The Tylosaurus was a large, water-bound lizard that evolved from its land-based ancestors by developing a long, powerful tail and sturdy limbs that looked and functioned like paddles. The prehistoric carnivore relied on an imposing and effective double set of cone-shaped chompers. Its muscular jaw allowed the creature to often swallow prey whole, while two rows of sharp teeth ensured that anything trapped inside a Tylosaurus' mouth wasn't getting out alive [source: National Geographic].
At about 45 feet (14 meters) long, the Tylosaurus was one of the largest members of the mosasaur family of marine reptiles. These beasts roamed the seas roughly 65 million years ago, but their remains have been discovered in some decidedly dry places. That includes parts of Texas and Kansas, which are believed to have once been covered by the Western Interior Seaway and where researchers have located Tylosaurus and other mosasuar fossils [sources: National Geographic, Fossil Guy]. If you didn't get to catch these sea monsters in real life, you can still see Hollywood's version on the big screen. The Tylosaurus is among the prehistoric beasts featured in the 2015 movie "Jurassic World."