Mammaliaformes Rowe 1988, nom. cl. inval. see Clade Mammaliaformes Rowe 1988 [Rowe 2020]
   [crown] Class Mammalia Linnaeus, 1758 - mammals
     Subclass Prototheria Gill, 1872 - monotremes
       Order Platypoda Gill, 1872 - platypuses see Order Monotremata Bonaparte, 1837
         Family Ornithorhynchidae Gray, 1825 - platypuses
           Genus †Steropodon Archer, Flannery, Ritchie & Molnar, 1985