| plesiosauria | (n) any of the plesiosaurs, Syn. suborder Plesiosauria |
| Plesiosauria | ‖n. pl. [ NL. See Plesiosaurus. ] (Paleon.) An extinct order of Mesozoic marine reptiles including the genera Plesiosaurus, and allied forms; -- called also |
| Plesiosaurian | n. (Paleon.) A plesiosaur. [ 1913 Webster ] |