Phylum [Vertebrata] (Lamarck, 1801) Class Reptilia Linnaeus, 1758 - reptiles Subclass †uncertain Order †Plesiosauria Blainville, 1835 - plesiosaurs Family †Elasmosauridae Cope, 1869 Genus †Elasmosaurus Cope, 1868 Genus †Muraenosaurus Seeley, 1874