Class Mammalia Linnaeus, 1758 - mammals
   Order Monotremata Bonaparte, 1837 - monotremes
     Family Ornithorhynchidae Gray, 1825 - platypuses
       ?Genus †Steropodon Archer, Flannery, Ritchie & Molnar, 1985
         1 †Steropodon galmani Archer, Flannery, Ritchie & Molnar, 1985