What is "mosasaurus"

Mosasaurus \Mos`a*sau"rus\, n. [NL., fr. L. Mosa the River Meuse (on which Meastricht is situated) + Gr. ? a lizard.] (Paleon.) A genus of extinct marine reptiles allied to the lizards, but having the body much elongated, and the limbs in the form of paddles. The first known species, nearly fifty feet in length, was discovered in Cretaceous beds near Maestricht, in the Netherlands. [Written also Mososaurus.]

marine dinosaur, 1830, from Latin Mosa "the river Meuse" + -saurus. the fossils of the ancient reptile were first discovered 1780 near Maastricht, on the Meuse.

Mosasaurus (; "lizard of the Meuse River") is a genus of mosasaur, extinct carnivorous aquatic lizards. It existed during the Maastrichtian age of the late Cretaceous period, between about 70 and 66 million years ago, in western Europe and North America. The name means "Meuse lizard", as the first specimen was found near the Meuse River (Latin Mosa + Greek sauros lizard).