recursal/Fanatic-Fandom huggingface dataset:
Ornithomimus

Ornithomimus is an ornithomimid theropod dinosaur from the Late Cretaceous of the United States of America and Canada. It was named in 1890 by Othniel Charles Marsh. It was one of the most unique early-discovered theropods to exist, due to its build and lifestyle; like the earliest discovered dinosaurs, Megalosaurus and Iguanodon, and all the other the earliest discovered Mesozoic reptiles, Pterodactylus, Rhamphorhynchus, Mosasaurus, Plesiosaurus and Ichthyosaurus, it was a wastebasket taxon, and many other ornithomimid remains similar to it were proved to be their own genus.

## Physiology

Ornithomimus was a very birdlike theropod, hence the meaning of its name, "bird mimic". It had long legs, a long tail, long, slender arms with moderately small hands, a moderately long neck, and an elongated, bird-like head with large eyes and a toothless beak. Most of its body (excluding most of its legs and all of its beak) would have been covered in short, fuzz-like feathers; however, its arms would have had long, vaned feathers, similar to all other advanced theropods.

## Diet

Ornithomimus would have been an herbivore, feeding on leaves and fruits by grabbing them with its beak before swallowing them, and using its sloth-like arms to pull down branches before feeding on vegetation growing off of them. However, some may speculate that it, like most herbivorous birds, would have also supplemented its diet with animal protein, snacking on insects, crustaceans, lizards, small mammals, and eggs from time to time.

## Ecology

Ornithomimus's long legs allowed it to run at swift speeds, making it one of the fastest dinosaurs. During its time, the top predators were the tyrannosaurs, giant carnivorous theropods with bone-crushing jaws, small arms, and bulky builds. Due to the very latter, they were somewhat slow predators, so in order to capture swift prey like Ornithomimus, they would have to ambush it; however, combined with its tremendous speed, it had big eyes on a head held up by a long neck, so it could see dinosaurs over sparse vegetational cover, making the task of sneaking up on it a rather hard one. A comparison of its sclerotic rings to those of modern reptiles and birds indicates that it was cathemeral.

## In popular culture

Ornithomimus was first introduced to the public in the *Rite of Spring* segment of the 1940 Disney musical movie, *Fantasia*. Since then, it has become extremely popular, appearing in major pieces of media like *The Valley of Gwangi* and *Prehistoric Park*. An interesting thing to note is that during the early 1900s, most theropods, such as Tyrannosaurus and Allosaurus, were depicted as sluggish reptilian giants with tails dragging on the ground. Ornithomimus, however, was depicted as having a bird-like posture with an erect tail; this also happened to its close relative, Struthiomimus.
Opabinia

This article is in need of updating.It contains info that may no longer be accurate, and will be revised to be more in line with modern research.

## Other Attributes

### Diet

Carnivore

Opabinia is an opabiniid radiodont dinocaridid arthropod from the Cambrian Series 3 of Canada. It was named in 1912 by Charles Doolittle Walcott. Like most animals from Cambrian Canada, it was a unique arthopod, and it had held middle ground in the food chain.

## Physiology

Opabinia looked similar to another fellow dinocaridid, Anomalocaris, as it also had a long body, long, fin-like lobes running down the sides of its body, and a rounded head with big eyes and a disk-like mouth. However, it also had some physical traits very different from those of Anomalocaris, as it had 5 eyes instead of just 2, and it had a long proboscis ending in a claw. Its body would have been covered in a semi-hard, chitinous exoskeleton.

## Diet

Opabinia was a predator, feeding on small invertebrates by picking them up with its claw and passing them down to its mouth. However, it would also sometimes settle for detritus suspended on the seafloor.

## Ecology

It is unknown if Opabinia's 5 eyes were complex eyes or not; however, all 5 eyes used together would achieve the effect of a single complex eye. As well as this, it had a swimming style similar to Anomalocaris, undulating its fin-like lobes on its body to propel itself through the water. Instead of directly facing down, Opabinia's mouth slightly slanted backwards, so its long, flexible proboscis would be used to pass food into it without any problems. Another interesting thing to note is that Opabinia's proboscis made up 1/3 of its body length.
Bradysaurus

Bradysaurus is a pareiasaurid procolonomorph reptile from the Guadalupian of South Africa. It was named in 1914 by David Meredith Seares Watson. It was one of the earliest pareiasaurs, as well as the most common ones in South Africa.

## Physiology

Bradysaurus resembled the generic pareiasaur. It was a reptile with 4 stout legs, a short tail, a broad, bulky body, and a relatively small head. Its body would have been covered in scaly skin, with crocodile-like scutes running down its back and lying in some other places of its body.

## Diet

Bradysaurus was an herbivore, feeding on plants low to the ground. Its leaf-shaped teeth were used to process vegetation; behind its jaws, it had a second set of teeth for processing them even further.

## Ecology

Like all pareiasaurs, Bradysaurus would have been a slow, clumsy, and mostly harmless animal, relying on its hard body armor to protect itself from predators like Anteosaurus. Despite the fact that those armor plates were well-developed, they were not as thick as those of later pareiasaurs such as Scutosaurus. As well as this, its somewhat large size showed that even in their early development, pareiasaurs reached an optimal size; further evidence comes from the fact that the later Scutosaurus was no larger. As well as this, Pareiasaurus was a solitary animal, but sometimes traveled in small herds for mutual protection.
Stethacanthus

Stethacanthus is a stethacanthid symmoriid cartilaginous fish from the Late Devonian-Pennsylvanian of the United States of America, Russia, China, and Scotland. It was named in 1889 by John Strong Newberry. It was one of the most successful symmoriids to exist, lasting for more than a period.

