Class [Mammalia] Linnaeus, 1758 - mammals Order †Plesiadapiformes Simons & Tattersall, 1972 see Suborder Plesiadapiformes Simons & Tattersall, 1972 Superfamily †Microsyopoidea Osborn & Wortman, 1892 Family †Microsyopidae Osborn, 1892 Genus †Arctodontomys Gunnell, 1985 †Arctodontomys simplicidens (Rose, 1981)