Remains of an enormous turtle, which was the size of a Smart car, have been unearthed in a Colombian coal mine.
The shell alone of the 60-million-year-old turtle, Carbonemys cofrinii aka "coal turtle," is large enough to be a small swimming pool. Its skull is roughly the size of a regulation NFL football.
The coal mine where it was found is part of northern Colombia's Cerrejon formation.
"We had recovered smaller turtle specimens from the site," Edwin Cadena, a North Carolina State doctoral student who discovered the turtle, said in a press release. "But after spending about four days working on uncovering the shell, I realized that this particular turtle was the biggest anyone had found in this area for this time period -- and it gave us the first evidence of giant-ism in freshwater turtles."
The find was described in the latest Journal of Systematic Paleontology.
Relatives of Carbonemys existed alongside dinosaurs, but these turtles were much smaller. This gigantic version appeared five million years after dinos went extinct, during a period when giant varieties of many different reptiles -- including Titanoboa cerrejonensis, the largest snake ever discovered -- lived in this part of South America.
Why were the animals so big?
Cadena and other experts believe that a combination of changes in the ecosystem, including fewer predators, a larger habitat area, plentiful food supply and climate changes, worked together to allow these giant species to survive. Carbonemys' habitat would have resembled a much warmer modern-day Orinoco or Amazon River delta.
Turtles today are usually seen slowly chewing plants, but this prehistoric species had massive, powerful jaws that would have enabled it to eat anything nearby, from mollusks to smaller turtles or even crocodiles.
Dan Ksepka, NC State paleontologist and research associate at the North Carolina Museum of Natural Sciences, thinks only one specimen of the turtle was found because a turtle of this size would need a large territory in order to obtain enough food to survive.
"It's like having one big snapping turtle living in the middle of a lake," said co-author Ksepka. "That turtle survives because it has eaten all of the major competitors for resources. We found many bite-marked shells at this site that show crocodilians preyed on side-necked turtles. None would have bothered an adult Carbonemys, though -- in fact smaller crocs would have been easy prey for this behemoth."