title: A Miocene hyperdiverse crocodylian community reveals peculiar trophic dynamics in proto-Amazonian mega-wetlands.
abstract: Amazonia contains one of the world's richest biotas, but origins of this diversity remain obscure. Onset of the Amazon River drainage at approximately 10.5 Ma represented a major shift in Neotropical ecosystems, and proto-Amazonian biotas just prior to this pivotal episode are integral to understanding origins of Amazonian biodiversity, yet vertebrate fossil evidence is extraordinarily rare. Two new species-rich bonebeds from late Middle Miocene proto-Amazonian deposits of northeastern Peru document the same hyperdiverse assemblage of seven co-occurring crocodylian species. Besides the large-bodied Purussaurus and Mourasuchus, all other crocodylians are new taxa, including a stem caiman-Gnatusuchus pebasensis-bearing a massive shovel-shaped mandible, procumbent anterior and globular posterior teeth, and a mammal-like diastema. This unusual species is an extreme exemplar of a radiation of small caimans with crushing dentitions recording peculiar feeding strategies correlated with a peak in proto-Amazonian molluscan diversity and abundance. These faunas evolved within dysoxic marshes and swamps of the long-lived Pebas Mega-Wetland System and declined with inception of the transcontinental Amazon drainage, favouring diversification of longirostrine crocodylians and more modern generalist-feeding caimans. The rise and demise of distinctive, highly productive aquatic ecosystems substantially influenced evolution of Amazonian biodiversity hotspots of crocodylians and other organisms throughout the Neogene.
authors.affiliation: Institut des Sciences de l'Évolution, Université de Montpellier, CNRS, IRD EPHE, Montpellier 34095, France Departamento de Paleontología de Vertebrados, Museo de Historia Natural, Universidad Nacional Mayor de San Marcos, Avenida Arenales 1256, Lima 14, Peru rodolfo.salas-gismondi@univ-montp2.fr.
authors.forename: Rodolfo
authors.initials: R
authors.lastname: Salas-Gismondi
authors.affiliation: Division of Paleontology, American Museum of Natural History, New York, NY 10024-5192, USA.
authors.forename: John J
authors.initials: JJ
authors.lastname: Flynn
authors.affiliation: Géosciences-Environnements Toulouse, Université de Toulouse, UPS (SVT-OMP), CNRS, IRD, 14 Avenue Édouard Belin, Toulouse 31400, France Convenio IRD-PeruPetro, Avenida Luis Aldana 320, San Borja, Lima, Peru.
authors.forename: Patrice
authors.initials: P
authors.lastname: Baby
authors.affiliation: Departamento de Paleontología de Vertebrados, Museo de Historia Natural, Universidad Nacional Mayor de San Marcos, Avenida Arenales 1256, Lima 14, Peru Florida Museum of Natural History and Department of Biology, University of Florida, PO BOX 117800, Gainesville, FL 32611, USA.
authors.forename: Julia V
authors.initials: JV
authors.lastname: Tejada-Lara
authors.affiliation: Naturalis Biodiversity Center, P.O. Box 9517, 2300 RA, Leiden, The Netherlands.
authors.forename: Frank P
authors.initials: FP
authors.lastname: Wesselingh
authors.affiliation: Institut des Sciences de l'Évolution, Université de Montpellier, CNRS, IRD EPHE, Montpellier 34095, France.
authors.forename: Pierre-Olivier
authors.initials: PO
authors.lastname: Antoine
mesh_terms: D000489:Alligators and Crocodiles / Q000033:anatomy & histology* / Q000145:classification / Q000502:physiology*; D000818:Animals; D044822:Biodiversity; D005075:Biological Evolution; D005580:Fossils; D049810:Genetic Speciation; D010568:Peru; D010802:Phylogeny; D053833:Wetlands
keywords: Miocene; Pebas System; caimanine crocodylians; durophagy; molluscs; proto-Amazonia