ancient crocodilian species
February 26, 2015

Seven ancient crocodilian species discovered in Amazon

Chuck Bednar for redOrbit.com - @BednarChuck

Researchers from the American Museum of Natural History and the Museum of Natural History in Lima, Peru have unearthed an incredible group of seven-different ancient crocodile species in what the western Amazon region of what is now northeastern Peru.

Crocodile fossils

Researchers uncovered fossils from seven different species of crocodiles that lived together about 13 million years ago in the Pebas Formation in what is now the Amazon Basin of northeastern Peru. Their skulls and jaws, shown here, are extremely diverse: (1) Gnatusuchus pebasensis, (2) Kuttanacaiman iquitosensis, (3) Caiman wannlangstoni, (4) Purussaurus neivensis, (5) Mourasuchus atopus, (6) Pebas Paleosuchus, and (7) Pebas gavialoid. The three new species (1-3) are shown in illustrations below the respective fossils. Reconstructions by Javier Herbozo. (Credit © Rodolfo Salas-Gismondi)

According to USA Today, the new fossils are of crocodilians that inhabited the same region of swampland approximately 13 million years ago. Those species range from “a powerful predator as long as a stretch limousine to a newfound croc with bulbous teeth for crushing clams.”

The find, which was detailed this week in the journal Proceedings of the Royal Society B, was the result of more than a decade of work in Amazonian fossil beds, the researchers said. It also marks the largest number of crocodile species ever found co-existing in one place at anyone one time, which was likely due to an abundant amount of food in the form of mollusks.

“The modern Amazon River basin contains the world’s richest biota, but the origins of this extraordinary diversity are really poorly understood,” explained co-author John Flynn, Frick Curator of Fossil Mammals at the AMNH. “Because it’s a vast rain forest today, our exposure to rocks – and therefore, also to the fossils those rocks may preserve – is extremely limited.”

“So anytime you get a special window like these fossilized ‘mega-wetland’ deposits, with so many new and peculiar species, it can provide novel insights into ancient ecosystems,” he added. “And what we’ve found isn’t necessarily what you would expect.”

Some history

Approximately 10.5 million years ago, before the Amazon basin had its river, it was home to a large wetland system filled with swamps, lakes, and rivers that drained northwards towards the Caribbean instead of eastwards towards the Atlantic Ocean, the authors noted. Learning which types of creatures lived there at the time may help understand modern Amazon biodiversity.

While invertebrates such as mollusks and crustaceans have been abundant in Amazonian fossil deposits, evidence of vertebrates other than fish have been very rare, they added. Flynn and his colleagues have been working at the fossil outcrops of the Pebas Formation in northeastern Peru, which has preserved species from the Miocene, including the newly discovered crocodiles.

Three of the species have never been seen before, and include a short-faced caiman with globular teeth known as the Gnatusuchus pebasensis. This species is believed to have used its snout to dig for clams and other mollusks in mud bottoms, and the increase of shell-crunching (durophagous) crocs like it are associated with a peak in mollusk diversity and numbers.

Gnatusuchus pebasensis

This model is a life reconstruction of the head of Gnatusuchus pebasensis, a 13-million-year-old, short-faced crocodile with globular teeth that was thought to use its snout to "shovel" mud bottoms, digging for clams and other mollusks. Model by Kevin Montalbán-Rivera. (Credit © Aldo Benites-Palomino)

Blunt snout, globular teeth

The scientists also found the first-ever unambiguous fossil representative of the living smooth-fronted caiman Paleosuchus, which had a longer and higher snout that would have been suitable for catching a variety of prey, including fish and other active swimming vertebrates.

In an interview with USA Today, co-author Rodolfo Salas-Gismondi of the Museum of Natural History in Lima called the find “amazing.” He went on to explain in a statement that he and his fellow researchers had uncovered a time in which the ancient wetland ecosystem had peaked in term of size and complexity, just before the rise of the modern Amazon River system.

“At this moment, most known caiman groups co-existed: ancient lineages bearing unusual blunt snouts and globular teeth along with those more generalized feeders representing the beginning of what was to come,” he added. As the modern Amazon River system emerged, there was a sharp decline in mollusk populations, leading durophagous crocodile species to become extinct.

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