Phylum [Vertebrata] Lamarck, 1801 see Infraphylum Vertebrata Lamarck, 1801
   Class Mammalia Linnaeus, 1758 - mammals
     Subclass Theria Parker & Haswell, 1897
       Infraclass Eutheria Gill, 1872
         Cohort Epitheria McKenna, 1975
           Superorder Ungulata Linnaeus, 1766
             Order Artiodactyla Owen, 1848 - even-toed ungulates see Order Cetartiodactyla Montgelard, Catzeflis & Douzery, 1997
               Suborder Suina Gray, 1868
                 Family Hippopotamidae Gray, 1821 - hippopotamuses
                   Genus Hippopotamus Linnaeus, 1758 - hippopotamus
                     1 †Hippopotamus gorgops Dietrich, 1926
                     2 Hippopotamus amphibius Linnaeus, 1758 - hippopotamus