Class Mammalia Linnaeus, 1758 - mammals
   Subclass Theria Parker & Haswell, 1897
     Order Artiodactyla Owen, 1848 - even-toed ungulates see Order Cetartiodactyla Montgelard, Catzeflis & Douzery, 1997
       Family Hippopotamidae Gray, 1821 - hippopotamuses
         Genus Hippopotamus Linnaeus, 1758 [monotypic] - hippopotamus
           1 ‡Hippopotamus lemerlei Grandidier, in Milne-Edwards, 1868
           2 ‡Hippopotamus laloumena Faure & Guérin, 1990
           3 Hippopotamus amphibius Linnaeus, 1758 - hippopotamus