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 Sigmodon Say & Ord, 1825 - cotton rats
01 Sigmodon alleni Bailey, 1902 - brown cotton rat
02 Sigmodon alstoni Thomas, 1880[1881]
03 Sigmodon arizonae Mearns, 1890 - Arizona cotton rat
04 Sigmodon fulviventer J.A. Allen, 1889 - tawny-bellied cotton rat
05 Sigmodon hispidus Say & Ord, 1825 - hispid cotton rat
06 Sigmodon inopinatus Anthony, 1924
07 Sigmodon leucotis Bailey, 1902 - white-eared cotton rat
08 Sigmodon mascotensis J. A. Allen, 1897
09 Sigmodon ochrognathus V. Bailey, 1902 - yellow-nosed cotton rat
10 Sigmodon peruanus J. A. Allen, 1897