also has asymmetry of transverse processes on the first four lumbar vertebrae. An adult male has asymmetry of the adjacent apophyseal facets on the eleventh and twelfth thoracic vertebrae. Hypoplasia of the spinous process of the third thoracic vertebra exists in one adult female. One adult male has a bifid spinous process of the axis vertebra (1/74 = 1.3%). Only one individual (1/13 = 7.6%) from the central Pajarito Plateau sites was found with a disturbance of developmental delay outside the sacrum. Aplasia of the left neural arch of the seventh cervical vertebral segment is present in the adult of indeterminate age and sex (NMNH 228999) with a
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Fig. 6.18 Aplasia of the left side of the neural arch of C7, with failure to completely segment from C6, from Tsankawi. Dorsal view of C6C7 from adult of indeterminate sex (NMNH 228999).
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C6C7 block vertebra from Tsankawi (Fig. 6.18). The right side of the seventh cervical vertebral segment is normal, and a norma-appearing spinous process developed from this half and then curved over to the left side when it felt no resistance from the absent left half. The spinous process of C6 overlaps that of C7, and the left lamina appears enlarged, compensating for the missing lower lamina of C7. The left pedicle of C7 is present, but the lamina and apophyseal facet are missing. The seventh rib on this side must have been affected (unfortunately, it is missing from the collection). The sixth cervical vertebral segment is misplaced on the left side because of this defect. This created asymmetry, leading to a scoliosis in the cervicothoracic junction (Fig. 6.19). There are compensatory degenerative joint changes in C3 through C6 and T1: the fifth and sixth cervical segments are fused as a result of degenerative changes. All of the cervical vertebrae and the upper five thoracic vertebrae are present. B. Prechordal Cranial Base Field Defect One adult female (NMNH 262926) in the Puye collection (Table 6.16) has hypoplasia of the parachordal cartilages. The basilar process is very short, only 12 mm long, compared to 2232 mm in other adult crania from Puye (Fig. 6.20). The trabecular cartilages (lesser wings, body and roots of greater wings of the sphenoid, and ethmoid) and the otic capsule (petromastoid of the temporal) were not affected. The nose is flat with facial prognathism, suggestive of achondroplasia. However, the normal postcranial skeletal elements rule this out, showing that this is strictly a field defect of the prechordal cranial base. Table 6.16. Frequency of Prechordal Cranial Base Defect Site N Occurrence Puye 103 1 Central plateau total 27 0 Otowi 17 0 Tsankawi 2 0 Tsirege 8 0
Frequency .09 0 0 0 0
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Fig. 6.19 Scoliosis of cervical spine resulting from unilateral aplasia of the neural arch of C7 from Fig. 6.18. Dorsal view of C3 to T2 shows scoliosis; the defect of C7 created compensatory reactions on adjacent vertebrae C3, C4, C5, C6, and T1 in the form of erosive lesions on apophyseal joints, osteophytic development anteriorly, and pathological fusion of C5 and C6; C1, C2, and other upper thoracic vertebrae were not affected.
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Fig. 6.20 Abnormally small basioccipital from Puye, resulting from hypoplasia of the parachordal cartilages. From adult female (NMNH 262926).
C. Blastemal Desmocranium Field Defects 1. Failure to Coalesce a. Primary Suture Ossicles (1) Numerous lambdoidal ossicles. Corruccini (1972) recognized a large number of adult crania with extra ossicles in the Puye collection. The crania of 141 individuals 89 females, 42 males, and 10 children were examined for extra ossicles in this study. Thirty females (30/89 = 33.3%), 14 males (14/42 = 33.3%), and 6 children (6/10 = 6 0%) have numerous lambdoidal ossicles (Fig. 6.21a). Obviously, there is a tendency for numerous ossicles to develop in the lambdoidal suture in the Puye population, suggesting a genetic causal relationship (Table 6.17). A similar frequency of numerous lambdoidal ossicles shows up in both the Tsirege (5/10 = 50%) and the Tsankawi (1/2 = 50%) collections. Otowi
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Fig. 6.21 Occipital with numerous lambdoidal ossicles and occipital with interparietal bones from Puye. A: occipital of adult male (NMNH 263028) with numerous lambdoidal ossicles. B: tripartite form of interparietal bones and lambda ossicle in adult female (NMNH 263015).
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has six adult crania (6/17 = 35.2%) with numerous ossicles in the lambdoidal suture, and only one individual (1/17 = 5.8%) is free of extra ossicles. Table 6.17. Frequency of Numerous Lambdoidal Ossicles Site N Occurrence Puye 141 50 Central plateau total 29 12 Otowi 17 6 Tsankawi 2 1 Tsirege 10 5
Frequency (%) 35.4 41.3 35.2 50.0 50.0
(2) Fontanelle bones. Fontanelle bones at lambda, bregma, and obelion were noted in eighteen adults (18/141 = 12.7%) from the Puye collection. Most of these seven females and five males were found at lambda (12/18 = 66.7%). Bregma bones (Fig. 6.22) appear in two adult females and one adult male (3/18 = 16.6%), and obelion bones occur in three adult females (3/18 = 1 6.6%). Bregma bones were not found in the other Pajarito Plateau skeletal collections. Sample size may be too small for detection. Lambda bones are present in two adults one female and one male (2/10 = 20%) from Tsirege and one adult female (1/17 = 5.8%) from Otowi. One adult male from Otowi has an obelion bone (1/17 = 5.8%) (Table 6.18). Table 6.18. Frequency of Fontanelle Bones Site N Lambda Puye 141 12 (8.5%) female 89 7 (7.9%) male 42 5 (11.9%) juvenile 10 0 Central plateau 31 3 (9.7%) total Otowi 17 1 (5.9%) female 9 1 (11.0%) male 8 0 Tsankawi 4 0 all females Tsirege 10 2 (20%)
Bregma 3 (2.1%) 2 (2.2%) 1 (2.4%) 0 0
Obelion 3 (2.1%) 3 (3.4%) 0 0 1 (3.2%)
0 0 0 0
1 (5.9%) 0 1 (12.5%) 0
0
0
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Fig. 6.22 Bregma fontanelle bones from Puye. Superior view of crania from a: adult male (NMNH 263042); b: adult female (NMNH 263035).
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Table 6.18 (conitnued) Site female male
N 5 4
Lambda 1 (17%) 1 (25%)
Bregma 0 0
Obelion 0 0
(3) Retention of the mendosa suture and multiple interparietal bones. Retention of the mendosa suture is present in two adults one female and one male from the Puye collection. Failure of the interparietal segments to coalesce appears in one female (tripartite formation, Fig. 6.21b) and one male (bipartite formation). The other Pajarito Plateau collections did not have these defects. This appears to be an uncommon occurrence in the central and northern Pajarito Plateau populations (Table 6.19). Table 6.19. Frequency of the Retention of the Mendosa Suture Site N Occurrence Frequency (%) Puye 141 2 1.4 Central plateau total 29 0 0
Hooton (1930:95) found that the Pueblo IV Towa from Pecos Pueblo east of Santa Fe also tended to have numerous ossicles in the lambdoidal suture, and only two crania had patent mendosa sutures in the occipital. Four (three males and one female) had bregma bones. This general distributional pattern of blastemal desmocranium anomalies is very similar to that of the Pajaritans. By contrast, El-Najjar (1974) found a high incidence (10.5%) of the mendosa suture in Western Anasazi Pueblo III crania from Canyon de Chelly, an increase from 4.8% during the Basket Maker period. There are one bregma bone, three obelion bones, and three adult crania with the mendosa suture in Hawikku (Pueblo IV-V Zuni) crania. One bregma bone and two crania with the mendosa suture are present in the Pueblo IV Zuni Heshotauthla collection. One bregma bone and one obelion bone are present in the Pueblo Bonito (Pueblo II-III) collection.
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Fig. 6.23 Metopism from Tsirege. Adult female (NMNH 228927).
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2. Metopism Metopism occurs in only one individual (Fig. 6.23) among all of the Pajarito Plateau collections, an adult female in the Tsirege collection. The metopic suture is continuous with the sagittal suture, and frontal bossing is present. This fits the general sporadic and infrequent pattern found in the Southwest (Table 6.20). Metopism was found in only one other Anasazi skeletal collection, in an adult female from the ancestral Zuni town of Hawikku. Table 6.20. Frequency of Metopism Site N Puye 141 Central plateau total 29 Tsirege 10
Occurrence 0 1 1
Frequency (%) 0 3.4 10.0
3. Sutural Agenesis Two Otowi adults one female and the other of indeterminate sex have absence of the sagittal suture without scaphocephaly. Both crania show signs of asymmetrical vertical cranial deformation that influenced the shape of the cranium. Because they are the only individuals with this defect, a familial tie is suggested (Table 6.21). Table 6.21. Frequency of Sutural Agenesis Site N Occurrence Puye 141 0 Central plateau total 29 2 Otowi 17 2
Frequency (%) 0 6.8 11.7
Agenesis of the sagittal suture does occur sporadically in other Anasazi populations. Agenesis was observed in three adults and one child from the Pueblo IV Towa population at Pecos (Hooton 1930:323328) and in one adult and one child from Chaco Canyon (Akins 1986). Sutural agenesis of the sagittal and lambdoidal sutures with scaphocephaly is present in one individual
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from Pueblo Bonito (Pueblo II-III) and in one female from Heshotauthla (Pueblo IV Zuni). One female from Hawikku (Pueblo IV-V Zuni) is missing the lambdoidal suture and the posterior portion of the sagittal suture. D. Branchial Arch I Ectodermal Groove Field Defect: Partial Atresia of the External Auditory Meatus The same adult female (NMNH 228927) in the Tsirege collection with metopism also has partial atresia of the external auditory meattus resulting from bilateral hypoplasia of the first branchial arch ectodermal groove (Table 6.22). The closing membranes are also affected by hypoplasia, producing short tympanic bony plates. The hypoplasia is mild, and the inner ear canals are probably patent (I was unable to radiograph this defect). There may have been some hearing impairement in this individual. Table 6.22. Frequency of Partial Atresia of the Auditory Meatus Site N Occurrence Frequency (%) Puye 103 0 0 Central plateau total 34 1 2.9 Tsirege 11 1 9.0
E. Branchial Arch I Closing Membrane Field Defects: Tympanic Aperture/Cleft Corruccini (1972) recorded the presence of the tympanic aperture (Huschke's foramen) in adult crania from the Puye skeletal collection, but he pooled the different sides into one for comparison with other populations. I found approximately 23% (24/103) of the adult crania twenty females and four males with this defect. Most of the tympanic apertures are bilateral (20/24 = 83.3%), and more than twice as many females (20/68 = 29.4%) are affected as males (4/35 = 11.4%). Only females (4/24 = 16.6%) exhibited this defect unilaterally, two on the left side and two on the right side. The size of the aperture varies from small to large, depending upon the degree of delay in the development of the closing membrane.
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Fig. 6.24 Tympanic cleft from Puye. Left tympanic of adult female (NMNH 263011); right side normal.
Two individuals one adult female (Fig. 6.24) and one adult male have clefts instead of apertures (2/103 = 1.9%). Apparently, they suffered a greater degree of developmental delay in the closing membrane than did the individuals with apertures. The female has a unilateral cleft on the left side with a normal tympanic plate on the right side. The male has bilateral clefts. Familial ties are suggested. In the other central Pajarito Plateau populations, females with the tympanic aperture also tend to outnumber males. Only bilateral expressions were found in the Otowi, Tsankawi, and Tsirege skeletal collections (Table 6.23).
Page 280 Table 6.23. Frequency of Tympanic Aperture Site N Occurrence Puye 103 24 female 68 20 male 35 4 Central plateau total 34 11 female 22 9 male 12 2 Otowi 20 5 female 11 4 male 9 1 Tsankawi 3 2 female 3 2 male 0 Tsirege 11 4 female 8 3 male 3 1
Frequency (%) 23.3 29.4 11.4 32.3 40.9 16.7 25.0 36.3 11.1 66.7 66.7 36.3 37.5 33.3
Otowi has a frequency similar to that of Puye, with 25% (5/20) of available crania affected four females (4/11 = 36.3%) and one male (1/9 = 11.1%). Four individuals three females (3/8 = 37.5%) and one male (1/3 = 33.3%) in the Tsirege collection have the tympanic aperture (4/11 = 36.3%). Tsankawi has only three female crania available for detection of this defect, and two (2/3 = 66.7%) have it. Were this a fair representation for Tsankawi and Tsirege, the frequency for the tympanic aperture is very high at Tsankawi, whereas Tsirege has a frequency just a little higher than those of both Otowi and Puye. Hooton (1930:107) also found that females (24%) with the tympanic aperture outnumbered males (16%) in the Pueblo IV-V Towa population at Pecos. He found that the frequency decreased through time, and he suggested that this occurred because of population admixture into the community from outside. The overall frequency of tympanic aperture in the Pecos skeletal collection (21.5%) differs little from the average frequency at Puye (23.3%). The Tompiro population at Gran Quivira shows a higher frequency (33.3%) than either Puye or Pecos, whereas Pueblo III western Anasazi from Canyon de Chelly (36.3%) and Hopi (44.0%) reveal even higher reported frequencies of tympanic aperture (El-Najjar 1974; Turner and Katich 1981:145) (Table 6.24).
Page 281 Table 6.24. Known Frequencies of Tympanic Aperture in Anasazi Populations Site Frequency (%) Eastern Anasazi Puye 23.3 Central Pajarito 32.3 Pecos 21.5 Gran Quivira 33.3 Western Anasazi Canyon de Chelly 36.3 Hopi 44.0
F. Developmental Delay Field Defects of the Sternal Plates Eighty-one sterna are represented in the Puye collection forty-nine females, twenty-eight males, three indeterminate adults, and one juvenile. All four types of mesosterna (Ashley 1956) are present in the adults. Types I (Fig. 6.25b) and II (Figs. 6.25a and 6.26a) are considered normal variants, and combined, they represent the majority of mesosterna present. Type II mesosternum occurs the most often, following the common trend that Ashley (1956) proposed. Type I appears more often in the females than in the males, and type III (Fig. 6.26b) occurs much more frequently in the males than in the females (Table 6.25). Table 6.25. Frequency of Sternal Types from Puye Females Males Type I 18/49 (36.7%) 6/28 (21.4%) Type II 28/49 (57.1%) 18/28 (64.2%) Type III 2/49 (4.0%) 4/28 (14.3%) Type IV 1/49 (2%) 0/28 ()
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Fig. 6.25 Variations of sternal defects from Puye. a: type II sternum (female NMNH 262962) with misplaced manubrio-mesosternal joint; b: type I sternum (male NMNH 262929) with xiphisternal joint fusion; c: type IV sternum (female NMNH 263059) with manubriomesosternal joint fusion.
1. Failure to Differentiate a. Manubrio-Mesosternal Joint Fusion Failure of the cartilaginous joint to form at the manubrio-mesosternal junction was found in approximately 26% (21/81) of the sterna available in the Puye collection. This is higher than the normal expected frequency of 10% to 15% for any population (Ashley 1954; Jit and Bakshi 1986). Most of the fusions occur in type II sterna (10/23 = 43.4%), and more females (15/49 = 30.6%) are affected than males (6/28 = 21.4%). Type I sterna are the least affected (2/23 = 8.6%).
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Fig. 6.26 Variations of sternal defects from Puye. A: type II sternum (female NMNH 269277) with xiphisternal fusion. B: type III sternum (male NMNH 269276) with manubrio-mesosternal and xiphisternal fusion.
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A similar frequency of failure of the manubrio-mesosternal junction to develop was found in the Tsankawi collection (2/8 = 25.0%), in one female and in one adult of indeterminate sex. Otowi presented a higher frequency than Puye and Tsankawi, with one female and two males (3/7 = 42.8%). No sterna are present in the Tsirege collection (Table 6.26). Table 6.26. Frequency of Manubrio-Mesosternal Fusion Site N Occurrence Puye 81 21 female 49 15 male 28 6 indeterminate 4 0 Central plateau total 15 5 female 2 2 male 9 2 indeterminate 4 1 Otowi 7 3 female 1 1 male 6 2 Tsankawi 8 2 female 1 1 male 3 0 indeterminate 4 1 Tsirege 0
Frequency (%) 25.9 30.6 21.4 0 33.3 100.0 22.2 0 42.8 100.0 33.3 25.0 100.0 0 25.0
b. Misplaced Manubrio-Mesosternal Joint Misplacement of the manubrio-mesosternal joint was found in only one individual (Fig. 6.25a) in the Pajarito Plateau skeletal collections. This was an adult female from Puye (1/84 = 1.1%). c. Xiphisternal Joint Fusion Xiphisternal joint fusion was found in seventeen adults (17/57 = 29.8%) from the Puye collection (Figs. 6.25b, 6.26, and 6.27). Seven of these occur in females (7/32 = 21.8%) and ten in males (10/25 = 40%). Male sterna appear to be affected more than female sterna, and the type II sterna are the most often affected. Only type III male sterna are affected, whereas type III females are not.
