Phylum [Vertebrata] Lamarck, 1801 see Infraphylum Vertebrata Lamarck, 1801
   Class Reptilia Linnaeus, 1758 - reptiles
     Subclass Diapsida Osborn, 1903 - diapsids see Clade Diapsida Osborn 1903 [Gauthier & de Queiroz 2020]
       Order †Ichthyosauria Blainville, 1835
         Family †Shastasauridae Merriam, 1902
           Genus †Cymbospondylus Leidy, 1868
           Genus †Shonisaurus Camp, 1976