RALEIGH — A team of paleontologists including scientists from N.C. State University has discovered the fossil remains of a new species of dining table-size freshwater turtle that apparently lived side-by-side with the 50-foot snakes and super-size crocodiles that they had found earlier in the same Colombian coal mine.
Carbonemys cofrinii, or coal turtle, was well over six feet long from nose to tail. It represents a rapid increase in size from the largest known to have lived just before it, which were about two feet long. That makes it an intriguing piece of the evolutionary puzzle.
In part, said the scientists, that growth spurt may have been a Darwinian strategy to fight off the giant crocs by making the turtle simply too big for dinner.
It was so large that it may actually have been chomping on some of the smaller crocodiles itself, said Dan Ksepka, an NCSU paleontologist and a research associate at the N.C. Museum of Natural Sciences. Once it grew to its full size, nothing much was going to be able to eat it.
The shell of the turtle they found had bite marks from a couple of crocodile attacks, but none that came close to piercing the thick carapace. The head was equipped with surprisingly large and powerful jaws.
Ksepka and NCSU doctoral student Edwin Cadena were among the authors of a research paper on the turtle published Thursday in the Journal of Systematic Paleontology.
Cadena was scouting for fossils in 2007 in the Cerrejón mine in northern Colombia when he spied part of the turtles shell protruding from clay-based rock about 120 feet down in the pit.
It took six days of painstaking labor with a hand broom and a screwdriver to uncover the full remains of the shell.
It was only when I was finished do I see that it was something different than we had found before, he said.
The two NCSU scientists have a facility for discovering outsize species. Ksepka was part of a team that found the remains of giant penguins in New Zealand.
Cadena, meanwhile, had discovered bones from the giant snake in 2005 in the same coal mine, though he initially believed it was a crocodile fossil. The snake Titanoboa cerrejonensis a water-dwelling constrictor, weighed an estimated 2,500 pounds and was more than a yard in diameter.
The open-pit mine is among the worlds largest, at 30 miles long by five miles wide. The turtle, snake and two large species of crocodiles found there lived about 60 million years ago, in the late Paleocene period.
The team of scientists, which includes representatives from the Smithsonian Tropical Research Institute in Panama and the Florida Museum of Natural History, is interested in the flora and fauna that lived there during that time not just because of their size, but because they are part of an explosion of species in the tropics.
Maybe we can understand more about why the tropics are so diverse now if we can build a good record to help us understand what happened then, Cadena said.
It was an interesting time. The dinosaurs had just died off, and global temperatures rose to about 11 degrees warmer than today. The warmer temperature, Cadena said, almost certainly helped make the size of the turtle possible.
Scientists have all kinds of questions about the plants and animals of that time and place, but paleontology can be difficult in the region because so much is covered by jungle. That makes the outsize coal mine an extraordinary window into the tropical past: It offers both a deep look under the soil of the region and a broad one, too.
You can look at kilometers and kilometers of the same time layer, Cadena said.
The information that they hope to glean from the turtle and other species found there could help understanding not only of the evolution of that time and place, but also how different species react to changes in global temperature.
That could be crucial in helping develop practical plans for dealing with the effects of global warming, he said, by helping understand which species are most likely to be affected.
Only one freshwater turtle species is known to have grown larger, by a couple of feet. An example of that one was found in Venezuela; it lived just 5 million to 6 million years ago.
The two are related, and Cadena said paleontologists are looking for others that lived in the tens of millions of years between them. That would close a massive gap in the understanding of turtle evolution and yield perhaps more information on how the turtles evolved as the climate cooled.
The scientists also expect to find more examples of the species theyve already discovered.
Probably, said Cadena, there are bigger ones waiting for us.