Plesiosaurus spec.; Print; Plesiosaurus is a genus of extinct; large marine sauropterygian reptile that lived during the early part of the Jurassic Period; and is known by nearly complete skeletons from the Lias of England. It is distinguishable by its small head; long and slender neck; broad turtle-like body; a short tail; and two pairs of large; elongated paddles. It lends its name to the order Plesiosauria; of which it is an early; but fairly typical member. It contains only one species; the type; Plesiosaurus dolichodeirus. Other species once assigned to this genus; including P. brachypterygius; P. guilielmiiperatoris; and P. tournemirensis have been reassigned to new genera; such as Hydrorion; Seeleyosaurus and Occitanosaurus.; 1700-1880