Final Gondwana breakup: The Paleogene South American native ungulates and the demise of the South America?Antarctica land connection

REGUERO, M.; GELFO, JAVIER N.; LOPEZ, G; BOND, M.; ABELLO, M. A.; SANTILLANA S. N.; MARENSSI, S. A,

GLOBAL AND PLANETARY CHANGE

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2014 vol. 123 p. 400 - 413

0921-8181

The biogeographic hypothesis more accepted today is that Antarctica (West Antarctica) and southern South America (Magellan region, Patagonia)were connected by a long and narrow causeway(Weddellian Isthmus) between the Antarctic Peninsula and South America since the Late Cretaceous (Campanian) until the Early Paleogene allowing terrestrial vertebrates to colonize new frontiers using this land bridge. Stratigraphically calibrated phylogenies including large, terrestrial native ungulates Litopterna and Astrapotheria taxa reveal long ghost lineages that extended into the Late Paleocene and provide evidence for the minimum times at which these -native ungulates- were present both on Antarctica and South America. Based on these results we estimate that the Weddellian Isthmus was functional as a land bridge until the Late Paleocene. Our data place the disconnection between Antarctica and South America in the Late Paleocene, indicating that the terrestrial faunistic isolation (Simpson´s -splendid isolation-) in South America begun at the end of the Paleocene (~56 to 57 m.y.). This faunistic isolation is documented to have occurred at least 25 Ma before the existence of deepwater circulation conditions in Drake Passage (~30 m.y.) based on the onset of seafloor spreading in the west Scotia Sea region.Wehypothesize that in the early stages of extension (Late Paleocene, ~55 m.y.) awide and relatively shallow epicontinental sea developed between the Antarctic Peninsula and South America drowning the Weddellian Isthmus and preventing the faunal interchange for obligate cursorial terrestrial forms.