title: Middle Eocene rodents from Peruvian Amazonia reveal the pattern and timing of caviomorph origins and biogeography.
abstract: 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.
authors: Institut des Sciences de l'Évolution, UMR-CNRS 5554, CC064, Université Montpellier 2, 34095 Montpellier, France.
authors: Pierre-Olivier
authors: PO
authors: Antoine
authors: Laurent
authors: L
authors: Marivaux
authors: Darin A
authors: DA
authors: Croft
authors: Guillaume
authors: G
authors: Billet
authors: Morgan
authors: M
authors: Ganerød
authors: Carlos
authors: C
authors: Jaramillo
authors: Thomas
authors: T
authors: Martin
authors: Maëva J
authors: MJ
authors: Orliac
authors: Julia
authors: J
authors: Tejada
authors: Ali J
authors: AJ
authors: Altamirano
authors: Francis
authors: F
authors: Duranthon
authors: Grégory
authors: G
authors: Fanjat
authors: Sonia
authors: S
authors: Rousse
authors: Rodolfo Salas
authors: RS
authors: Gismondi
mesh_terms: D025041:Animal Migration; D000818:Animals; D005075:Biological Evolution; D005580:Fossils; D049690:History, Ancient; D010568:Peru; D058974:Phylogeography; D012377:Rodentia / Q000033:anatomy & histology / Q000145:classification; D014070:Tooth / Q000033:anatomy & histology