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
               1 [Equus hemionus hemionus] Pallas, 1775
               2 Equus hemionus blanfordi (Pocock, 1947)
               3 ‡Equus hemionus hemippus Geoffroy, 1855
               4 Equus hemionus khur Lesson, 1827
               5 Equus hemionus kulan (Groves & Mazák, 1967) - kulan
               6 Equus hemionus luteus Matschie, 1911
               7 Equus hemionus onager Boddaert, 1785 - onager