Mesozoic Era Prepared by: Mhel Angelo C. Policarpio Erica Bianca D. Bote
Interval of geological time from
about 250 million years ago to about 65 million years years ago. Often referred to as the Age of
Reptiles because reptiles, namely non-avian dinosaurs, were the dominant terrestrial and marine vertebrates of the time.
Mesozoic Means "middle life", deriving from
the Greek prefix meso meso-- for "between" and zōon meaning "animal" or "living being". One of three geologic eras of the
Phanerozoic Eon, preceded by the Paleozoic ("ancient life") and succeeded by the Cenozoic ("new life").
It ext extends ends from about 251 my mya a
to 65 mya and is separated into three geologic periods Triassic Jurassic Cretaceous Often called the "Age of the
Dinosaurs," after the dominant fauna of the era.
The Triassic Period an interval of about 51 million years
defined on the geologic time scale as spanning roughly from 251 to 200 million years ago (mya). Noteworthy for a great increase in the
biodiversity of both marine and continental life, beginning from the starkly impoverished biosphere that followed the Permian-Triassic extinction.
Lies
between the preceding Permian period, which ended the Paleozoic era, and the following Jurassic period.
Laid the foundation for subsequent
stages of life, including the dominance of dinosaurs seen during the Jurassic and Cretaceous periods.
Named in 1834, by Friedrich Von Alberti from the three distinct layers—red beds, capped by chalk, followed by black shales, called as the "Trias" (Latin trias , meaning triad).
Usually separated into Early,
Middle, and Late Triassic epochs, and the corresponding rocks are referred to as Lower, Middle, or Upper Triassic. The faunal stages (divisions based on fossils) from the youngest to oldest are:
Upper/LateTriassic (Tr3) •
Rhaetian
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Norian
Carnian
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Middle Triassic (Tr2) •
Ladinian
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Anisian
Lower/Early Triassic (Scythian) •
Olenekian •
Induan
Climate •
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Generally hot and dry, forming typical red bed sandstones and evaporites There is no evidence of glaciation at or near either pole; in fact, the polar regions were apparently moist and temperate, a climate suitable for reptilelike creatures. Pangea's continental climate was highly seasonal, with very hot summers and cold winters.
Life •
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In marine environments, new, modern types of corals appeared in the Early Triassic The shelled cephalopods called ammonites recovered, diversifying from a single line that survived the Permian extinction The fish fauna was remarkably uniform, reflecting the fact that very few families survived the Permian extinction.
Marine Reptiles •
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Sauropterygia •
Placodonts
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Plesiosaurs
Thalattosauria
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Ichthyosaurs
On land, the holdover plants included Lycophytes dominant cycads ginkgophyta (represented in modern
times by Ginkgo biloba) glossopterids. •
Glossopteris (a seed fern) - the dominant southern hemisphere tree during the Early Triassic period.
The Triassic period ended with a mass extinction, which was particularly severe in the oceans; the conodonts disappeared, and seemingly all the marine reptiles except ichthyosaurs and plesiosaurs. Invertebrates like brachiopods, gastropods, and mollusks were severely affected. In the oceans, 22 percent of marine families and possibly about half of marine genera vanished.
The Jurassic Period An interval of about 55 million years
defined on the GTS as spanning roughly from 200 to 145 million years ago (mya), from the end of the Triassic period to the beginning of the Cretaceous period. Noteworthy as the first of two periods
that together comprise the Age of Dinosaurs.
The start of the Jurassic period is marked by the major Triassic-Jurassic extinction event, which happened just before the supercontinent Pangea started to break apart. It is estimated that over 20 percent of marine families and 40 percent of terrestrial tetrapod (fourlegged vertebrate) families went extinct, including all large Crurotarsi (a group of non-dinosaurian reptiles) and many of the large amphibians.
An immense wealth of fossils have been found from the Jurassic period. These provide valuable information in understanding the evolution of life on Earth. The Jurassic period is important for another reason: The oilfields of the North Sea, near the United Kingdom and Norway, have much of their origin in this period.
Named
by Alexander Brogniart for the extensive marine limestone exposures of the Jura Mountains in the region where Germany, France, and Switzerland meet.
Usually divided into lower, middle,
and upper subdivisions, also known as Lias , Dogger , and Malm originally referred to British sediments,
where so many of the early fossils for this period were found Faunal stages are also used to further delineate the period. The faunal stages for this period, from youngest to oldest, are:
Upper/Late Jurassic •
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Tithonian
Kimmeridgian •
Oxfordian
Middle Jurassic Callovian Bathonian Bajocian Aalenian •
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Lower/Early Jurassic •
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Toarcian
Pliensbachian
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Sinemurian
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Hettangian
Life Highest life forms living in the seas •
Fish
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marine reptiles Ichthyosaurs Plesiosaurs marine crocodiles Teleosauridae Metriorhynchidae.
