A colossal sea beast longer than a semi-truck prowls the ancient oceans, jaws lined with crushing teeth snapping up sharks like snacks. This is Mosasaurus, the ultimate Late Cretaceous predator that dominated the seas for millions of years.
The first clues to Mosasaurus surfaced in 1764 when quarry workers near the Meuse River in the Netherlands unearthed massive bones and a skull. Initially mistaken for a whale or crocodile, it was French naturalist Georges Cuvier who in the early 1800s identified it as an enormous extinct marine lizard, far surpassing any living reptile. The genus name honors the Meuse River (Mosa in Latin) where the fossils were found.
Towering at up to 55 feet long and weighing around 16 tons, Mosasaurus was built for speed and power with a streamlined body, flippered limbs and a massive tail fluke. Fossil stomachs reveal a menu of fish, ammonites, sea turtles, seabirds and even other mosasaurs. One astonishing find shows a Mosasaurus snout with bite marks from a shark, healed over, proving these titans engaged in fierce underwater duels.
Mosasaurus thrived until the catastrophic asteroid strike 66 million years ago doomed it alongside the dinosaurs. Recent digs, like a gigantic snout from Israel in 2021 and size-boosting skulls from North America, continue to unveil its reign as the ocean’s deadliest hunter.
Note: The Mosasaurus was technically not a dinosaur but a marine reptile. However, I’ve decided to include it in my dinosaur encyclopedia anyway because it’s widely recognized as closely associated with popular dinosaurs.