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Examples of xiphisternal joint fusion were also found in the Otowi and Tsankawi collections. Three (3/7 = 42.8%) of the sterna present in the Otowi collection one female and two males have xiphisternal fusion, yielding a much higher frequency than that for Puye despite the small sample size. The female has a type II sternum with manubriomesosternal fusion (1/7 = 14.2%) and a large sternal aperture (Fig. 6.28). Xiphisternal fusion is present in three sterna two males and one adult of indeterminate sex (3/8 = 37.5%) in the Tsankawi collection. The adult of indeterminate sex also has manubrio-mesosternal fusion in a type III sternum (1/8 = 12.5%) (Table 6.27). Table 6.27. Frequency of Xiphisternal Fusion Site N Occurrence Puye 57 17 female 32 7 male 25 10 Central plateau total 15 6 female 2 2 male 9 4 indeterminate 4 0 Otowi 7 3 female 1 1 male 6 2 Tsankawi 8 3 female 1 0 male 3 2 indeterminate 4 1 Tsirege 0
Frequency (%) 29.8 21.8 40.0 40.0 100.0 44.4 0 42.8 100.0 33.3 37.5 0 66.7 25.0
More males (3/25 = 12%) than females (3/32 = 9.7%) have both the xiphoid and the manubrium fused to the mesosternum in the Puye collection, and most of these (4/6 = 66.7%) are associated with type III sterna (Fig. 6.26b). Only two type II sterna are affected; both are female. One of these females also has a small sternal aperture. The other female has a small xiphoid aperture (Fig. 6.27c). Two of the males with type III sterna have large sternal apertures and large clefts in the xiphoid (Fig. 6.27b). Ten percent (6/60) of the sterna of Puye have both manubrio-mesosternal and xiphisternal fusion (Table 6.28).
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Fig. 6.27 Variations of sternal defects from Puye. a: type II sternum (male NMNH 262914) with large xiphoid aperture; b: type III sternum (male NMNH 269255) with sternal aperture, cleft xiphoid, manubrio-mesosternal and xiphisternal joint fusion; c: type II sternum (female NMNH 262966) with small xiphoid aperture, manubrio-mesosternal and xiphisternal joint fusion.
Page 287 Table 6.28. Frequency of Manubrio-Mesosternal and Xiphisternal Fusion in the Same Individual Site N Occurrence Frequency (%) Puye 60 6 10.0 Central plateau total 15 2 13.3 Otowi 7 1 14.2 Tsankawi 8 1 12.5 Tsirege 0
2. Caudal Fusion Delay Defects a. Delayed Caudal Cohesion Both type III (Figs. 6.26b and 6.27b) and type IV sterna (Fig. 6.25c) are present in the Puye collection. They may be considered extreme sternal variants resulting from delayed caudal cohesion of the sternal bands. Type III sterna are present in six individuals (6/80 = 7.5%), two females and four males. Four of the type III sterna (4/8 = 50%) also have incomplete caudal fusion defects. Sternal apertures are present in three of the males, and two also have a cleft xiphoid. One female has a small sternal cleft. Another female is missing the last sternal segment, producing a wide, short sternum. Only one sternum (1/8 = 12.5%) from Tsankawi, an adult of indeterminate sex, has a type III mesosternum. It is not accompanied by any other caudal fusion delay defects. Three adult males (3/7 = 42.8%) from Otowi have type III sterna. One of these also has a large, shallow depression, indicating an incomplete sternal aperture (Table 6.29). Table 6.29. Frequency of Type III Sterna Site N Occurrence Puye 80 6 Central plateau total 15 4 Otowi 7 3 Tsankawi 8 1 Tsirege 0
Frequency (%) 7.5 26.7 42.8 12.5
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b. Incomplete Caudal Cohesion Incomplete caudal cohesion is represented by the presence of an aperture or cleft in the caudal end of the sternum or in the xiphoid. It often accompanies type III sterna. Sternal apertures were found in 14.7% (9/61) of the sterna (five males, two females, and two adults of indeterminate sex) from Puye. Sternal clefts were found in 4/61 (6.5%) of adult sterna (two females and two adults of indeterminate sex) and in one child (Table 6.30). The xiphoid was affected by clefting in 8/20 sterna (four males, three females, and one indeterminate) and by an aperture in 3/20 sterna (two females and one male) (Table 6.31). Some individuals had more than one of these defects. Table 6.30. Frequency of Sternal Aperture and Cleft Site N Aperture Puye 61 9 (14.7%) female 32 2 (6.2%) male 25 5 (20.0%) indeterminate 4 2 Central plateau total 15 2 (13.3%) female 1 male 1 Otowi 7 2 (28.5%) female 1 male 1 Tsankawi 8 0 Tsirege 0 Table 6.31. Frequency of Xiphoid Aperture and Cleft Site N Aperture Puye 20 3 (15.0%) female 10 2 male 9 1 indeterminate 1 0 Central plateau total 15 0 female 0 male 0
Cleft 4 (6.5%) 2 (6.2%) 0 2 0 0 0 0 0 0 0
Cleft 8 (40.0%) 3 4 1 1 (6.7%) 0 1
Page 289 Table 6.31 Site Otowi female male Tsankawi Tsirege
N 7
8 0
Aperture 0 0 0 0
Cleft 1 0 1 0
Twelve Puye individuals with type II sterna (12/48 = 25%) five females, five males, one adult of indeterminate sex, and one child have incomplete caudal cohesion defects. Only one type I sternum (female) has such a defect in the form of a small fissure on the dorsal side of the sternum. Incomplete caudal cohesion defects rarely occur in type I sterna; they have only single ossification centers in each sternebra. In his study of modern chest radiographs, McCormick (1981) found that sternal apertures are twice as common in males as in females, with a total frequency of 7.7%. The overall frequency of sternal apertures in the Puye collection is twice the frequency (9/61=14.7%) found in McCormick's study. Here, too, males outnumber females (5 to 2). The number and severity of incomplete caudal cohesion defects tend to increase with the increase in sternal width. Males tend to have larger sterna, and thus larger defects, than females. Sternal apertures were found in two individuals (2/7 = 28.5%) one male and one female from Otowi. This frequency is twice as high as that at Puye. The female has a type II sternum with an oblong sternal aperture (Fig. 6.28a). The male was mentioned before, with a type III sternum and incomplete sternal aperture in the shape of a large, shallow depression. Another adult male with a type II sternum (Fig. 6.28b) has a large cleft in the xiphoid (1/7 = 14.2%). Of eight sterna from Tsankawi with caudal ends present, one adult male had a shallow depression in the last segment, and none had apertures or clefts. Approximately 86% (6/7) of the Otowi sterna have either delayed or incomplete caudal cohesion defects of the sternum. Only about 28% (17/61) of the Puye sterna are affected with one or both types of defects. Otowi clearly has an unusually high frequency of caudal fusion defects, and the frequency at Puye is much higher than would be expected, yet is much lower than the frequency at Otowi. Tsankawi has the lowest frequency (1/8 = 12.5%). Otowi has a greater percentage of type III sterna represented (3/7 = 42.8%) than do
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Fig. 6.28 Variations of sternal defects from Otowi. a: type II sternum (female NMNH 228925) with large sternal aperture, manubrio-mesosternal and xiphisternal joint fusion; b: type II mesosternum (male NMNH 228917) with large xiphoid cleft and xiphisternal joint fusion; manubrium was not fused to mesosternum and was not present.
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either Puye (6/80 = 7.5%) or Tsankawi (1/8 = 12.5%). Type III sterna occur more frequently in males in both Otowi and Puye (Table 6.32). Table 6.32. Frequency of Individuals Affected by One or More Caudal Cohesion Defects of the Sternum Site N Occurrence Frequency (%) Puye 61 17 27.8 Central plateau total 15 7 46.6 Otowi 7 6 85.7 Tsankawi 8 1 12.5 Tsirege 0
Although the frequencies for the different types of sternal defects vary among the Pajaritan communities, the patterns of sternal defects are similar, suggesting a common gene pool. Marriage patterns may have influenced the variation in frequencies of the different forms of sternal defects from one site to another. Reed (1981:81) found incidences of incomplete caudal cohesion defects in the form of sternal apertures and clefts in the xiphoid in the Pueblo IV-V Tompiro of Gran Quivira. Reed also noted some cases of manubrio-mesosternal joint fusion and xiphisternal joint fusion, as well as one case of misplaced manubrio-mesosternal joint. The pattern he described is similar to that of sternal defects found in the Pajarito Plateau skeletal collections. This may be significant, because both the Pueblo IV Pajaritans and the Pueblo IV-V Gran Quivirans are considered to belong to the Tanoan linguistic family. No other examples of sternal defects have been reported from the other Tanoan groups. Conclusions Based on the Data The data from the Puye skeletal analysis show a definite pattern of developmental defects of the axial skeleton. The morphogenetic criteria made it easy to identify and classify defects. It is important to remember that the developmental field defects detected in the Puye skeletal collection arise from sensitive genetic backgrounds that allow genetic or epigenetic alterations to take place (Gruneberg 1963; Saxen and Rapola 1969). Underlying genetic tendencies that allow certain defects to develop are seen in the paraxial
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mesoderm in the form of block vertebrae (failure of segmentation); minor variations of vertebral border shifting, with occasional major shifts at the thoracolumbar and lumbosacral borders; supernumerary vertebral segments; and developmental delay of the neural arches in the sacrum, with occasional developmental delay on the posterior arch of the atlas vertebra. The blastemal desmocranium is also influenced by underlying genetics, with the frequent occurrence of numerous primary ossicles in the lambdoidal suture and occasional fontanelle bones. The closing membrane of the first branchial arch is also strongly influenced by underlying genetics, with the frequent occurrence of the tympanic aperture. Frequent delayed or incomplete cohesion defects and failure of the manubrio-mesosternal and xiphisternal joints to differentiate suggest strong genetic tendencies for delay in the development of the sternal bands. The pattern of defects present in the Puye skeletal collection provides a profile of underlying genetic factors in the population, as well as a profile of the types of developmental disturbances that were present. Frequency variation for the different types of defects, from relatively high to relatively low percentages, indicates relative trends in the genetic structure. Within the Puye skeletal collection, there are relatively high frequencies (over 20%) for the following: 1. cranium a. numerous lambdoidal ossicles (35.4%); b. tympanic aperture (23%); 2. sternum a. delayed or incomplete caudal cohesion (28%); b. manubrio-mesosternal joint fusion (28%); c. xiphisternal joint fusion (28%); 3. vertebral column a. lumbosacral border shifting, minor and major (38.7%); and b. sacrocaudal border shifting (21.5%).
Relatively moderate frequencies, approximately 9.5% to 19.5%, were found in the following: 1. 2.
cranium a. fontanelle bones (12.7%); sternum a. sternal aperture (14.7%);
Page 293 3. vertebral column a. minor occipitocervical border shifting (11.7%); and b. sacral neural arch defects (9.8%).
Defects with relatively minor frequencies (4.5% to 9%) were found in the vertebral column in the form of: a. thoracolumbar border shifting (5.9%); b. block vertebra (5.6%); and c. cleft atlas (4.5%).
Tendencies for certain defects to occur more frequently than others are apparent. Little is known about the frequency distribution of most of these defects in other populations. Clinical studies do provide some idea of expected frequencies for cleft neural arch, sternal aperture, and manubrio-mesosternal joint fusion. Clinical studies indicate that the frequency for cleft neural arch can be as high as 25% in any given population (Hoffman 1965; Laurence, Bligh, and Evans 1968; Saluja 1988). Puye has a frequency of 9.8% for sacral clefting, well within the expected frequency range. The expected frequency for cleft atlas in any given population is 5%, according to clinical studies (Bailey 1974). The frequency for this defect in the Puye collection (4.5%) approaches the expected frequency. Sternal aperture can be expected in about 8% of any given population and occurs twice as often in males as in females (McCormick 1981). Puye has a higher than expected frequency (14.7%), with males outnumbering females 5:2. The frequency for manubriomesosternal joint fusion (28%) in the Puye collection is much higher than the expected clinical frequency of 10% to 15% (Ashley 1954; Jit and Bakshi 1986). Occasionally, a defect shows up in only one or a few individuals and represents a sporadic occurrence. Such defects tend to appear infrequently (below 4%) and along familial lines, where there is opportunity for expression (either intrinsic or extrinsic) on a susceptible genetic background. Sporadic defects in the Puye collection include: 1. cranium a. retention of the mendosa suture (1.4%); b. failure of the interparietals to coalesce (1.4%); c. hypoplasia of the basilar process (.09%);
Page 294 2. sternum a. misplaced manubrio-mesosternal joint (1.1%); 3. vertebral column a. asymmetry of the transverse process (.07%); b. asymmetry of adjacent apophyseal facets (.07%); c. hypoplasia of T3 spinous process (.07%); d. bifid spinous process of C2 (.07%); e. hemimetamere defect (.07%); and 4. ribs a. minor irregular segmentation (2.7%).
Remains of infants born with severe defects generally are not found in archaeological skeletal collections. However, the very presence of mild expressions of these defects in older individuals suggests that the more severe forms probably existed in the living population. The presence of asynchronous hemimetamere defect in an adult female from Puye indicates that the potential for this type of disturbance in the paraxial mesoderm existed within the living population. The presence of various type II block vertebrae indicates the probability that the more severe types of failure of segmentation within the paraxial mesoderm types I and III may have been present. Despite small sample sizes from Otowi and Tsankawi, similar patterns of developmental defects of the axial skeleton can be seen especially in the areas of sacral clefting, precondylar facets, tympanic apertures, sternal defects, block vertebrae, minor cranial shifting at the lumbosacral border, caudal shifting at the sacrocaudal border, and the presence of numerous ossicles in the lambdoidal suture. Although the Tsirege skeletal material lacks representation of the vertebral column and sternum, many of the cranial anomalies resemble those from Otowi, Tsankawi, and Puye. Similar patterns of developmental defects among the Puye and central plateau communities suggest a common gene pool. This evidence agrees with both the ethnohistoric and archaeological evidence of a homogeneous population, considered to be ancestral Tewa, living on the northern and central portions of the Pajarito Plateau during the Pueblo IV time period that preceded the Spanish invasion. Small sample sizes from Otowi, Tsankawi, and Tsirege may be influencing frequency variations among the Pajaritan communities. If not, frequency variations of the developmental defects of the axial skeleton from one community to another may indicate selective mating practices typical of community endogamy. Frequencies would tend to be similar with community exogamy.
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Sexual differences in traits recognized by Corruccini (1972) in the Puye skeletal collection were similar in this study. Females in all of the Pajarito skeletal collections have higher frequencies of some defects than do males. Females outnumber males 2:1 in the frequency of the tympanic aperture (Table 6.23). Hooton (1930) reported a similar 2:1 ratio in the Pecos skeletal collection. Pecos is considered to be ancestral Towa, belonging to the same Tonoan language group of the ancestral Tewa of the Pajarito Plateau. Females are reported to outnumber males in the frequency of this defect in some modern populations as well (Williams et al. 1989), but marriage patterns for these populations are not known. Caudal shifting at the thoracolumbar border occurs more often than cranial shifting and more often in females than in males (Table 6.9). Hypoplasia-aplasia leading to bifurcation or a cleft in the posterior arch of the atlas vertebra also occurs more frequently in females than in males. Manubriomesosternal joint fusion is found more often in females than in males (Table 6.26). Sporadic developmental defects occur primarily in females. Some defects, such as sacral clefting, occur more often in males than in females. Males tend to have more xiphisternal fusions (Table 6.27) and delayed or incomplete caudal cohesion sternal defects (Table 6.30) than do females. This is because these defects usually occur with the wider sterna that are found most often in males. More research is needed to determine why these sexual differences in frequencies occur. Marriage and residential patterns may be contributing factors to the high frequency of so many defects in females, as Corruccini (1972) hypothesized for a matrilocal society. Similar disturbances of the paraxial mesoderm, blastermal desmocranium, and first branchial arch closing membrane have been reported for other Anasazi populations. Further studies of the patterns of developmental defects occurring in other Anasazi populations would provide underlying genetic data for determining population relationships and, hence, population movements out of the Four Corners country into the northern Rio Grande and Little Colorado River drainages. Differences in the expression of developmental defects would be expected to increase through genetic drift as migrating populations diverged. The more elapsed time between the initial separation, the more the pattern of frequencies and expressions would be different. Reports of some developmental defects occurring in other Pueblo IV Tanoan populations that migrated into the northern Rio Grande offer some intriguing but incomplete comparative data. Pecos Pueblo, considered to be Towa, belongs to the Tanoan-speaking group that separated from the Tewa
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speakers in the upper San Juan River drainage before moving south into the northern Rio Grande drainage (Ford, Schroeder, and Peckham 1972). Hooton (1930) identified some developmental defects in the Pecos skeletal collection involving the blastemal desmocranium and the first branchial arch closing membrane. Both are similar in expression and frequency to the Pajaritans. As stated earlier, he also noted that more females than males had tympanic apertures, with an overall frequency rate (21.5%) not unlike that of Puye (23.3%). Numerous ossicles in the labdoidal suture were as common in the Pecos material as in the Pajaritan material, and bregma bones appeared in four individuals, compared with three at Puye. The presence of the mendosa suture and sutural agenesis was as uncommon at Pecos as among the Pajaritans. Unfortunately, Hooton did not analyze any of the Pecos vertebral columns. However, those data he reported concerning developmental defects of the axial skeleton tend to support a genetic relationship between the northern and central Pajarito Plateau communities and Pecos Pueblo. The southern Tewa, known as the Tano (Hewett and Dutton 1945; Ortiz 1979), are represented by small skeletal collections reported from Arroyo Hondo, Pueblo Largo, and Pa-ako. The Arroyo Hondo and Pueblo Largo collections have the complete expression of caudal shifting of the occipitocervical border (occipitalization of the atlas), which is lacking in the Pajarito skeletal material. Arroyo Hondo also has a complete cranial shift at the cervicothoracic border (type IV cervical ribs), which is not found in the Pajaritans, and type II block vertebrae with failure of separation only in the neural arches, unlike those in the Pajaritans but similar to those found at Mesa Verde in the Northern San Juan region. These limited data suggest a relatively long separation from the northern Tewa. The Tompiro from Gran Quivira appear to be related to the Pajaritans in the following ways: a frequency of tympanic aperture (33.3%) similar to the combined frequency for the central plateau communities, and similar low incidence of agenesis of the sagittal suture. They are less like the Pajaritans in these ways: fewer block vertebrae (N = 3); the tendency for more caudal shifting (lumbarization of S1) of the lumbosacral border (2.7%) than cranial shifting (sacralization of L5,.09%) compared to the Pajaritans, who have more cranial shifting (12.8%) than caudal shifting (2.7%); and the presence of complete occipitalization of the atlas and type IV cervical ribs, similar to the Tano. Similar developmental disturbances of the paraxial mesoderm and blastemal desmocranium have been reported in the southern Southwest Hohokam skeletal collections. Unlike the Anasazi populations, the Hohokam
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tend to have a greater frequency of reported cases of complete caudal shifting of the occipitocervical border (occipitalization of the atlas). Block vertebrae appear to be less common than in the Anasazi populations. Another Southwest population, the Mogollon, has an unusually high frequency of metopism (5/208 = 2%), unlike any other population in the Southwest. This study provides a pivot for comparing patterns of developmental defects of the axial skeleton in the Southwest skeletal populations. Additional data regarding the various types of defects resulting from disturbances in the developmental fields of the axial skeleton can provide the information needed to determine underlying genetic relationships and to verify migration patterns. Cultural and environmental influences may be determined from this type of research.
