Sigmodontinos (Mammalia, Rodentia) del Pleistoceno tardío del Valle de Tafí (Tucumán, Argentina): taxonomía, tafonomía y reconstrucción paleoambiental

Abstract

An exceptionaliy rich rodent assemblage of Lujanian age (latest Pleistocene) at La Angostura (26°55´30"S, 65°41´50" W, Tafí valley, Tucuman province; 1900 m above sea level) provides the first evidence of sigmodontine rodents in the fossil record of northwestern Argentina. Identified taxa are: Abrothrix illuteus Thomas, Akodon sp., Necromys cf. N. lactens ( Thomas), Oxymycterus cf. O. paramensis Thomas, Oligoryzomys cf. O. flavescens (Waterhouse), Oligoryzomys cf. O. “longicaudatus” (Benett), Andinomys edax Thomas, Calomys cf. C. laucha/musculinus, Neotomys ebriosus Thomas, Phyllotis sp., Reithrodon auritus (Fischer), and †Tafimys powelli Ortiz et al. These include the first fossils of the genera Neotomys Thomas and Andinomys Thomas in Argentina. Taphonomic analysis indicates that the assemblage is a fossil owl pellet accumulation. Consequently, it can be assumed to be a biased representation of the small mammal fauna of a relatively small area over a relatively brief time span. This association has no modern analogue because today these species live at different altitudinal vegetation belts. The fauna indicates a community from the high-altitude grassland ecotone, with elements of the Yungas, Puna and High Andeans. Temperatures may have been lower than today. Although the species composition is similar to the modern sigmodontine community in the area, quantitative variations in proportional representation can be attributed to Holocene climatic conditions and, probably, to the impact of human populations in historical times.