A new porcupine (Rodentia, Erethizontidae) from the early-middle Miocene of Patagonia

CANDELA

AMEGHINIANA

ASOCIACION PALEONTOLOGICA ARGENTINA

Año: 2003 p. 483 - 494

0002-7014

A new erethizontid, Branisamyopsis australis gen. et sp. nov., from Colhuehuapian sediments (early Miocene) of the Sarmiento Formation cropping out at Gran Barranca, Chubut Province, Argentina, is described. The new genus is also identified in the middle Miocene (Collón Cura Formation) at Cañadón del Tordillo (Neuquén, Argentina). The comparative study of the mandibular and tooth morphology of erethizontids indicates that Branisamyopsis australis gen. et sp. nov. is closely related to Patagonian porcupines Eosteiromys Ameghino and Steiromys Ameghino. Branisamyopsis australis gen. et sp. nov. shows that extinct erethizontids reached their greatest taxonomic diversity during the Colhuehuapian. The cheektooth morphology of Patagonian Colhuehuapian erethizontids could correspond to different dietary adaptations. The temporal and geographic distribution and the phylogenetic affinities of Branisamyopsis, Eosteiromys and Steiromys suggest that Patagonia was a marginal area of differentiation for the family, unconnected with the radiation of living porcupines.