## Physiology

Stethacanthus resembled a shark, with a torpedo-shaped body, triangular pectoral fins, a crescent-shaped caudal fin, a mid-sized head, and large jaws. However, it had one major defining characteristic: instead of a regular, triangular dorsal fin, it had an anvil-shaped dorsal fin with bristle-like scales on top of it. Its body would have been covered in scaly skin.

## Diet

Stethacanthus was a predator, preying on small fish, cephalopods, and brachiopods. Although its teeth were relatively small, they were still sharp, and were used to get a hold of any struggling prey.

## Ecology

The function of Stethacanthus's unique, anvil-shaped dorsal fin has been open to debate for a long time, with many theories that emerged including attaching onto larger marine animals, as well as scaring predators its size by mimicking the mouth of a bigger fish. Today, the most widely accepted theory is that it was used for attracting mates, as studies have shown that it was only present in males. Along with well as this, its large size and bristle-like scales would have created a lot of drag during attempted bursts of speed, impeding the fish's movement; therefore, Stethacanthus would have been a slow swimmer. Like some modern sharks, Stethacanthus would have swam in coastal waters, feeding on any fish and cephalopods that shared the waters with it.

## In popular culture

Stethacanthus was featured in the 1st episode of the 2003 documentary *Chased by Sea Monsters*, where it gets attracted to the smell of a dead Bothriolepis before getting scared off by a Dunkleosteus. It appeared again in a similar documentary, *Walking with Monsters*, where it chases a Hynerpeton right before a Hyneria shows up to snap it up.
Giraffatitan

Giraffatitan is a brachiosaurid sauropod sauropodomorph dinosaur from the Late Jurassic of Tanzania. It was officially named in 1988 by Greg S. Paul. It was another of the tallest dinosaurs to walk the Earth, and it was thought to be a species of Brachiosaurus before finally being described as its own genus.

## Physiology

Giraffatitan was a sauropod with a bulky, downwards-sloping body, a deep torso, 4 large, erect, pillar-like legs, a moderately long tail, a long neck, and a small head with a large, bony arch above its eyes and just behind its nostrils. Its body would have been covered in scaly skin.

## Diet

Giraffatitan was an herbivore, feeding on leaves from large trees. Its peg-like teeth were used to strip branches of their leaves, and its long neck and limbs allowed it to access vegetation some 11 meters in the air without rearing.

## Ecology

Due to Giraffatitan's proportionally small head and braincase, people thought it would have needed a second brain in its abdomen in order to function normally; this theory has now been discredited, and the extra abdominal orifice once said to have housed that second brain is now thought to be a source of glycogen for the animal's body. As well as this, a close look at its teeth shows that instead of just grinding up plant matter, it bit and tore leaves off branches before swallowing them; this disproved the possibility of trunked sauropods, as trunks would serve the same purpose as the dinosaur's mouth. Along with this, in a similar situation to its cousin Brachiosaurus, the large, bony arch located just above its eyes and behind its snout was once thought to house the nostrils (which would be used as a snorkel when the animal was underwater); however, it was found out that sauropods were completely terrestrial, and had fleshy nostrils that ran down from the openings in the arch and opened up near the tip of their snout. Now, it is hypothesized that the bony arch served as a resonating chamber used for amplifying the animal's loud calls.

## In popular culture

When Brachiosaurus was introduced to the general public, Giraffatitan was still thought to be a species of Brachiosaurus, and so, was consistently used as the general basis for the appearance of pop culture brachiosaurs. Even 5 years after it was officially made into its own genus, it still served as the appearance for the Brachiosaurus in the 1993 science fiction movie *Jurassic Park*, which would cause the confusion between the two to persist up until now.
Megalosaurus

Megalosaurus is a megalosaurid theropod dinosaur from the Middle Jurassic of the United Kingdom. It was officially named in 1824 by William Buckland. It was the first non-avian dinosaur known to science, and when it was discovered, a part of its upper leg bone was confused for being the testes of a giant (hence its early name, *Scrotum humanum*); as well as this, it was a wastebasket taxon, as many theropods, such as Dilophosaurus, Eustreptospondylus, Carcharodontosaurus, and Majungasaurus were once considered to be species directly related to this genus, right before being classified as their own genera.

## Physiology

Megalosaurus resembled a large, bipedal lizard. It had a semi-bulky body, a long tail, moderately-sized arms with 3 fingers on each hand, and a large head with a mouth containing lots of big teeth. Its body would have been covered in scaly skin.

## Diet

Megalosaurus was a predator, preying on mid-sized sauropods, small pterosaurs, and smaller theropods. Its teeth had knife-like serrations from front to back, and were used to cut into the hides of large prey.

