Class Mammalia Linnaeus, 1758 - mammals
   Subclass Boreosphenida Luo, Cifelli & Kielan-Jaworowska, 2001 - tribotherians see Clade Boreosphenida Luo, Cifelli & Kielan-Jaworowska 2001
     1 Order †Aegialodontia Butler, 1978
     2.1 Infraclass Metatheria Huxley, 1880
     2.2 Infraclass Eutheria Gill, 1872