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 Hippopotamus Linnaeus, 1758 - hippopotamus
               1.1? †aff. Hippopotamus dulu Boisserie, 2004
               1.2.1 †aff. Hippopotamus afarensis (Gèze, 1985)
               1.2.2 †aff. Hippopotamus coryndonae (Gèze, 1985)
               2.1? [ancestor] †aff. Hippopotamus protamphibius Arambourg, 1944
               2.1.d1 †aff. Hippopotamus karumensis Coryndon, 1977
               2.1.d2 †aff. Hippopotamus aethiopicus Coryndon & Coppens, 1975
               2.2? [ancestor] †Hippopotamus kaisensis Hopwood, 1926
               2.2.d.1? †Hippopotamus gorgops Dietrich, 1926
               2.2.d.2? [ancestor] Hippopotamus amphibiusᵀ Linnaeus, 1758 - hippopotamus
               2.2.d.2.d? ‡Hippopotamus laloumena Faure & Guérin, 1990
               2.2.d.3? ‡Hippopotamus lemerlei Grandidier, in Milne-Edwards, 1868
               2.2.d.4? ‡Hippopotamus madagascariensis Guldberg, 1883