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