First small mammals assemblage (Didelphimorphia and Rodentia) from upper Pliocene in northwestern Argentina

ORTIZ P. E.; BABOT, J.; JAYAT, J. P.; PARDIÑAS, U. F. J.; GARCÍA LÓPEZ D.

Mendoza

Congreso; X Imternational Mammalogical Congress; 2009

IADIZA-CONICET-SAREM

Small mammals record for Pliocene in Northwestern Argentina is scarce. In this region, the period is mainly represented by the Uquía Formation, mostly characterized by medium and large mammals that document the GABI. We describe the first fossil assemblage of small mammals for Pliocene times in Northwestern Argentina. The remains were found in the middle unit of Uquía Formation, corresponding to the Marplatan stage, in Jujuy province. The assemblage is constituted by 32 individuals belonging to 9 species, including didelphimorph marsupials, sigmodontine rodents, and caviomorph rodents. The sample is dominated by an undescribed phyllotine, constituting more than 90% of the recorded specimens. These specimens show morphological affinities with the nowadays widespread Calomys and Eligmodontia, but some cranial, mandibular and dental characters indicate that they pertain to a new genus. The species registered characterize open environments with rocky outcrops in Puna and High Andean eco-regions. Moreover, the record of the Octodontidae indet. supports the idea of an arid or semiarid environment. This report constitutes the first mention in the fossil record for taxa assignable to N. amoenus, and the oldest record for specimens that can be referred to A. sublimis and A. albiventer.