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 asinus group Linnaeus, 1758 [monotypic]
             Equus asinus Linnaeus, 1758 - ass
               1 [Equus asinus asinus] Linnaeus, 1758 - domestic ass
               2 Equus asinus africanus Heuglin & Fitzinger, 1866 - wild ass
               3 Equus asinus somalicus Sclater, 1885