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Chapter 7 Puye and the Pajarito: Historical Background The analysis of the human remains from Puye and its neighboring communities for developmental defects is not complete until it is placed in a historical context. Understanding the information gathered from the underlying genetic patterns of developmental defects of the skeletal collections requires knowledge of the people's cultural history and environment. The Puye skeletal collection was procured by Edgar L. Hewett during his third season of excavation of the Puye ruins of northern New Mexico in 1909. ''In our excavations this year we have uncovered the long sought burial place at Puye," Hewett wrote in a letter to W. H. Holmes, chief of the Bureau of American Ethnology. Puye is located in the northern region of the Pajarito Plateau, which abuts the west side of the Rio Grande in northcentral New Mexico (Fig. 7.1). The prehistoric ruins on Puye Mesa, overlooking Santa Clara Creek, are forty miles northwest of Santa Fe and ten miles west of Española and the Rio Grande. The Tewa people of the modern-day Santa Clara Pueblo, situated just outside Española near the confluence of Santa Clara Creek and the Rio Grande, claim to be the descendants of Puye's inhabitants (Hewett 1953). A large, rectangular masonry pueblo on top of the mesa is skirted below by the remains of houses built against the cliffs for more than a mile along the south face of the mesa (Fig. 7.2). They continue around to the east and west faces of the mesa, connected by well-worn trails. The cliffs consist of soft tuff formed from consolidated volcanic ash, easily carved to create cavate rooms that served as the rear portions of the cliff houses. Masonry rooms were added in front of the cavates, sometimes standing to two or three stories high (Fig. 7.3). The south cliff is divided by a ledge that separates the cliff houses above and below it. Stepped pathways carved into the tuff connect the upper ledge
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Fig. 7.1 Maps of site locations. A: Location of Pajarito Plateau. B: Site locations of Puye, Otowi, Tsankawi, and Tsirege on the Pajarito Plateau.
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Fig. 7.2 Puye Mesa from the east, looking west toward the mesa-top pueblo and cliff house ruins along the south face.
to the mesa top. Similar tree-ring dates for both the cliff houses and the mesa-top pueblo indicate that they were occupied contemporarily (Hewett 1953). An estimated two thousand people lived in this settlement at one time (Ferguson and Rohn 1987). Runoff rainwater was impounded in a reservoir located 120 feet west of the mesa-top pueblo ruin. Water management was also employed through the use of an irrigation canal that can be traced for nearly two miles along the arroyo south of the mesa; the canal funneled water from the mountains above the mesa to fields to the southeast (Hewett 1906, 1953:67). Water management was necessary in this semiarid environment, with its erratic patterns of rain and snowfall, for the survival of such a large community (Cordell 1979). Tree-ring dates of A.D. 15071561 place Puye in the Pueblo IV Rio Grande Classic cultural stage (Hewett 1953:2930). Hewett (1953) excavated about one-third of the ruins. He found evidence that some of the abandoned cliff houses may have been reused when the Pueblos rebelled against the Spaniards in 1680. Cordell (1979:145) believes the earlier components of Puye may date from the late 1300s to the mid-1400s.
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Fig. 7.3 Reconstructed cliff house along south face of Puye Mesa.
Puye appears to have been the focus of a larger community that included a number of smaller villages and hamlets nearby (based on the number of ruins of small houses with two to fifty rooms each), connected by well-worn pathways. Shupinna (narrow point), a small pueblo located on a high mesa across from Puye on the north side of Santa Clara Creek, is claimed to have been an earlier residence of the Puye population (Hewett 1953). Pajarito Plateau Puye is only one of many large Pueblo IV settlements found along the Pajarito Plateau and on mesas along the neighboring Chama River to the north. The Pajarito Plateau between 6,100 and 8,000 feet in elevation ranges from ten to twenty miles wide and about forty miles long, extending from Cochiti in the south to the Rio Chama in the north. It is flanked by the Jemez Mountain range on the west. The Pajarito Plateau, named by Hewett (reference to "little bird" in Spanish), was created from successive layers of basaltic lava and tuff spewed forth centuries ago from adjacent volcanoes
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within the Jemez range (Hewett 1906, 1953; Rohn 1989). Erosion from water action combined with freezing and thawing to carve deep canyons through the huge, expansive layers of tuff, leaving several upland finger mesas between deep recesses in the plateau. Streams and arroyos meander through the canyon bottoms toward the Rio Grande, supporting thickets of brush, willow, box elder, and cottonwood trees. Up to one thousand feet above the floor of the canyons, the higher elevations of the mesas present a different environment. Sparse stands of juniper and piñon trees in the east give way to a mature forest of ponderosa pines in the higher flanks of the Jemez mountains. An average of ten to fifteen inches of rain per year keeps the area semiarid. Permanent streams are few in number, and springs depend upon winter moisture cycles. Summer rains tend to be destructive through arroyo cutting. The moisture pattern, especially summer rainfall, is variable in the Pajarito Plateau region (Hewett and Dutton 1945). Normally, slightly more than half of the yearly moisture falls as summer rain and the remainder comes as winter snow; the spring and fall seasons tend to be dry. Erratic moisture patterns, such as successive drier years for two-year and three-year periods (Cordell 1979:133), must have had severe impacts on the populations living on the plateau. The mesa tops themselves are poor in natural foods, but the canyon bottoms, the nearby mountain region, and the river valleys offer a wide range of plant foods and game. Mule deer, cottontail rabbits, jackrabbits, squirrels, black bears, mountain lions, foxes, raccoons, coyotes, and beavers are found in the region. Native plant foods include yucca fruit and seeds, prickly pear, beeweed, amaranth, chenopodium, piñon nuts, wild plums, grapes, and chokecherries (Arnon and Hill 1979:303; Rohn 1989). The rich volcanic soil attracted Anasazi farmers when water sources were sufficient. Cultivation of crops took place in a variety of settings, wherever ample soil existed to support farming. Some of the agricultural fields of the large mesa-top Pueblo IV settlements were probably located some distance away, so sufficient suitable soil and moisture could be found to raise enough food for a large population (Traylor 1982). Pajarito Plateau Prehistory The earliest known Anasazi occupation of the Pajarito Plateau dates back to Pueblo II (A.D. 9001100). It is represented by scattered small house units with pit houses. The overall Pueblo II population appears to have been
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sparse on the plateau (Cordell 1979:137). Hunting and gathering of wild plant foods supplemented diets of maize, beans, and squash. Hunting and gathering continued, along with agriculture, into the early historic period (Arnon and Hill 1979), providing a balanced diet of nutrients. During Pueblo III (A.D. 11001300), the number of scattered small house settlements on the Pajarito above White Rock Canyon began to increase, with aggregation in localities that had reliable water sources. As this was happening, Anasazi culture in the Four Corners region of northwestern New Mexico, northeastern Arizona, southeastern Utah, and southwestern Colorado had reached its peak (Cordell 1979; Ferguson and Rohn 1987). Archaeological evidence in the form of pottery and architectural attributes indicates populations were moving from the Four Corners into the northern Rio Grande region during this time (Cordell 1979; Schoenwetter and Dittert 1968). By A.D. 1300, the Anasazi had abandoned the Four Corners (Fig. 7.4) as they gradually moved southeastward into the northern Rio Grande region and southward to the Little Colorado River region. Several explanations have been given for the migrations out of the Four Corners: increased population putting pressure on scarce natural resources; shortened growing season; soil depletion; drops in precipitation leading to long droughts, with starvation and disease; nomadic raids by intruding Athabaskans; intertribal warfare or social disruption; and changes in precipitation patterns (Cordell 1979; Dozier 1970; Ferguson and Rohn 1987; Hewett and Dutton 1945). The influx of migrating Anasazi from the Four Corners signaled the beginning of the building of large towns as the foci of enlarging communities during Pueblo IV (A.D. 13001540). Most of these towns had been abandoned before the Spaniards arrived as the inhabitants moved into the Rio Grande valley and southward to their present or last locations (Cordell 1979; Dozier 1970; Ferguson and Rohn 1987). Some of these movements reflected colonization in areas with more abundant water supplies and fertile land, whereas other movements are thought to have resulted from enemy attacks, internal feuding, localized famine, and witchcraft (Parsons 1939:1416). The modern-day Pueblo people are these peoples' descendants.
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Fig. 7.4 Map showing A: Four Corners region. B: Pajarito Plateau.
Ethnohistory Hewett (1953) pointed out three major foci of prehistoric settlements on the Pajarito Plateau. The northern portion centers around Puye, with cultural associations extending into the adjacent Chama River valley. The central portion focuses upon a cluster of large Pueblo IV towns Tsankawi, Otowi, and Tsirege above White Rock Canyon near Los Alamos. The southern portion extends from the Rito de los Frijoles to Cochiti Canyon, centering around Tyuonyi and Yapashi. Ancestors of the modern Keresans migrated into the southern portion of the Pajarito, whereas ancestors of the modern Tanoan-speaking groups migrated ahead of the Keresans into the northern and central portions of the plateau after coming down the Chama River (Cordell 1979; Dozier 1970; Ferguson and Rohn 1987). The Puebloan Tanoans are subdivided into the Tewa, Tiwa, Towa, and the now extinct Tano, Piro, and Tompiro languages. They are linguistically related to the Kiowa of the Plains.
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Fig. 7.5 Map showing area in which northern Rio Grande pueblos are located.
The Tanoans all share common origins and socioreligious practices, but they speak different, yet related, languages. The Kiowa are thought to have split off from the others very early, following the bison into the Plains. The Tiwa split off soon afterward, moving into the northern Rio Grande drainage. The Tewa and Towa shared a common history in the upper San Juan River drainage east of the Animas River, before the Towa moved south. The Tewa
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moved southward at a later time. Eggan (1979:233) thinks the Tewa came from Mesa Verde. Little is known of the extinct Tano (Southern Tewa), Piro, and Tompiro (Ford, Schroeder, and Peckham 1972). Since the arrival of the Spaniards, the Tiwa have occupied the northernmost part of the Rio Grande region in northern New Mexico (Taos and Picuris). They also occupied twelve pueblos (known as Tiguex) to the south, northwest of Albuquerque. Only two Southern Tiwa Pueblos survive today, Sandia and Isleta. The northern and southern Tiwa groups have been separated long enough to form distinct dialect differences (Dozier 1970; Schroeder 1979). The Tewa have occupied most of the central portion of the northern Rio Grande valley (Tesuque, Nambe, Pojoaque, San Ildefonso, Santa Clara, San Juan, and formerly Yunge and several other pueblos) from just north of the Rio Grande's confluence with the Rio Chama to just north of Santa Fe. The Galisteo Basin southeast of Santa Fe was occupied by a Southern Tewa group known as the Tano (Hewett and Dutton 1945; Ortiz 1979). The Towa finally settled on the edge of Keresan territory, establishing pueblos in the Jemez Mountains and San Diego Canyon near the last remaining Towa pueblo of today, Jemez (Fig. 7.5). The protohistoric pueblo of Pecos (Cicuique), located eighteen miles southeast of Santa Fe, was also occupied by Towa (Dozier 1970; Ford et al. 1972, 1979; Schroeder 1979). The extinct Piro once inhabited eight pueblos around the confluence of the Rio Grande and the Rio Puerco, south of the Southern Tiwa. The extinct Tompiros inhabited several pueblos in the Salines area on the east side of Sierra Morena (Schroeder 1979). Keresan Pueblos are divided into eastern and western groups. The western group lives at Acoma and Laguna, west of Albuquerque. The eastern group occupies the area between the Jemez River northwest of Albuquerque to twenty-five miles southwest of Santa Fe and to the west bank of the Rio Grande above its confluence with the Jemez River. The surviving Pueblos are Cochiti, Zia, San Felipe, Santa Ana, and Santo Domingo (Fig. 7.5). The Eastern Keresan Pueblos are the descendants of the inhabitants of the southern portion of the Pajarito Plateau (Dozier 1970; Schroeder 1979). The Pueblo rebellion against the Spaniards in 1680 led to several migrations and the mixing of survivors from Pueblos abandoned in fear of the retaliating Spaniards in 1692. Survivors of one group of Southern Tewa migrated to the Hopi Pueblos in the west. One group of Southern Tiwa fled south to establish a pueblo near El Paso, Texas. Moving about from one pueblo to another was not foreign to the Northern Rio Grande Pueblo
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peoples prior to the disturbance by the Spaniards. Puebloan oral accounts tell of many movements of Pueblos or certain clans in prehistoric and protohistoric times, as either migrations or colonizations. Tewa living in the lower Chama River drainage apparently moved in with kin groups living in the Northern Tewa Rio Grande Pueblos prior to and shortly after the arrival of the Spaniards (Dozier 1970; Schroeder 1979). The Tewa claim their ancestors migrated down the Chama River to the Rio Grande in two groups, establishing ten different communities through time. The two groups rejoined at Posi'owinge, near Ojo Caliente, and eventually split off to establish the Tewa Pueblos discovered by the Spaniards. Prehistoric ruins, extending up into the Chama River drainage from its confluence with the Rio Grande and on to the northern and central portions of the Pajarito Plateau, all share common archaeological characteristics and have been claimed by the Tewa since Bandelier's investigations in 18901892 (Ortiz 1979:280). The Tewa of Santa Clara (Ka'po) Pueblo claim Puye and ruins associated with it in the northern portion of the Pajarito Plateau as their last ancestral home. The Tewa of San Ildefonso (Po hwo ge) Pueblo claim the ancient community of Otowi (Potsuwi'i = "gap where the water sinks"), located south of Puye near Los Alamos, as one of the early homes of their ancestors. They also claim the Tsankawi community (Sankewi'i = "gap of the sharp, round cactus"), situated on a high mesa between Otowi and Sandia Canyon. Tsirege ("down at the bird place''), the largest of the prehistoric towns on the plateau and located south of Tsankawi, is probably related to Otowi and Tsankawi. All three are clustered in the central portion of the plateau (Hewett 1953, 1968; Hewett and Dutton 1945). Hewett excavated cemetery mounds in all of these sites and sent skeletal collections from each to the National Museum of Natural History. Pajarito Plateau Burials Puye Burials Puye ("place where the cottontail rabbits assemble") is a large, quadrangular mesa-top pueblo ruin with associated cliff-type houses along the cliff face of Puye Mesa. The once multistoried masonry pueblo structure crowds the southern edge of the mesa.
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Fig. 7.6 Sketch map of Puye Pueblo and burial mound, excavated by E. L. Hewett in 1909.
