Only a few, rare species of plesiosaur were larger in size, although some marine crocodiles were certainly as formidable. The skulls of Tylosaurus sp. The relative abundance of small, immature mosasaurs living in a hostile mid-ocean environment, hundreds of miles from land or sheltered areas seems to indicate that mosasaurs lived in groups and protected their young. Mosasaurs fed on all types of prey, including ammonites, squid, fish, plesiosaurs, turtles, birds, pteranodons and other mosasaurs. Mosasaur bone is denser than fish bone, but not as dense as plesiosaur or turtle bone, and has a distinct surface texture.
Mosasaur vertebra are concave on the anterior end and convex on the posterior end.
Sometimes, the remains of cartilage, particularly from the rib cage and the tympanic membrane covering the ear, is fossilized in specimens. Imprints of the scales covering the skin have been found in several sets of remains. Although mosasaurs had large paddles, it is more likely that they used their strong, sinuous tails to propel themselves rapidly through the water. Tylosaurus - Tylosaurs were the largest of the mosasaurs in the chalk, reaching forty feet or more feet in length. In Platecarpus the teeth in the premaxillary extend to the end of the bone.