Tylosaurus was a mosasaur, a big, predatory marine lizard closely related to contemporary monitor lizards and to snakes. Along with plesiosaurs, sharks, fish and other genus of mosasurs, it was a dominant predator of the Western Interior Seaway during the Upper Cretaceous era.

Tylosaurus proriger was among the biggest of all the mosasaurs (along with Hainosaurus and Mosasaurus hoffmanni), reaching utmost lengths of 15 metres or more (49 feet).

A distinguishing trait of Tylosaurus is its elongated, cylindrical premaxilla (snout) from which it takes its name and which may have been used to ram and stun prey and moreover in intraspecific combat.

Stomach contents connected with specimens of Tylosaurus proriger indicate that this fierce mosasaur had a varied diet, including fish, sharks, lesser mosasaurs, plesiosaurs and flightless diving birds such as Hesperornis.

In some paleoenviroments, Tylosaurus seems to have favorite shallow, nearshore waters (as with the Eutaw creation and Mooreville Chalk of Alabama), while favouring deeper water further out from coast in other environments .

Scientific Classification:

Kingdom: Animalia

Phylum: Chordata

Class: Sauropsida

Order: Squamata

Suborder: Lacertilia

Family: Mosasauridae

Genus: Tylosaurus