Class Mammalia Linnaeus, 1758 - mammals
   Subclass Theria Parker & Haswell, 1897
     Order Perissodactyla Owen, 1848 - odd-toed ungulates
       Family Equidae Gray, 1821 [monotypic] - horses, zebras, and asses
         Genus Equus Linnaeus, 1758 - horses, zebras, and asses
           Equus hemionus group Pallas, 1775
             Equus hemionus Pallas, 1775 - onager
               Equus hemionus kulan (Groves & Mazák, 1967) - kulan