Working with scientists from North Carolina State University and the Smithsonian Tropical Research Institute, researchers at the Florida Museum of Natural History on the UF campus name the species in a study published online today in the Journal of Systematic Palaeontology. The study's findings could be useful for understanding the impacts of a warmer climate in the future.
The description of one of the largest known freshwater turtles is based on a nearly complete skull and shell. Brought to life as a critical part of the ecosystem in the recent Smithsonian Channel documentary "Titanoboa: Monster Snake," the 60-million-year-old reptile is the largest turtle from the Paleocene Epoch, reaching about 8 feet in length.
"At that size, I would imagine that it was swimming around without too much fear," said co-author Jonathan Bloch, Florida Museum associate curator of vertebrate paleontology. "The only animals it probably would've had to worry about were the dyrosaurids (ancient crocodile relatives) – we have turtle shells from the same place with bite marks on them."
Lead author Edwin Cadena, now a doctoral candidate at North Carolina State University, conducted the research while working with Bloch and earning his master's at UF.
"The tropics are a very biodiverse region on the planet today, so we're very interested in terms of conservation and our own survival," Bloch said. "Tropical ecosystems are very important, and if you want to understand the region, you have to understand its history, especially in terms of climate change."
Named Carbonemys cofrinii for the coal mine in which it was discovered and Dr. David Cofrin, whose contributions made the paleontological excavations possible, the species is a primitive relative of modern turtles living in the tropics. Specimens, including an exceptionally well-preserved three-dimensional skull, were prepared at the Florida Museum. Using phylogenetic analyses of morphological and molecular data, researchers determined the species belongs in the order Pleurodira, which bend their necks sideways into their shells, rather than Cryptodira, which pull their heads straight back into their shells.
"In tropical South America today you find many pleurodires on the banks and in the water of the rivers, so they are still a critical part of the ecosystem," Bloch said.
Two additional distinct turtle species are discussed in the study but remain unnamed without identifiable skulls. Other animals found in the Paleocene environment in South America include several species of crocodiles, snakes and large fish.
"This discovery is showing us that after the extinction of the dinosaurs, the tropics were a place where animals can actually succeed and get really big," Cadena said. "They had a lot of space and a lot of food sources so they didn't have to worry about competition with other big animals. We're seeing that the tropics 60 million years ago had so much diversity and it keeps that diversity for a long, long time."
Phylogenetic analysis shows the newly described turtle is most closely related to living species in Venezuela and Madagascar, supporting the theory the continents were once connected in northern South America, rather than southern South America through Antarctica. The wet conditions in the tropics make fossil evidence of ancient flora and fauna rare, so much of the study's value is the in the animals' Colombian origin, said Walter Joyce, a researcher at the University of Tubingen.
"We don't know much about the tropics at all," Joyce said. "So everything the Florida group has been getting the last 10 years has been pretty interesting because it's basically new – it's a new part of the world we know nothing about."
Home to the oldest known rainforest ecosystem, the potential for fossils from the tropics to offer insights about animal biogeography and responses to climate change should not be underestimated, Cadena said. Yet, human impacts make the area's future prosperity uncertain.
"Some of the modern living species in the tropics related to these fossils that we found in the mine are in danger of extinction now," Cadena said. "Changes that occurred over millions of years in the past are happening in just a few thousand years – it's kind of sad to see."
Paul Ramey | EurekAlert!
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