Palaeoenvironmental constraints on the diversity of eutherian terrestrial mammals through the Cenozoic of South America, and the emergence of\ud the modern-day latitudinal biodiversity gradient on the continent

South America has a unique geobiological history that is at heightened risk from the current climate emergency. Its fossil record provides empirical evidence of long-term interactions between biodiversity and climate, but our understanding of South America’s faunal evolution is still in its infancy. Applying subsampling and Bayesian approaches to a comprehensive dataset of South American terrestrial eutherian mammal fossil occurrences, I demonstrate increases in diversity throughout the Paleogene, resulting from several intervals of high speciation rate. The remainder of the Cenozoic is characterized by greater variability, including a diversity peak in the late Miocene and pulses of heightened extinction rate in the Plio-Pleistocene. These results suggest that the present-day latitudinal biodiversity gradient first appeared in South America in the Plio-Pleistocene, at a similar time as proposed for North American mammals. This appears to have been driven by a decline in mean annual temperatures at higher latitudes in South America, in tandem with an increase in precipitation at lower latitudes that might have been accentuated by Andean uplift in the Pleistocene. Although the Great American Biotic Interchange played a role, Andean uplift appears to have been the primary underlying mechanism driving eutherian diversity patterns in the Cenozoic, radically reshaping the continent’s climate and habitats