XL 2.15" Mosasaur (Prognathodon) Tooth

About Mosasaurs

Mosasaurs were large, carnivorous marine reptiles that lived during the Late Cretaceous Period, approximately 90 to 66 million years ago. Though often mistaken for dinosaurs, they were actually more closely related to modern monitor lizards, including the Komodo dragon. Over time, their ancestors transitioned from land to sea, evolving paddle-like flippers, streamlined bodies, and powerful tails that made them highly efficient swimmers. Some species developed crescent-shaped, shark-like tail fins that allowed for strong, sustained propulsion through open water. Sizes varied widely, with many species measuring 20 to 30 feet long, while the largest—such as Mosasaurus hoffmannii—may have exceeded 50 feet in length.

As apex predators, mosasaurs occupied the top of the marine food chain. Their long jaws were lined with sharp, conical teeth ideal for gripping slippery prey, and fossil evidence shows they fed on fish, sharks, ammonites, seabirds, and even other mosasaurs. Despite their fully aquatic lifestyle, mosasaurs were air-breathing reptiles and had to surface regularly, much like modern whales. They thrived in oceans around the world until the Cretaceous–Paleogene extinction event 66 million years ago, which wiped out the dinosaurs and many marine reptiles, bringing the age of mosasaurs to an end.