The Collaborative International Dictionary
Mosasaur \Mos"a*saur\, Mosasaurian \Mos`a*sau"ri*an\, n. (Paleon.) One of an extinct order of reptiles, including Mosasaurus and allied genera. See Mosasauria.
Wiktionary
n. An large extinct marine reptile in the family ''(taxlink Mosasauridae family noshow=1)'', dominant marine predator of the Cretaceous; the ancestor of modern snakes. (from ''c''. 1840)
Wikipedia
Mosasaurs (from Latin Mosa meaning the ' Meuse river', and Greek σαύρος sauros meaning 'lizard') are an extinct group of large marine reptiles. Their first fossil remains were discovered in a limestone quarry at Maastricht on the Meuse in 1764. Mosasaurs probably evolved from an extinct group of aquatic lizards known as aigialosaurs in the Early Cretaceous. During the last 20 million years of the Cretaceous period ( Turonian- Maastrichtian ages), with the extinction of the ichthyosaurs and decline of plesiosaurs, mosasaurs became the dominant marine predators. They became extinct as a result of the K-T event at the end of the Cretaceous period, approximately 66 million years ago.
Usage examples of "mosasaur".
About 120 million years after the placodonts became extinct, the giant marine lizards, the mosasaurs, appeared.
We’ve also got a dramatic Albertosaurus, a formidable Chasmosaurus, two dynamic mounts of Allosaurus, an excellent Stegosaurus, plus a Pleistocene-mammals display, a wall covered with casts of primate and hominid remains, a La Brea tar-pits exhibit, a standard evolution-of-the-horse sequence, and a wonderful late-Cretaceous underwater diorama, with plesiosaurs, mosasaurs, and ammonites.
This was my first word of the discovery, and it told of the identification of early shells, bones of ganoids and placoderms, remnants of labyrinthodonts and thecodonts, great mosasaur skull fragments, dinosaur vertebrae and armor plates, pterodactyl teeth and wing bones, Archaeopteryx debris, Miocene sharks’ teeth, primitive bird skulls, and other bones of archaic mammals such as palaeotheres, Xiphodons, Eohippi, Oreodons, and titanotheres.
This was my first word of the discovery, and it told of the identification of early shells, bones of ganoids and placoderms, remnants of labyrinthodonts and thecodonts, great mosasaur skull fragments, dinosaur vertebrae and armor plates, pterodactyl teeth and wing bones, Archaeopteryx debris, Miocene sharks' teeth, primitive bird skulls, and other bones of archaic mammals such as palaeotheres, Xiphodons, Eohippi, Oreodons, and titanotheres.
Many other large and/or dramatic reptiles died out at the end of the Cretaceous, notably the plesiosaurs (famous as a possible 'explanation' of the mythical Loch Ness monster), the ichthyosaurs (enormous fish-shaped predators, reptilian whales and dolphins), the pterosaurs (strange flying forms, of which the pterodactyls appear in all the dinosaur films and are labelled, wrongly, dinosaurs), and especially the mosasaurs .
But others would not: there were many ancient species of squid, the ammonite itself—and, dimly visible as shadows passing through the blue reaches of the deeper ocean—giant marine reptiles, mosasaurs and plesiosaurs, the dolphins and whales of the age.