Mammalia Linnaeus 1758 [Rowe 1988], nom. cl. inval. see Class Mammalia Linnaeus, 1758
   Metatheria Huxley 1880 [O'Leary, Allard, Novacek, Meng & Gatesy 2004] see Infraclass Metatheria Huxley, 1880
     Marsupialiformes Vullo, Gheerbrant, de Muizon & Néraudeau, 2009
       Notometatheria Kirsch, Lapointe & Springer 1997
         Family †Herpetotheriidae Trouessart, 1879 [monotypic]
           Genus †Herpetotherium Cope, 1873