Class Mammalia Linnaeus, 1758 - mammals Order Monotremata Bonaparte, 1837 - monotremes Family Ornithorhynchidae Gray, 1825 - platypuses 1 Genus Ornithorhynchus Blumenbach, 1800 - duck-billed platypus 2 ?Genus †Steropodon Archer, Flannery, Ritchie & Molnar, 1985 3 Genus †Obdurodon Woodburne & Tedford, 1975