A vast diversity of specialized crocodilian species dominated the mega-wetlands of South America before the Amazon River flowed, a remarkable fossil find has revealed.

Rodolfo Salas-Gismondi at the University of Montpellier in France and his colleagues found two bone beds in Peru containing seven species of crocodilian — the largest diversity of such species ever found in one place.

As well as two known large-bodied species, they found five animals that are new to science, including several caimans with teeth that seem to be specialized for consuming shellfish. The numbers of these animals declined as Amazon River systems began forming around 10.5 million years ago, draining the wetlands and allowing more-generalist caiman predators to dominate.

Proc. R. Soc. B 282, 20142490 (2015)