Kingdom [Animalia] Linnaeus, 1758 - animals
   Subkingdom Metazoa Haeckel, 1874 see Kingdom Animalia Linnaeus, 1758
     Division Eumetazoa Butschli, 1910 see Subkingdom Eumetazoa Butschli, 1910
       Subdivision Bilateralia
         Phylum Chordata Bateson, 1885 - chordates
           Subphylum Vertebrata Cuvier, 1812 - vertebrates
             Class Reptilia Linnaeus, 1758 - reptiles
               Subclass †Synapsida Osborn, 1903 - synapsids see Class Synapsida Osborn, 1903
                 Order †Pelycosauria Cope, 1878 - pelycosaurs
                   Suborder †Ophiacodontia (Romer & Price, 1940) see Order Pelycosauria Cope, 1878
                     1 Family †Ophiacodontidae Nopsca, 1923
                     2 Family †Eothyrididae Romer & Price, 1940