Mosasaurs (clade Mosasauridae) evolved during the late Mesozoic when a group of monitor-like lizards entered the ocean. These toothy, serpentine predat predators ors migh mightt have have seemed seemed chunk chunky y and ill-made ill-made when when compared compared to to the other other marine marine predat predators ors of the the time. time. However, However, while while the ichth ichthyos yosaurs aurs went went extin extinct ct before before the end of the the Cretaceou Cretaceouss and the plesio plesiosaur saurss soon after, after, the mosasa mosasaurs urs have have gone on to becom becomee one of the largest largest and and most diverse diverse clades clades of marine marine vertebrates. Most present-day mosasaurs are quite unlike their serpentine forebears. Whatever environmental catastrophe that mauled the archaeocetaceans in our world almost had the same effect on the Late Eocene mosasaurs. Gone were the huge, 15m long tylosaurine sea-serpents and their kin, never to return.
ANGUILLACERTIDAE (Ti-Lung) Years after specbiologists had concluded that none of the ancestral, long-bodied mosasaurs survived to the present day, the illustrious Tiina Aumala proved the existence of Anguillacerta Anguillacerta sinensis sinensis,, the ti-lung.
(fig. 1) Yangtze mosasaur, Anguilla mosasaur, Anguillacerta certa sinensis (Central and southern Asia) Anguillacerta Anguillacerta possesses nostrils placed above the eyes, as in the saurocetes, but its body is long, the tail is laterally flattened and possesses no fluke, and the hind limbs are missing altogether. This cryptic piscivore is clearly a mosasaur, but is only distantly related to the saurocetes and is loosely allied with the archaic forms that supposedly died out at the end of the Eocene.
ARCHAEOSAUROCETACIDAE (Apeps) The early-Eocene radiation that produced the eel-like river mosasaurs also resulted in the birth of the saurocetes, the most common of the extant mosasaur groups. The first saurocetes, from the Eocene, are similar to modern forms, but fossil impressions show that they did not possess the paired tail-fluke of the advanced lizardwhales. Only a single species remains of this once mighty group. The apep is a piscivorous aquatic lizard that today seems to be restricted to the river Nile. Apeps can reach the length of 4.5 meters, though such venerable individuals are rarely seen, and 2-3 meter long mosasaurs are more common. (fig. 2) Apep, Apep Apep, Apep aegypianus (Northern Africa) Though at first the apep seems to resemble the serpentine long-bodied yangtze mosasaur, it is acutally the last remaining archaeosaurocetid, or ansestral saurocete, closely resembling fossil species such as Bala as Balaenang enanguis uis.. Based on the patchy fossil record, genus Apep genus Apep seems to date back at least to the Oligocene (and possibly the Eocene) and has barely changed at all after it first appeared.
GIGANTOSERPENTIDAE (Leviathans) The first evidence of one of Spec's most enigmatic sea-giants washed up on a stony beach in eastern Africa after a particularly stormy night. The discoverer, a certain Calvin Hobb, was apparently walking dangerously near the choppy shore when a sudden, violent surge practically dumped the specimen at his feet. It was a cylindrical mass of rotting flesh over twelve metres in length. Within one end of the carcass, researchers recovered the two-metre long skull minus the lower jaw, the vertebral column up to the 17th dorsal and parts of right forepaddle. An examination of the bones made it clear that the carcass, now dubbed "Hobb's Leviathan" represented a new species of mosasaur, but of what kind? Popular initial reports claimed that it represented a "living fossil", an archaic long-bodied mosasaurid that had escaped the Eocene extinction. More cautious researchers noted apparent similarities with the needle-like teeth and gracile body-form body-form of the the Yangtze Yangtze mosa mosasau saur, r, sugges suggestin ting g a relatio relationsh nship ip with with angui anguillac llacert ertids ids.. Regardl Regardless ess of of where where it fitted fitted amon amongst gst the the Mosas Mosasaur auria, ia, the the skull skull and and vertebrae were sufficient cause to warrant it's description as a new species - Gigantoserpens microdon, microdon , "the teeny-toothed gigantic serpent"
