Mammalia Linnaeus, 1758 - mammals
   Cetartiodactyla Montgelard, Catzeflis & Douzery 1997 see Order Cetartiodactyla Montgelard, Catzeflis & Douzery, 1997
     Cetancodonta Arnason, Gullberg, Gretarsdottir, Ursing & Janke 2000
       Hippopotamoidea Gentry & Hooker 1988 [Boisserie 2007]
         Family Hippopotamidae Gray, 1821 - hippopotamuses
           Subfamily Hippopotaminae Gray, 1821
             Genus †Phanourios Boekschoten & Sondaar, 1972
             1.1? Genus †Saotherium Boisserie, 2005 [monotypic]
             1.2? Genus Choeropsis Leidy, 1853 [monotypic] - pygmy hippopotamus
             2.1? Genus †Archaeopotamus Boisserie, 2005
             2.2.1 Genus Hippopotamus Linnaeus, 1758 - hippopotamus
             2.2.2 Genus †Hexaprotodon Falconer & Cautley, 1836