Résumé
The Eocene−Oligocene transition (EOT, ca. 34 Ma) marked the most dramatic global climatic cooling of the Cenozoic. On a planetary scale, palaeontological evidence suggests that this transition was associated with major faunal turnovers, now regarded as a mass extinction crisis. In South America, there is no consensus on the response of the endemic mammals to this transition. Here, using a vetted fossil dataset and cutting-edge Bayesian methods, we analysed the dynamics of South American mammal (SAM) diversification and their possible drivers across latitude (tropical vs. extratropical), taxonomic groups, and trophic guilds throughout the Eocene−Oligocene (ca. 56−23 Ma). Our results did not evidence any mass extinction among SAMs at the EOT. Instead, they experienced a gradual and long-term diversity decline from the middle Eocene to the early Oligocene, followed by a sudden waxing-and-waning diversity associated with a large taxonomic – but not ecological – turnover. Tropical and extratropical lineages have had very distinct macroevolutionary histories, and no effective change in tropical diversification rates was found. Diversity-dependent effects, temperature, and Andean uplift were recovered as probable drivers of SAM diversification across the period but not the abundance of open landscapes, thereby rejecting the common hypothesis linking Oligocene faunal changes to grassland expansion.