## Ecology

The way how Megalosaurus should be constructed was under debate for a long time, with people reconstructing it as a dragon, a bipedal, tail dragging, kangaroo-like reptile, and a bipedal, digitigrade saurischian; today, the latter prevails as the most accepted reconstruction. As well as this, it was one of the largest Eurasian theropods during the Middle Jurassic, and so, it would be presumed that would be an apex predator; however, Western Europe was starting to break up into islands at the time, and due to the fact that Megalosaurus fossils were found in marine habitats, we can assume that the theropod went near the shore sometimes. Of course, one explanation is that it was just like any other theropod, and would only come onto the beach whenever it moved from place to place; other explanations are that it ran near the shore to eat any aquatic testudines resting there, and that it was a full-blown beach comber, scavenging washed-up marine reptile carcasses and snagging fish trapped in tidal pools with its jaws. Either way, with the shrinking landmasses of Europe during the time, Megalosaurus would have had to exploit any available food resources for its own well-being.

## In popular culture

Megalosaurus was one of the 1st Mesozoic animals discovered, so it was featured in Crystal Palace Park (a pleasure ground in London) as a large, quadrupedal dragon, alongside Iguanodon (depicted as an herbivorous dragon), Pterodactylus, Mosasaurus (depicted as a large, iguana-like squamate), Plesiosaurus, and Ichthyosaurus. Since then, it has been featured in major pieces of media such as the *Lost World* novel and the 1991 sitcom *Dinosaurs*; however, after getting overshadowed by the later-discovered Allosaurus and Tyrannosaurus, the megalosaur received a drop in popularity, only appearing in certain dinosaur games.
Hynerpeton

Hynerpeton is an amphibian from the Late Devonian of the United States of America. It was named in 1994 by Ted Daeschler and his crew. It was one of the first amphibians to equally live on both land and water, and has reevaluated the perception about how the tetrapods colonized the land.

## Physiology

Hynerpeton resembled the basic primitive amphibian. It was a fish-like tetrapod with 4 legs, a long tail similar to that of a tadpole, a bulky body, and a big, semi-flat head with big jaws. Its body would have been covered in scaly skin.

## Diet

Hynerpeton was a predator, preying on insects and small fish. Its teeth were small yet sharp, and were used to get a hold of struggling prey as the amphibian swallowed them whole.

## Ecology

Hynerpeton was an evolutionary step-up from earlier tetrapods, as it had features that more resembled those of later amphibians as well as reptiles. For example, it had legs that were longer and more adapted to exhibiting a quadrupedal gait than earlier tetrapods, whose legs were more useful for crawling over underwater obstacles and dragging themselves across the land. As well as this, while earlier tetrapods only had simple lungs as well as gills, Hynerpeton had no gills at all, using semi-complex lungs as its main breathing system. In fact, Hynerpeton is generally thought to be a link between the primitive tetrapods of the Devonian and the advanced amphibians of the Carboniferous.

## In popular culture

Hynerpeton was featured in the 1st episode of the 2005 documentary *Walking with Monsters*, where it is shown as evolving straight from Cephalaspis over a course of 63 (or 59 million years (of course, many evolutionary steps such as Eusthenopteron and Tiktaalik are ignored)); as well as this, it is shown as competing for mates by doing push-up contests (this behavior is based on the fact that its forelimbs were strong, and could actually be used to lift the body upwards). At the end of the segment, one male gets killed by a Hyneria during the mating process; despite this, the eggs are successfully deposited in the water, later evolving into Petrolacosaurus eggs over a course of 58 million years.
Jaekelopterus

Jaekelopterus is a pterygotid eurypterid merostomate arthropod from the Early Devonian of Germany and the United States of America. It was named in 1914 by Otto Jaekel. It was the biggest eurypterid to exist, surpassing even the Pterygotus, Acutiramus, and Arthropleura.

## Physiology

Like its cousin, Pterygotus, Jaekelopterus resembled the generic eurypterid. It was a large chelicerate with a rounded cephalothorax, large eyes, long arms with serrated claws, 4 pairs of walking legs, a pair of paddles for swimming, and a long tail ending in a paddle. Its body would have been covered in a hard, chitinous exoskeleton.

## Diet

Jaekelopterus was a predator, preying on fish, trilobites, ammonites, and smaller eurypterids. Its serrated claws were used for catching and getting a hold of any struggling prey, as well as crushing them and ripping them apart.

## Ecology

Unlike its marine cousin, Pterygotus, Jaekelopterus lived in freshwater rivers and estuaries, lying on the riverbed in order to ambush prey. Its robust, serrated claws were used to grab and rip apart any unsuspecting fish, trilobites, cephalopods, or small chelicerates, allowing access to their innards. As well as this, its paddles, as well as its tail, were used to propel itself through the water. A study on all pterygotid eurypterids had shown that its eyesight was on par with that of modern predatory arthropods, such as dragonflies and mantids.
Fruitafossor

Fruitafossor is a mammal from the Late Jurassic of the United States of America. It was named in 2005 by Zhe-Xi Luo and John R. Wible. It was yet another, unique, specialized Mesozoic mammal, as it was specialized towards digging.

## Physiology

Fruitafossor was a unique mammal. It had a somewhat slender, barrel-shaped body, 4 semi-erect legs (with the forelegs being more robust than the hind legs), large, blunt claws on each finger (for digging), a long tail, and a mid-sized head with small jaws. Its body would have been covered in fur.

## Diet

Fruitafossor was an insectivore, preying on termites. Its small, peg-like teeth were used to crunch up termites, while its robust arms had blunt claws on each finger, and were used for digging into termite mounds.