(fig. 3) Early reconstruction of Hobb's Leviathan done prior to its description. Illustration by Tiina Aumala Despite the incompleteness of the remains, the idea of a giant sea-serpent was irresistable and a number of popular reconstructions depicted the animal as an vast eel-like creature with a stated length of over 25 metres. Soon sightings of giant killer serpents began cropping up everywhere from the Caribbean to the bottom of Tiina's beer stein. Hoaxes pertaining to leviathan-related fatalities at sea soon led to much hysteria. Nothing more was heard from the real Gigantoserpens for over three years until a vessel surveying the west coast of South America produced blurry photogr photograph aphss of a huge sea sea creature creature near San San Ambrosio Ambrosio.. They appear appeared ed to show show nothing nothing less less than than a supposedl supposedly y extinct extinct long-necked long-necked plesi plesiosau osaur, r, an animal that seemed to possess a small head, long-neck and a bulbous, flippered body. An expedition to learn more of this creature was
ast y spatc e an t was soon ascerta ne t at t ese p es osaurs were n act t e rea
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The true appearance of these giant mosasaurs was completely unexpected and nothing like the snake-like hypothetical reconstructions. Instead of a vicious predator, the real leviathan proved to be a sluggish, passive hunter of small prey. Rather than a relic of the Eocene or some giant ocean-going river-mosasaur, Gigantoserpens turned out to be a highly aberrant true-saurocetean although different enough to be placed, along with subsequently discovered Pliocene fossil forms, into a new clade - the Gigantoserpentidae.
(fig. 4)A living Gigantoserpens photographed off the west coast of South America. At "only" 11 metres in length, this is a relatively small individual. HOBB'S LEVIATHAN DESCRIBED
(fig. 5)Skeletal silhouette of Hobb's leviathan alongside the incomplete holotype specimen and a human diver (diver courtesy Tiina Aumala) Gigantoserpens is a bizarre saurocetacean that can reach a length of 21 metres and weigh in at an estimated 60 tonnes making it by far the largest known squamate. The head is comparatively small and flat, sitting on a very short neck behind which sprout a pair of small flippers. These are often held against the neck and can be difficult to discern from a distance. The anterior dorsal vertebrae are lightweight while the associated ribs are greatly reduced in size. Thus in life, the forequarters of the animal appear slender and snake-like, creating the illusion of an elongated neck. Further down the trunk the vertebrae become drastically larger and more robust while the length and girth of the ribs increases causing the body to balloon out. The pelvic girdle and hindflippers are incredibly large by mosasaur standards whilst the tail is exceptionally long and deep with prominant lateral keels, terminating in a huge caudal-fin. A low, triangular dorsal fin is located midway along the tail. The dentition consists of numerous fine needle-like teeth and the lower jaw is loosely attached to the skull allowing for a very wide gape. The interior of the mouth contains a series of rugosities called gnathochromes which are infested with growths of luminescent bacteria that are clearly visible when the jaws are opened.
(fig. 6) (left) Frontal view of open mouth showing gnathochromes - rugosities on which grow clusters of luminescent bacteria. The pterygoid teeth have been reduced to a small row of nodules that are not externally visible on large adults. (right) Appearance of glowing gnathochromes in dark water. The precise arrangement varies between individuals.
