Long-term mammalian stable isotopic record across the Great American Biotic Interchange

TOMASSINI, RODRIGO; MONTALVO, CLAUDIA; KOCH, PAUL; DOMINGO, SOLEDAD

Londres

Encuentro; 61st Palaeontological Association Annual Meeting; 2017

Imperial College London

The South American late Cenozoic fossil record provides a unique natural laboratory for the study of mammalian paleoecology in the context of changing biotic and abiotic forces. South America remained largely isolated from other continents for more than 50 Ma. First, the presence of emerging land and then, the permanent establishment of the Isthmus of Panama (~3.1?2.7 Ma) triggered an interchange of terrestrial taxa with North America, an event known as Great American Biotic Interchange (GABI). We investigate resource use through stable isotope analysis of mammals from a long-term fossil record from the Pampean Region (La Pampa and Buenos Aires provinces, Argentina) spanning from ~9 Ma to ~12 Ka. Our analyses point to a major shift in resource use by most of endemic herbivorous taxa, as they switched from a pure C3 diet to a mixed C3-C4 diet at the Late Miocene-Early Pliocene. Carnivorous taxa mirrored this shift, with endemic Sparassodonta consuming prey from pure C3 environments, whereas immigrant Felidae preferred prey from mixed C3-C4 areas. Flexible dietary behavior (e.g., gomphotheres, equids), as indicated by our stable isotope data, may have facilitated the successful settlement of some immigrant groups in the Pampean area.