The pueblo consists of four masonry buildings, with multiple rooms enclosing a large plaza, with the main entrance at the southeast corner and a smaller entrance at the southwest corner. Round kivas lie both inside and outside the plaza. Hewett (1909, 1953) found the main cemetery mound northeast of the pueblo on top of the mesa in 1909 (Fig. 7.6). One hundred and seventy-one burials were retrieved from the mound. Some additional burials were removed from the southern section of the pueblo, and a few more were removed from the cavate rooms on the cliff face. A few infant burials were found in some of the rooms of the pueblo (Hewett 1953). Two hundred and thirty individuals are represented in the Puye skeletal collection deposited in the National Museum of Natural History. Unfortunately, burial provenances were lost when the collection was acquisitioned in 1911. All burials were flexed, and most faced downward with the head toward the west. Fragments of fabric and small corn cobs were found with some burials. Some had stones placed above the skull. Fiber resembling buffalo hair was found beneath one individual. A wooden flute and prayer stick came from one of the graves. The head of one adult was forced under its body, and another had a mended red bowl inverted over the body. One burial is
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described with the "lower bones of the leg much deformed" (Chapman 1910). An adult female with a severe, deforming compound fracture of the tibia and fibula, complicated by chronic osteomyelitis, in the Puye skeletal collection matches this description. Kidder (n.d.) mentions the burial of a baby in a fireplace within one of the rooms (room 8, tier II) in the pueblo at Puye. The sunken fireplace "was carefully cleaned out, then a layer of yellowish clay three-fourths inch thick was laid over the whole bottom; then a small amount of rather fine earth was placed in the depression and the baby put in with more earth of the same quality filled in level with the floor. The baby lay on its left side, rolled toward the supine, in such a way that the face was downward and toward the back of the fireplace, legs to chin." No grave goods were buried with the infant. Otowi Burials Prior to the excavations at Puye, Hewett located two burial mounds at Otowi in 1905 (Fig. 7.7). Otowi Pueblo is located on a high bench between two canyons, with associated clifftype houses along the canyon cliff face across from the north side of the bench. The pueblo consists of five multi-storied room blocks surrounding a plaza that opens to the south. Three of the room blocks are parallel to one another (northeast by southwest), connected by a north wall. The fourth room block lies southwest of these three and is connected to them by a wall on its north side. The fifth room block lies southeast of the plaza. Unique conical "tent" rocks of tuff east of the pueblo were also utilized for cavate structures, and several small house ruins are found nearby (Hewett 1906). The main cemetery mound at Otowi (Fig. 7.7b), located a few feet south of the pueblo ruins, was an oblong artificial mound (100 × 80 feet in diameter) three to six feet deep, consisting of black soil hauled from the valley floor below. Layers of ash ran through the black soil in the mound, but there was no evidence of cremation of skeletal material. Three Indian workmen trenched through one-third of the mound for nine days, removing approximately 150 burials, most of them in poor condition. Many were reported as secondary, incomplete burials, and about 20% were infants. Most of the burials within the mound were found at two levels. New burials disturbed old burials, causing some mixing of skeletal material within the mound. Several burials were found in subsurface gravel and gray tuff beneath the mound. All of the primary burials lay in the flexed position, most on their backs and facing
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Fig. 7.7 Sketch map of Otowi Pueblo and burial mounds, excavated by E. L. Hewett in 1905 (redrawn from Hewett 1906). a: small burial mound; b: main cemetery mound.
east. Grave goods included pottery, bone awls, flutes and whistles, and pipes. Three adult secondary burials were placed in large bowls. Hewett noted that two bowls had the same design as those found at Tsankawi and Tsirege. The remains of eighty individuals and parts of twenty or more others were saved, and the rest were discarded. None of the infants was saved (Hewett 1905, 1953). A small, circular burial mound of volcanic tuff (thirty feet in diameter and one to three feet deep) a few feet west of the pueblo (Fig. 7.7a) produced twenty-five individuals. Seven of these were infants. Hewett (1905) noted that pottery was rarely buried with children. What skeletal material he collected from Otowi was sent to the National Museum of Natural History in 1905, where eighty-six incomplete and poorly preserved individuals from Otowi are represented.
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Fig. 7.8 Sketch map of Tsankawi Pueblo and burial mounds A, B, and C, excavated by E. L. Hewett in 1900 and 1905 (redrawn from Hewett 1906).
Tsankawi Burials Hewett moved on to Tsankawi that same year, where he spent five days excavating two burial mounds. Tsankawi Pueblo sits on a mesa top surrounded by canyon valleys. Numerous cliff-type houses and well-worn trails are found on the east and south faces of this mesa. The mesa-top pueblo has a somewhat rectangular layout surrounding a large plaza, with openings in the northwest, southwest, and southeast corners. A large reservoir lies to the east of the pueblo, on the down slope to the eastern edge of the mesa. Trash mounds can be located all around the pueblo. Hewett (1905) trenched through three of the mounds. He had excavated the first mound (A), near the southeast corner of the pueblo (Fig. 7.8), in 1900 on an earlier visit to the Pajarito Plateau. Thirty-two burials were found (Hewett 1953:109). The other two mounds were excavated in 1905 (Fig. 7.8). Mound B, an oblong mound measuring one hundred feet long and ten to sixty feet wide, located near the northwest corner of the pueblo, was trenched only on its east end. Rocks were encountered, and only six burials with six ceramic bowls were
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found. Two of the bodies had been wrapped in matting and cordage, with corn cobs placed on top of them. Hewett quickly abandoned this mound as "nonproductive," and work then concentrated on mound C, just south of the pueblo. This oblong, shallow (eighteen inches deep) mound was relatively free of rock and easy to work in. The center of the mound was trenched, concentrating on its southern edge. Twenty-nine burials were found, with pottery and some bone implements. Hewett described one burial with a bowl, matting, and "curious sticks" and another containing remnants of basketry. Twenty-eight skeletons were saved (Hewett 1905). Only twenty-five incomplete and poorly preserved individuals represent Tsankawi in the National Museum of Natural History's human skeletal collections. Tsirege Burials One hundred individuals were removed from a burial mound at Tsirege (Hewett 1953:111). Tsirege, the largest of the Pajarito Plateau ruins, lies south of Tsankawi near the low eastern end of a finger mesa top, with extensive cliff-type houses along the south cliff face of the mesa. Several small house ruins associated with Tsirege are scattered around the mesa. The pueblo is roughly rectangular, with the south end open toward the cliff edge. Numerous room blocks cluster up against the southwest corner of the main structure, with a defensive wall extending to the cliff edge (Hewett 1906). The cemetery mound was found southwest of the plaza, near the cluster of room blocks (Fig. 7.9). Only thirteen incomplete individuals in poor condition represent Tsirege in the skeletal collections of the National Museum of Natural History. Three crania from Tsirege were sent to the Museum of the American Indian, Heye Foundation, from the National Museum of Natural History in 1922 (they were recently sent back to their place of origin for reburial), and a few were traded to Russia in 1935. Summary of Pajarito Plateau Burials Hewett (1953:110) mentions other types of burials from Puye, Otowi, Tsankawi, and Tsirege, in addition to the majority found in cemetery mounds, Some were found in cavates or caves, children were buried under fireplaces that were then plastered over and the room abandoned, and seated burials in narrow chambers within houses were also found. Urn burials of infants and
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Fig. 7.9 Sketch map of Tsirege Pueblo and burial mound excavated by E. L. Hewett in 1905 (redrawn from Hewett 1906).
fetuses are mentioned from Puye. They were usually covered with a large bowl and placed in a corner of a room and covered with clay. Cavate charnels filled with disarticulated bones to depths of several feet were noted. Unfortunately, Hewett does not identify which of the sites yielded these unusual burials. Primary burials in the cemetery mounds and in cavates or caves were always in the flexed position, usually placed on their backs, except at Puye, where most were placed facedown. Some of the cave burials were found wrapped in feather robes or yucca fiber mats. Cemetery mounds were usually located just outside the plaza areas of the mesa-top pueblos. They measured fifty feet to one hundred feet in diameter and were sometimes stratified into layers. Puebloan Socioreligious Organization Hewett (1953) thought the geographical isolation of the Pajarito Plateau led to homogeneity among its occupants in both physical and cultural characteristics.
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More likely, marriage patterns were responsible for maintaining this homogeneity, because archaeological and ethnohistorical evidence demonstrates regular contact with other cultural groups throughout the history of the Pajarito Plateau and the Northern Rio Grande Pueblos (B. Larson, Los Alamos Scientific Laboratories archaeologist, personal communication, 1990). Hewett (1953, 1968) speculated that the small Pueblo IIIII settlements during the early occupation of the plateau were clan-oriented or family-oriented, with a basic matrilocal social system similar to what is known of the Western Pueblos. He thought the move to larger settlements and wider community interaction led to a dual socioreligous system, which was needed to take charge of the religious ceremonies that continue today. This duality is often present in the structure of a pueblo, which was divided into northern and southern sections, and it is probably older than Hewett thought (A. E. Dittert, personal communication, 1991). Duality may also be represented by the two types of dwellings present in the Pueblo IV towns, with mesa-top or valley pueblo and cliff houses (Ferguson and Rohn 1987:249). Both the Western and Eastern Pueblos have some form of duality of religious ceremonial responsibility. Ceremonial duties are partitioned according to the two recognized seasons winter and summer. This duality is reflected in the ceremonial moieties present in the Eastern Pueblos. They serve many more functions than those represented by the ceremonial duality present in the Western Pueblos of Hopi, Zuni, and the Western Keresans (Parsons 1939:945). The Western Pueblo clans are aligned with society and kiva groups representative of the ceremonial moieties. Clans are matrilineal and matrilocal and have practiced clan exogamy within town (pueblo) endogamy in the past. The loss of a female meant the loss of a lineage and a household. The loss of a male could mean the loss of a needed society or kiva member, because ceremonial duties were passed down from maternal uncle to nephew. High infant mortality rates usually kept family units small, which made girl children especially prized (Parsons 1939:7, 44, 155). In the Eastern Pueblos, clanship has been weakened by the more intense pressures exerted upon them by the Spanish and the Catholic church since A.D. 1598. The Western Pueblos were less affected, escaping the brunt of Spanish rule and "missionization." Religious suppression among the Eastern Pueblos may have led to a greater emphasis on the ceremonial moieties and less on clanship as patrilineal descent was enforced by the Catholic church. The kiva moieties were encouraged to take on more authority in all political
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and communal activities as Eastern Puebloan culture blended with Spanish culture in the Tewa Pueblos. Males inherited their kiva moiety association, and when they married, their wives were "adopted" by their moeity if the wives were not already members. Underlying the Spanish and Catholic church influences, matrilineal descent was often favored, and patrilocal residency was not emphasized (Arnon and Hill 1979; Ortiz 1979:284; Parsons 1939:11, 61, 945, 1,138). The Tewa moieties appear to have a strong prehistoric connection. Ortiz (1979) describes the moiety system as already in place when the original migrations from the north into the northern Rio Grande region took place. He describes the moieties as a temporal ceremonial structure, designed to coordinate activities associated with the seasons and cutting across a tripartite social and spatial system. The tripartite system is described in concentric circles, with the females in the center, in charge of home (matrilocal), family, and society (matrilineal). The outer circle belongs to the males, for hunting, gathering, and religious pilgrimages; thus it represents the areas farthest away from the village. The circle between these two represents the environment near the village, a "mediating" environment, into which women and children can go if accompanied by a man. Genetic Aspects The socioreligious organization of the prehistoric towns has a direct impact on the genetics of the populations within these towns. Population homogeneity would have maintained a specific pattern of developmental defects within each group of closely related communities. Community endogamy, with matrilocal and matrilineal affinities, would have affected the frequency patterns of these defects within each village. Hrdlicka published a report of the craniometric variation of the pueblo populations (including Puye and Otowi) in 1931. He concluded that two unrelated types dolichocephalic (long head) and brachycephalic (round head) had intermixed to form the Puebloans. Puye was the most brachycephalic (Fig. 7.10) of the groups he examined and was very different from the others. Seltzer (1944), using Hrdlicka's data, also found Puye to be different from the other Puebloan groups, with smaller facial dimensions and larger crania. Seltzer thought that all of the Puebloan peoples were heterogeneous and that they related back to the early Basket Makers of the region. El-Najjar (1978) expanded upon these studies and agreed that the Southwest
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Fig. 7.10 Crania of A: adult female (NMNH 269281) and B: adult male (NMNH 262947) from Puye.
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Puebloan peoples were of the same stock but with some minor degrees of biological differences. Corruccini (1972) performed a comparative statistical analysis of fifty-seven male and seventy-five female adult crania from Puye (Tewa) and a number of individuals from Pueblo Bonito (possibly Keresan) and Hawikku (Zuni), using selected discontinuous, craniometric, and odontometric traits to determine genetic distances. He found that all three groups appear to be equally distant genetically from one another, yet they are physically heterogeneous. Corruccini interpreted this variability as the result of genetic drift from geographic and cultural separation, with nonrandom mating practices maintaining genetic isolation even during migrations. According to Corruccini (1972), genetically, Puye differed the most from the other sample collections. Puye was also the only group that showed marked sexual differences. Puye females differed the most from the other groups, yet they were most alike among themselves, whereas Puye males were not so closely alike. Corruccini interpreted these data to reflect a matrilocal social order with exogamous matrilineal clans, similar to the Zuni tradition. He hypothesized that related females stayed in the same clan settlement, increasing the effects of genetic drift. Husbands came from outside the clan, yet were from the same community. The patterns of developmental defects of the axial skeleton in the Puye and other Pajarito collections support Corruccini's interpretations, adding further support to the cultural influences upon the genetics of the Pajarito population.
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Chapter 8 Summary and Interpretations The morphogenetic approach to the investigation of developmental defects of the axial skeleton proved successful in defining the pattern of the different types of field defects occurring in the Puye skeletal collection. Approximately 67% of the individuals represented have some type of developmental disturbance of the axial skeleton, even though most of these are very mild. The blastemal desmocranium, first branchial arch closing membrane, sternal plates, and paraxial mesoderm are the most commonly affected developmental fields. Approximately one-third of the individuals affected by developmental disturbances of the axial skeleton display more than one defect. There is no consistent pattern of association among the various types of defects found in the same individuals. A few individuals have two similar defects (such as occipitocervical border shifting and failure of cervical vertebrae to segment), but other individuals have one without the other. This confirms that the defects developed independently of each other as separate field defects and not as part of a polytropic pattern. Additional analyses of the skeletal collections from the contemporary communities of Otowi, Tsankawi, and Tsirege from the central portion of the Pajarito Plateau provided some comparative data to Puye. They all shared a common culture, the same environment, and similar patterns of developmental defects, but with variable frequencies. Similar patterns of defects suggest a common gene pool, whereas variable frequencies suggest cultural influences in the form of marriage and residence patterns. The abilities to define the different expressions of the defects according to embryonic development, and to classify them accordingly, proved to be of great value in determining the pattern of developmental disturbances. It is not enough to identify only one expression of a defect within a population; it is more important to determine the underlying genetic trends for the development of the various expressions of a defect.
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In order to determine the pattern of developmental defects within a population, it is important to understand their development and to know their variable expressions. The morphogenetic approach provides this information. Delay in development at a critical threshold event within a particular developmental field is the most common developmental disturbance in the embryo. Timing of critical events during morphogenesis is crucial, and delay leads to incomplete formation resulting in various expressions of hypoplasia-aplasia, failure to separate properly, interference with normal differentiation, abnormal segmental border shifting, failure of normal regression of embryonic tissue, and failure to coalesce normally. The opposite phenomenon, accelerated development leading to hyperplasia, rarely occurs during morphogenesis. Most hyperplasias begin after morphogenesis, during the growth period, and they result from irritation or infection of the growing bony element. Sometimes a bony developmental defect is a by-product of a soft tissue developmental delay defect, such as the solitary developmental cyst known as Stafne's defect occurring in the mandible, the developmental fissural (inclusion) cysts found in the palate, cranial dermoid cysts, and neural tube defects. Each defect has an underlying genetic template that allows disturbance in the timing of specific events to appear when certain factors are present. The influencing factors can be genetic (intrinsic), such as a variant gene, or environmental (extrinsic), such as a maternal nutrient imbalance. Sporadic occurrences of defects appear in all populations. They are produced by extrinsic or intrinsic factors acting upon an occasional sensitive genetic background. The clustering of any unusual defects within a single population indicates a sporadic defect following a familial line. Hoffman (1976a) provides an excellent example of this in a northern California Late Horizon population in which several individuals have enlarged parietal foramina. Some developmental disturbances such as neural tube defects, cleft lip, and cleft palate result from deficits in maternal nutrition that affect genetically susceptible embryos during specific critical threshold events. We now know that some mothers require more of certain nutrients, such as zinc and folic acid, than do other mothers in order to carry out normal metabolic functions. If the required nutrient intake or absorption rate is below what is needed by the mother, the developing genetically susceptible embryo will suffer. This type of extrinsic upset in the developing embryo is known as an epigenetic disturbance. When such disturbances appear in a population, environmental factors need to be evaluated.
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Many of the developmental field defects are known to be caused by intrinsic factors acting upon a susceptible genetic background. Most of the segmentation errors in the paraxial mesoderm, block vertebra, border shifting, and rib segmentation defects are caused by intrinsic factors. The range of expression of some developmental field disturbances causes no interference with normal growth and development. Such disturbances are generally considered anomalous deviations from normal, and most are clinically insignificant. This is particularly true of the developmental disturbances affecting the blastemal desmocranium in the form of primary suture ossicles. Because most of these disturbances have a genetic origin, they are especially valuable for genetic studies. We have not been able to track down severe defects in prehistoric populations, because most of these rarely find their way into skeletal collections primarily because of low neonatal survival rates for most. However, the occurrence of severe, debilitating defects can be postulated by the presence of minor expressions of these defects within a skeletal population, thus providing insights into the natural history of the severe forms. The morphogenetic approach makes such projections possible. We may be able to interpret cultural influences upon developmental defects from variations in frequencies occurring in related skeletal populations sharing the same environment. Fluctuations in frequencies from one site location (community) to another probably reflect marriage patterns. For example, community endogamy can isolate the breeding population, thereby altering the frequencies of certain defects; at the same time, it can heighten the expression of certain defects. Community exogamy encourages admixture, thereby lessening the expressions of certain defects and maintaining a stable frequency pattern. Patterns of expression of developmental field defects vary among genetically different populations. Some examples of this can be seen in the following. Snow (1974) found a tendency for prechordal cranial base disturbances and blastemal frontonasal process disturbances in the formation of the nasal bones in prehistoric Hawaiians. Merbs and Wilson (1962) discovered that the Sadlermiut had a tendency to develop delay disturbances in the regression of the notochord, thus forming sagittal cleft vertebrae. The solitary developmental cyst known as Stafne's defect is not unusual among Plains Archaic and middle Mississippian populations (Finnegan and Marcsik 1980). The proto-Arikara of the northern Plains of the Upper Missouri River Basin had a tendency to develop fissural (inclusion) cysts in the palate and blastemal branchial arch II disturbances in the form of ossification of the epihyal to form
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extra-long-appearing styloids (Gregg and Gregg 1987). The Pajaritan populations tended to develop disturbances in the paraxial mesoderm in the form of precondylar facets reflecting minor caudal shifting at the occipitocervical border, blastemal desmocranium disturbances in the form of extra lambdoidal ossicles, branchial arch I closing membrane defects in the form of tympanic apertures, and sternal caudal cohesion defects. Each population has its own unique pattern of developmental defects. This study also provides the first investigation into the various forms of the sternum in prehistoric skeletal material. The morphogenetic approach to the sternum provides a way to interpret sternal morphology and defects resulting from genetic disturbances. Future studies can build on this research and enhance our knowledge of the genetics governing sternal development. Sternal patterns add another dimension to our understanding of human variability. Because developmental field defects arise from underlying genetic disturbances (Gruneberg 1963), the morphogenetic approach to the interpretation of developmental defects of the axial skeleton provides another avenue for the analysis of genetic traits among skeletal populations. Re-examination of previously studied skeletal collections using the morphogenetic approach can expand our capabilities for interpreting genetic linkages. Relative genetic linkages based upon the patterns of developmental defects within skeletal populations can shed light on past migrations beyond the capabilities of archaeological approaches. Unfortunately, all of the skeletal collections that have been reburied can no longer contribute to this rapidly developing corpus of historical knowledge. This investigation into the nature of developmental defects of the axial skeleton represents ongoing research. Additional disturbances of the various developmental fields of the axial skeleton will no doubt be discovered. This study provides the framework for additions as they arise. The next step in the ongoing investigation is the study of disturbances occurring in the appendicular skeleton. Once all of the developmental fields of the entire skeleton have been worked out, the investigation should expand to include the polytropic defects (clinically known as syndromes). The embryo is a microcosm of evolution, reflecting the variability necessary for change. The risk of aberrant change is inevitable. Disturbances in development are common in all populations, and each gene pool harbors a select group of its own making.
