Tylosaurus proriger

Last updated: September 24, 2022
Verified by: AZ Animals Staff
© Michael Rosskothen/Shutterstock.com

Tylosaurus was a marine reptile that is closely related to modern-day snakes and monitor lizards.

Tylosaurus Scientific Classification

Scientific Name
Tylosaurus proriger

Read our Complete Guide to Classification of Animals.

Tylosaurus Conservation Status

Tylosaurus Locations

Tylosaurus Locations

Tylosaurus Facts

Fish, sea birds, and marine reptiles
Group Behavior
  • Solitary
Fun Fact
Tylosaurus was a marine reptile that is closely related to modern-day snakes and monitor lizards.
Most Distinctive Feature
Tylosaurus' had a long and strong snout.
Distinctive Feature
The Tylosaurus' snout has an elongated conical rostrum.
Warm, shallow inland seas
Favorite Food
fish, sea birds, and other marine reptiles
Number Of Species
North America's Western Interior Seaway

Tylosaurus Physical Characteristics

Skin Type
440–1,100 lb

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View all of the Tylosaurus images!

Tylosaurus is a genus of Mosasaur, a group of large, predatory marine reptiles that lived during the Late Cretaceous (about 85 million years ago). This 45-foot-long lizard-like beast lived alongside the dinosaurs and other prehistoric creatures of the Cretaceous period. However, it wasn’t a dinosaur. Instead, it is more closely related to modern-day snakes and monitor lizards. Tylosaurus ruled supreme in an ancient body of water known as the Western Interior Seaway, which cut through a region in present-day North America.

Description & Size

Tylosaurus was around 45 feet long and relied on its long and muscular tail to propel itself through the water.


Tylosaurus is a genus of beastly marine reptiles that lived in the western interior seaway during the Late Cretaceous period. It is a genus of mosasaur reptiles belonging to the order Squamata (the same order as modern-day snakes and monitor lizards.) 

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Tylosaurus was undoubtedly one of the largest members of the mosasaur group of reptiles. The genus name means “Knob Lizard,” a reference to Tylosaurus‘s long and strong snout. The snout has an elongated conical rostrum, one of its most prominent features. 

Like other mosasaurs, Tylosaurus relied on its long and muscular tail (which had up to 80 vertebrae) to propel itself through the water. This feature distinguished the mosasaurs from their ancestors, the pliosaurs that relied on their flippers. Although Tylosaurus also had flippers, they were mainly used for steering rather than propulsion. Tylosaurus‘s tail was laterally compressed, which made it more effective for pushing the reptile through the water. 

Tylosaurus was a formidable predator with a large, strong chest and big flippers. The largest member of this genus is the Tylosaurus proriger. Palaeontologists estimate that this species might have been between 39–52 feet long. It weighed about 2,400 lb by some estimates. 

Fossil evidence suggests that Tylosaurus had diamond-shaped scales all over its body. These scales were arranged in oblique rows, similar to that of rattlesnakes. The scales were small compared to the reptile’s overall size and were shaped in a way that would have reduced water drag. 

Diet – What Did Tylosaurus Eat?

The massive size of Tylosaurus’s head meant it would have been capable of swallowing medium-sized animals whole. 


Reaching up to 49 feet in length, the Tylosaurus was a dominant predator. It was a carnivore, feeding on fish, sea birds, and the abundant supply of marine reptiles such as the plesiosaurs and other mosasaurs. The massive size of Tylosaurus‘s head meant it would have been capable of swallowing medium-sized animals whole. 

Tylosaurus is closely related to modern reptiles like snakes and monitor lizards; the feeding habit of this prehistoric monster is quite similar to theirs. Tylosaurus‘s teeth were not adapted to chewing prey. However, rather than swallowing them whole like snakes, it could tear its prey apart and swallow the pieces. 

Tylosarus was an agile predator, capable of swimming really fast and catching prey in its powerful jaws. It was a top predator that ruled the seas of the Cretaceous period. Given its size, this marine reptile could take on anything, including sharks, giant squids, turtles, and other marine reptiles. There is no evidence to suggest that it ate dinosaurs. However, it might have scavenged on the remains of dead dinosaurs. 

