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
           1 Equus asinus group Linnaeus, 1758 [monotypic]
           2 Equus caballus group Linnaeus, 1758 [monotypic]
           3 Equus grevyi group Oustalet, 1882 [monotypic]
           4 Equus hemionus group Pallas, 1775
           5 Equus quagga group Boddaert, 1785
           6 Equus zebra group Linnaeus, 1758 [monotypic]