## Ecology

Fruitafossor had many adaptations similar to modern armadillos and aardvarks; for example, its teeth were small and shaped like pegs, which tells us that it would have relied on termite mounds for sustenance (since ants had evolved in the Cretaceous). As well as this, it had powerful arms and blunt claws, which allowed it to dig into the ground. With those adaptations, it would have been able to break into termite mounds and feed on all the termites there; as well as this, it would have been able to dig into the ground and hide once predators like Ornitholestes showed up. In general, Fruitafossor was yet another unique early mammalian discovered, succeeding Repenomamus and preceding Castorocauda and Volaticotherium.
Argentinosaurus

Argentinosaurus is a sauropod sauropodomorph dinosaur from the Late Cretaceous of Argentina. It was named in 1993 by Jose F. Bonaparte and Rodolfo Coria. It has been routinely described as one of the largest - if not the largest - known dinosaurs to roam the Earth.

## Physiology

Argentinosaurus was a large sauropod with a bulky, downwards-sloping body, a deep torso, 4 large, erect, pillar-like legs, a long tail, a long neck, and a small head. Its body would have been covered in scaly skin.

## Diet

Argentinosaurus was an herbivore, feeding on leaves from large trees. Its peg-like teeth were used to strip branches of their leaves, and its long neck and limbs allowed it to access vegetation some 15 meters in the air without rearing.

## Ecology

Despite its massive size, Argentinosaurus was a competent terrestrial walker, with one study concluding that it was able to walk at a maximum of 5 mph across the vast scrublands it lived in; however, the Argentinosaurus mount used for this study was inaccurate, and its top speed is likely to have been underestimated. As well as this, its neck was able to be used in two different ways, from reaching up high in order to feed on conifers to sweeping the ground in search of bushes and ferns. Along with this, the sauropod would have traveled in small herds in order to protect juveniles from harm; juveniles and subadults would have fallen prey to predators such as Mapusaurus, while adults were impervious to predation. An interesting thing to note is that Argentinosaurus never stopped growing, and that babies would have to grow 25000 times their size in order to reach adult size.

## In popular culture

Argentinosaurus was first introduced to the public in the 2nd episode of the 2002 documentary *Chased by Dinosaurs*, where it is shown as the biggest dinosaur to ever live; as well as this, it was featured alongside many animals misplaced through time (and space), such as Giganotosaurus (mentioned as the biggest land carnivore), Macrogryphosaurus, Sarcosuchus, Tropeognathus, and Pteranodon (the latter of which was very egregious). It appeared again in another documentary, *Planet Dinosaur*, where it was accurately shown alongside other dinosaurs that did live with it; however, it was depicted as being a prey item for Mapusaurus, no matter what age (on the other hand, it was shown as more than capable of killing the theropod).
Birkenia

Birkenia is a birkeniid birkeniiform jawless fish from the Llandovery-Pridoli of the United Kingdom, Norway, Sweden, Finland, Denmark, Estonia, and Canada. It was named in 1899 by Ramsay H. Traquair. It was one of the many jawless fishes to swim in the Silurian seas, as well as one of the most successful.

## Physiology

Birkenia had a build similar to jawless fish; it had a mobile tail, a large, oval-shaped body, eyes positioned on the side of its head, and a toothless mouth. However, it is a bit different from all others, as it has a crown-shaped projection on its back (followed by smaller, spike-like projections running down its tail), its mouth was slightly bigger than those of other jawless fish, and the fleshy part of its fin faced downwards, as opposed to the upwards-facing tails of other jawless fish. Its body would have been covered in scaly skin.

## Diet

Birkenia was a planktivore, sucking up colonies of plankton drifting through the water. Its small, toothless mouth would have been used to filter plankton from the water.
Iguanacolossus

Iguanacolossus is an ornithopod dinosaur from the Early Cretaceous of the United States of America. It was named in 2010 by Andrew T. McDonald and his crew. It was one of the many iguanodontians that roamed North America, and was discovered alongside Hippodraco.

## Physiology

Iguanacolossus was a quadrupedal ornithopod with a bulky body, long forelimbs, long, muscular hindlimbs, a moderately long tail, and a large head with a small beak in front of its mouth. Its body would have been covered in scaly skin.

## Diet

Iguanacolossus was an herbivore, feeding on leaves, horsetails, cycads, and conifers. Its round beak was used to strip leaves off branches, while the many teeth in the back of its mouth would grind together, processing the leaves.
Marrella

Marrella is a marrellid marrellid marrellomorph arthropod from the Cambrian Series 3 of Canada. It was named in 1912 by Charles Doolittle Walcott. It was the most common arthropod in Cambrian Canada, and it was thought to be either a trilobite, chelicerate, or crustacean, before finally being discovered to be an arthropod of its own class.

## Physiology

Marrella had a body plan very similar to modern arthropods. It has a segmented body (comprised of 26 body segments), 4 pairs of walking legs, 2 feathery gills near its head, 2 pairs of antenna (1 pair is long, while the other is short), and a head shield with 2 pairs of backwards-facing spines protruding from it. Its body would have been covered in a hard, chitinous exoskeleton.

## Diet

Marrella was a scavenger, feeding on the dead bodies of other arthropods like trilobites. However, it would also sometimes settle for detritus suspended on the seafloor.

