The record of Paleogene Ugulates and the demise of the South America-Antarctica land connection

GELFO J. N.; LÓPEZ, G. M; ABELLO, M. A.; REGUERO, M.,; SANTILLANA, S.; MARENSSI, S. A.

Granada

Simposio; The Scotia Arc: Geodynamic Evolution and Global Implications; 2013

The history of dispersal and evolution of the Antarctic land mammal faunas is closely related to the fate of the land bridge between South America and the Antarctic Peninsula and in the end to its interruption during the Paleogene. The greatest insight can be obtained from taxa that were the most unlikely to have rafted, swum, or flown across expansive marine barriers (e.g. those that were large-bodied and inferred to have been restricted to terrestrial locomotion). In contrast to Mesozoic mammalian lineages (i.e. Gondwanatheria)already present in the ancient Gondwana continent, therian mammals passed from North to South America by the ?Late Cretaceous or early Paleocene (Goin et al., 2006). Setting aside marsupials, which arrived to Australia via Antarctica, the fossil record of South American native ungulates (SANU) are reliable tools in order to test paleogeographic hypotheses. Particularly, the stratigraphic calibration of Antarctic and South American SANUs phylogenies (i.e. litoptern Sparnotheriodontidae and astrapothere Astrapotheriidae) here presented, evidence the minimum age (middle Paleocene) at which their common ancestor were present on both land masses. Additionally, Notoungulata, the most diverse SANU group, provides further paleogeographic information. Their absence from Antarctic Paleogene and Patagonian middle Paleocene (Peligran Land Mammal Age) records, suggest that their radiation occurred after the final break-up of both continents.