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Glossary achondroplasia Hereditary developmental disturbance of epiphyseal chondroblastic (cartilage) growth and maturation resulting in limb defects and dwarfism. acrocephaly Oxycephaly; pointed, tower-shaped, short skull, with the back of the skull flat and the front having a high, steep bulge; caused by agenesis of the lambdoidal and coronal sutures. adhesions Fibrous bands holding adjacent structures or parts together abnormally. agenesis Failure of development of the embryonic precursor of a part or structure. ala of sacrum Broad, winglike lateral projection of the first sacral segment, formed from the transverse process and costal element. alveolar ridge Mandibular and maxillary margins containing the root sockets for the teeth. Anasazi Navajo name for prehistoric Southwest Indians who primarily inhabited the Colorado Plateau in the Four Corners region of Arizona, New Mexico, Colorado, and Utah. anencephaly Absence of brain formation, with failure of formation of the overlying cranial bones. anlage Primordial embryonic tissue that forms the pattern for development of cartilaginous and membranous bone. annulas fibrosus Outer layerlike margin of the intervertebral disc, consisting of a narrow band of collagen surrounding a wide fibrocartilaginous zone that forms a ring around the central portion of the disc, the nucleus pulposus. anomaly Minor deviation from normally accepted development. anterior neuropore The open cranial end of the neural tube of the embryo before the neural plates complete their closure at this end at between twenty-two and twenty-six days. aperture A bony opening, formed by developmental delay, that has no blood vessels or nerves passing through it. apical Refers to the pointed edge of a structure or the top of a part or structure. aplasia Failure of the embryonic precursor of a structure or part to develop.
aplastic Refers to a structure or part that never developed. apophyseal joint Bony outgrowths of adjacent vertebrae that form an articulation with each other. appendicular skeleton That part of the skeleton governing the extremities: the upper limbs (including the clavicles and scapulae) and the lower limbs (including the innominate bones). Arnold-Chiari malformation Pathological condition associated with neural tube defect in which the cerebellar hemispheres and the medulla of the brain protrude through the foramen magnum into the spinal canal, causing hydrocephalus.
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asterion The point at which the posterolateral fontanelle gives way to the junction of the posterior inferior angle of the parietal bone, the occipital bone, and the mastoid portion of the temporal bone. asymptomatic When a developmental defect causes no symptoms of pathology. atlanto-occipital junction Pertains to the articulation between the basioccipital and the atlas vertebra. atresia Abnormal absence of an opening that has failed to develop during embryogenesis. atrophy Abnormal decrease in size of a bony structure or part, caused primarily by disuse. axial skeleton The cranium, vertebral column, ribs, and sternum. basilar impression Abnormal depression in the base of the occipital. basioccipital Base portion of the occipital that projects forward from the foramen magnum and is derived from the parachordal cartilages of the embryonic prechordal cranial base. basion Midpoint of anterior rim of foramen magnum, used in craniometric analysis. Basket Maker Earliest phases of Anasazi culture of the Southwest Colorado plateau from around 700 B.C. to A.D. 450. bifid Narrow cleft or separation of two parts. bifurcated Divided into two segments. bipartite Having two parts. blastema Primordial embryonic cells that give rise to a structure or part. blastemal skeleton Primordial skeletal structure composed of mesenchymal tissue. block vertebra Two or more vertebrae joined together because of failure of the embryonic precursors to separate. bossing Rounded protrusion of the frontal bone. brachycephalic Broad or round headed. branchial arches Five pairs of barlike ridges separated by ectodermal grooves and endodermal pouches on the ventrolateral surface of the embryonic head; branchial arch I gives rise to the maxilla and mandible, branchial arch II produces the stylohyoid chain, and branchial arch III provides the body and greater horns of the hyoid.
bregma The point at which the anterior fontanelle in the midline of the anterior portion of the skull gives way to the junction of the sagittal and coronal sutures. bulbar Refers to the medulla oblongata, the lower portion, or bulb end, of the brain stem that attaches to the spinal cord; contains vital cardiac, vasomotor, and respiratory reflex centers. calvaria (calvarium) Top portion of the skull derived from membranous bone that includes the frontal, squamosal portions of the temporals, and interparietal of the occipital bone. canalization Formation of an enclosed tubular passageway. cartilaginous skeleton Occurs when developing blastemal skeletal tissue in the embryo is replaced with cartilage prior to ossification. cauda equina Divergent sheaf of long spinal nerves descending from the terminal end of the spinal cord near the inferior border of the first lumbar vertebra into the lumbosacral neural canal. caudal Pertaining to the tail end or inferior part. centrum (centra) The vertebral body. cephalic Pertaining to the cranial or head end, or superior part.
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charnel Structure used for disposing of dead bodies or skeletons. chondrification Conversion of mesenchymal tissue into cartilage. chondroblasts Cartilage-forming cells. chondrocranium That portion of the embryonic cranium derived from cartilage: the basioccipital and anterior portions of the occipital condyles; the petromastoids of the temporals; the body, lesser wings, and roots of the greater wings of the sphenoid; the ethmoid (excluding the perpendicular plates); and the supraoccipital. chondrodysplasia Abnormal development of cartilaginous tissue. cleft lip Most common form of facial clefting that occurs when one or both of the blastemal maxillary prominences fail to unite with the premaxillary prominence (unilateral or bilateral) or when the two halves of the premaxillary prominence fail to unite (midline). cleft neural arch Wide separation of the vertebral neural arch resulting from hypoplasia or aplasia of the precursors of one or both parts of the pedicles, laminae, or spinous process. cleft palate Results from hypoplasia or aplasia of one or both blastemal palatal processes; can be unilateral or bilateral, and a minor form appears as a dorsal notch. cleidocranial dysostosis Defective ossification of the membranous cranial bones and hypoplasia or aplasia of the membranous clavicle bones. congenital Developmental defect detectable at birth. consanguinity Having the same biological ties. conus medullaris The conical end, or apex, of the spinal cord. cornu Bony conical projections: the greater and lesser cornu of the hyoid, the sacral cornu that flank the sacral hiatus and connect with the coccygeal cornu via intercornual ligaments. coronal suture Separates the frontal bone from the parietals. costal element Anterior portion of the lateral process of the developing vertebral segments; the thoracic costal elements develop into the ribs. craniad The head end or superior part. cranial Toward the head end, or the superior part. craniorachischisis Developmental fissure of the skull and spinal column resulting from
failure of the embryonic anterior neuropore of the neural tube to close. craniosynostosis Premature closure of the cranial sutures. critical threshold An event of rapid change during embryonic development, usually when newly formed cells are proliferating, migrating, or differentiating. Crouzon's syndrome A group of disorders caused by developmental delay in the cranium and face, characterized by hypertelorism, exopthalmos, optic atrophy, agenesis of the lambdoidal and coronal sutures, hypoplasia of the maxilla with mandibular prognathism, and a short, stubby nose. deformation Alteration of normally developing structures by mechanical forces in utero or postnatally. dens The upright portion of the axis (C2) vertebra that articulates with the anterior inner aspect of the atlas (C1) vertebra; also known as the odontoid process. dermatome That portion of the embryonic somite that gives rise to the dermis. dermis Skin tissue derived from mesoderm that forms below the epidermis (outer skin layer), consisting of moderately dense connective tissue and containing blood vessels, lymphatic vessels, nerves, hair follicles, sweat glands, and sebaceous glands. desmocranium The primordial membranous cranial vault in the embryo.
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desquamation Shedding of epidermal cells. developmental field The close embryonic interaction of select developing tissues involved in the complex composition of a specific structure or set of closely related structures during morphogenesis. diastema Abnormal space between teeth, usually the central incisors, or a notch or cleft in the maxilla or mandible resulting from developmental delay of respective embryonic parts coming together. diastematomyelia Congenital fissure of the spinal cord caused by failure of the embryonic posterior neuropore to close. diploe Inner portion of cranial bones containing trabecular (cancellous) bone tissue and red marrow, sandwiched between the inner and outer tables of compact (cortical) bone. dolichocephalic Having a long or narrow cranium. dorsal Toward the backside; posterior. dura Pertaining to the dura mater, the outermost layer of the three membranes (meninges) that envelop the brain and spinal cord; the cerebral dura adheres to the internal surfaces of the cranial bones. dysplasia Abnormally developed tissue. ectoderm External layer of embryonic primordial tissue from which the neural plate evolves to form the neural tube, whereas ectodermal cells remaining on the surface contribute to the development of epidermal and epithelial tissue. ectodermal groove Furrow in the embryonic surface ectoderm between two branchial arches; the dorsal end of the ectodermal groove between the first and second branchial arches produces the external auditory meatus. encephalocele Postneurulation defect of the cranial end of the neural tube when brain tissue covered by a skin sac protrudes outside the cranium; the cranium fails to fuse normally because of the neural tube defect. endodermal pouch Internal counterpart to the ectodermal groove between two branchial arches. endogamy Marriage within the social group. endogenous Refers to genetic factor(s) affecting embryonic development; intrinsic factor. enlarged parietal foramina Large, bilateral bony openings in the posterior portion of the
parietals caused by developmental delay of the blastemal precursors of the parietals. epidermis Outer layer of skin composed of keratinized stratified squamous epithelium containing melanocytes. epigenetic The combined effects of genetic and environmental factors that create a disturbance in development. epihyal The portion of the embryonic stylohyoid chain that becomes the styloid ligament. epipterion Location of anterolateral fontanelle, between the merging of the frontal bone with the greater wing of the sphenoid, parietal, and temporal bones at a junction known as the pterion. epithelial Refers to the layer of skin cells covering the surfaces of the body. epitransverse Refers to a bony process or extension on the superior margin of the transverse process of the atlas, associated with mild caudal shifting at the occipitocervical border. exoccipitals Derived from the embryonic occipital somites to form the lateral portions of the base of the occipital around the foramen magnum; contain the major portion of the occipital condyles. exogamy Marriage outside the social group.
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exogenous Refers to an external or environmental factor affecting embryonic development; extrinsic factor. extrinsic Refers to an external or environmental cause of disturbance in embryonic development; exogenous factor. familial Occurring within family lineages. fibrocartilaginous Pertaining to a type of cartilage with a matrix of thick bundles of collagenous fibers; major component of the intervertebral discs. fibrolipomatous Fibrous tumor with a fatty tissue component. fibrous dysplasia Abnormal development of fibrous tissue. filum terminale Threadlike connective tissue descending from the conus medullaris to the dorsal part of the first caudal vertebral segment. fissure Cleft or groove. flail feet Excessive mobility of the ankle joints, usually caused by paralysis of the muscles in control. flange Bony buildup of a border. fontanelle Membranous region of the incompletely ossified infant skull, commonly known as a ''soft spot." foramen A bony opening for the passage of blood vessels or nerves. fossa Bony depression of hollow. frontosal process Primordial embryonic developmental field that produces the nasal bones, premaxilla, perpendicular plates of the ethmoid, vomer, lacrimals, and frontal process of the maxilla. fusiform Tapered at both ends. genetic background Basic genetic information governing the development of the embryo. glabella Most prominent point in the midline of the frontal bone above the nose and between the brow ridges. hemimetamere One of a pair of segmented halves known as somites that move to the midline and fuse during morphogenesis to form the vertebral precursor. heterozygote Fertilized ovum containing inherited dominate and recessive genetic
material. Hohokam Prehistoric desert farmers of the middle Gila and Salt River drainage basins of the Sonoran Desert of southern Arizona. homozygote Fertilized ovum containing inherited identical genetic material from each parent. hydrocephaly (hydrocephalus) Enlargement of the head caused by abnormal accumulation of cerebrospinal fluid within the cranial vault, frequently associated with neural tube defect and Arnold-Chiari deformity. hyperplasia Excessive growth or development of a tissue. hypertelorism Wide distance between the eye orbits caused by developmental delay resulting in hypoplasia of one or both parts of the embryonic median nasal prominence. hypochondroplasia Abnormal development of cartilaginous tissue. hypoglossal canals Bony openings (foramina) situated on the inner aspect of the basilar occipital, anterior to each condyle, that transmit the hypoglossal nerves and meningeal branches of the ascending pharyngeal arteries. hypohyal Part of the embryonic stylohyoid chain that becomes the lesser cornu of the hyoid. hypophysis The pituitary body.
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hypoplasia Underdevelopment of embryonic tissue resulting from delay in development of the blastemal precursor. hypotelorism Eye orbits are too close together as a result of aplasia of the embryonic median nasal prominence. inca bone Retention of the embryonic mendosa suture, creating a separate interparietal bone from the supraoccipital. incisive canal Small, shallow, oval depression in the palate behind the central incisors, where the two halves of the maxilla meet the premaxilla; contains two small, lateral channels transmitting terminations of the greater palatine artery and nasopalatine nerve. incontinence Inability to control discharge of urine or feces. inductive tissue Embryonic tissue that is capable of causing changes in other tissues it comes in contact with during morphogenesis. inion External occipital protuberance. interparietal of occipital The squamosal upper part of the occipital that ossifies directly from membranous tissue, situated between the upper nuchal line and the lambdoidal suture. intrinsic Refers to genetic factor(s) affecting embryonic development; endogenous factor. keratohyalin Dense basophilic protein produced by squamous epithelial cells, which secrete a glycolipid that coats the cell surface to form a thick, sticky, water-resistant substance for holding epithelial skin cells together. Keresan Puebloan group that migrated into the southern portion of the Pajarito Plateau and eventually settled west and northwest of Albuquerque. kyphosis The spine has an abnormal convex curve, forming a humpback appearance. lambda Junction of the lambdoidal and sagittal sutures in the midline preceded by the posterior fontanelle. lambdoidal Suture separating the occipital from the parietals. lamina The bilateral, vertically flattened dorsomedial portions of the vertebral neural arch that join the spinous process to form the vertebral foramen; also refers to a thin, flat layer of bone or membrane. lipoma Fatty tumor.
lordosis The spine has an abnormal or exaggerated concave curve; "swayback." lumbarization Complete or incomplete separation of the first sacral vertebral segment from the sacrum, with caudal shifting of the lumbosacral border. malformation Abnormality resulting from disruption of normal embryonic development. mammillary process Small, bony process on the posterior border of the superior articular process of the lumbar vertebra. manubrium Cranial portion of the sternum that articulates with the clavicles and first ribs, usually separate from the body of the sternum (mesosternum). matrilineal Descent is traced through the maternal line. matrilocal Nuclear family residence is with the mother's side of the family. meatus An opening to a passageway, such as the external ear opening (external meatus) (plural: meattus). Meckel's cartilage Embryonic cartilaginous bar extending from the otic capsule into the first branchial arch, surrounded by mesenchymal tissue; acts as support for the developing mandible. membranous bone Parts of the skeleton that ossify directly from blastemal or membranous tissue.
