Tylosaurus
Tylosaurus is an absolutely massive mosasaur marine reptile, its only rival being the even bigger Mosasaurus with which it fight to the death if given the occasion, often resulting in itself dying. Unlike Mosasaurus however, Tylosaurus lives comfortably in pairs in a large lagoon, and will live off the fish dispensed by feeders. Other than that it would behave similarly to other marine reptiles, simply wandering around and killing and eating smaller creatures if given the chance for guest entertainment, with which Tylosaurus gives a lot, being extremely popular and one of the highest rating among prehistoric animals. They sometimes brawl with the Mosasaurus and the Kronosaurus over territory.