Vertebrata Cuvier, 1812 - vertebrates
   Gnathostomata
     Teleostomi
       Tetrapoda Hatschek & Cori 1896 [Gauthier, Kluge & Rowe 1988]
         Amniota Haeckel, 1866 [Gauthier, Kluge & Rowe 1988] - amniotes
           Class Mammalia Linnaeus, 1758 - mammals
             Subclass Theria Parker & Haswell, 1897
               Theria of Metatherian-Eutherian grade
                 Infraclass Eutheria Gill, 1872
                   Order Perissodactyla Owen, 1848 - odd-toed ungulates
                     Suborder Hippomorpha Wood, 1937
                       Superfamily Equoidea (Gray, 1821) Hay, 1902 see Family Equidae Gray, 1821
                         Family Equidae Gray, 1821 - horses, zebras, and asses