1825, from Modern Latin Pleisiosaurus (1821), coined by English paleontologist William Daniel Conybeare (1787-1857) from Greek plesios "near," related to pelas, + -saurus.
Online Etymology Dictionary, © 2010 Douglas Harper
Examples from the Web for plesiosaurus
The other huge reptile was the Plesiosaurus, the meaning of which is “Near to a Reptile.”
Perhaps of all the extinct reptiles, the Plesiosaurus was the most extraordinary.The Cruise of the Betsey
Another animal which lived at this period was the Plesiosaurus.
The Plesiosaurus was scarcely so large as the Ichthyosaurus.The World Before the Deluge
The similarity of such an animal to the Plesiosaurus of old was remarkable.