Mosasaurus lived during the Late Cretaceous period 75-65 million years ago. They died out with the dinosaurs at the end of the Cretaceous. While Tyrannosaurus Rex was the largest and top predator on land, Mososaurus was the top predator of the Cretaceous seas.
Mosasaurus was arguably the largest predator in the seas of the Cretaceous. Close to shores, there would only be babies and tiddlers merely over 10 feet, 3 meters, long. But offshore in the deep open oceans lived giant adults that measured 60 feet in length. As the top predators of the Cretaceous seas, Mosasaurs were the ruling class of marine reptiles in the Cretaceous. Their serpentine body shape was no accident, as they were closely related to snakes, however Mososaurus were even much larger and far more ferocious.
Mosasaurus was an immensely dangerous ocean predator, by far the most dangerous that ever lived on planet earth in the Cretaceous seas. And if there was anything worse than swimming with these 60-foot carnivorous sea reptiles, it would be swimming with its family. Interestingly, Mosasaurus often travel in groups to protect their young. They attacked and ate virtually anything that moved – sharks, turtles, giant squid, even other Mososaurs.