A new acaremyid rodent (Caviomorpha, Octodontoidea) from Scarritt Pocket, Deseadan (late Oligocene) of Patagonia (Argentina)

Abstract

Octodontoidea is the most diverse caviomorph clade presently represented in South America by Octodontidae, Echimyidae and Abrocomidae. Some evidences suggests that in the past they were taxonomically even more diverse, including several independent lineages with no modern representatives, sometimes considered as families. One of them is Acaremyidae, known until now from the Colhuehuapian?Colloncuran (early to early-middle Miocene) of Patagonia. Here we describe a new octodontoid rodent from the Deseadan (late Oligocene) of Scarritt Pocket (Patagonia): Changquin woodi gen. et sp. nov. Cladistic analysis indicates that the new species is an acaremyid related to the Santacrucian (early Miocene) Sciamys. Acaremyidae was recovered as a monophyletic group. C. woodi gen et sp. nov. the oldest representative of Acaremyidae, extends the family biochron back to the late Oligocene, and indicates that acaremyids differentiated before the Deseadan. C. woodi represents the first Deseadan octodontoid displaying protohypsodont cheek teeth, showing that the Deseadan was a period of important diversification for octodontoids as it was for the cavioids. C. woodi adds a new element to the faunal differences observed between Patagonian and Bolivian Deseadan faunas. A new U-Pb LA-ICPMS date (27.17 +/- 0.54 Ma) for Scarritt Pocket is provided.