Class Reptilia Linnaeus, 1758 - reptiles
   Subclass †Synapsida Osborn, 1903 - synapsids see Class Synapsida Osborn, 1903
     Order †Pelycosauria Cope, 1878 - pelycosaurs
       1 Suborder †Ophiacodontia (Romer & Price, 1940) see Order Pelycosauria Cope, 1878
       2 Suborder †Sphenacodontia Marsh, 1878 see Order Pelycosauria Cope, 1878
       3 Suborder †Edaphosauria Cope, 1882 see Order Pelycosauria Cope, 1878