Editing Squirrel (section)

== Taxonomy ==
[[File:One squirrel open mouth.jpg|thumb|A [[fox squirrel]] (''Sciurus niger'') outside the [[Cleveland Museum of Art]]]]
[[File:Taiwanrisu-2009.ogv|thumb|A squirrel (''Callosciurus erythraeus thaiwanensis'') in [[Japan]]]]
[[File:Prevostova vjeverica u Zagrebu.2.jpg|thumb|Three-coloured [[Prevost's Squirrel]] (''Callosciurus prevostii'') in [[Zagreb Zoo]], [[Croatia]]]]
The living squirrels are divided into five [[subfamilies]], with about 58 [[genera]] and some 285 [[species]].<ref>{{cite journal|author1=Wilson, D.E. |author2=Reeder, D.M. | title=Class Mammalia Linnaeus, 1758. In: Zhang, Z.-Q. (Ed.) Animal biodiversity: An outline of higher-level classification and survey of taxonomic richness | journal=Zootaxa| volume=3148| year=2011| pages=56–60|doi=10.11646/zootaxa.3148.1.9 | url=http://mapress.com/zootaxa/2011/f/zt03148p060.pdf}}</ref> The oldest squirrel fossil, ''Hesperopetes'', dates back to the [[Chadronian]] (late [[Eocene]], about 40–35 [[million years ago]]) and is similar to modern flying squirrels.<ref>{{Cite journal | last1 = Emry | first1 = R. J. | last2 = Korth | first2 = W. W. | title = A new genus of squirrel (Rodentia, Sciuridae) from the mid-Cenozoic of North America | journal = Journal of Vertebrate Paleontology | volume = 27 | issue = 3 | pages = 693–698 | year = 2007 | doi = 10.1671/0272-4634(2007)27[693:ANGOSR]2.0.CO;2 | s2cid = 85847849 }}</ref>

A variety of fossil squirrels, from the latest [[Eocene]] to the [[Miocene]], have not been assigned with certainty to any living lineage. At least some of these probably were variants of the oldest [[basal (evolution)|basal]] "protosquirrels" (in the sense that they lacked the full range of living squirrels' [[autapomorphy|autapomorphies]]). The distribution and diversity of such ancient and ancestral forms suggest the squirrels as a group may have originated in North America.<ref name = tolweb>Steppan & Hamm (2006)</ref>

Apart from these sometimes little-known fossil forms, the [[phylogeny]] of the living squirrels is fairly straightforward. The three main lineages are the [[Ratufinae]] (Oriental giant squirrels), Sciurillinae and all other subfamilies. The Ratufinae contain a mere handful of living species in tropical [[Asia]]. The [[Neotropical Pygmy Squirrel|neotropical pygmy squirrel]] of tropical [[South America]] is the sole living member of the Sciurillinae. The third lineage, by far the largest, has a near-cosmopolitan distribution. This further supports the hypothesis that the common ancestor of all squirrels, living and fossil, lived in North America, as these three most ancient lineages seem to have [[evolutionary radiation|radiated]] from there; if squirrels had originated in [[Eurasia]], for example, one would expect quite ancient lineages in [[Africa]], but African squirrels seem to be of more recent origin.<ref name = tolweb />

The main group of squirrels can be split into five subfamilies: the [[Callosciurinae]], 60 species mostly found in [[South East Asia]]; the [[Ratufinae]], 4 cat-sized species found in [[South Asia|south]] and [[southeast Asia]]; the [[Sciurinae]], which contains the [[flying squirrel]]s (Pteromyini) and the [[Sciurini|tree squirrels]], 83 species found worldwide;<ref>Steppan, S. J. B. L. Storz, and R. S. Hoffmann. 2004. [http://www.bio.fsu.edu/~steppan/Steppan_et_al_Sciuridae.pdf Nuclear DNA phylogeny of the squirrels (Mammalia: Rodentia) and the evolution of arboreality from c-myc and RAG1]. Molecular Phylogenetics and Evolution, 30:703-719.</ref> [[Sciurillinae]], a single [[South America]]n species; and [[Xerinae]], which includes three [[Tribe (biology)|tribes]] of mostly terrestrial squirrels, including the [[Marmotini]] ([[marmot]]s, [[chipmunk]]s, [[prairie dog]]s, and other [[Holarctic]] ground squirrels), [[Xerini]] (African and some Eurasian ground squirrels), and [[Protoxerini]] (African tree squirrels).

=== Taxonomy list ===

* [[Basal (evolution)|Basal]] and ''[[incertae sedis]]'' Sciuridae (all [[fossil]])
** ''[[Hesperopetes]]''
** ''[[Kherem (genus)|Kherem]]''
** ''[[Lagrivea]]''
** ''[[Oligosciurus]]''
** ''[[Plesiosciurus]]''
** ''[[Prospermophilus]]''
** ''[[Sciurion]]''
** ''[[Similisciurus]]''
** ''[[Sinotamias]]''
** ''[[Vulcanisciurus]]''
* Subfamily [[Cedromurinae]] (fossil)
* Subfamily [[Ratufinae]] – Oriental giant squirrels (1 genus, 4 species)
* Subfamily [[Sciurillinae]] – neotropical pygmy squirrel ([[monotypic]])
* Subfamily [[Sciurinae]]
** Tribe [[Sciurini]] – tree squirrels (5 genera, about 38 species)
** Tribe [[Pteromyini]] – true flying squirrels (15 genera, about 45 species)
* Subfamily [[Callosciurinae]] – Asian ornate squirrels
** Tribe [[Callosciurini]] (13 genera, nearly 60 species)
** Tribe [[Funambulini]] palm squirrels (1 genus, 5 species)
* Subfamily [[Xerinae]] – terrestrial squirrels
** Tribe [[Xerini]] – spiny squirrels (3 genera, 6 species)
** Tribe [[Protoxerini]] (6 genera, about 50 species)
** Tribe [[Marmotini]] – ground squirrels, marmots, chipmunks, prairie dogs, etc. (6 genera, about 90 species)