Class Mammalia Linnaeus, 1758 - mammals Subclass Theria Parker & Haswell, 1897 Infraclass Metatheria Huxley, 1880 Order Marsupialia Jameson, 1818 - marsupials see Cohort Marsupialia Jameson, 1818 Superfamily Didelphoidea Gray, 1821 1 Family Didelphidae Gray, 1821 - American opossums