## Ecology

Marrella was once thought to be a crustacean (often called a lace crab), right before being hypothesized to be a trilobite, due to its flat shape and spines. However, none of these hypotheses are correct, as it was later classified as an arthropod of its own class, due to having too many antenna, too few legs, and too few segments per leg to be a trilobite. Marrella was a bottom-feeder living on the seafloor, feeding on any piece of organic debris found there. As well as this, it would sift through the seafloor to find organic particles to eat.
Compsognathus

Compsognathus is a compsognathid theropod dinosaur from the Late Jurassic of Germany and France. It was named in 1859 by Johann Andreas Wagner. It was once known as the smallest dinosaur ever, right before smaller dinosaurs like Mononykus and Microraptor were discovered.

## Physiology

Compsognathus was a small, bird-like theropod with a slender body, long legs, an extremely long tail, moderately-sized arms with 3 fingers on each hand, a moderately long neck, and a small, conical head with large jaws. Most of its body (excluding its legs, its snout, and its tail) would have been covered in short, fuzz-like feathers.

## Diet

Compsognathus was a predator, preying on insects, lizards, small pterosaurs, and primitive birds. Its teeth were small yet sharp, and were used to get a hold of struggling prey (along with its arms).

## Ecology

Despite its small size, Compsognathus was very likely the apex predator of the dry lagoons that it lived in. Thanks to its long legs, it was a very fast runner; this would have allowed it to quickly catch lizards that would hide in the undergrowth once spotted, as well as pterosaurs and birds which would fly up at the first sight of danger. As well as this, it had large eyes which allowed for good eyesight, as well as a moderately long neck which allowed for swerving its head without having to move its entire body; all these features could tell us that Compsognathus was a generally agile creature with fast reflexes. In order to hunt, Compsognathus would run up to a small animal before grabbing onto it with its jaws, holding it in place with its arms, and finishing it off with a bite; when dealing with lizards hiding in the undergrowth, it would use its moderately long neck to crane forward and grab them out of their hiding spots.

## In popular culture

Compsognathus was first introduced to the public in the 1997 science fiction movie *The Lost World: Jurassic Park*, where it is depicted as a vicious pack hunter that swarms its prey (usually unlucky humans) in large groups like piranhas; as well as this, like any other theropod in the film, it is depicted with scaly skin. Since then, this depiction has been perpetuated in every major piece of media containing Compsognathus.
Kronosaurus

Kronosaurus is a pliosaurid plesiosaurian reptile from the Early-Late Cretaceous of Australia and Colombia. It was named in 1924 by Albert Heber Longman. It was the biggest plesiosaur to exist, as well as one of the more well known prehistoric animals from Australia.

## Physiology

Kronosaurus was a plesiosaur with a bulky body, 4 flippers, and a short tail. However, like most pliosaurids, and unlike most other plesiosaur families, it had a short neck and a large head with massive jaws. Its body would have been covered in scaly skin.

## Diet

Kronosaurus was a predator, preying on turtles and smaller plesiosaurs. Its large, conical teeth were designed for crushing bone, which would have been useful for penetrating the defenses of turtles.

## Ecology

Like its cousin, Pliosaurus, Kronosaurus was also a large plesiosaur that established itself as the apex predator of its habitat. However, unlike Pliosaurus, as well as other pliosaurs, Kronosaurus did not have serrated teeth. Due to this, it would have mainly preyed on animals half its size by ripping them apart and swallowing them whole; the only way it could have successfully fed on larger prey was by ripping a chunk of flesh off of their bodies. A fragmentary elasmosaur specimen known from a severely crushed skull has round bite marks that match the teeth of Kronosaurus; due to this, we can assume that the elasmosaur got preyed on by the pliosaur.
Nothosaurus

Nothosaurus is a nothosaurid nothosauroid reptile from the Middle-Late Triassic of Germany, Italy, Spain, the Netherlands, Israel, and China. It was named in 1834 by Georg zu Munster. It was representative of one of the most dominant marine reptile orders of the Triassic, and was also relatively widespread.

## Physiology

Nothosaurus was a reptile with a slender body, short legs, a long tail, and a big head with a mouth filled with sharp, interlocking teeth. Like the plesiosaurs it was distantly related to, it also had a decently long neck. Its body would have been covered in scaly skin.

## Diet

Nothosaurus was a predator, preying on fish, cephalopods, and baby marine reptiles. Its sharp teeth were used to get a hold of slippery fish, and its long neck would have helped it grab prey a meter away from its body and snake into large groups of fish.

## Ecology

Nothosaurus is often called "the seal of the Triassic" due to the fact that it was at home on both the rocky coasts and the deep oceans. When swimming, Nothosaurus would use a combination of moving its tail from left to right and pushing forward with its legs to propel itself through the water. As well as this, Nothosaurus would have jumped into the water only to look for aquatic prey, otherwise walking around and sunbathing on the coast. This lifestyle would save Nothosaurus from getting eaten by bigger aquatic predators such as Cymbospondylus; however, it wouldn't be completely safe, as giant predatory archosaurs such as Batrachotomus would probably have seldom walked onto the coast.

