Class Mammalia Linnaeus, 1758 - mammals Subclass Trechnotheria McKenna, 1975 see Superlegion Trechnotheria McKenna, 1975 1 Superorder †Symmetrodonta Simpson, 1925 see Infraclass Symmetrodonta Simpson, 1925 2 Superorder †Dryolestoidea Butler, 1939 3 Superorder Zatheria McKenna, 1975 see Clade Zatheria McKenna 1975