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 Choeropsis Leidy, 1853 [monotypic] - pygmy hippopotamus
               Choeropsis liberiensisᵀ (Morton, 1844) - pygmy hippopotamus
                 1 ‡Choeropsis liberiensis heslopi
                 2 Choeropsis liberiensis liberiensis