An analysis of Antartic Paleogene terrestrial mammal biogeography: evidence for the existence of vicariance and dispersal patterns caused by geological event

REGUERO, MARCELO A.; ABELLO, MARÍA A.; POSADAS, PAULA; ORTIZ JAUREGUIZAR, EDGARDO; CHRONOGUBSKY, L.; SANTILLANA, S.N.; CORIA, N.R.

Goa

Simposio; XII International Symposium on Antartic Earth Sciences; 2015

SCAR-NCAOR

West Antarctica terrestrial mammals were diverse, geographically widespread,stratigraphically long lived and largely terrestrial: they therefore provide an almost ‗ideal? case study in Southern Paleogene biogeography. This mammal association includes eutherian (SAANUs Litopterna and Astrapotheria), metatherian (marsupials Polydolopidae, Derorhynchidae and Microbiotheria) and nontherian mammals (Gondwanatheria and Meridiolestida). A more complex picture of the origin of the Cenozoic Antarctic and South American mammalian faunas is starting to emerge, showing integration of faunal elements from different biogeographic events: surviving members of Mesozoic non-therian mammalian lineages, metatherian and eutherian lineages that presumably dispersed to Antarctica in the latest Cretaceous or early Paleocene. These biogeographic events are thought to be linked to geological events of connection and disconnection of these two land masses (Antarctica and South America). From the results obtained we conclude that the biogeographic histories of eutherians(Astrapotheria and Litopterna) were different from those of metatherians (i.e. Polydolopidae), but all of them support the hypothesis of an early stage (late Paleocene) of the paleogeogeographic event leading to the development of a shallow epicontinetal sea which might be interpreted as the earliest tectonicphase (Paleocene) that eventually later led to the opening of the Drake Passage (Miocene). These analyses reveal biogeographical patterns that closely correlate with palaeogeography. The conclusions drawn from the biogeographical analyses of two eutherian and one metatherian clades reinforce the hypothesis that vicariance and dispersal patterns documented in the early Paleogene between West Antarctica and Patagonia are linked to geological events like an early stage of rifting produced stretching causing crustal thinning and widespread subsidence during the Paleocene leading to the development of a shallow but wide epicontinetal sea.