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 †Meridiungulata McKenna, 1975 see Grandorder Meridiungulata McKenna, 1975
             Order †Notoungulata Roth, 1903
               Suborder †Toxodonta Haeckel, 1866 see Suborder Toxodontia Owen, 1853
                 Family †Notohippidae Ameghino, 1894
                   1 Genus †Rhynchippus Ameghino, 1897