Neoreomys and Scleromys (Rodentia, Hystricognathi) from the Pinturas Formation, late Early Miocene of Patagonia, Argentina

Abstract

The rodent genera Neoreomys and Scleromys Ameghino from the late Early Miocene Pinturas For-mation (Ameghino´s «Astrapothericulan» beds) of Patagonia are here studied. A new species for each genus are recognized: Neoreomys pinturensis sp. nov., Scleromys quadrangulatus sp. nov. They are recorded exclusively in this unit and represent the oldest record of these genera. Both species differ from the typical Santacrucian species N. australis and S. osbornianus, respectively, by having less hypsodont cheek teeth with more persistent and larger flexi and flexids. These characters indicate a more primitive condition of their dentitions, and sug-gest they are their potential structural ancestors. Neoreomys australis and Scleromys osbornianus are also recorded in the Pinturas Formation, but they mostly occur in higher stratigraphic levels than their «Pinturan» counterparts.