Middle Tertiary marsupials from Central Patagonia (Early Oligocene of Gran Barranca): Understanding South America’s Grande Coupure

GOIN FJ; ABELLO MA; 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 recovered from La Cancha and La Cantera localities, along the southern cliffs 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 five 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 are representative of the most dramatic faunal turnover in South American marsupials (and, probably, of all other mammalian clades present in the continent as well) during the Cenozoic Era, an event named here as the Bisagra Patagónica (“Patagonian Hinge”). This turnover coincides with a sudden fall of global temperatures by the latest Eocene-early Oligocene times.  Some of the features that characterized this turnover are, among marsupials, 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.