Class [Mammalia] Linnaeus, 1758 - mammals
Order Rodentia Bowdich, 1821 - rodents
Family Muridae Batsch, 1788 - rats, mice, hamsters, voles, lemmings, and gerbils
Subfamily Hesperomyinae Murray, 1866 - New-World mice and rats
see Subfamily Sigmodontinae Wagner, 1843
Genus Baiomys True, 1894 - pygmy mice
Baiomys musculus Merriam, 1892 - southern pygmy mouse