Vertebrata Cuvier, 1812 - vertebrates
   Gnathostomata
     Teleostomi
       Tetrapoda Hatschek & Cori 1896 [Gauthier, Kluge & Rowe 1988]
         Amniota Haeckel, 1866 [Gauthier, Kluge & Rowe 1988] - amniotes
           Class Reptilia Linnaeus, 1758 [paraphyletic] - reptiles
             Subclass †Synapsida Osborn, 1903 - synapsids see Class Synapsida Osborn, 1903
               Order †Pelycosauria Cope, 1878 - pelycosaurs
                 1 Family †Ophiacodontidae Nopsca, 1923
                 2 Family †Varanopseidae Romer & Price, 1940 see Family Varanopidae Romer & Price, 1940
                 3 Family †Eothyrididae Romer & Price, 1940
                 4 Family †Sphenacodontidae Marsh, 1878
                 5 Family †Edaphosauridae Cope, 1882
                 6 Family †Caseidae Williston, 1912