SYSTEMATIC REVISION AND EVOLUTIONARY HISTORY OF ACARECHIMYS PATTERSON IN KRAGLIEVICH, 1965 (RODENTIA, CAVIOMORPHA, OCTODONTOIDEA)

ARNAL, MICHELLE; VUCETICH, MARIA; CROFT, DARIN; BARGO, SUSANA; FERNICOLA, JUAN; VIZCAINO, SERGIO

AMEGHINIANA

ASOCIACION PALEONTOLOGICA ARGENTINA

Lugar: Buenos Aires; Año: 2017 vol. 54 p. 1 - 90

0002-7014

The octodontoid rodent Acarechimys 25 was abundant during theearly Miocene and had the widest temporal and geographic distribution of anyextinct caviomorph. Despite this extensive fossil record Acarechimys hasnot been well characterized. In this work, we systematically revise Acarechimys,describe new early?middle Miocene fossils from Argentina and Bolivia,corroborate its monophyly, and study its evolutionary history. Acarechimys hasbrachydont molars, retained deciduous premolars, four crests on upper molars,lowers with variably developed mesolophid and metalophulid II, and absence of mentalforamen in the mandible. Acarechimys includes: Acarechimys leucotheae(late Oligocene, Chubut, Argentina), A. gracilis and A.constans (early Miocene, Chubut and Santa Cruz, Argentina), and A.minutus and A. minutissimus (early?middle Miocene of PatagoniaArgentina, Bolivia, and Colombia). The temporal and geographic distributionssuggest that Acarechimys could have evolved in Patagonia, by the earlylate Oligocene. Its acme was during the late early Miocene in SouthernPatagonia. By the middle Miocene, Acarechimys decreased in diversity andwas last recorded in high latitudes of South America (Patagonia). In lowerlatitudes, the oldest record is from the late early Miocene of Chucal, northernChile, and during the late middle Miocene, the genus is recorded in localitiesof Colombia, Bolivia, and Peru. The available evidence suggests that Acarechimyswas probably not present in lower latitudes (N of ~ 30° S) before the earlyMiocene. The reasons Acarechimys dispersed northward at this time remainto be elucidated, but the timing coincides with a massive disappearance ofother octodontoids from Patagonia.