Vertebrata Cuvier, 1812 - vertebrates
   Gnathostomata
     Teleostomi
       Tetrapoda Hatschek & Cori 1896 [Gauthier, Kluge & Rowe 1988]
         Amniota Haeckel, 1866 [Gauthier, Kluge & Rowe 1988] - amniotes
           Class Mammalia Linnaeus, 1758 - mammals
             Subclass Prototheria Gill, 1872 - monotremes
               1 Order Monotremata Bonaparte, 1837 - monotremes
               2 Order †Triconodonta Osborn, 1888
               3 Order †Docodonta Kretzoi, 1946 [monotypic] - docodonts