Antoine P. O. auteur aut IRD Marivaux L. auteur aut IRD Croft D. A. auteur aut IRD Billet G. auteur aut IRD Ganerod M. auteur aut IRD Jaramillo C. auteur aut IRD Martin T. auteur aut IRD Orliac M. J. auteur aut IRD Tejada J. auteur aut IRD Altamirano A. J. auteur aut IRD Duranthon F. auteur aut IRD Fanjat G. auteur aut IRD Rousse Sonia auteur aut IRD Gismondi R. S. auteur aut IRD text journalArticle eng text/pdf born digital access The long-term isolation of South America during most of the Cenozoic produced a highly peculiar terrestrial vertebrate biota, with a wide array of mammal groups, among which caviomorph rodents and platyrrhine primates are Mid-Cenozoic immigrants. In the absence of indisputable pre-Oligocene South American rodents or primates, the mode, timing and biogeography of these extraordinary dispersals remained debated. Here, we describe South America's oldest known rodents, based on a new diverse caviomorph assemblage from the late Middle Eocene (approx. 41 Ma) of Peru, including five small rodents with three stem caviomorphs. Instead of being tied to the Eocene/Oligocene global cooling and drying episode (approx. 34 Ma), as previously considered, the arrival of caviomorphs and their initial radiation in South America probably occurred under much warmer and wetter conditions, around the Mid-Eocene Climatic Optimum. Our phylogenetic results reaffirm the African origin of South American rodents and support a trans-Atlantic dispersal of these mammals during Middle Eocene times. This discovery further extends the gap (approx. 15 Myr) between first appearances of rodents and primates in South America. specialized South America Hystricognathi Mid-Eocene climatic optimum phylogeny Platyrrhini 080 020 064 279 1732 1319-1326 2012 0962-8452 https://www.documentation.ird.fr/hor/fdi:010055715 10.1098/rspb.2011.1732 0962-8452 [F B010055715] https://www.documentation.ird.fr/hor/fdi:010055715 https://www.documentation.ird.fr/intranet/publi/2012/04/010055715.pdf Accès réservé (Intranet de l'IRD) IRD - Base Horizon / Pleins textes 2012-05-04 2017-08-23 fdi:010055715 fre