Horizon 1 1 17 ACL : Articles dans des revues avec comité de lecture répertoriées par l'AERES Proceedings of the Royal Society B-Biological Sciences art. 20142490 [10 p.] Miocene caimanine crocodylians proto-Amazonia Pebas System molluscs durophagy PEROU AMAZONIE AMAZONE COURS D'EAU 2015 fdi:010064020 ENG Proceedings of the Royal Society B-Biological Sciences 0962-8452 ISI:000350797400004 1804 10.1098/rspb.2014.2490 https://www.documentation.ird.fr/hor/fdi:010064020 https://www.documentation.ird.fr/intranet/publi/2015/04/010064020.pdf 282 Horizon (IRD) 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 hyper-diverse 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. 036 ; 082 ; 021 ; 064 UR226 / UR234