Class Mammalia Linnaeus, 1758 - mammals
   Order Rodentia Bowdich, 1821 - rodents
     Suborder Sciurognathi (Tullberg, 1899) see Suborder Sciuromorpha Brandt, 1855
       Family Sciuridae Batsch, 1788 - squirrels, chipmunks, marmots, and prairie dogs
         Subfamily Sciurinae Batsch, 1788 - tree and ground squirrels
           Genus Spermophilus Cuvier, 1825 - ground squirrels
             01 Spermophilus adocetus Merriam, 1903 - tropical ground squirrel
             02 Spermophilus alashanicus Büchner, 1888
             03 Spermophilus annulatus Audubon & Bachman, 1842 - ring-tailed ground squirrel
             04 Spermophilus armatus Kennicott, 1863 - Uinta ground squirrel
             05 Spermophilus atricapillus W. Bryant, 1889 - Baja California rock squirrel
             06 Spermophilus beecheyi (Richardson, 1829) - California ground squirrel
             07 Spermophilus beldingi Merriam, 1888 - Belding's ground squirrel
             08 Spermophilus brunneus (A.H. Howell, 1928) - Idaho ground squirrel
             09 Spermophilus canus Merriam, 1898 - gray ground squirrel
             10 Spermophilus citellus Linnaeus, 1766 - European souslik
             11 Spermophilus columbianus (Ord, 1815) - Columbian ground squirrel
             12 Spermophilus dauricus Brandt, 1843 - Daurian ground squirrel
             13 Spermophilus elegans Kennicott, 1863 - Wyoming ground squirrel
             14 Spermophilus erythrogenys Brandt, 1841
             15 Spermophilus franklinii (Sabine, 1822) - Franklin's ground squirrel
             16 Spermophilus fulvus Lichtenstein, 1823 - large-toothed souslik
             17 Spermophilus lateralis (Say, 1823) - golden-mantled ground squirrel
             18 Spermophilus madrensis Merriam, 1901 - Sierra Madre ground squirrel
             19 Spermophilus major Pallas, 1778 - russet souslik
             20 Spermophilus mexicanus (Erxleben, 1777) - Mexican ground squirrel
             21 Spermophilus mohavensis Merriam, 1889 - Mohave ground squirrel
             22 Spermophilus mollis Kennicott, 1863 - Piute ground squirrel
             23 Spermophilus musicus Ménétries, 1832
             24 Spermophilus parryii (Richardson, 1825) - Arctic souslik
             25 Spermophilus perotensis Merriam, 1893 - Perote ground squirrel
             26 Spermophilus pygmaeus Pallas, 1778 - little souslik
             27 Spermophilus relictus Kashkarov, 1923 - Tien Shan souslik
             28 Spermophilus richardsonii (Sabine, 1822) - Richardson's ground squirrel
             29 Spermophilus saturatus (Rhoads, 1895) - Cascade golden-mantled ground squirrel
             30 Spermophilus spilosoma Bennett, 1833 - spotted ground squirrel
             31 Spermophilus suslicus Güldenstaedt, 1770 - spotted souslik
             32 Spermophilus tereticaudus Baird, 1858 - round-tailed ground squirrel
             33 Spermophilus townsendii Bachman, 1839 - Townsend's ground squirrel
             34 Spermophilus tridecemlineatus (Mitchill, 1821) - thirteen-lined ground squirrel
             35 Spermophilus undulatus Pallas, 1778 - long-tailed souslik
             36 Spermophilus variegatus (Erxleben, 1777) - rock squirrel
             37 Spermophilus washingtoni (A.H. Howell, 1938) - Washington ground squirrel
             38 Spermophilus xanthoprymnus Bennett, 1835
             39 Subgenus Otospermophilus Brandt, 1844
             40 Subgenus Spermophilus F. Cuvier, 1825
             44 Subgenus Poliocitellus Howell, 1938
             45 Subgenus Callospermophilus Merriam, 1897
             46 Subgenus Ictidomys J. Allen, 1877
             47 Subgenus Xerospermophilus Merriam, 1892