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Sciurini is a tribe that includes about forty species of squirrels,〔Thorington and Hoffmann, 2005, p. 754〕 mostly from the Americas. It includes five living genera—the American dwarf squirrels, ''Microsciurus''; the Bornean ''Rheithrosciurus''; the widespread American and Eurasian tree squirrels of the genus ''Sciurus'', which includes some of the best known squirrel species; the Central American ''Syntheosciurus''; and the American red squirrels, ''Tamiasciurus''. Like other arboreal squirrels, they are sometimes referred to as tree squirrels.〔Thorington and Ferrell, 2006, p. 18〕 ==Taxonomy== The name "Sciurini" was first employed by Hermann Burmeister in 1854, who used it for the entire squirrel family.〔Burmeister, 1854, p. 145; McKenna and Bell, 1997, p. 122〕 In his influential 1945 classification of mammals, George Gaylord Simpson included four genera of squirrels in Sciurini, which he recognized as one of eight tribes within the subfamily Sciurinae (including all squirrels except the flying squirrels): ''Sciurus'', ''Syntheosciurus'', ''Microsciurus'', and ''Sciurillus''. He also classified ''Rheithrosciurus'' as "?Sciurini ''incertae sedis''" (of uncertain placement).〔Simpson, 1945, p. 78〕 This grouping derives from Reginald Innes Pocock, who united these squirrels in 1923 as the subfamily Sciurinae.〔Moore, 1959, p. 177〕 In 1959, Joseph Curtis Moore published a review of the interrelationships of the squirrels. His definition of Sciurini was similar to Simpson's, but he no longer considered ''Rheithrosciurus'' to be ''incertae sedis''. He noted that the members of Sciurini were united only by the possession of a special type of baculum (penis bone).〔Moore, 1959, pp. 177–178〕 He also divided the tribe into subtribes, producing the following classification:〔Moore, 1959, pp. 177–180〕 *Tribe Sciurini * *Subtribe Sciurina * * *Genus ''Sciurus'' * * *Genus ''Guerlinguetus'' (currently included in ''Sciurus'')〔Thorington and Hoffmann, 2005, p. 758〕 * * *Genus ''Rheithrosciurus'' * *Subtribe Microsciurina * * *Genus ''Microsciurus'' * * *Genus ''Syntheosciurus'' (including two species currently placed in ''Sciurus'', ''S. granatensis'' and ''S. pyrrhinus'') * *Subtribe Sciurillina * * *Genus ''Sciurillus'' In their 1997 update to Simpson's classification, McKenna and Bell retained a similar definition for Sciurini, but also included several extinct genera, as follows:〔McKenna and Bell, 1997, p. 122〕 *Tribe Sciurini * *''Freudenthalia'' (fossil, early Miocene of Europe; assignment to Sciurini "uncertain")〔 * *''Rheithrosciurus'' * *''Plesiosciurus'' (fossil, middle Miocene of Asia) * *Subtribe Sciurina * * *''Douglassciurus'' (fossil, late Eocene of North America; McKenna and Bell used ''Douglassia'', a preoccupied name replaced by ''Douglassciurus'')〔Emry and Korth, 2001〕 * * *''Protosciurus'' (fossil, early Oligocene to early Miocene of North America) * * *''Miosciurus'' (fossil, early Miocene of North America) * * *''Sciurus'' (including ''Syntheosciurus'') * * *''Microsciurus'' * *Subtribe Sciurillina * * *''Sciurillus'' }} }} }} }} }} In the early 2000s, several studies were published using DNA sequences to study the interrelationships of squirrels. Two, published in 2003 and 2004 and both based on several different genes, produced largely concordant results, concluding that ''Sciurillus'' is not related to other Sciurini, but rather forms one of the most distinctive lineages of all squirrels; that ''Tamiasciurus'' is the closest relative to the other Sciurini; and that the group of ''Tamiasciurus'' and the other Sciurini is most closely related to the flying squirrels.〔 The authors of the 2004 study formalized these results into a revised classification of squirrels. They removed ''Sciurillus'' from Sciurini, placed ''Tamiasciurus'' in it, and classified Sciurini with the flying squirrels (tribe Pteromyini) in a subfamily Sciurinae.〔Steppan et al., 2004, p. 715〕 Their classification was adopted in the 2005 third edition of ''Mammal Species of the World''〔 and remains current. The same studies also provided insights into the interrelationships of genera within Sciurini. ''Microsciurus'', ''Syntheosciurus'', and ''Rheithrosciurus'' all appear among the various species of ''Sciurus'' included, making the latter genus paraphyletic; additionally, the two species of ''Microsciurus'' included in Mercer and Roth's 2003 study did not cluster with each other.〔 A morphological study of Central American Sciurini also found that ''Microsciurus'' and ''Syntheosciurus'' are part of the ''Sciurus'' radiation, and suggested that ''Syntheosciurus'' be lumped into ''Sciurus'' while further work is needed on ''Microsciurus''.〔Villalobos and Cervantes-Reza, 2007〕 In a 2008 monograph on Brazilian rodents, Bonvicino and others considered ''Guerlinguetus'' and ''Urosciurus'', conventionally placed in ''Sciurus'', as separate genera.〔Bonvicino et al., 2008, pp. 15–16, 18〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Sciurini」の詳細全文を読む スポンサード リンク
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