Mosasaurus

Mosasaurus was a large, 12-metre long sea carnivore from the Late Cretaceous. It gave its name to a group of snake-like sea carnivores - Mosasaurs.

More real-life information - Mosasaurus on Wikipedia

Jurassic Park Franchise
Mosasaurus has not appeared in any Jurassic Park movies or novels, but has appeared in the comic Jurassic Park: Redemption V.