March 27, 2008

Paleontologists Discover Ancient Crocodilian Ancestor

Researchers in Brazil reported their discovery of a new marine crocodile species on Wednesday, showing that the reptiles survived the mass extinction of dinosaurs 65 million years ago.

In the report published in the Proceedings of Royal Society B research journal, paleontologists said they found the new dyrosaurid crocdylomorph in the Poty Quarry, a limestone quarry located close to Recife in northeastern Brazil.

Researchers suggested that the Guarinisuchus munizi survived the Cretaeceous-Palaeogene (K-P) extinction crisis by crossing the Atlantic Ocean before the K"“P boundary and spread into North America and other parts of South America, including the regions of Colombia and Bolivia. The fossils include the skull reaching only 525 mm in length, jaw and vertebrae and represent the most complete member of this group collected in South America to date.

Researchers noted another hypothesis that dyrosaurids could also have dispersed westwards and then south along the marginal basins of the African coast, crossing the Atlantic Ocean from there. However, more evidence is needed to test the hypothesis, they said.

Based on the cervical vertebra, the team estimates that the specimen represents a sub-adult at the time of death. The skull has an elongated tubular rostrum, which is a typical feature of dyrosaurids.

The Dyrosauridae group replaced mosasaurs, or serpentine marine lizards, becoming the dominant marine predators in the Paleocene epoch.

"Based on the discovery, we know that's what happened near the Brazilian coast. Now the question is whether the same happened worldwide. We believe it did," said Alexander Kellner of the National Museum in Rio de Janeiro.

Paleontologists named the creature Guarinisuchus, derived from the word "warrior" in Brazil's Tupi Indian language.  

"One of the reasons we called it a warrior is because it survived the phenomenon that made dinosaurs extinct ... And they were the dominant predators even though this one was relatively small, at 3 meters in length. But we know the size isn't always important, just take the piranha fish," Kellner said.


Photo Courtesy Federal University


On the Net:

"New dyrosaurid crocodylomorph and evidences for faunal turnover at the K"“P transition in Brazil"

National Museum in Rio de Janeiro