(fig. 7)Near the Azores, a Hobb's leviathan disappears in a great cloud of poo. One unusual internal feature is a large sac on the lower intestine that can be filled with over 90 litres of reddish-brown syrupy faecal matter. When threatened by a large carnivore, this liquid is expelled in a great, dense cloud that confuses or repels the attacker and gives the slow- moving leviathan the chance of escape. A similar strategy is used (on a much smaller scale) by the Home-Earth pygmy sperm whales of the family Kogiidae. The leviathan is primarily a mesopelagic predator that has been characterised as a "mosasaur trying to be an elasmosaur". Based on the stomach contents of stranded individuals, it mostly feeds on non-shelly pelagic prey of up to a metre in length. It is not a choosy feeder and takes whatever happens to be abundant in the area. While it has yet to be witnessed, it's feeding strategy probably involves cruising through the inky blackness with it's jaws agape. The twinkling bacterial colonies in it's mouth give the impression of a swarm of bioluminescent plankton attracting shoals of fish, shrimp and squid to within easy striking distance. The slender forequarters can curl and dart around with great speed, allowing it to snap up faster-swimming prey. The presence of injested echinoderms and small skates suggest it also forages on the benthos, perhaps while gathering stones for ballast. One particularly scarred individual that was recently stranded on New Caledonia was found to have a belly full of piranhakeets. The giant hindflippers are used for stability and steering, effectively filling the role of pectoral fins on a more conventional sea creature. The stubby forepaddles seem to act as canard foreplanes, conferring a degree of hydrodynamic stability to the anterior of the animal when on the move. While feeding, they are probably held conformally to avoid drag as the neck sweeps around. Alternatively the forelimbs might play a role in sheperding prey although they seem a little too far from the mouth for this. Strandings and sightings indicate a cosmopolitan species of deep offshore tropical to warm temperate seas. Although sparsely distributed, they are sometimes found in large feeding concentrations and appear to have a habitat requirement for deep slope waters with steep depth gradients. Except for infrequent forays to the surface for air, they follow the vertical migration of their prey, cruising at depths of over 900m during the day before rising to within 100m of the surface at night. Much remains to be discovered about these remarkable giants and as yet we know nothing of their seasonal migrations, reproduction and development.
SAUROCETACIDAE (Mosarks and lizardwhales)
(fig. 8) A sampling of saurocetacidae (with apep) 1. Prownose lizardwhale 2. Apep 3. Zahn 4. Mosapoise 5. Mosark 6. Sawsnout lizardwhale 7. Long-tailed lizardwhale
8. Sakhala Currently the most highly specialized of marine reptiles, saurocetes do not bear much resemblance to their sea-serpent ancestors, and rather resemble the dolphins and whales of RL. Like the Jurassic ichthyosaurs before them and the odontocetaceans of our Earth, the ancestors of these creatures were long bodied serpentine inshore predators (see above) that developed an increasingly fishlike body for a pelagic existence. Saurocetes are fish-like marine squamates ranging from 1.5 to 15 metres in length. They are broadly analogous with our world's odontocetes but have not produced a big-game carnivore in the same league as the orca. The scales have been completely lost and have been replaced with a smooth, leathery hide. The paired nostrils are positioned at the top of the head. Propulsion is by strokes of a fish-like tail bearing 2 vertical flukes. All saurocetes are viviparous. The precursors of the saurocetaceans were the huge predatory mosasaurs, marine squamates that evolved in the Cretaceous and were amongst the top ocean predators from the Santonian to the Eocene. The decline of inland seas in the Maastrichtian put pressure on the mosasaurs to more fully exploit the open oceans. One lineage abandoned the serpentine mosasaur-body, becoming more fishlike with a large falcate caudal fin replacing the simple spatulate form. While the Late Eocene disaster decimated their long-bodied kin, the early saurocetaceans flourished, developing ever larger and larger forms. Today over 40 species ply the tropical to warm temperate oceans of the world, feeding mainly on cephalopods and small fish. However, they have been unable to venture into the cooler sea. Those rich, polar killing grounds are the domains of warm- blooded predators: birds like seaguins and penguins, and mammals like walduks. While Home-Earth's cetaceans cover a wide range of body types (from dolphins to whales), sarurocetes do not display so wide a diversity. There are no filter-feeding mosasaurs, and the disparity between large and small species is relatively minimal. However, clear distinctions within Saurocetacidae do exist. The carcharosaurines, or mosarks, are powerfully-built predators. Some, like the zahn, are truly enormous. The mosark, cousin of the sakhala and zahn, is a 8-10 m long predator of temperate oceans around the world. A medium-sized pelagic predator, the mosark gained its name mainly from its sharklike appearance and behaviour, and many of its relatives are also often unofficially referred to as mosarks for the same reason.
