Phylum [Vertebrata] (Lamarck, 1801)
   Class Reptilia Linnaeus, 1758 - reptiles
     Subclass †Synapsida Osborn, 1903 - synapsids see Class Synapsida Osborn, 1903
       Order †Pelycosauria Cope, 1878 - pelycosaurs
         Family †Ophiacodontidae Nopsca, 1923
           Genus †Archaeothyris Reisz, 1972
           Genus †Ophiacodon Marsh, 1878