Class Mammalia Linnaeus, 1758 - mammals
   Clade Yinotheria Chow & Rich 1982 [Kielan-Jaworowska, Cifelli & Luo 2004]
     Subclass Australosphenida Luo, Cifelli & Kielan-Jaworowska, 2001 see Clade Australosphenida Luo, Cifelli & Kielan-Jaworowska 2001
       Order Monotremata Bonaparte, 1837 - monotremes
         Family †Steropodontidae Flannery, Archer, Rich & Jones, 1995
           Genus †Steropodonᵀ Archer, Flannery, Ritchie & Molnar, 1985 [monotypic]
             1 †Steropodon galmani Archer, Flannery, Ritchie & Molnar, 1985