MIDDLE TERTIARY MARSUPIALS FROM CENTRAL PATAGONIA

GOIN, F. J.; ABELLO, M. A.; CHORNOGUBSKY, L.

The paleontology of Gran Barranca: evolution and environmental change through the middle Cenozoic of Patagonia.

Cambridge University Press

Lugar: Cambridge ; Año: 2010; p. 69 - 105

We describe two new marsupial assemblages from GBV-4 “La Cancha” and GBV-19 “La Cantera,” localities at Gran Barranca south of Lake Colhue-Huapi in central Patagonia (Sarmiento Department, Chubut Province, Argentina). These remarkable new faunas (around 400 specimens referable to 24 species, 18 genera, 14 families, and 5 orders)correspond to a time interval Previously unknown for central Patagonia: the post-Mustersan, pre-Deseadan, early Oligocene. A Tinguirirican age (SALMA) can be inferred for the La Cancha levels and fauna (18 species), based on its similarity with the marsupials of Tinguiririca in Chile. In turn, the La Cantera Association (10 species) represents a younger, pre-Deseadan age. The La Cancha marsupials represent the most dramatic faunal turnover in South American marsupials (and probably of all other mammalian clades in the continent as well) during the Cenozoic Era, an event here termed the Patagonian Hinge (“Bisagra Patago´nica”). This turnover coincides with a sudden drop in global temperatures at latest Eocene – early Oligocene time. Some of the features that characterize this turnover among marsupials are the last records of Polydolopiformes and bonapartherioid Bonapartheriformes, the beginning of the Argyrolagoidea (and of hypsodonty in marsupials), a rapid radiation of paucituberculatans, and the development of gigantism among borhyaenid sparassodonts and the last polydolopines.