## In popular culture

Nothosaurus was featured in the 1st episode of the 2003 documentary *Chased by Sea Monsters*, where it is featured as a mesopredator of the Triassic aquatic ecosystems, mainly overshadowed by Cymbospondylus. As well as this, even though it is mentioned to be a danger to Nigel Marven (the explorer of the prehistoric seas), it is shown as relatively harmless, even fleeing from him when he decided to clamp down on its jaws with his hands.
Nautili

Side view of the chambered nautilus (credits to ARKive)

The nautili are a successful family of widespread cephalopod mollusks from the Late Triassic-Holocene of the entire world. They were named in 1825 by Henri Marie Ducrotay de Blainville. They are one of the few animals to be called "living fossils" (due to surviving up until now), and are the closest living relatives of Paleozoic cephalopods such as Cameroceras.

## Physiology

Nautili are unique mollusks. They are mainly squid-like in body plan, with a soft body, a mass of tentacles in the front of their body, large eyes, and a small, keratinous beak hiding in their of tentacles; however, they have 90 small tentacles instead of 8 long ones, large "pinhole" eyes, and a large, curly shell. Their bodies are covered in smooth skin, and mostly covered by their hard shells.

## Diet

Nautili are predators, feeding mainly on fish and small crustaceans, but also scavenging carcasses. Their tentacles are used to get a hold of struggling prey, while their beaks are used to crush them and tear them into pieces.

## Ecology

The shells of nautili serve three purposes: protection from predators (the cephalopods would hide in their shells when threatened), stabilization, and buoyancy control. In order to swim, they pull water into their mantle before propelling themselves forward with a jet of water pushed out from the siphon; this causes them to swim with a seesaw-like motion. Unlike other cephalopods, who have eyes with large lenses, nautili have eyes with small, pinhole-esque lenses, which would only detect simple images; due to this, they detect prey using their sense of smell. As well as this, they are nocturnal, and sink to the seafloor in order to rest during the day; it is only at night that they rise from the depths in order to forage and find mates.
Lystrosaurus

### Physical Dimensions

1 meter long for L.murrayi; 1.5 meters long for L.curvatus; 2 meters long for L.maccaigi

### Diet

Herbivore

Lystrosaurus is a lystrosaurid therapsid synapsid from the Lopingian-Early Triassic of South Africa, Antarctica, and India. It was named in 1870 by Edward Drinker Cope. It was the most common anomodont therapsid synapsid in the Early Triassic, and it was one of the most notable disaster taxa, surviving the cataclysmic extinction event of the Permian.

## Physiology

Lystrosaurus was an anomodont with 4 legs, a regularly-shaped body, a short tail, and a big head with a small beak and two downwards-facing tusks. Its body would have been covered in smooth skin.

## Diet

Lystrosaurus was an herbivore, feeding on seeds, leaves, roots, and tubers. Behind its horny beak, it had a horny secondary mouth roof used for grinding up food; as well as this, its tusks were used for digging up roots and tubers.

## Ecology

Due to having very little pelvic vertebrae, Lystrosaurus assumed a semi-sprawling gait; however, its forelimbs were massive, and so, it is thought to have been able to burrow into the ground. As well as this, once it sheared off pieces of vegetation, it would chew with its jaw moving back and forth, grinding up its food. Why it managed to survive the Permian extinction has remained a mystery for a long time; possible (and plausible) theories included having anatomical features leaving it capable of coping with stale air, being relatively unspecialized, having barely any large predators to prey on it, being semi-aquatic (which was disproved, as it was a primarily terrestrial anomodont, and contemporary Early Triassic amphibians weren't as common as it), or just being extremely lucky. Now, recent findings have put forth the most accepted theory; it had a short lifespan (15 years), so it bred as quickly and as commonly as possible, procreating lots of individuals.

## In popular culture

Lystrosaurus was featured in the 3rd episode of the 2005 documentary *Walking with Monsters*, where it is shown as evolving from Diictodon over a course of 9.8 (or 4.8) million years. As well as this, it is shown as a herd animal capable of not getting completely destroyed by dangerous events such as Euchambersia ambushes or Proterosuchus attacks; it is only later in the Triassic that it, along with all other large dicynodonts, gets outcompeted by the later dinosaurs.
Deinonychus

Deinonychus is a dromaeosaurid theropod dinosaur from the Early Cretaceous of the United States of America. It was named in 1969 by John Ostrom. It was a very important discovery, as it helped fuel a new age of dinosaur perception.

## Physiology

Deinonychus was a theropod with a sleek body, moderately long legs, a long tail, long arms with 3 fingers on each hand, a moderately long neck, and a long head with a mouth containing lots of teeth. Like its semi-close cousin, Velociraptor, each second toe on its foot was held off the ground, and brandished a large, sickle-shaped claw; as well as this, its eye sockets were placed near the front of its head, allowing for binocular vision. Most of its body (excluding some of its legs and all of its snout) would have been covered in long, vaned feathers.

## Diet

Deinonychus was a predator, preying on small mammals, small to midsized ornithischians, and smaller theropods. Its teeth had knife-like serrations from back to back, and its sickle claw was used for stabbing larger prey and restraining smaller prey.

