During the late Cretaceous period, Kansas was covered by a vast sea. There, scientists have found fossils of Squalicorax sharks (also called crow sharks) that lived 70-80 million years ago. They were typically seven feet in length (although a nine-foot fossil has been found)—which makes them smaller than many of the marine reptiles, like mosasaurs and pleisiosaurs, that ruled the sea at the time. Squalicorax sharks likely fed mainly on fish, turtles and other sea creatures. But they also scavenged on their bigger rivals. Bite marks of their triangular, blade-like serrated teeth have been found on mosasaur and pleisiosaur fossils, suggesting that it ate them after they died.