In the invertebrate world, several new groups appeared, such as: •
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Planktonic foraminifera and calpionelids Rudists, a reef-forming variety of bivalves Belemnites (an extinct type of marine cephalopod) Brachiopods of the terebratulid and rinchonelid groups
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Ammonites (extinct, shelled cephalopods) were particularly common and diverse, forming 62 biozones. Ichthyosaurs were abundant in the Jurassic period
giant marine reptiles that had a
porpoise-like head and a long, toothed snout, as well as a large tail fin.
Plesiosaurs
were large aquatic reptiles as well. Despite being large Mesozoic reptiles, they were not a type of dinosaur. The typical plesiosaur had a broad body and a short tail, as well as limbs in the form of flippers.
Terrestrial animals Large archosaurian reptiles remained
dominant Sauropods
- great, plant-eating dinosaurs that roamed the land, feeding on prairies of ferns and palmlike cycads and bennettitales
-Were preyed upon by the theropods, the large carnivorous dinosaurs.
Plants The warm, humid climate allowed lush jungles to cover much of the landscape. Flowering plants had not evolved yet, and conifers dominated the landscape, as they had during the Triassic period. Conifers, in fact, were the most diverse group of trees, and constituted the greatest majority of large trees during this period.
The Cretaceous Period One of the major divisions of the GTS,
reaching from the end of the Jurassic period, from about 146 to 136 million years ago (Mya) to the beginning of the Paleocene epoch of the Paleogene period, or Tertiary sub-era (about 65.5 to 64 Ma). longest
geological period, constitutes nearly half of the Mesozoic.
Dinosaurs were dominant during this period, while mammals remained small. An interesting development during the Cretaceous was the growing importance and diversity of flowering plants, an advance aided by a harmonious interaction with bees and other insects.
The Cretaceous (from Latin creta meaning "chalk") as a separate period was first defined by a Belgian geologist Jean d'Omalius d'Halloy in 1822, using strata in the Paris basin (GSE 1974) and named for the extensive beds of chalk, found in the upper Cretaceous of the continental Europe and Great Britain.
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As with other older geologic periods, the rock beds that define the Cretaceous are well identified but the exact dates of the period's start and end are uncertain by a few million years. No great extinction or burst of diversity separated the Cretaceous from the Jurassic. However, the end of the period is most sharply defined, being placed at an iridium-rich layer found worldwide.
The Cretaceous is usually separated into Early and Late Cretaceous epochs. The faunal stages (divisions based on changes in the observed fossil assemblages) from youngest to oldest are listed below. Time is referred to as early or late, and the corresponding rocks are referred to as lower or upper:
Upper/Late Cretaceous •
Maastrichtian
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Campanian
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Santonian
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Coniacian
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Turonian
Cenomanian
Lower/Early Cretaceous Albian Aptian Barremian Hauterivian Valanginian Berriasian •
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Climate Considered to have been very warm
and without any ice at the poles. Sea level was much higher than today and large areas of the continental crust were covered with shallow seas. Sediment cores also show that temperatures in the deep ocean were 15-20°C higher than today.
Flora Flowering plants (also known as angiosperms), spread during the Cretaceous, although they did not become predominant until near the end (Campanian age). Their evolution was aided by the appearance of bees.
Fauna On land, mammals were a small and still relatively minor component of the fauna. The fauna was dominated by archosaurian reptiles, especially dinosaurs, which were at their most diverse.
During the Cretaceous, the insects began to diversify, and the oldest known ants, termites, and some lepidopterans appeared. Aphids, grasshoppers, and gall wasps appeared. Another important insect to evolve was the eusocial bee, which was integral to the ecology and evolution of flowering plants.
Marine animals In the seas, rays, modern sharks, and teleosts became common. Marine reptiles included ichthyosaurs in the early and middle of the Cretaceous, plesiosaurs throughout the entire period, and mosasaurs in the Late Cretaceous.
Baculites, a straight-shelled form of ammonite, flourished in the seas. The Hesperornithiformes were flightless, marine diving birds that swam like grebes. The Cretaceous also saw the first radiation of the diatoms in the oceans
Extinction In the extinction event that defines the end of the Cretaceous, a significant number of species (around 50 percent) and known families (around 25 percent) disappeared. Plants appeared to be nearly unscathed, while marine organisms apparently were hit the hardest.
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Dinosaurs are the most famous victims of the Cretaceous extinction. Dinosaurs that were unique to the very end of the period were wiped out. The last of the pterosaurs became extinct and the vast majority of birds. The intensive, mid-Cretaceous insect extinction began during the Albian.
