An intertropical opossum (Mammalia, Marsupialia, Didelphidae) from the late Middle–Late Pleistocene of austral South America

Abstract

The record of an opossum is reported here coming from a Middle–Late Pleistocene fluvial sedimentary sequence outcropping in the austral Chaco geomorphological region, Santa Fe province. Despite this family has different living forms widely distributed in South American plains, with great tolerance to diverse habitats conditions, the Pleistocene occurrence of didelphoids is very scarce and only limited to Holocene deposits sensu lato from austral pampean plains. The specimen found represents at the moment the only Pleistocene didelphoid opossum from Argentina with an accurate stratigraphical context. In a taphonomic framework, MFA-Pv 1582 shows no evidence of abrasion produced by transport, probably resulting of a very short time-transport. This intertropical form of Didelphis genus from Pleistocene sequences displays undoubtedly novel and sustancial paleoenvironmental and ecomorphological conditions to test in the austral Chaco region. Although the specimen shares a generalized didelphoid form, some morphologies in the humerus are closer with arboreal habits. In this context, added to the sedimentological and stratigraphical framework, it’s possible to suggest that subtropical conditions with some woodlands and wetlands dominate the provenance region of the fossil material, over a late Middle–Late Pleistocene interglacial period.