Vertebrata Cuvier, 1812 - vertebrates
   Gnathostomata
     Teleostomi
       Tetrapoda Hatschek & Cori 1896 [Gauthier, Kluge & Rowe 1988]
         Amniota Haeckel, 1866 [Gauthier, Kluge & Rowe 1988] - amniotes
           Class Mammalia Linnaeus, 1758 - mammals
             Subclass Theria Parker & Haswell, 1897
               Theria of Metatherian-Eutherian grade
                 Infraclass Eutheria Gill, 1872
                   Order †Notoungulata Roth, 1903
                     Suborder †Notoprongonia
                       1 ?Family †Arctostylopidae Schlosser, 1923
                       2 Family †Henricosborniidae Ameghino, 1901
                       3 Family †Notostylopidae Ameghino, 1897