Image: A Tylosaur

Tylosaurus may have ruled the Late Cretaceous seas because all other would-be competitors, such as ichthyosaurs, were already extinct. Though they evolved from terrestrial lizards, the paddle-like limbs of giant mosasaurs like Tylosaurus were useless on land.

Copyright © MMVII NGHT, Inc.

Fast Facts

Type:
Prehistoric
Diet:
Carnivore
Size:
Length, 45 ft (14 m)
Protection status:
Extinct
Did you know?
Mosasaurs gave birth to live young. A baby Tylosaurus was 3 to 6 ft (1 to 2 m) long—small enough for predatory fish and sharks to eat.
Size relative to a bus:
Illustration: Tylosaurus proriger compared with bus

Tylosaurus was the deadliest hunter of the ancient seas, ready to seize and kill just about any smaller 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. 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.

Tylosaurus grew more than 45 feet (14 meters) long, making it the largest of the marine reptiles called mosasaurs. 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. Though not a dinosaur, Tylosaurus lived alongside them and went extinct at around the same time. Many Tylosaurus remains have been found in Kansas, which was once covered by a large ocean called the Western Interior Seaway.

Prehistoric Features

  • Photo: Gully bones

    Digging Up Sea Monsters

    Follow the blog from the Spitsbergen Expedition as they unearth "sea monsters″ from the Upper Jurassic Period 150 million years ago.

  • Image: A bacculite

    Photo Gallery: Sea Monsters

    Get a glimpse of what prehistoric sea creatures may have looked like millions of years ago.

  • Photo: A Dimorphodon flies across the forest in a scene from the movie Flying Monsters 3D

    Flying Monsters 3D

    Could flying monsters have existed? With cutting-edge 3-D filming technology and CGI, Flying Monsters 3D recreates spectacular pterosaurs and brings these giant flying creatures to life.

  • 2565.jpg

    Bizarre Dinosaurs

    A bizarre gallery of Mesozoic monsters prompts John Updike to ask: What has evolution wrought?

Please select a test to run

Animals

The Innovators Project

See more innovators »

From the Magazine

  1. Photo: Two adult preen, Ireland

    Gannets Pictures

    Champion divers but clumsy landers, doting parents but hostile neighbors—northern gannets abound in contradictions.

  2. Photo: Silent Ural owl

    Estonia's Ural Owls

    Photographer Sven Začek provides an intimate view of this large raptor.