An international group of paleontologists writing in the journal Nature Communications has described two new prehistoric species of crocodile from fossils found in the region of Urumaco, Venezuela.

Their study has also revealed that 14 crocodile species existed in South America 9 to 5 million years ago during the late Miocene, and at least 7 of them lived in the same area at the same time.

The deltas of the Urumaco, a river on the Gulf of Venezuela that no longer exists, and the Amazonas, boasted an abundance of extremely diverse, highly specialized species of crocodile that has remained unparalleled ever since, according to the study.

“Venezuela’s fossils include all the families of crocodile species that still exist all over the world today: the so-called true crocodiles (Crocodylidae); the Alligatoridae, which, besides the true alligators, also include caimans; and the gharials (Gavialidae), which are characterized by their extremely long, thin snouts and are only found in Southeast Asia nowadays.”

“Gharials occupied the niche in the habitat that was filled by dolphins after they became extinct,” said senior author Dr Sánchez-Villagra from the University of Zurich.

While studying Miocene crocodile fossils from the Urumaco region, the team discovered two new species – Globidentosuchus brachyrostris, a creature that belonged to the caiman family and had spherical teeth, and Crocodylus falconensis, a crocodile that grew up to over 13 feet (4 m) long.

“With its spherical teeth Globidentosuchus brachyrostris most likely specialized in shellfish, snails or crabs.”

“Giant crocodiles, which grew up to 39 feet (12 m) long, fed on turtles, giant rodents and smaller crocodiles.”

“There were no predators back then in South America that could have hunted giant turtles or rodents. Giant crocodiles occupied this very niche,” added first author Dr Torsten Scheyer, also from the University of Zurich.

The unusual variety of species in the coastal and brackish water regions of Urumaco and Amazonas came to an end around 5 million years ago when all the crocodile species died out. The reason behind their extinction, however, was not temperature or climate changes – temperatures in the Caribbean remained stable around the Miocene-Pliocene boundary.

“Instead, it was caused by a tectonic event. The Andean uplift changed the courses of rivers. As a result, the Amazon River no longer drains into the Caribbean, but the considerably cooler Atlantic Ocean,” Dr Sánchez-Villagra said.

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Bibliographic information: T. M. Scheyer et al. Crocodylian diversity peak and extinction in the late Cenozoic of the northern Neotropics. Nature Communications 4, article number: 1907; doi: 10.1038/ncomms2940