Class [Mammalia] Linnaeus, 1758 - mammals
   Order Rodentia Bowdich, 1821 - rodents
     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 granatensis Humboldt, 1811 - tropical red squirrel
           12 Sciurus griseus Ord, 1818 - western grey squirrel
           13 Sciurus ignitus Gray, 1867
           14 Sciurus igniventris Wagner, 1842
           15 Sciurus lis Temminck, 1844 - Japanese squirrel
           16 Sciurus nayaritensis J.A. Allen, 1890 - Nayarit squirrel
           17 Sciurus niger Linnaeus, 1758 - eastern fox squirrel
           18 Sciurus oculatus Peters, 1863 - Peters' squirrel
           19 Sciurus pucheranii Fitzinger, 1867
           20 Sciurus pyrrhinus Thomas, 1898
           21 Sciurus richmondi Nelson, 1898 - Richmond's squirrel
           22 Sciurus sanborni Osgood, 1944
           23 Sciurus spadiceus Olfers, 1818
           24 Sciurus stramineus Eydoux & Souleyet, 1841
           25 Sciurus variegatoides Ogilby, 1839 - variegated squirrel
           26 Sciurus vulgaris Linnaeus, 1758 - Eurasian red squirrel
           27 Sciurus yucatanensis J. A. Allen, 1877 - Yucatan squirrel