(fig. 9) Mosark, Pristrix monstrum (worldwide) This lizardwhale is in many respects similiar to the zahn, though smaller and swifter. Though their diet mostly consists of cephalopods and fish, mosarks are also known to attack small lizardwhales and other marine vertebrates. The zahn is one of the largest lizardwhales. This 14 m long solitary predator is large enough to swallow small wingsquid whole and tear fully grown mantasquid into pieces. Zhans attack just about anything big enough to fit between their enormous jaws, including seabirds, rays, sharks, swimming or wading dinosaurs, other lizardwhales and inflatable boats filled with marine biologists. There have been at least two unfortunate incidents where Spec scientists have nearly ended up in a zahn's belly---they were apparently saved only by the foul taste of the boat. After that, small rubber boats haven't been used in zahn-infested waters.
(fig. 10) Zahn, Carcharosaurus atrox (Equatorial)
(fig. 11) Chubby mosark, Carcharosaurus crassus (Western Atlantic) Warmed by the Gulf Stream, the waters off the coast of eastern North America are home to many predators, from walduks to sharks, but the most feared of all is the chubby mosark. These odd little mosasaurs dart around the shallows from Florida to Newfoundland, snatching up anything that moves. Despite its common name, the chubby mosark is only distantly related to the true mosarks (genus Pristrix). These creatures, are, in fact, close kin to the zahns, massive, orca-like predators that hunt upper levels of the deep ocean. The chubby mosark, on the other hand, is one of several Carcharosaurus lineages that have adapted for a life hunting the nutrient-rich shallows of the continental shelves. These hunters are small, and rely upon their sensitive Jacobson's organs to taste the water and home in on prey, rather than the easily confused eye. As a result, the eyes of the chubby mosark are rather small and not very sensitive, while their chemical sense is superb. Another way in which the chubby mosarks distinguish themselves is in their geographical range, which extends further north than any other marine mosasaur. Although they winter in the warm waters off the coast of Florida, chubby mosasaurs spend the summer months rearing their pups in the Gulf of St. Lawrence. This behavior is quite useful, since the habitat is devoid of competing mosasaurs, and the native pods of selkies make a tasty snack for the larger reptiles. However, the northern water, although made bearable by the Gulf Stream, are still frigid to the cold-blooded mosasaurs, and so chubby mosarks must produce internal "coats" of insulating blubber, the source of their name.
(fig. 12) Sakhala, Carcharosaurus velox (Great Barrier Reef) The Sakhala is a small (3 m long) and swift shark-like mosasaur that lives in the Great Barrier Reef. Though it mainly eats small fish and cephalopods, it may attack anything smaller than a meter across if it looks edible.
(fig. 13) Nodens, Nodens incredibilis (Great Barrier Reef) Ironically the largest known saurocete was not first discovered in the sea, but on dry land. During the first years of spexploration, some of the spexplorers studying seaside ecosystems came across a gargantuan rotting hulk that had been washed ashore. It 18 meters long and was easily recognized as a lizardwhale, but as the spexplorers lacked the appropriate equipment to transport that tonnage of meat, and the carcass was in such an advanced state of decomposition that a further analysis was impossible to make at the time. The remains were hastily measured and photographed, and later some of the skeletal remains were retrieved. These fragments became the holotype specimen of Nodens incredibilis. Later, several other Nodens skeletons were discovered, and the largest of these, consisting of little more than a skull measuring over 4 meters long, lead to an estimate of the adult size of Nodens, some 20 meters long, making it longest known marine vertebrate on Spec. It still took some time before the first verified eyewitness sighting of a living specimen, but through a lucky coincidence, a group of marine biologists happened to be near a Nodens mating area, and managed to film the animals both above and under water. The film revealed that much of the forequarters of the giant lizardwhales were covered in curious looking scars, some resembling those left by giant squid tentacles on sperm whales and others more unusual in appearance. It was deduced that the main diet of Nodens consisted of giant cephalopods , but the peculiar scars lead to some dispute over what had caused them. Some claimed the lesions were bitemarks of some kind, while others blamed the infamous great ktulu, which was reported as having feeding tentacles ending in hand-like extensions covered in wicked hooks. A photograph of a large Nodens individual with a severed end of a tentacle ending in just such finger-like extensions still stuck on its skin only helped to fuel the controversy. While the actual hunting and feeding of Nodens is yet to be observed, we do know that they are solitary most of the year and find their prey in the murky depths of the ocean teeming with myriads of exotic cephalopod species. These saurocetes seem to fill the niche of HE sperm whales, although we can only speculate at the differences in their hunting strategies. Despite having eyes not much larger than a human head, they are known to have a keen vision especially in the dark. It is worth noting that Nodens are much more likely to move close to the surface at night than during the day. While Nodens seemingly has a lot in common with mosarks, the latest analysis places it closest to nauticratisaurs. Though reports of Nodens individuals longer than 20,5 meters are unverified, it still holds the record of the largest known mosasaur, being more massive (though not quite as long) as the leviathan.