Habitat—When and Where It lived

Although Tylosaurus and other Mosasaurs breathed air, they were well-adapted to living in warm, shallow inland seas, which were quite common during the Late Cretaceous period. Tylosaurus was the dominant species in the Western Interior seaway, which once submerged the Central portion of North America. The seaway cut through an area that is now present-day in United States of America and Canada

Threats and Predators

Given its large size, Tylosaurus was no doubt an apex predator. It had a large snout and hinged jaws that could open wide, which would have given it a fearsome bite. Although it lived alongside the dinosaurs and other large predators, none of them would have preyed on an adult Tylosaurus. Their biggest threat would have been from members of their own genus. Fossil evidence suggests that Tylosaurus were most likely aggressive towards each other. Many of the fossils had signs of injuries inflicted by their own kind. 

Discoveries and Fossils – Where It was Found

The discovery of Tylosaurus fossils came at a controversial period in paleontologic history known as the “bone wars.” This was a period of fierce rivalry between the most prominent paleontologists of the 19th century, notably Edward Drinker Cope and Othniel Charles Marsh. Thus, the naming history of the members of this genus is a bit messy. 

Paleontologists found the first Tylosaurus specimen in Kansas in 1868. It was the specimen of a skull and vertebrae. Edward Cope gave these fossils the name Macrosaurus prioger and put them in the Liodon genus. In 1872, Othniel Marsh discovered a more complete specimen and named it Rhinoceros‭ (‬Nose lizard‭)‬. However, the name and the replacement he chose were already in use by another animal. Eventually, he had to settle for the name Tylosaurus‭ (‬Knob lizard‭)‬.‭ 

Although many fossils associated with the Tylosaurus genus have been discovered in Central United States and Canada, paleontologists now think many of these discoveries are not actual Tylosaurus. Rather, they belong to other older species in the Mosasaurid family. 

Extinction – When Did It Die Out?

Tylosaurus and other mosasaurs are descendants of the aigialosaurs, a group of much smaller previously terrestrial lizards that took to the sea in the early Cretaceous to escape from the dinosaurs on land. They evolved into the Mosasaurs and dominated the seas for several million years. They eventually died off during the K/T extinction (the extinction event that occurred at the end of the Cretaceous period). This event wiped out all the non-avian dinosaurs about 65 million years ago. 

Similar Animals to The Tylosaurus

Similar animals to the Tylosaurus include: 

Hainosaurus: another large-sized member of the mosasaurs group. The Hainosaurus looks similar to the Tylosaurus but has more vertebrae. 

Plotosaurus: The Plotosaurus was a large marine lizard that lived in North and South America during the Late Cretaceous. 

View all 131 animals that start with T

About the Author

Abdulmumin is a pharmacist and a top-rated content writer who can pretty much write on anything that can be researched on the internet. However, he particularly enjoys writing about animals, nature, and health. He loves animals, especially horses, and would love to have one someday.

Tylosaurus FAQs (Frequently Asked Questions) 

When was the Tylosaurus alive?

Tylosaurus lived during the Cretaceous period about 85 million years ago.

How big was Tylosaurus?

Tylosaurus grew to over 45 feet in length. This makes it the longest of all the marine reptiles in the mosasauridae family. On average, it might have weighed about 1100lbs.

What's the difference between Mosasaurus and Tylosaurus?

Tylosaurus and Mosasaurus are separate genera of marine reptiles that belong to the family Mosasauridea. They’re collectively known as mosasaurs. However, unlike other mosasaurs, the Tylosaurus does not have teeth at the end of its snout or on its bony rostrum.

Thank you for reading! Have some feedback for us? Contact the AZ Animals editorial team.

  1. Walking With Wikis, Available here: https://walkingwith.fandom.com/wiki/Tylosaurus
  2. Prehistoric Wildlife, Available here: http://www.prehistoric-wildlife.com/species/h/hainosaurus.html
  3. National Geographic Kids/KAREN DE SEVE, Available here: https://kids.nationalgeographic.com/animals/prehistoric/facts/tylosaurus-proriger
  4. Wikipedia, Available here: https://en.wikipedia.org/wiki/Tylosaurus
  5. Wikipedia, Available here: https://en.wikipedia.org/wiki/Mosasaur

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