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.
KEYWORDS: Miocene, caimanine crocodylians, proto-Amazonia, Pebas System, molluscs, durophagy
Rodolfo Salas-Gismondi, John J. Flynn, Patrice Baby, Julia V. Tejada-Lara, Frank P. Wesselingh and Pierre-Olivier Antoine. 2015. A Miocene Hyperdiverse Crocodylian Community reveals Peculiar Trophic Dynamics in proto-Amazonian Mega-Wetlands. Proceedings of the Royal Society B.
Crocs rocked pre-Amazonian Peru: New research uncovers 7 crocodile species in single 13-million-year-old bone bed http://phy.so/344017318 via @physorg_com
Ancient Croc with 'Shovel Mouth', Likely Enjoyed Clam Dinners, Roamed the Amazon http://shar.es/1WdZVx Photos: http://shar.es/1WdZED via @LiveScience
Three New Prehistoric Caiman Species Found in Peruvian Amazonia: http://www.sci-news.com/paleontology/science-gnatusuchus-pebasensis-three-new-prehistoric-caiman-species-peruvian-amazonia-02536.html