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 Sigmodon Say & Ord, 1825 - cotton rats
           1 Sigmodon alleni Bailey, 1902 - brown cotton rat
           2 Sigmodon alstoni Thomas, 1880[1881]
           3 Sigmodon arizonae Mearns, 1890 - Arizona cotton rat
           4 Sigmodon fulviventer J.A. Allen, 1889 - tawny-bellied cotton rat
           5 Sigmodon hispidus Say & Ord, 1825 - hispid cotton rat
           6 Sigmodon leucotis Bailey, 1902 - white-eared cotton rat
           7 Sigmodon mascotensis J. A. Allen, 1897
           8 Sigmodon ochrognathus V. Bailey, 1902 - yellow-nosed cotton rat