Phylum Chordata Bateson, 1885 - chordates
   Subphylum Vertebrata Cuvier, 1812 - vertebrates
     Class Mammalia Linnaeus, 1758 - mammals
       Order Perissodactyla Owen, 1848 - odd-toed ungulates
         Family †Amynodontidae Scott & Osborn, 1883
         Family †Brontotheriidae Marsh, 1873
         Family †Chalicotheriidae Gill, 1872
         Family †Deperetellidae Radinsky, 1965
         Family †Eomoropidae Matthew, 1929
         Family Equidae Gray, 1821 - horses, zebras, and asses
         Family †Helaletidae Osborn, 1892
         Family †Hyracodontidae Cope, 1879
         Family †Isectolophidae Peterson, 1919
         Family †Lophialetidae Matthew & Granger, 1925
         Family †Lophiodontidae Gill, 1872
         Family †Palaeotheriidae Bonaparte, 1850
         Family Rhinocerotidae Gray, 1821 - rhinoceroses
         Family Tapiridae Gray, 1821 - tapirs