Class Mammalia Linnaeus, 1758 - mammals
   Order Rodentia Bowdich, 1821 - rodents
     Suborder Sciurognathi (Tullberg, 1899) see Suborder Sciuromorpha Brandt, 1855
       Family Muridae Batsch, 1788 - rats, mice, hamsters, voles, lemmings, and gerbils
         Subfamily Sigmodontinae Wagner, 1843
           Genus Baiomys True, 1894 - pygmy mice
             1 Baiomys musculus Merriam, 1892 - southern pygmy mouse
             2 Baiomys taylori (Thomas, 1887) - northern pygmy mouse