Geographic isolation, land connection, and evolution of the terrestrial mammalian associations during the Cenozoic in South America: the carnivorous zone

FORASIEPI, A.M.; CARRILLO, J.D.

Lausanne

Jornada; 11th Swiss Geoscience Meeting; 2013

The physical isolation of the South American continent during most of the Cenozoic resulted in an endemic fauna. The eutherians and metatherians were the major components of the mammalian associations with the carnivorous adaptative zone occupied by metatherian sparassodonts. The Sparassodonta has been registered from the Paleocene to the Pliocene. They were predominantly hypercarnivores and with a broad range of body sizes, locomotory capabilities, and morphologies, including some extreme specializations, such as the sabre-tooth thylacosmilids. Placental Carnivora started to occupy the carnivorous adaptative zone since the Late Miocene in South America. However, after the complete formation of the Panama Bridge, during the Pleistocene, the richness of the placental carnivores massively increased. There was temporal overlap of Sparassodonta and Carnivora during the Late Miocene?Early Pliocene but no ecological superposition. This suggests an opportunistic ecological replacement, as part of a larger faunistic turnover, in contrast to a competitive displacement. The oldest placental carnivores in South America currently found are in Argentina, in the south tip of the continent. Recent discoveries in northern South America provide further information about the interchange with North America. Fossil and and present day distribution of mammals in South America highlight the importance of the tropics and the Andes during the interchange. The diversity of northern immigrants in South America abruptly increased since the Late Miocene, reaching in the Quaternary about half of the total mammalian fauna. In fossil and current terrestrial ecosystems from South America, mammals with North American origin dominate in temperate and high altitude zones, whereas mammals with South American origin dominate in the tropics.