Mosasaurus

extinct reptile · ocean hunter · Late Cretaceous · giant predator

Massive marine lizard. Mosasaurus was a giant aquatic squamate reptile, meaning it was related to modern lizards and snakes, but was far bigger and lived entirely in the ocean hunting prey.

Connected to modern animals. Scientists still debate whether Mosasaurus was more closely related to monitor lizards or snakes, since its exact family connections remain somewhat mysterious.

First discovery changed science. When Mosasaurus skulls were found in a chalk quarry near Maastricht, Netherlands in the late 1700s, scientists didn't know what they were looking at, initially thinking they belonged to crocodiles or whales.

Proof of extinction. Georges Cuvier's 1808 conclusion that Mosasaurus was a real giant lizard unlike any living animal was revolutionary and helped convince the scientific world that species could actually go extinct.

Named after a river. In 1822, the creature was officially named Mosasaurus after the Meuse River in the Netherlands, where its fossils were first uncovered.