Fossilized Mosasaurus tooth
30 - 50mm in length. Chosen at random.
Mosasaurus is an extinct aquatic reptile that lived over 66 million years ago in the Campanian and Maastrichtian stages of the late Cretaceous period.
They were apex predators (top of the food chain) that dominated the ocean. Mosasaurus was not a dinosaur, but a reptile, more closely related to modern day snakes and lizards. Due to their aquatic lifestyle, over time they developed shark-like tails to help them move more swiftly through the water.
The Mosasaurus is a genus of a diverse group called Mosasaurs. Some were small. Some, like the Mosasaurus reached up to 56 feet in length. Possibly larger, though the largest specimen ever found was 56ft. This means the Mosasaurus rivals the size of the Megalodon that lived millions of years later.