New insights into the origins of Amazonian biodiversity
Based on a 13-million-year-old deposit found in the Peruvian Amazon containing seven species of fossilized crocodiles, a team from ISEM (University of Montpellier, IRD, CNRS) in partnership with Géosciences-Environnement Toulouse, Paul Sabatier University/CNRS/IRD) and the Natural History Museum of Lima (Peru), sheds light on the origin of the Amazon's exuberant biodiversity.
These results have just been published in the journal Proceedings of the Royal Society B.
An unexpected discovery
Since 2002, this international team has been exploring northeastern Peru and excavating fossil-rich layers dating back to the Miocene epoch.
"Only fossils can provide us with a better understanding of how the Amazonian ecosystem emerged and characterize how it functioned in the past. And these fossils, particularly vertebrate fossils, are very rare! In other words, given the appalling conditions on the ground, discovering such a deposit is a real tour de force," explains Pierre-Olivier Antoine, professor of paleontology at the University of Montpellier and co-author of the article.
"Every time such a window into the past opens, it provides completely new data on these past ecosystems. And what we find there is rarely what we expected to discover," says John Flynn, co-author of the article and curator of fossil mammals at the American Museum of Natural History in New York .
Hyperdiversity linked to unexpected diets
The abundance of crocodile species discovered in the deposit is probably due to the use of a food source that is unusual for modern crocodiles: shellfish (such as clams, mussels, and whelks). Indeed, among the seven crocodile species described in the article, three of them, completely new to science, probably ate shellfish. The strangest is Gnatusuchus pebasensis, a small duck-billed caiman with bulbous teeth, which probably used its open mouth to stir up the muddy bottom of water holes and crunch on clams and other shellfish...
"When we analyzed the skull and jaws of Gnatusuchus and deduced that it crunched shellfish using lateral head movements similar to those of platypuses, we immediately realized that this was an exceptional animal," recalls the lead author of the article, Rodolfo Salas-Gismondi, director of the paleontology department at the Natural History Museum in Lima and doctoral student at the Institute of Evolutionary Sciences in Montpellier (University of Montpellier/IRD/CNRS).
Alongside the shell-eating caimans, the researchers also discovered the first fossil representative of the modern Amazonian caiman, with a longer, narrower snout adapted to more traditional prey.
Study partners:
- Patrice Baby from the Research Institute Research Development (Geosciences-Environment Toulouse, Paul Sabatier University/CNRS/IRD)
- Julia Tejada-Lara from the Natural History Museum of Lima (Peru) and the University of Florida in Gainesville
- Frank Wesselingh from the Naturalis Biodiversity Center in Leiden (Netherlands)
This study was funded by NASA, the Field Museum (Chicago), the American Museum of Natural History (Frick Fund, New York), the ECLIPSE II Program, the National Center for Research , and the Research Institute Research Development.
Researcher contact information:
- Rodolfo Salas-Gismondi
- Pierre-Olivier Antoine – +33 (0)4 67 14 32 51