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