Tylosaurus was one of the larger mosasaurs that lived towards the end of the Cretaceous period, and would have been‭ '‬the‭' ‬predator of the late Cretaceous seas,‭ ‬specifically the Western Interior Seaway that once submerged the central portion of the United States and Canada.

Reconstruction for Regina's Royal Saskatchewan Museum showing the animal in life (a monster nearly as large as the iconic T rex), about to chomp onto another smaller mosasaur at the water's surface.