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mendosa suture Embryonic suture between the membranous interparietal of the occipital and the cartilaginous supraoccipital before they fuse together; this suture sometimes persists into adulthood, creating a separate occipital interparietal bone commonly known as the inca bone. meningocele Postneurulation defect of the neural tube that allows a portion of the meninges surrounding the brain and spinal cord to protrude outside the cranium or vertebral column inside a skin-covered cyst. meningomyelocele (mylomeningocele) Neurulation defect of the neural tube that allows a portion of the brain, spinal cord, and meninges to protrude outside the cranium or vertebral column as an open lesion. mesenchymal Primitive cells with amoeboid characteristics derived from various regions of the early intraembryonic mesoderm with the potential to develop into a wide variety of cellular types when triggered to do so. mesoderm Embryonic germ layer between the outer ectoderm and the inner layer (entoderm) that gives rise to connective tissues, bone, cartilage, muscles, circulatory and lymph systems, urogenital system, and linings of the body cavities. mesosternum The major portion of the sternum, derived from the sternebrae formed from the primordial sternal bands; also known as the body, corpus, or gladiolus. metopism Abnormal persistence of the metopic suture separating the frontal halves in the older child and adult; this suture normally disappears by the second year. microcephaly Abnormally small cranium resulting from developmentally reduced brain size, accompanied by severe mental retardation. microencephaly Reduced brain size, accompanied by severe mental retardation and small cranium. microtia Hypoplasia or aplasia of the external ear. modifying genes Certain genes that can change the course of a developmental function in the presence of a specific gene. Mogollon Prehistoric culture spreading out from the mountains along the Arizona and New Mexico border. moiety One of two social subdivisions. morphogenesis Embryonic development of the various parts of the body according to
species type. mucolipidoses Group of genetic disorders of lipopolysaccharide metabolism, characterized by skeletal deformities, dwarfism, and other metabolic disturbances. mucopolysaccharidoses Group of genetic disorders of mucopolysaccharide metabolism, characterized by skeletal deformities, dwarfism, mental retardation, heart disease, and liver enlargement (Hurler's syndrome, Hunter's syndrome, Sanfilppo's disease). multifactorial Refers to disorders resulting from the interaction among various genetic factors or between genetic and environmental factors. myelodysplasia Defective development of the spinal cord, usually caused by neural tube defect. myotome Portion of the somite that gives rise to striated muscle tissue. nasion Point at which the nasofrontal suture intersects with the midplane (sagital plane) of the skull. neonate Period of infancy from birth to six weeks. neural crest Band of ectomesenchymal cells along the length of the neural tube that gives rise to peripheral neurons and connective tissue in the cephalic region, sense organs,
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specialized glands, skin tissue, smooth muscle, dentin in the teeth, cartilage, and the bones of the face. neural plate Primordium of the central nervous system created from a grooved median strip of ectoderm in the developing embryo. neural tube Slitlike canal, created by the folding of the embryonic neural plate in a craniocaudal direction, that ultimately becomes the spinal cord and brain. neurofibromastosis Common genetic developmental disorder characterized by changes in the nervous system, mental deficiency, pedunculated skin tumors with areas of pigmentation, and bone defects. neuromere One of four primordial segmentations of the hindbrain and one of two primordial segmentations of the midbrain in the embryo prior to closure of the anterior neuropore. neurulation Development of the neural tube from the neural plates. nonviable Unable to live outside the uterus. notochord Primordial flexible rod of cells enclosed by a thick, membranous sheath that provides the structural frame and inductive tissue for the development of the vertebral column, base of the skull, and neural tube. nuchal lines Two transverse ridges on the occipital, with the superior nuchal line midway between the superior and posterior borders where the supraoccipital and interparietal of the occipital meet and the inferior nuchal line about one inch below it. nucleus pulposus Inner portion of the intervertebral disc formed from entrapped notochordal cells invaded by cells from the annulus fibrosus that are eventually replaced by fibrocartilage. obelion Point on the sagittal suture that is usually situated between the locations of the parietal foramina. occipitalization Complete or incomplete incorporation of the atlas vertebra into the occipital by caudal shifting of the occipitocervical border. odontogenic Pertaining to morphogenesis of dental structures. odontoid The upright portion of the axis (C2) vertebra that articulates with the anterior inner aspect of the atlas (C1) vertebra; also known as the dens. opisthion Midpoint of the posterior border of the foramen magnum on the skull.
osseous Having bony qualities. osteitis deformans Chronic skeletal disease found in individuals over age forty, characterized by excessive and abnormal remodeling of bone (Paget's disease). osteogenesis Formation and development of bone tissue. osteogenesis imperfecta Genetic disorder of connective tissue, producing abnormal maturation of collagen in both mineralized and nonmineralized tissues that creates an abnormally fragile skeleton, leading to multiple pathological fractures and deformities. osteomalacia Inadequate or delayed mineralization of bones, leading to deformities. osteopetrosis Complex genetic disturbance of at least four different types, characterized by osteosclerosis, obliteration of the medullary cavities, and pathological fractures. otic capsule One of a pair of primordial cartilaginous encapsulations of the developing otocytes that is part of the prechordal cranial base that gives rise to the petromastoid of the temporal bone. otocyst Embryonic auditory vesicles. oxycephaly High and wide cranium resulting from agenesis of the lambdoidal and coronal sutures; also known as acrocephaly or turricephaly.
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Paget's disease See osteitis deformans. paleopathology Study of disease processes and the natural history of diseases in human remains from the past. parachordal cartilages Pair of primordial cartilages created from mesenchyme parallel to the cranial end of the notochord as part of the prechordal cranial base that become the basioccipital and anterior portion of the occipital condyles. paracondylar Refers to a location beside the occipital condyles. paraxial mesoderm Pair of primordial mesenchymal columns along both sides of the notochord, straddling the developing neural tube, that segment into the somites and give rise to the vertebral column, ribs, and exoccipitals. paresthesia Sensation of numbness, burning, prickling, or tingling. pars interarticularis Junction of the lamina and pedicle of the neural arch from which the superior and inferior articular processes project. pars obelica That part of the sagital suture situated between the parietal foramina. pedicle Bilateral short, thick projections from the dorsolateral margins of the vertebral body, forming the lateral portions of the vertebral foramen. peduncle Connecting stem or band of tissue. pedunculated Having a stem or attached band of tissue. petromastoid Mastoid and petrous portion of the temporal bone created from the embryonic cartilaginous otic capsules of the prechordal cranial base. petrotympanic (Glaserian) fissure Narrow slit posterior to the mandibular fossa of the temporal bone that leads into the tympanic cavity and allows for the passage of a blood vessel and nerve. phenotype Physical expression of inherited traits in an individual. Pierre Robin Syndrome Group of developmental disturbances characterized by a very small mandible and cleft palate. plagiocephaly Asymmetrically shaped cranium caused by partial agenesis of one or more cranial sutures. plantar Pertaining to the inferior surface, or sole, of the foot. pluripotent Primordial cell capable of developing or acting in different ways.
polydactyly Supernumerary (extra) fingers or toes. polytropic Affecting more than one kind of tissue; pertaining to multiple developmental defects occurring in the same or related developmental fields. posterior neuropore The open caudal end of the neural tube of the embryo before the neural plates complete their closure at this end at between twenty-six and thirty days. postneurulation Time period during embryonic development, following the closure of the neuropores, when the neural tube continues to grow by canalization. prechordal cranial base Antecedent of the chondrocranium that contains the embryonic otic capsules, trabecular cartilages, and parachordal cartilages. precondylar Located anterior to the occipital condyles. precostal process Embryonic mesenchymal condensation between the suprasternal structures that unites with them and the cranial ends of the sternal plates to form the manubrium of the sternum. premaxilla Midfacial region created from the blastemal frontonasal process that fuses with the maxillae and contains the upper incisor teeth.
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primitive streak Dense band of primordial cells appearing during the second postfertilization week at the caudal midline of the embryonic disc from which the axial skeleton evolves. proatlas Separate occipital bone in birds and reptiles that evolves from the last occipital sclerotome; in humans (spondylo-cranium) it becomes the exoccipital portions of the base of the skull. prognathism Marked projection of the mandible or lower face. Pueblo I A.D. 700900 time period in Anasazi culture of the Southwest. Pueblo II A.D. 9001100 time period in Anasazi culture of the Soutwest. Pueblo III A.D. 10001300 time period in Anasazi culture of the Southwest. Pueblo IV A.D. 13001540 time period in Anasazi culture of the Southwest. Pueblo V A.D. 15401850 time period in Anasazi culture of the Southwest. rachishisis Developmental defect of the neural tube, creating a fissure in the spinal cord; spina bifida. Reichert's cartilage Embryonic band of cartilage that evolves from the second branchial arch, extending from the otic capsule to form the stylohyoid chain. sacral hiatus Normal space or cleft between the last two segments of the dorsal plate of the sacrum. sacralization Complete or incomplete incorporation of the last lumbar vertebral segment into the sacrum, with cranial shifting of the lumbosacral border; can also be applied to the complete or incomplete incorporation of the first caudal segment into the sacrum, with caudal shifting of the sacrocaudal border. sagittal Anteroposterior plane to the long axis of the body; also refers to the suture that separates the parietals. scalene tubercle Triangular-shaped bony elevation on the superior surface of the first rib for the insertion of the scalenus anticus muscle. scaphocephaly Cranium shaped like the keel of a boat, resulting from agenesis of the sagittal suture. sciatica Severe pain radiating from the sacral area and down the leg, caused by compression or trauma of the sciatic nerve that arises in the sacral plexus and passes through the greater sciatic foramen and down the back of the thigh.
sclerotic Bony part that has become thick and hard. sclerotome Ventromedial part of the embryonic somite that develops into the vertebra and rib. sclerotomic fissure Anlage of the intervertebral disc that develops as intersegmental arteries separate the cranial and caudal portions of the primary sclerotome. scoliosis Abnormal lateral curvature of the spine. sella turcica Concavity on the upper surface of the sphenoid body that holds the hypophysis (pituitary gland). septum (septa) Tissue partition separating adjacent parts or structures. Sinagua Prehistoric Western Anasazi group found in the vicinity of Flagstaff, Arizona. somite One of a pair of primordial mesenchymal blocklike masses subdividing the paraxial mesoderm that give rise to the vertebral column and exoccipitals. somitomere One of the incomplete segmentations of the paraxial mesoderm in the developing cranial region that give rise to the desmocranium and muscle tissue associated with the branchial arches. spina bifida Failure of the vertebral neural arches to fuse because of a neural tube defect.
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spondylo-cranium Refers to the last occipital sclerotome in humans, which becomes the exoccipitals while remaining as a separate bone in birds and reptiles (proatlas). sternal plates Bilateral bands of mesenchyme that come together and fuse to form the mesosternum, xiphoid process, and a portion of the manubrium. sternebra One of four segments of the immature mesosternum. stylohyal Segment of the stylohyoid chain that forms the tip of the styloid process. stylohyoid chain Formed from a band of embryonic cartilage (Reichert's cartilage) of the second branchial arch, it consists of the styloid process, the stylohyoid ligament, and the lesser cornu of the hyoid. subluxation Partial or incomplete dislocation. sulcus Groove or slight depression. supraoccipital Portion of the occipital derived from the occipital somites and ossifying from cartilage; situated between the superior nuchal line and the foramen magnum. suprasternal structures Derived from a pair of embryonic mesenchymal condensations above the sternal plates, they fuse with the sternal plates and precostal process to become part of the manubrium and to form cartilaginous joints with the clavicles. syndrome Complex of signs and symptoms that characterize a specific abnormality. synergistic Acting together. systemic defect Developmental disturbance caused by enzymatic upsets at the cellular level, producing defects in specific tissues that affect all of the structures incorporating the defective tissue into their development. Tanoan Southwest Puebloan language group subdivided into the Tewa, Tiwa, Towa, and extinct Tano (Southern Tewa), Piro, and Tompiro; also linguistically related to the Plains Kiowa. Tewa Tanoan Puebloan group that migrated down the Chama River Basin into the northern and central portions of the Pajarito Plateau and eventually settled in the central portion of the northern Rio Grande region, with a branch known as the Tano occupying the Galisteo Basin southeast of Santa Fe, New Mexico. thanatophoric dysplastic dwarf Caused by generalized failure of endochondral bone formation; characterized by large head, hypertelorism, saddle nose shape, and very short limbs extending straight out from the trunk; usually die soon after birth.
threshold event A time of rapid change during morphogenesis, usually when newly formed cells are proliferating, migrating, or differentiating. Tiwa Tanoan Puebloan group that separated into a northern branch, with settlement in the northern part of the Rio Grande region, and a southern branch that occupied an area southwest of Albuquerque, New Mexico. Tompiro Extinct Tanoan Puebloan group that inhabited several pueblos in the Salines area on the east side of Sierra Morena in central New Mexico. Towa Tanoan Puebloan group that settled in the Jemez Mountains and San Diego Canyon in northern New Mexico. trabecular cartilages As part of the embryonic prechordal cranial base, they are created from primordial bilateral condensations of mesenchyme in the interorbitonasal region and ossify into the body, lesser wings, and roots of the greater wings of the sphenoid and major portions of the ethmoid of the chondrocranium. trephination The process of excising a piece of bone from the skull. trigonocephaly Cranium with triangular, pointed frontal bone caused by agenesis of the metopic suture.
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tubercle Small, rounded bony elevation. tuberosity Bony protuberance or elevated rounded process. turricephaly Pointed, tower-shaped cranium resulting from agenesis of the coronal and sagittal sutures (also known as oxycephaly or acrocephaly). tympanic plate Created from the closing membrane of the first branchial arch, this thin bony plate becomes part of the temporal bone and forms the floor of the external auditory canal and the posterior wall of the mandibular fossa. tympanic sheath Bony extension of the inferior border of the tympanic plate that forms a covering around the base of the styloid process. tympanohyal Base of the styloid process that is formed from the stylohyoid chain. uvula Small soft tissue mass suspended from the edge of the soft palate in midline above the root of the tongue; it consists of the levator and tensor palati muscles, uvula muscle, connective tissue, and mucous membrane. ventral Anterior, or front, side of the body. vertex Highest point; usually at midpoint of the sagittal suture on the skull. vertigo When an individual has the sensation of the external world moving around him or her (objective vertigo), or the individual feels he or she is revolving in space (subjective vertigo); frequently associated with inner ear disease (Meniere's syndrome). viable When a human fetus is mature enough to live outside the uterus, usually after twenty-eight weeks of development. visceral Pertaining to internal organs. viscerocranium Cranial components derived from the branchial arches. vomer Small, flat bone, shaped like a plowshare, that forms part of the inferior and posterior portions of the nasal septum and articulates with the ethmoid, sphenoid, palate bones, and superior portion of the maxillary bones. xiphoid process Lower end of sternum produced by caudal ends of the embryonic sternal bands; its shape is variable, and it may or may not be fused to the mesosternum.
