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.]

Source: Webster's Revised Unabridged Dictionary (1913)