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Amazon swamps were home to seven crocodile species

25 February 2015

Title: A Miocene hyperdiverse crocodylian community reveals peculiar trophic dynamics in proto-Amazonian mega-wetlands

Authors: Rodolfo Salas-Gismondi , John J. Flynn , Patrice Baby , Julia V. Tejada-Lara , Frank P. Wesselingh , Pierre-Olivier Antoine

Journal: Proceedings of the Royal Society B

A study in Proceedings of the Royal Society B reveals that 13 million years ago the Amazon was swarming with crocodiles. Seven species lived side by side including two large bodied species which could grow up to 8 metres long.

The study is the result of more than a decade of work on two Amazon bone-beds in what is now north-western Peru. Work on the fossilised beds have unearthed a hyper diverse assemblage of creatures who lived in the region millions of years ago including the largest number of co-existing crocodile specials at any time in Earth’s history.

Of the seven crocodiles unearthed three have never been seen before and are described for the first time in Proceedings of the Royal Society B today. The team say one of the strangest new discoveries was a short snouted caiman. By analysing the fragments of skull and teeth the team calculated that the snout of the newly discovered Gnatusuchus pebasensis was wider than it was long.

The team say that the fossilised megawetlands were probably so rich in different crocodile species because of the abundance of food sources - many of which are no longer a large part of the modern crocodile’s menu.

The researchers think the Gnatusuchus pebasensis might have used its stout snout to shovel the muddy bottoms of the swaps to dig for clams and other molluscs which lived in the region at the time but which disappeared 10.5 million years ago when the wetland system transformed into the rainforest and river.

The vastness of the Amazon rainforest means that exposure to rocks - and to the fossils rocks preserve - is very limited so the fossilised bone beds offered an extremely rare insight into the ancient ecosystems. The team hope that their study which reveals some of the ecosystem of that time might help fill in the gaps in our understanding of the origins of current Amazonian biodiversity.