Mosasaurs were air-breathing, marine predators, living in shallow inland seas in the late Cretaceous period. These large animals (up to 50') are not dinosaurs, but reptiles related to snakes and monitor lizards. Mosasaurs gave birth to live young in water, not on land as turtles do. Due to the delicate nature of their scales, mosasaurid fossil specimens rarely show scale imprints. Teeth are a different matter! They ate ammonites, fish, turtles, plesiosaurs, and even sea birds. Check out our selection, which changes with new items found in our travels.