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Index A Achondroplasia. See Chondrodysplasias; Dwarfs Acrocephaly. See Oxycephaly Africa: metopism, 148 variation of numbers of vertebrae, 78-79 Alar ligament, 16 Alkali Ridge, Utah: cervical rib, 101 misplaced manubrio-mesosternal joint, 213 thoracic rib defects, 72, 241 Amoxiumqua, New Mexico: block vertebra, 71, 240 cervical ribs, 102, 106 (figure) cleft neural arch, 122, 265 dermoid cyst, 57-58 (figure) developmental cyst of the mandible (Stafne defect), 170 (figure), 171 developmental cyst of the maxilla, 179 lumbar ribs, 103, 110 (figure), 250 odontoid type II defect, 88, 90 (figure), 246 paracondylar protuberance and precondylar tubercle, 84, 247 rib defect, 74 scaphocephaly, 155, 157 (figure) sternum defects, 223 (figure) transitional lumbosacral vertebrae, 111, 255 Anencephaly: defect 9, 41, 44 (figure), 54
prehistoric case, 44. See also Neural tube: defects Annulus fibrosus, 36 Anomalies, 2, 3, 12, 32, 140. See also Defects, developmental: minor variations Anterior fontanelle, 55-57 Anterior neuropore, 23 (figure), 42-43 (figure), 44, 56. See also Neural tube: development Apical ligament, 16 Arikara groups, South Dakota: sacral clefting, 120. See also Upper Missouri River Basin Arkansas: external auditory meatus atresia, 201 Arnold-Chiari malformation, 46 Arroyo Hondo, New Mexico: block vertebra, 70, 240, 296 cervical ribs, 101, 296 occipitalized atlas, 89, 248, 296 odontoid type II defect, 88, 246 pueblo, 296 Atlanto-occipital fusion. See Vertebral border shifting: occipitocervical Atlas vertebra: clefting, 120, 293 (see also Cleft neural arch) development, 19, 21 (figure), 29, 33 (table), 80-81 occipitalization, 81, 83 (figure), 88-90, 92, 96, 130, 239 (See also Vertebral border shifting: occipitocervical) posterior bridge, 89 prehistoric cases of clefting, 121-122 (figure), 265-266 (figure), 267, 293, 295 prehistoric cases of occipitalization, 89-90, 92, 98 (figure), 116, 136, 248, 296-297 Auricle (external ear): development, 199, 201 microtia, 201 Australia: cleft lip and cleft palate, 189 cleft palate, 175 cranial meningocele, 53
Crouzon's syndrome, 154 metopism, 148 Axis vertebra: associated ligaments, 16 development 19, 21 (figure), 33-34 (table) B Basilar impression: defect, 92, 96, 99 prehistoric cases, 90, 136 Basioccipital: affected by notochord, 16 clefts, 82-83 (figure), 84, 87 (figure), 130 defects, 136 development, 30, 35, 81, 135 developmental field, 13 (table), 134, 138 (see also Prechordal cranial base) prehistoric cases of defects, 84 (cleft), 136-138 Basisphenoid: affected by notochord, 16, 35 development, 16 (see also Chondrocranium) Binder's syndrome, 192-193 (figure), 197 Birth defects. See Congenital defects Blastemal desmocranium: defects, 140-160, 240, 321 development, 23, 33 (table), 138-139, 320 developmental field, 6, 14 (table), 24 (figure), 134 prehistoric cases of defects, 141-146, 148-150 (figure), 152, 154-158 (figures), 159, 271-278 (figures), 295-296, 319 Block vertebra: development, 66-57, 320 with occipitalized atlas, 88
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prehistoric cases, 38, 69 (figure), 70-71, 73 (figure), 116, 235-241, 246, 293-294, 196297 types, 67-69, 129 Brachycephaly, 153 (figure), 154, 160, 232, 315 Bradford House III site, Colorado: cervical ribs, 101 Brain: development, 21-22, 33 (table), 42 developmental field, 13 (table), 41 encephalocele, 52 fissure, 43-44 (figure) (see also Craniorachischisis) Branchial arch I: defects, 161-180 development, 23, 25, 33 (table) developmental field, 6, 14 (table), 17 (figure), 23-24 (figure), 30, 43 (figure), 134, 160, 181 (figure). See also Mandible Maxilla Branchial arch II: the developmental field, 6, 14 (table), 17 (figure), 23-24 (figures), 25, 33 (table), 134, 201, 205. See also Stylohyoid chain Stylohyoid ligament Styloid process Branchial arch III, 25, 208 Bright Angel, Arizona: block vertebra and occipitalized atlas, 89, 248 Broadway and McClintock site, Arizona: rib defect, 76 Butterfly vertebra. See Sagittal cleft vertebra C California: achondroplastic dwarf, 136 agenesis of sutures, 144-145 cleft lip and palate, 187
enlarged parietal foramina, 144-145 (figure), 319 hemifacial microsomia, 163, 165 (figure) metopism, 144 microcephalic, 159 trigonocephaly, 154 Calvarium, 134, 139, 154 Canary Islanders: metopism, 148 Canyon de Chelly, Arizona: precondylar tubercle, 84, 247 mendosasuture, retention, 142, 275 tympanic aperture, 204, 280 Carlsbad, New Mexico: external auditory meatus atresia, 201 Casa Buena, Arizona: occipitalized atlas, 92 Cashion site, Arizona: hemi-proatlas and occipitalized atlas, 92 Cat's face, 184-185 (figure). See also Facial cleft: median Catlin mark, 144. See also Parietal foramina: enlarged Cauda equina: bifurcated, 40 development, 42, 47 Cementum, 23 Centrum: absence, 129, 133 attached osseous spike, 40 bifid (butterfly), 36-37, 40 (see also Sagittal cleft vertebra) coronal cleft, 36, 40 development, 19, 27, 28, 36, 40, 117, 126. See also hemivertebra Cervical ribs: development, 29, 72, 250 expressions, 77 (figure), 100-103 (figure), 104-105, 131 prehistoric cases, 74, 101-102, 106-107 (figures), 116. See also Vertebral border shifting: cervicothoracic
Cervical spine: development, 18 Chaco Canyon, New Mexico: block vertebra, 70, 240 cranial sutureagenesis, 155, 277 occipitalized atlas, 89, 248 transitional lumbosacral vertebrae, 111, 255. See also Pueblo Bonito Chavez Pass, Arizona: precondylar protuberance, 84-85 (figure) Chinese: bifid mandibular condyles, 166 metopism, 148 Chondrocranium, 28, 33-34 (table), 134, 139 Chondrodysplasias: achondroplastic, 13 definition, 12 hypochondroplasia, 13 thanatophoric dysplastic dwarf, 12 Chorda dorsalis. See Notochord Cleidocranial dysostosis, 92, 141 Cleft lip: bilateral, 183 (figure), 184-5, 187, 196 causes, 187, 319 frequency, 9, 174, 187 midline, 183 (figure), 184, 189, 196 prehistoric cases, 187-192 (figures) with secondary cleft palate, 186-188, 196-197 simple (mild), 185, 196 unilateral, 183 (figure), 196, 184, 187-188 (figure). See also Facial clefts Cleft mandible, 161-162 (figure), 179 Cleft neural arch: defect, 45 (figure), 47, 49, 120-124, 133 development, 117, 119 frequency, 49, 119, 293
prehistoric cases, 38, 48 (figure), 116, 120-123 (figures), 259-267, 293-295 with spina bifida (see Spina bifida) Cleft palate: bilateral, 9, 173-174, 180 causes, 319 development, 171-172 (figure) frequency, 9, 174-175 minor (dorsal notch), 171, 174-175, 179, 189 unilateral, 174, 180 prehistoric cases, 175-176 (figure) secondary to cleft lip, 184, 186-188 (figures), 189, 196-197 (see also Cleft lip) X-linked, 175 Cleft palate, submucous. See Cleft palate: minor (dorsal notch) Closing membrane, branchial arch I: defects, 202-204, 295-296, 318, 321 the developmental field 6, 14 (table), 33 (table), 134, 202. See also Tympanic plate Coccyx, 18, 30, 33 (table), 42, 114 Colorado: cleft lip and palate, 190 (figure), 192
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Congenital defects: causes, 10 definitions, 1-3 frequency, 9 reported in prehistoric skeletal collections, 1-2. See also Defects, developmental Conus medullaris, 47 Costal cartilages, 30 Costal processes: development, 19, 29, 71 with vertebral border shifting, 99-100 Cranial-caudal shifting. See Vertebral border shifting Cranial sutures: agenesis, 152-157 (figures), 159-160 growth, 139 prehistoric cases of agenesis, 154-157 (figures), 277-278. See also Ossicles Cranial vault: development, 22 developmental field, 6. See also Blastermal desmocranium Craniorachischisis, 43-44 (figure) Craniosynostosis, 1, 152. See also Cranial sutures: agenesis Crouzon's syndrome, 154, 160 Cultural factors, 3, 5, 8, 294, 297, 315, 317-318, 320 Cyst, developmental inclusion: mandibular (Stafne defect), 170-171, 177 (figure), 179, 319 maxillary, 177 (figure), 178-179, 319 prehistoric cases of mandibular, 170 (figure), 171, 320 prehistoric cases of maxillary, 178-180, 320 D Defects, developmental: causes, 10, 15, 28, 319 definition, 2
field defects, 7, 13-14, 36, 41, 320 frequency variations, 5, 292-297, 320 major, 5, 9, 12, 320 minor, 2-3, 5, 9, 12, 35, 320 multiple (polytropic), 11-12, 32, 141, 148, 152, 181, 186, 321 origins, 3, 9 patterns, 5, 7-8, 232, 292-295-297, 315, 317-321 sporadic, 293, 319 systemic tissue, 12 (see also Dysplasias) variable expressions, 3, 7, 9, 11 Deformations, 12 Denmark: enlarged parietal foramina, 146 Dens, of the atlas. See Odontoid Dentine, 23 Dermatome, 19, 59 Dermoid cyst: defect, 55-57, 319 prehistoric case, 57-58 (figure). See also Ectodermal inclusion cysts Dermoid sinus, 56-57. See also Ectodermal inclusion cysts Diastema, 161-162 (figure), 179 Dwarf: achondroplasia, 1, 13, 136 thanatophoric dysplastic, 12. See also Chondrodysplasias Dysostosis cleidocranialis, 32 Dysplasias, skeletal: 6, 12-13, E Easter Islanders: metopism, 152 Ectodermal cells, 15, 35, 55 Ectodermal groove, branchial arch I: development, 23
developmental field, 6, 14 (table), 24 (figure), 26 (figure), 134, 197-198 (figure). See also External auditory meatus Ectodermal inclusion cysts: development, 55-57. See also Dermoid cyst Dermoid sinus Epidermoid cyst Egypt: achondroplastic dwarf, 136 anencephaly, 44 basioccipital absence, 136 enlarged parietal foramina, 146 microcephaly, 158-159 parietal thinning, 148-150 (figures) premaxilla aplasia, 189 Elden Pueblo, Arizona: block vertebra, 71 cleft neural arch, 121 precondylar facet, 92 scaphocephaly, 157 transitional lumbosacral vertebra, 111 Encephalocele, 52. See also Brain England: cleft palate, 175 basioccipital absence and basilar impression with occipitalization of atlas, 136 hemivertebrae, 60 microcephaly, 158 parietal thinness, 148 Environmental factors, 3, 5, 10, 41, 152, 158, 187, 297, 319. See also Extrinsic factors Epidermoid cyst, 55-57. See also Ectodermal inclusion cysts Epigenetic interaction, 10, 32, 59, 291, 319 Epitransverse process, 83 (figure), 89, 131
Eskimo: bifid mandibular condyles, 166 cleft palate, 175 enlarged parietal foramina, 146 extra vertebrae, 78 metopism, 148. See also Sadlermiut Ethmoid: defects of perpendicular plates, 182, 184, 196 development, 30, 33 (table), 135 developmental fields, 6-7, 13-14 (table), 138, 180 Exoccipitals: development, 18-19, 21 (figure), 30, 80-81, 134-135 developmental field, 6, 13 (table), 24 (figure), 58-59 External auditory meatus: defects, 197-202, 205 development, 23, 33 (table), 197-198 (figure) developmental field, 6, 14 (table), 24 (figure), 134 with hemifacial microsomia, 161 prehistoric cases of defects, 200 (figure), 201, 278 Extrinsic factors, 3, 10-11, 293, 319. See also Environmental factors F Face: development, 25, 26 (figure), 33 (table), 180. See also Frontonasal process
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Facial clefts: development, 180-182, 196 nasomaxillary, 182-183 (figure) nasoocular, 182-183 (figure) median, 182-183 (figure). See also Cleft lip Ferguson Farm in Accokeek, Maryland: hypoplasia of basilar occipital, 136 Fibrous dysplasia, 13 Filum terminale, 42, 47 Fields, developmental: definition, 6 development, 32 disturbances in morphogenesis, 3, 6-7, 11-14, 49, 297, 318-320. See also Defects, developmental Folic acid, 41, 187, 319 Fontanelles: bones (ossicles), 140 (figure), 141-142 development, 139 prehistoric cases of fontanelle bones, 142-143, 273, 274 (figure), 275, 292, 296 types, 139, 142, 159, 273-274 (figure) Frijoles Canyon, Bandelier National Monument: sutural agenesis with metopism, 155 Frontal bone: development, 22, 30, 138, 180 developmental field, 14 (table). See also Blastemal desmocranium Frontal sinus defects, 184, 197 Frontonasal process: development, 25, 33 (table), 171, 181 (figure), 192 developmental field, 7, 14 (table), 134, 175 disturbances, 180-197 prehistoric cases, 187-196, 320 G Genes: autosomal dominant, 11, 67, 144, 154, 237 autosomal recessive, 67, 158, 237
modifying, 11 mutants, 11 Genetics: assessment, 1, 315, 317, 321 background, 11, 187, 236-237, 291, 293, 319-320 control, 89 drift, 295, 317 isolation, 38, 70 links, 72, 321 origin, 320 programming, 141 tendency, 80 trends, 318 underlying basis, 2-3, 41-42, 59, 201, 232, 241, 292, 295, 297-298, 319, 321 upsets, 11-12, 32 Genetic factors, 3, 8, 9-10, 58, 120, 158, 319. See also Intrinsic factors Giusewa, New Mexico: block vertebra, 71, 240 cleft neural arch, 121-122, 265 lumbar ribs, 103, 250 sternum defects, 221 (figure) transitional lumbosacral vertebra, 111, 255 Glaserian fissure. See Petrotympanic fissure Glen Canyon, Utah: sutural agenesis, 155 Gran Quivira, New Mexico: block vertebra, 70, 240, 296 cervical ribs, 101, 296 cranial sutural agenesis, 155, 296 extra vertebrae, 79, 243 occipitalized atlas, 89, 248
small twelfth ribs, 103, 250 sternum defects, 212-213, 215, 223, 225, 291 transitional lumbosacral vertebrae, 111, 252, 296 tympanic aperture, 204, 280, 296 H Haley's Point, Oklahoma: cleft neural arch, 123 (figure) Hawaii: basioccipital defect, 137-138 nasal bone defects, 193-195, 320 (figure) tympanic sheath of styloid defects, 205 Hawikku, New Mexico: basilar cleft, 84 block vertebra, 69 (figure), 71, 240 cervical rib (class I), 102 cleft neural arch, 48 (figure), 122, 265 cranial suture agenesis, 155, 278 extra vertebra, 79, 243 fontanelle bones, 142, 275 genetic distance study, 317 hemifacial microsomia, 163 mendosa suture, retention, 143, 275 metopism, 152, 277 paracondylar protuberance, 84 precondylar facet, 92, 97 (figure), 246 precondylar protuberances, 84 precondylar tubercle, 84, 247 rib defect, 76, 241 scaphocephaly, 155, 278 sternum defects, 212, 214 (figures), 215, 217 (figure), 220 (figure), 222 (figure)
sutural agenesis, 155 transitional lumbosacral vertebrae, 111, 113, 115 (figures), 255 ventral hypoplasia of centra, 127 (figure) Hemifacial microsomia: prehistoric cases, 163, 165 (figure) types, 161-164 (figure), 179. See also Mandible: defects Hemivertebra: dorsal, 126, 128 (figure), 133 from hemimetameric aplasia, 62, 129 from hemimetameric shift (asynchronous development), 60-61 (figure), 129 from hemimetameric hypoplasia 62, 65-66 (figures), 129 prehistoric cases of hemimetameric hemivertebra, 60-62, 92, 234-236 (figure), 294 ventral, 126-128 (figure), 133 Henderson site, New Mexico: sagittal cleft centrum, 38 Hensen's node, 16, 17 (figure), 33 (table) Heritability: risk, 5, 140 familial, 11, 41, 144, 158, 169, 174, 293, 319 67 prehistoric cases of familial, 38, 70, 265 Heshotauthla: basilar depression, 90, 96, 99 bifid mandibular condyle, 166, 168 (figure) block vertebra, 71, 90, 99, 240, 248 cleft neural arch, 122, 124 (figure), 265 cranial meningocele, 54 cranial suture agenesis, 155-156 (figure), 278 fontanelle bones, 142, 275 lumbar ribs, 108, 250 mendosa suture, retention, 275 occipitalized atlas, 90, 98 (figure), 99, 248 rib defect, 74, 76 (figure)
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scaphocephaly, 155, 278 sternum defects, 225 (figure) transitional lumbosacral vertebrae, 111, 115 (figure), 255 Homol'ovi, Arizona: hemifacial microsomia, 163 type III Klippel-Feil syndrome, 70, 241 Hungary: bifid mandibular condyles, 166 incomplete cleft palate, 192 mandibular developmental inclusion cyst (Stafne defect), 170 Huschke's foramen. See Tympanic aperture Hydrocephaly, 1, 46, 54 Hyoid, 25, 205, 207, 209 Hyoid lesser horns: developmental field, 6, 14 (table), 25 Hypertelorism, 183 (figure), 184, 196 Hyperthyroidism, 152 Hypoglossal canals: bipartite, 82-83 (figure), 84, 130 prehistoric cases of defect, 237, 246 Hypophosphatasia, 152 Hypotelorism, 182, 196 I Inca phenomenon. See Mendosa suture Incisors: disturbances associated with defects, 179, 186, 189, 196-197 supernumerary associated with defects, 186 Incus, 23, 31 Induction, embryonic, 16 Intersegmental septae, 18 Intervertebral disc, 19, 66
Intrinsic factors, 3, 10, 293, 320. See also Genetic factors Ireland: microcephaly, 158 J Japan: microcephaly, 158 K Kayenta, Arizona: block vertebra, 69 border shifting, 70 cleft neural arch, 70 extra vertebra, 70, 79, 243 Kentucky: cleft palate, 175-176 (figure) Klippel-Feil syndrome, 1, 67, 69. See also block vertebra Kodiak Islanders: bifid mandibular condyles, 166 Kyphosis, 38, 40, 76, 82, 126, 128, 133 L Lacrimals: defects, 194, 196 development, 33 (table) developmental field, 7, 14 (table), 180 prehistoric cases of defects, 196-197 Lapoint, Utah: occipitalized atlas, 89 Lapps: metopism, 148 Lateral nasal prominence, 26 (figure) Lewistown, Illinois: cervical ribs, 101 Lordosis, 133 Los Muertos, Arizona: block vertebra, 71, occipitalized atlas, 92 retention of mendosa suture, 142 sutural agenesis, 155
