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 Sciurus Linnaeus, 1758 - tree squirrels
01 Sciurus aberti Woodhouse, 1853 - tassel-eared squirrel
02 Sciurus aestuans Linnaeus, 1766
03 Sciurus alleni Nelson, 1898 - Allen's squirrel
04 Sciurus anomalus Schreber, 1785 - Persian squirrel
05 Sciurus arizonensis Coues, 1867 - Arizona grey squirrel
06 Sciurus aureogaster F. Cuvier, 1829 - Mexican grey squirrel
07 Sciurus carolinensis Gmelin, 1788 - eastern grey squirrel
08 Sciurus colliaei Richardson, 1839 - Collie's squirrel
09 Sciurus deppei Peters, 1863 - Deppe's squirrel
10 Sciurus flammifer Thomas, 1904
11 Sciurus gilvigularis Wagner, 1842
12 Sciurus granatensis Humboldt, 1811 - tropical red squirrel
13 Sciurus griseus Ord, 1818 - western grey squirrel
14 Sciurus ignitus Gray, 1867
15 Sciurus igniventris Wagner, 1842
16 Sciurus lis Temminck, 1844 - Japanese squirrel
17 Sciurus nayaritensis J.A. Allen, 1890 - Nayarit squirrel
18 Sciurus niger Linnaeus, 1758 - eastern fox squirrel
19 Sciurus oculatus Peters, 1863 - Peters' squirrel
20 Sciurus pucheranii Fitzinger, 1867
21 Sciurus pyrrhinus Thomas, 1898
22 Sciurus richmondi Nelson, 1898 - Richmond's squirrel
23 Sciurus sanborni Osgood, 1944
24 Sciurus spadiceus Olfers, 1818
25 Sciurus stramineus Eydoux & Souleyet, 1841
26 Sciurus variegatoides Ogilby, 1839 - variegated squirrel
27 Sciurus vulgaris Linnaeus, 1758 - Eurasian red squirrel
28 Sciurus yucatanensis J. A. Allen, 1877 - Yucatan squirrel
29 Subgenus Otosciurus
30 Subgenus Guerlinguetus
31 Subgenus Sciurus Linnaeus, 1758
32 Subgenus Tenes
33 Subgenus Hadrosciurus
34 Subgenus Hesperosciurus
35 Subgenus Urosciurus