Class Mammalia Linnaeus, 1758 - mammals
   Subclass Boreosphenida Luo, Cifelli & Kielan-Jaworowska, 2001 - tribotherians see Clade Boreosphenida Luo, Cifelli & Kielan-Jaworowska 2001
     Infraclass Metatheria Huxley, 1880
       Cohort Marsupialia Jameson, 1818 - marsupials
         Superorder "Ameridelphia" Szalay, 1982 [paraphyletic] see Clade Ameridelphia Szalay 1982
           Order "Didelphimorphia" Gill, 1872 [paraphyletic]
             Family †Alphadontidae Marshall, Case & Woodburne, 1990 [paraphyletic]
               Genus †Alphadonᵀ Simpson, 1927
                 †Alphadon perexiguus Cifelli, 1994