generic revision was undertaken in 2007 by means of phylogenetic analyses using the mitochondrial gene cytochrome b. This resulted in the splitting of Spermophilus into eight genera, which with the prairie dogs, marmots, and antelope squirrels are each given as numbered clades. The exact relations between the clades are slightly unclear. Among these, these exclusively Palearctic species are retained as the genus Spermophilus sensu stricto (in the strictest sense). Spermophilus sensu stricto, Old World ground squirrels Alashan ground squirrel, Spermophilus alashanicus Brandt's ground squirrel, Spermophilus brevicauda European ground squirrel, Spermophilus citellus Daurian ground squirrel, Spermophilus dauricus Red-cheeked ground squirrel, Spermophilus erythrogenys Yellow ground squirrel, Spermophilus fulvus Russet ground squirrel, Spermophilus major Caucasian Mountain ground squirrel, Spermophilus musicus Tian Shan ground squirrel, Spermophilus nilkaensis Pallid ground squirrel, Spermophilus pallidicauda Little ground squirrel, Spermophilus pygmaeus Relict ground squirrel, Spermophilus relictus Speckled ground squirrel, Spermophilus suslicus Taurus ground squirrel, Spermophilus taurensis Asia Minor ground squirrel, Spermophilus xanthoprymnus Prehistoric species Discovery and examination of one of the best preserved Eurasian ground squirrel fossils yet recovered allowed the study of many previously unknown aspects of ground squirrel cranial anatomy, and prompted a critical reassessment of their phylogenetic position. As a result, three Pleistocene species previously considered members of the Urocitellus genus were moved to Spermophilus: †Spermophilus nogaici †Spermophilus polonicus †Spermophilus primigenius Spermophilus citelloides is known from the Middle Pleistocene to early Holocene of Europe. It appears to be most closely related to the living S. suslicus. References External links Rodents of Europe Mammals of North America Mammals of Asia Rodent genera Taxa named by Frédéric Cuvier