## Ecology

Like other dromaeosaurids, Deinonychus is often said to be a really fast runner, and is said to be able to pursue prey into exhaustion; however, it has been found out that its lower leg was a little shorter than its upper leg, and that it actually was slower than previously thought, needing to ambush prey in order to get an advantage over them. Fortunately, it was able to ambush well, as its forward-facing eyes would have allowed it to have good binocular vision. When hunting smaller prey, it would rush up to a prey item before pinning it to the ground with its sickle claw and tearing chunks of flesh off its body while it was still alive. Due to a massive bonebed containing multiple Deinonychus individuals situated around a single Tenontosaurus, we can assume that the raptors hunted in packs in order to take down herbivores like these; however, while pack-hunting is suitable for almost any carnivorous theropod, these bonebeds actually show that the theropods descended into a feeding frenzy and cannibalized their younger brethren, very similarly to modern reptiles such as crocodiles and Komodo dragons.

## In popular culture

Since its discovery, Deinonychus has fuelled a great period of time for paleontology in the 1900s: the famed Dinosaur Renaissance of 1970. During this period of time, all of science had started to see dinosaurs in a new light, and they were no longer perceived as the slow, lethargic reptilian giants everyone thought them to be during the early 1900s; instead, they were starting to be seen as fast-moving, warm-blooded avian creatures. In fact, Deinonychus was so popular at the time that two years later, it would be incorporated into the production of the influential science fiction movie *Jurassic Park*, where it would serve as the basis for the appearance of another, soon-to-be-popular theropod: the dreaded Velociraptor.
Onchopristis

Onchopristis is an ischyrhizid sclerorhynchiform cartilaginous fish from the Early-Late Cretaceous of the entire world. It was officially named in 1917 by Ernst Stromer. It was one of the most widespread saw-nosed rays during the Cretaceous, as well as one of the most successful.

## Physiology

Onchopristis resembled modern sawfish. It was a fish with a flat, shark-like body, triangular pectoral (arm) and dorsal (back) fins, a crescent-shaped, upwards-pointing caudal (tail) fin, small jaws just on the underside of its mid-sized head, eyes on the top of its head, 5 gills located on each corner of its head's underside, and a flat, long, barbed rostrum that extended from the tip of its head. Its body would have been covered in scaly skin, with a row of thorn-like bumps running down its back.

## Diet

Onchopristis was a predator, preying on smaller fish, crustaceans, and mollusks. Its small and blunt teeth were used to get a hold of prey, and its large, saw-like rostrum was used to either swipe at prey to knock them out or pin them down as it ate them.

## Ecology

Onchopristis was quite similar to modern sawfish; it had an elongated, barbed rostrum that it used to detect and catch prey. Its head and rostrum contained thousands of sensory organs that it used to detect movements in the water, allowing to find prey in the murky waters it likely swam through; once it spotted a prey item, it would either use its rostrum to incapacitate the prey item by swiping at it or pin it against the seafloor or riverbed as the large ray ate it up. However, despite its large size, it would have fallen prey to larger predators such as Spinosaurus; due to this, its eyes were positioned on the top of its head so that it could detect predators swimming above it, and, unlike modern sawfish, its back was covered in a row of thorny spines in order to stop predators from effortlessly biting into it (similarly to thornback rays). As is the case with modern sawfish, Onchopristis would have mainly lived in coastal and estuarine waters, but, due to its presumed ability to adapt to various salinities, would have been able to live in a freshwater environment; in fact, it is somewhat likely that it would have been anadromous (migrating into freshwater in order to breed), and that juveniles would have spent the first years of their life in freshwater environments before moving into saltier waters in adulthood.

## In popular culture

Onchopristis was featured in the 1st episode of the 2011 documentary *Planet Dinosaur*, where it is shown as an anadromous fish that migrates into the freshwater rivers of Cretaceous North Africa to breed. In the episode itself, a school of the saw-nosed rays migrate the freshwater rivers; a Spinosaurus takes advantage of this migration and hunts a few of them, eats a few large chunks of flesh from their bodies, and then leaves the rest to scavengers like Rugops.
Tapinocephalus

Tapinocephalus was a tapinocephalid therapsid synapsid from the Guadalupian of South Africa. It was named in 1876 by Richard Owen. It was the most common dinocephalian therapsid synapsid in South Africa, as well as the largest herbivore there.

## Physiology

Tapinocephalus was a dinocephalian with 4 erect legs, a short tail, a broad, bulky body, and a mid-sized head. Its most notable feature is the large, bony dome atop its forehead. Its body would have been covered in smooth skin.

## Diet

Tapinocephalus was an herbivore, feeding on tough vegetation. Its teeth were small and stout, and were used to process vegetation before the synapsid swallowed it.

## Ecology

So far, all we know about Tapinocephalus is that it was an herbivore that ate tough plants like cycads, its anatomy allowed it to have a more erect gait than other tetrapods at the time, and during mating season, it would have butted heads like a goat or pushed heads like an ox.
Yi

Yi
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Yi is a scansoriopterygid theropod dinosaur from the Early Jurassic of China. It was named in 2015 by Xu Xing and his crew. It was one of the most unique dinosaurs, as it had wings held together by a large, bony rod and large flaps of skin; as well as this, it has the shortest name out of any prehistoric animal.

## Physiology

Yi was a unique theropod; it was a small, bipedal saurischian with a small body, a short tail, long arms with 3 fingers (of differing lengths), and a large head with mid-sized jaws. As well as this, a long bony rod was attached to its arms (right on its wrists) and held up large flaps of skin, resulting in wings somewhat similar to those of bats and pterosaurs. Most of its body (excluding some of its legs, most of its wings, and all of its snout) would have been covered in long, vaned feathers, with some extremely long, strap-like feathers protruding from its tail; most of its body would have been black in color, with a reddish-brown head.