Lumbar ribs: defect, 105, 132 development, 29 prehistoric cases, 105, 108, 109-110 (figures), 248-249 (figure), 250. See also Vertebral border shifting: thoracolumbar Lumbar sacralization. See Vertebral border shifting: lumbosacral Lumbar vertebra, extra: development, 78 prehistoric cases, 50, 78-79. See also Vertebral column: numerical variations M Malformations. See Defects, developmental. Malleus, 23, 31 Mammillary processes, lumbar vertebra, 29 Mandible: defects, 161-171 development, 25, 30-31, 33 (table), 161 developmental field, 6, 14 (table), 24 (figure), 134, 160 prehistoric cases of defects, 163, 165-168 (figures). See also Branchial arch I Mandibular condyles: bifid (double), 166-167 (figure), 179 development, 163, 166 hyperplasia, 167, 179 prehistoric cases of bifid, 166-167 (figure) Mandibular coronoid hyperplasia, 169 (figure), 179 Manubrium: defects, 215-217, 230 development, 25, 31, 33 (table), 210-211 developmental fields. See also sternal plates Manubrio-mesosternal joint: development, 211 fusion, 211-214 (figures), 220-223 (figures), 225-226 (figures), 227, 293, 282-286 (figures) misplaced, 212-213 (figure), 227 Maxilla: defects, 171-180
development, 25, 30-31, 33 (table), 171 developmental fields, 6-7, 14 (table), 24 (figure), 134, 160, 180 with hemifacial microsomia, 161 Meckel's cartilage, 31, 161 Median nasal prominence, 26 (figure) Melanesians: metopism, 148 Mendosa suture: prehistoric cases of retention, 142-143, 275, 293, 296 retention, 140 (figure), 142, 159 Meningocele: cranial, 52-54, 56-57 cranial prehistoric cases, 52-54 sacral, 50-51 spinal, 45 (figure), 46-47, 54. See also Neural tube: defects Meningomyelocele, 32, 41, 44-45 (figure), 46-47, 50, 54. See also Neural tube: defects Mesa Verde, Colorado: block vertebra, 70, 240, 296 lambdoidal ossicles, 141
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odontoid type II defect, 88, 246 rib defects, 72, 74, 241 sutural agenesis, 155 transitional lumbosacral vertebra, 111, 255 Mesenchymal diastematomyelia, 39-40 Mesosternum: defects, 215-230 development from sternebrae, 25, 33 (table), 110-111 developmental field, (see sternal plates) prehistoric types, 214 (figure), 225-227 (figures), 230, 281-290 (figures), 321 types, 217-219, 221 Metopic suture: absence, 154 development, 138 retention. See metopism Metopism, 148, 151 (figure), 159 prehistoric cases, 148, 152, 155, 276 (figure), 277, 297 Microcephaly, 1, 157-160 Middle Mississippi: mandibular developmental inclusion cyst (Stafne defect), 170 Modoc site, California: cleft lumbosacral vertebrae, 120 transitional lumbosacral vertebrae, 111 Mongolians: bifid mandibular condyles, 166 metopism, 148 Morphogenetic approach, 1-3, 6, 318-321 Moundville, Alabama: achondroplastic dwarfs, 136 Mucolipidoses, 13 Mucopolysaccharidoses, 13 Mustang Mesa: sutural agenesis, 155
Myelomeningocele. See Meningomyelocele Myotome, 19, 59 N Nasal bones: absent, 182, 193 defects, 184, 193-194 (figure), 196-197 development, 33 (table), 192 developmental field, 6-7, 14 (table), 180 prehistoric cases of defects, 193-195 (figure), 320 Netherlands: enlarged parietal foramina Neural arches: with block vertebra, 66 with border shifting, 80 cleft (see Cleft neural arch) development, 19, 29, 33-34 (table), 71, 117 developmental delay defects, 117, 119, 121 (figure), 122, 125, 133 joint defects, 76, 125 prehistoric cases of defects, 239, 259-269, 267-269, 294 with sagittal cleft centrum, 36, 40 Neural crest, 15, 21, 23, 25, 28 Neural plate, 15, 17 (figure), 21, 33 (table), 42, 43 (figure) Neural tube: defects, 9, 11, 18-19, 32, 41-54, 55, 57, 120 developmental field, 6, 13 (table), 15, 17, 33 (table), 35, 43 (figure), 46, 55, 59, 117 development of defects, 18, 42, 319 incidence of defects, 41 Neurofibromatosis, 13 Neurulation: primary, 43, 44 (figure). See also Neural tube Northwest Coast: patterns of vertebral border shifting, 116 Notochord: affects on other tissues, 35
developmental field, 6, 13 (table), 16, 17 (figure), 18-19, 20 (figure), 22 (figure), 24 (figure), 33-34 (table), 36, 59, 134 failure to regress defects, 36-40, prehistoric cases, 38-39 (figure) 320 Nubian: cleft palate, 175 Nucleus pulposus, 16, 36 O Occipital condyles: bipartite (bifid), 82-83 (figure), 84, 87 (figure), 130 development, 18, 30, 80, 135 hypoplasia, 83 (figure), 89, 131, 138 prehistoric case, 246. See also Vertebral border shifting: occipitocervical Occipital interparietal: development, 22, 30, 139 developmental field, 14 (table) multiple, 143, 159 separate bone, 142, 159 Occipital vertebra, 81-83 (figure), 84, 88, 130 prehistoric case (minor), 84-85 (figure). See also Vertebral border shifting: occipitocervical Odontoid, (dens): with basilar impression, 96 defects, 82-83 (figure), 86-88, 91 (figure), 130-131 development, 19, 21 (figure), 29, 33 (table), 81 prehistoric cases of type II defect, 88, 90 (figure), 237, 246. See also Vertebral border shifting: occipitocervical Ossicles: development, 140, 320 patterned extra, 141, 159 prehistoric cases, 141-142, 271-275, 292, 294, 296, 321 secondary, 141 (see also Fontanelles: bones) Osteitis deformans, 92 Osteogenesis imperfecta, 13, 92
Osteomalacia, 92 Osteopetrosis, 13 Osteoporosis, senile, 92, 146 Otic capsule, 21, 22 (figure), 28, 30-31, 136, 138, 205 Otocysts, 21, 134 Otowi, defects: block vertebrae, 239, 294 cleft sacral neural arch, 48 (figure), 262-264 (figures), 265, 294 cranial suture agenesis, 277 fontanelle bones, 273 lumbosacral border shifting, 251-252, 294 occipitocervical border shifting, 239, 244, 248 ossicles, lambdoidal, 272-273, 294 precondylar facet, 239, 244, 294
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sacrocaudal border shifting, 255, 257, 294 sternal defects, 284-285, 287, 289-290 (figure), 291, 294 tympanic aperture, 279-280, 294 Otowi: burials, 309-310 (map), 312 pueblo, 304, 307 skeletal collection, 8, 232-234, 310, 318 Oxycephaly, 153 (figure), 154, 160, 196 P Paget's disease, 92 Pajarito Plateau, New Mexico: genetics, 315, 317 the place, 232-233, 294-295, 298-299 (map), 301-302, 304 (map) Puebloan history, 302-307, 313-315, 318 Palate: development, 23, 33-34 (table) Palatine bones: development, 33 (table) developmental field, 6, 14 (table), 160 Palestine: external auditory meatus atresia, 201 Parachordal cartilages: development, 21, 22 (figure), 28, 30, 81, 84, 134 prehistoric cases of defects, 136-138 Paracondylar processes, 82-83 (figure), 88, 131 prehistoric cases, 246-247 (figure). See also Vertebral border shifting: occipitocervical Paramastoid processes, 88 Paraplegia, 46 Paraxial mesoderm: affected by neural tube, 44-49 (figure) affected by notochord, 16 defects, 59, 62, 295, 318, 320-321
developmental field, 6, 13 (table), 18-19, 24 (figure), 28, 33 (table), 35, 41, 58-59 Parietal bones, bilateral symmetrical thinning. See Parietal bones: developmental thinness Parietal bones: development, 22, 30, 138 developmental field, 14 (table) developmental thinness, 146-150 (figures), 159 prehistoric cases of developmental thinness, 148-150 (figures) Parietal foramina: development, 143, 148 enlarged, 1, 144-145 (figure), 146, 152, 159 prehistoric cases of enlarged, 144-146, 319 Pars interarticularis, 29, 117 Pars obelica, 144 Pecos, New Mexico: cranial suture agenesis, 155, 277, 296 extra lambdoidal ossicles, 141, 275, 296 fontanelle bones, 275, 296 mendosa suture retention, 275, 296 pueblo, 295-296, 306 scaphocephaly, 155 styloid processes elongated, 208 tympanic aperture, 204, 280, 295-296 Pedicles, aplasia, 121 (figure), 124-125, 133. See also Cleft neural arch Peru: bifid mandibular condyles, 166 bipartite hypoglossal canals, 84 block vertebra, 38 cleft lip and palate, 188 (figure), 189 cleft nares and palate, 191 (figure), 192 cleft palate, 175
cranial meningocele, 52-53 (figure) external auditory meatus atresia, 200 (figure), 201 extra vertebra, 50 fused ribs, 61, 63 (figure) hemivertebrae, 60-61, 63 (figure) lacrimal bones, aplasia, 196 lumbar ribs, 103 metopism, 152 occipitalized atlas, 92-95 (figure) occipital vertebra, 85 (figure) paracondylar process, 92 parietal thinning, 148 precondylar tubercle, 86 (figure) retention of mendosa suture, 143 sagittal cleft vertebra, 38 spina bifida, 50 sternum defects, 212, 215 transitional lumbosacral vertebrae, 111 transitional sacrocaudal vertebrae, 114 tympanic aperture, 204 Petromastoid: development, 30, 136 developmental field, 13 (table), 138 Petrotympanic fissure, 198, 202 Pierre Robin syndrome, 163 Plagiocephaly, 145 (figure), 146, 153 (figure), 154, 160 Plains Archaic: mandibular developmental inclusion cyst (Stafne defect), 170 Pluripotent tissue, 16
Point of Pines, Arizona: lambdoidal ossicles, 141 metopism, 152 Poland: mandibular bilateral hypoplasia, 163 Polydactyly, 9 Posterior neuropore, 43 (figure), 44, 50. See also Neural tube: development Postlateral bar, 62, 65 (figure), 129 Postneurulation, 45 (figure), 46. See also Neural tube Prechordal cranial base: development, 21, 22 (figure), 33 (table), 134-136 the developmental field, 6, 13 (table), 24 (figure), 28, 134 disturbances, 136-138 prehistoric cases, 136-138, 320 Precondylar facet: defect 83 (figure), 89, 131 prehistoric cases, 92, 97 (figure), 237, 239, 244-245 (figure), 246, 321. See also Vertebral border shifting: occipitocervical Precondylar tubercle: defect, 82-83 (figure), 130 prehistoric cases, 84, 86 (figure), 237, 246-247. See also Vertebral border shifting: occipitocervical
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Precostal process: defects, 215-217 development, 25, 33 (table), 110 the developmental field, 7, 14 (table), 27 (figure) Premaxilla: absent, 182, 189 development, 25, 31, 33 (table), 171-172 (figure) developmental field, 6-7, 14 (table), 180 hypoplasia, 182 notched or cleft, 184, 196 prehistoric cases of defects, hypoplasia, 175, 192, 197 (see also Cleft lip: midline) Primitive streak, 15-16, 17 (figure), 33 (table) Proatlas, 19, 80-81 Pterygoid processes: developmental field for lamina, 14 (table) Pueblo Bonito, New Mexico: cervical ribs, 74, 102, 107 (figure) cleft atlas, 121-122 (figure), 267 cleft neural arch, 121-122 (figure), 265 cranial suture agenesis, 155, 277 fontanelle bones, 142, 275 genetic distance study, 317 precondylar tubercle, 84 rib defects, 74 sacral segment, extra 79 scaphocephaly, 155, 277-178 sternum defects, 226 (figure), 227-228 (figure) transitional lumbosacral vertebra, 113 (figure) Pueblo Largo, New Mexico: occipitalized atlas, 89, 248, 296 pueblo, 296
Puye, defects: apophyseal facets, asymmetry, 267, 294 basilar process, hypoplasia, 269, 280 (figure), 293 block vertebrae, 235 (figure), 236-238 (figure), 293 cleft atlas, 265-266 (figure), 267, 293, 295 cleft sacral neural arches, 259-263 (figures), 265, 293, 295 frequencies of defects, 292-295 fontanelle bones, 273-274 (figure), 292 hemimetamere pairs, asynchronous development, 234-235 (figure), 236, 294 hypoglossal canals, bipartite, 237, 246 hypoplasia, 267, 294 lumbar ribs, 248 lumbosacral border shifting, 242, 250-254 (figures), 258-259, 262, 292 mendosa suture, retention, 275, 293 occipital condyle hypoplasia, 246 occipitocervical border shifting, 237, 244-248, 258-259, 293 odontoid defect, type II, 237, 246 ossicles, lambdoidal, 271-272 (figure), 275, 292 paracondylar process, 246-247 (figure) patterns of vertebral border shifting, 257-259 precondylar facet, 237, 245 (figure) precondylar tubercle, 237, 246 rib defects, 241-242 (figure), 294 sacrocaudal border shifting, 255-256 (figure), 257-259, 292 spinous process, bifid, 267, 294 sternal defects, 282 292-293, 295 sternal types, 281 thoracolumbar border shifting, 248-250, 258-259, 293, 295
transverse processes, aymmetry, 267, 294 twelfth ribs, rudimentary and absent, 250 tympanic aperture, 278-280, 292, 295 Puye: biological history, 315, 317 burials, 308 (map), 309, 312-313 pueblo, 298-299 (map), 300-301, 304, 307-308, skeletal collection, 7-8, 231-234, 308-309, 319 Q Quarai, New Mexico: bifid atlas, 121, 267 extra sacral segment, 79 hemivertebra, 61-62, 64 (figure) lumbar ribs, 103, 250 scaphocephaly, 157 transitional lumbosacral vertebrae, 111, 255 R Reichert's cartilage, 205-207, 209 See also stylohyoid chain Ribs, thoracic: associated defects, 37, 60 defects, 38, 62, 71-72, 74-75 (figures), 77 (figure), 100, 102-103 (figure), 104, 109 (figure), 129-131, 320 development, 19, 25, 28, 30, 33 (table), 35, 99, 105, 110 developmental field, 6, 13 (table), 24 (figure), 58 prehistoric cases of defects, 61, 63 (figure), 241-242 (figure), 250 Rickets, 92, 152 Riviera aux Vase site, Michigan: microcephaly, 158 S Sacrum: agenesis, 50-51 (figure), 54 associated defects, 40
defects, 49, 119 development, 18, 29 See also vertebral border shifting: lumbosacral Sacral hiatus, 50, 119-120, 261 Sacral lumbarization. See Vertebral border shifting, lumbosacral Sadlermiut Eskimo: cleft vertebral arch, 38, 120 patterns of vertebral border shifting sagittal cleft defect, 38, 320 Sagittal cleft vertebra: development, 36-38, 40, 60 prehistoric cases, 38-39 (figure) Samoans, 72 Santorini's emissary veins, 143 Scaphocephaly, 152-155, 157, 160 Sclerotomes: with border shifting, 80 cervical, 21 (figure), 80-81, 88 development, 19, 20 (figure), 33 (table), 59, 63, 65, 117, 258 occipital, 30, 80-81, 84, 135 Scoliosis: developmental causes, 1, 38, 40, 60, 62, 66 (figure), 82, 110, 129 prehistoric cases, (61-62, 90, 269-270 (figure) Selenium, 41-42
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Segmentation errors: disturbances, 7 Somites: abnormal number, 78 cervical, 21-22 (figures) defects, 59-61 (figure), 62-63 (figure) (see also Hemivertebra) development, 17 (figure), 18, 23 (figure), 33 (table), 42, 43 (figure), 59, 117, 258 occipital, 18-19, 22 (figure), 92, 134 Somitomeres, 21-22 Sphenoid: development, 19, 30 developmental field for body, lesser wings and roots of greater wings, 13 (table), 135, 138 developmental field for greater wings, 14 (table) Spheno-mandibular ligament, 23, 31 Spina bifida: associated defects, 40 cystica, 32, 45 (figure), 46-47 (figure), 54 defect, 1, 32, 44-45 (figure), 49 incidence, 9 occulta, 45 (figure), 49-50, 54, 119 prehistoric cases, 50. See also Neural tube: defects Spinal cord: bifurcated, 40 development, 42 developmental field, 13 (table), 17, 27, 33 (table), 39, 41 fissure, 43-44 (figure) tethering, 40, 47. See also Craniorachischisis Spina bifida Spondylo-cranium, 80 Spruce Swamp site, Connecticut: cranial meningocele, 52
Stafne defect, 170, 320. See also Cyst, developmental inclusion: mandibular Stapes, 23, 205 Sternebrae. See Mesosternum Sternal plates (bands): defects, 215-230, 318 development, 25, 28, 31, 33 (table), 210-211, 215 the developmental field, 7, 14 (table), 27 (figure) Sternal aperture: development, 217, 221-224 (figure), 230 frequency, 223, 293 prehistoric cases, 221-227 (figures), 229 (figure), 286 (figure), 287-290 (figure), 291293 Sternal foramen. See Sternal aperture Sternum, bifid, 215-217, 230 Sternum: defects, 72, 211-230 development, 25, 27 (figure), 30-31, 33 (table), 110 developmental fields, 7, 210-211 prehistoric cases of defects, 212-215, 217, 220-223, 225-227 (figures), 292-295, 321 types (see Mesosternum) Styloid process: development, 23, 31, 207-208 developmental field, 6, 14 (table) elongated, 208 with external auditory meatus defect, 198, 202 prehistoric case of sheath hyperplasia, 204-205. See also Stylohyoid chain Stylohyoid chain: defects, 206 (figure), 207-209, 320-321 development, 205-206 developmental field, 14 (table), 24 (figure), 33 (table), 134 (see also Branchial arch II) prehistoric cases of defects, 207-208 Stylohyoid ligament: development, 23, 205, 207
developmental field, 6, 14 (table). See also stylohyoid chain Supraoccipital: development, 134-135, 139 developmental field, 6, 13 (table), 18 separated from interparietal, 142 (see also Mendosa suture) Suprasternal ossicles: development, 215-216 (figure), 227 prehistoric case, 215, 217 (figure) Suprasternal structures: defects (see suprasternal ossicles) development, 25, 33 (table), 110 the developmental field, 7, 14 (table), 27 (figure) T Taforalt Cave, Morocco: cleft sacra, 120 Temporal bone: development, 31 Temporal squamosa: development, 22, 30 developmental field, 14 (table) (see also Blastemal desmocranium) Thoracic vertebra, extra (supernumerary): development, 78 prehistoric cases, 78-79. See also Vertebral column: numerical variation Threshold event, 7, 10-12, 16, 32, 35, 59-60, 80, 180, 184, 207, 215, 258, 319 Trabecular cartilages, 21, 22 (figure), 28, 30, 134-135, 138 Transitional thoracolumbar facets: eleventh thoracic, 104, 109 (figure), 131 first lumbar, 105, 109 (figure), 132, prehistoric cases, 116, 248 supernumerary thoracic, prehistoric cases, 105, 242-243 (figure) Transverse processes: changes, 80, 102-103 (figure), 108, 112 (figure), 125, 131-132, 251 development, 18, 29, 117 Triangular area, developing face, 26 Trigg site: sagittal cleft centrum, 38-39 (figure)
Trigonocephaly, 153 (figure), 154, 160 Tsankawi, defects: block vertebrae, 239, 294 cleft sacral neural arch, 263-264 (figures), 265, 294 lumbosacral border shifting, 251-252, 259, 294 neural arch aplasia, unilateral, 239, 267-268 (figure) occipitocervical border shifting, 239, 244, 248 ossicles, lambdoidal, 271, 294 precondylar facet, 239, 244, 245 (figure), 294 sacrocaudal border shifting, 255, 257 (figure), 259, 294
