Real Dictionary

plesiosaur in American English
any of an extinct group (order Sauropterygia) of large water reptiles of the Mesozoic Era, characterized by a small head, long neck, short tail, and four paddlelike limbs
noun: any marine reptile of the extinct genus Plesiosaurus, from the Jurassic and Cretaceous periods, having a small head, a long neck, four paddlelike limbs, and a short tail

plesiosaur in British English
noun: any of various extinct marine reptiles of the order Sauropterygia, esp any of the suborder Plesiosauria, of Jurassic and Cretaceous times, having a long neck, short tail, and paddle-like limbs