Mosasaurus is a genus of extinct aquatic reptiles that existed in the late Cretaceous Period, between 70 and 66 million years ago. The name means 'Meuse lizard', as the first specimen of this prehistoric animal was found near the Meuse River in the Netherlands.
Mosasaurus was one of the largest predators in its day. It ruled the Cretaceous seas, using its fearsome array of teeth to catch fish, birds, and other marine reptiles, event great white sharks. In fact, it had two sets of teeth - a second set was on its upper palate to ensure that any prey sliding down its throat would not be able to escape.
Mosasaurus was up to 18 m long, and weighed about five tons. Its legs and feet were modified into flippers - these paddle-like limbs had five digits in front and four in back. The body ended in a strong tail which had a fluke similar to those of sharks.
Mosasaurus gave birth to live young. The huge sea monster, like many other oceanic animals, gave birth beneath the waves.
As it was wildly successful, its fossils have been found in every continent, even in Antarctica.