The number of species in the genus is subject to change.
In 2005, Thorington & Hoffman- whose taxonomic interpretation is followed by the IUCN website- accepted 28 species in the genus:[a]
In 2015, 15–17 species were left in the genus Sciurus after de Vivo & Carmignotto comprehensively reviewed South American Sciuridae for the first time in many decades and proposed numerous changes; synonymising some species and many subspecies, splitting another species, and naming new species. They followed Joel Asaph Allen's unsatisfying 1914 attempt in splitting the genus Sciurus by raising the South American subgenera to the rank of genus, adding Urosciurus to Hadrosciurus, and splitting the genus Guerlinguetus in three. Their taxonomic treatment might also require Sciurus deppei to be moved to Notosciurus.[3]
A 2020 paper published on the taxonomy of Sciurinae split Sciurus into multiple new genera and elevated several subgenera. The paper included genetic sampling from almost all recognized species and recommends the following species assignments:[4]
Additionally, the paper suggests moving Andean squirrel back to subtribe Microsciurina, the dwarf squirrels, and assigns it to the newly described genus Leptosciurus. The paper's findings agree with prior assessments to synonymize Richmond's squirrel into Red-tailed squirrel and reassigns the Red-tailed squirrel into the previously monotypic Asian genus Syntheosciurus, also in Microsciurina. The paper did not include genetic sampling or taxonomic suggestions for gilvigularis, meridionalis, sanborni, or flammifer.
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