FANDOM Tylosaurus. A Mosasaur. That is why this place is called "Hell's Aquarium", and why we must not swim in these waters.
— Allen, describing Tylosaurus
in Fall of a Kingdom: Hell's Aquarium

Tylosaurus (name meaning "Protuberance Lizard"), also known as the Giant Mosasaur, is a genus of large mosasaur that originated during the Late Cretaceous period in what is now North America. Measuring 18 meters in length and weighing 17 tons, this prehistoric, marine reptilian monster of the deep was the apex predator of the Cretaceous seas as well as the largest mosasaur of all time, having nothing to fear but others of its own kind when fully grown. They ate practically anything they could get their jaws around; such as fish, sharks, squid, turtles, Plesiosaurs, Hesperornis, and even other Mosasaurs.

In the Season 2 finale, "Fall of a Kingdom Part I Hell's Aquarium", a couple of Tylosaurus were brought to the park from Late Cretaceous 65 million years ago. They reside in the Marine Exhibit of the park.


Era & DiscoveryEdit

Tylosaurus lived during the Late Cretaceous period, around 75 – 65 million years ago. While Tyrannosaurus ruled over the land, Tylosaurus was at the top of the food chain in the Cretaceous seas. It shared the waters with creatures like Elasmosaurus, Xiphactinus, Squalicorax, Archelon, and Hesperornis as well as other sea creatures at the time.

Tylosaurus and other mosasaurs descended from aigialosaurs, much smaller lizards that took to the seas earlier in the Cretaceous to escape predation by the dinosaurs - and they died-out alongside the dinosaurs during the K/T extinction. Though not a dinosaur, Tylosaurus lived at the same time and region as them and went extinct at around the same time at the end of the Cretaceous period.

Since their first discovery in 1868, many Tylosaurus remains have been found in Kansas, which was once covered by a large ocean called the Western Interior Seaway. Additionally, they have also become one of the most famous prehistoric creatures in the world.

Physical AttributesEdit

SM1x3 Tylosaurus

The dominant marine carnivore of the Late Cretaceous seas, Tylosaurus was a giant predator that grew to reach more than 45 – 60 feet (13 – 18 m) in length and weighing 15 – 20 tons (33,000 – 44,000 lbs.), making it the largest of the mosasaur family of marine reptiles and one of the largest carnivorous animals the world had ever seen. Their serpentine shape was no accident, as they were close relatives of snakes. However, they were far more ferocious and even much larger. Smaller species, such as Halisaurus, lived in shallow waters close to shore. However, offshore in the deep oceans lurked true giants. 

Like all mosasaurs, a long and muscular, vertically flattened tail powered Tylosaurus through the water, allowing it to ambush its prey with rapid bursts of acceleration. Paddle-like limbs helped steer the slim body covered in lizard-like scales through the water. Preserved stomach contents indicate a diet heavy on fish, but seabirds, sharks, plesiosaurs, and other mosasaurs also failed to escape Tylosaurus's lethal grip. These sea monsters were feeding on fish (Xiphactinus and sharks), sea birds (Hesperornis), and other reptiles (Archelon), plesiosaurs and other - smaller - species of mosasaurs, as well as other prey items. Its immense head size meant that it could have swallowed medium-sized animals like Squalicorax whole. 

Tylosaurus was the deadliest hunter of the ancient seas, ready to seize and kill just about any creature that crossed its path with true jaws of death—lined on each side with two rows of pointy, cone-shaped teeth. Tylosaurus used its snout to locate prey, which, once inside the mosasaur's menacing jaws, was swallowed whole or torn to pieces. When the sea monster opened wide for the final gulp, two extra rows of teeth on the roof of its mouth allowed crippled captives no escape. 

Behavior & TraitsEdit

Tylosaurus was an immensely dangerous ocean predator, by far the most dangerous that ever lived on planet Earth in the Cretaceous seas. It hunted slow-moving prey like ammonites, birds, and turtles as well as larger creatures like sharks and Elasmosaurus. Tylosaurus was not the fastest of predators. Instead of chasing its prey, Tylosaurus would stalk and then it ambushed its prey in a short burst of speed. Being caught in its jaw meant almost certain death.

And if there was anything worse than swimming with these carnivorous sea reptiles, it would be swimming with its family. Interestingly, Tylosaurus lived and travel in groups of around 20 individuals to provide protection to their offspring. They attacked and ate virtually anything that moved – sharks, turtles, giant squid, even other Mososaurs, making Tylosaurus a cannibal as well as a predator.



  • The sound effects of Tylosaurus are that of crocodile, elephant, seal, tiger, walrus, and whale sound effects.
  • Tylosaurus was the largest mosasaur brought to the park.
  • Tylosaurus is described as being the deadliest and most dangerous aquatic animal brought to the park.
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