Phylum [Vertebrata] Lamarck, 1801 see Infraphylum Vertebrata Lamarck, 1801 Class Reptilia Linnaeus, 1758 - reptiles Order †Plesiosauria Blainville, 1835, incertae sedis - plesiosaurs Family †Elasmosauridae Cope, 1869 Genus †Elasmosaurus Cope, 1868