## Diet

Yi was a predator, preying on insects. The only teeth it had were in the front of its mouth, and protruded from its jaws; this would allow it to get a hold of struggling prey.

## Ecology

Yi's most defining traits are the bony rods situated on its wrists; combined with large, membranous flaps of skin that stretched all the way from the sides of its body to its third fingers, those would have formed large, leathery wings that would allow the scansoriopterygid to glide from tree to tree. Of course, there are two interpretations to how its wings were shaped; some say that the bony rods that held up the wings pointed in a straight fashion, leading to big, broad wings, while others say that those rods pointed backwards, leading to thinner but longer wings. Due to this revolutionary discovery, many people consider other scansoriopterygids like Epidexipteryx to have had those bony rods and membranous wings. As well as this, like Epidexipteryx, Yi had a downwards-turning lower jaw that moved away from the upper jaw, as well as huge front teeth and smaller back teeth; similarly, this suggests that the theropod used a special prey capture method with these jaws.
Megamastax

Megamastax is a lobe-finned bony fish from the Pridoli-Early Devonian of China. It was named in 2014 by Brian Choo and his team. It was the world's first vertebrate apex predator, and it was the biggest vertebrate during the Silurian.

## Physiology

Megamastax resembled the generic lobe-finned fish. It was a coelacanth-like fish with a bulky body, fleshy, lobe-like fins, and a semi-small head. Its body would have been covered in scaly skin.

## Diet

Megamastax was a predator, preying on trilobites, small orthoconic cephalopods, small eurypterids, and smaller fish. Its front teeth were used for catching prey, while its back teeth were used for crushing it, meaning that it was capable of both tearing smaller fish apart and cracking the shells of mollusks and arthropods.
Castorocauda

Castorocauda is a docodontid therapsid synapsid from the Middle Jurassic of China. It was named in 2006 by Qiang Ji. It was one of the biggest Mesozoic mammalians, as well as one of the few specialized ones.

## Physiology

Castorocauda looked like a mix between a beaver and an otter. It had a somewhat slender, barrel-shaped body, 4 semi-erect legs with webbed toes, a long, flat, broad tail (similar to that of a beaver), and a mid-sized, conical head with small jaws. Most of its body (excluding its feet and tail) would have been covered in thick fur, while its tail and feet would have been covered in smooth skin.

## Diet

Castorocauda was a predator, preying on fish and small invertebrates. Unlike the teeth of other mammals, its teeth had points aligned in a straight row, and were designed for getting a hold of slippery prey rather than grinding them into a paste.

## Ecology

Castorocauda had adaptations similar to modern beavers, like webbed feet and a flat, broad tail; this tells us that it would have spent about half of its time in the water. More notable tools that it had included sturdy, muscular forelegs, which would allow the cynodont to dig in a similar manner to the platypus, a mammal that is capable of both swimming and digging. Along with this, its front teeth were different from those of other mammals; instead of having 4 points packed together in a cube-like fashion, it had 3 points lining up together in a row; those teeth would have been similar to those of mesonychids like Mongolonyx and even those of seals. In general, Castorocauda would have been one of the most unique and specialized Mesozoic mammalians to exist; other specialized Mesozoic mammalians included the badger-like Repenomamus, the armadillo-like Fruitafossor, and the flying squirrel-like Volaticotherium.

## In popular culture

Castorocauda was featured in the 3rd episode of the 2011 documentary *Dinosaur Revolution*, where it was chased by a pair of Guanlong. When cornered by the theropods, it was depicted as being able to spray a strong-smelling liquid at them, similar to a modern skunk.
Guiyu

Guiyu is a lobe-finned bony fish from the Pridoli-Early Devonian of China. It was named in 2009 by Min Zhu. It was the earliest lobe-finned fish known, and marked the split between ray-finned fish and lobe-finned fish.

## Physiology

Guiyu was a unique fish. It had the regular lobe-finned fish build (a coelacanth-like fish with a bulky body, fleshy, lobe-like fins, and a small head); however, it had the same scale articulation as early ray-finned fish. Its body would have been covered in scaly skin.
Andesaurus

Andesaurus is a sauropod sauropodomorph dinosaur from the Late Cretaceous of Argentina. It was named in 1991 by Jorge Orlando Calvo and José Fernando Bonaparte. It was one of the many sauropods that walked the Southern Hemisphere during the Late Cretaceous, as well as one of the largest from the geological formation it was found in.

## Physiology

Andesaurus was a large sauropod with a bulky, downwards-sloping body, a deep torso, 4 large, erect, pillar-like legs, a moderately long tail, a long neck, and a small head. Its body would have been covered in scaly skin.

## Diet

Andesaurus was an herbivore, feeding on leaves from large trees. Its peg-like teeth were used to strip branches of their leaves, and its long neck and limbs allowed it to access vegetation some 7 meters in the air without rearing.

## Ecology

So far, all we know about Andesaurus is that its long, upwards-pointing neck allowed it to feed off trees without having to rear up, and could also be used to feed off plants closer to the ground. As well as this, it would have traveled in small herds in order to protect juveniles from harm; juveniles and subadults may have fallen prey to many kinds of predators, while adults were impervious to predation from all but fully-grown Giganotosaurus.