Long-tailed lizard-whales are a common species that form large schools off the western coast of North America. They feed on a variety of small fish and cephalopods.
(fig. 13) Long-tailed lizardwhale Naucratisaurus gracilis (Pacific) A close relative of the long-tailed lizardwhale, the 4-5 meter long azure lizardwhale forms large pods off the in the warm waters of the Gulf Stream.
(fig. 14) Azure lizardwhale Naucratisaurus atlanticus (Atlantic) The saurocetacines, on the other hand, are the more streamlined lizardwhales. Some possess long snouts and closely resemble the ichthyosaurs of Earth's past and the dolphins of our home timeline.
One of the larger saurocetaceans, the prownose lizardwhale usually lives alone but feeding aggregations of over 50 have been sighted. There are no teeth in the upper jaw while 12-14 conical teeth of each side of the dentary. The prownose lizard-whale feeds primarily on cehalopods, including huge barrelfish. (fig. 15) Prownose lizardwhale Saurocetaceus pelagios (worldwide) This cephalopod-hunting saurocetacean lives in the Indian ocean. Though closely related to the prownose lizardwhale, Choo's lizardwhales rarely grow larger than 7 meters long. These animals greatly resemble the Mesozoic ichtyosaurs, which at first caused some confusion among the first explorers of Spec.
(fig. 16) Choo's lizardwhale Saurocetaceus brianchooi (Indian Ocean)
(fig. 17) Mosapoise, Phocoenalacerta nigra (Equatorial Pacific) The mosapoise is a 3.5 meters long saurocete specialized mostly on ammonoids, crabs, shellfishes and other hard-shelled marine invertebrates it crushes with its impressive battery of teeth. The sawsnout lizardwhale, while clearly a saurocete, does not fit in with either the mosarks or the mosapoises. Some have allied this odd creature to apep, the Nile mosasaur, but further studies are necessary to prove such a theory. The sawsnout lizardwhale is undoubtedly one of the weirdest mosasaurs in existence. Its upper jaw is disproportionally long and armed with sharp outwards-pointing teeth. Sawsnout lizardwhales use this weapon to stun fast-moving prey and to rake out buried prey from the bottom.
(fig. 18) Sawsnout lizardwhale, Pristisaurus peculiaris(Caribbean) Brian Choo, Daniel Bensen, and Tiina Aumala
,=Anguillacertidae=Anguillacerta sinensis (Yangtze mosasaur) =Mosasauridae=| | ,=Archaeosaurocetacidae=Apep aegyptianus (Nile Mosasaur) `=| | ,=Gigantoserpentidae=Gigantoserpens microdon (Hobb's leviathan) | | |
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,=Pristrix monstrum Mosark ,=| |
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,=C. atrox (Zahn)
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|=? Nodens incredibilis (Nodens) |
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,= N. gracilis (Long-tailed lizardwhale)
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`= Naucratisaurus=|
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`=C. velox (Sakhala)
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,=C. crassus (Chubby mosark)
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`=N. atlanticus (Azure lizardwhale) ,=S. pelagios (Prownose lizardwhale) ,=Saurocetaceus=| |
`=S. brianchooi (Choo's lizardwhale)
`=| `= Phocoenalacerta nigra (Mosapoise)
`=Saurocetaciodea=| | `=Saurocetacidae=| `=Pristisaurus peculiaris (Sawsnout lizardwhale)
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