Horned turtles were as big as cars
In the swamps of northern South America 10 million years ago, life-or-death battles unfolded at epic scale. Giant caimans, in the same family as alligators, stalked the wetlands of modern-day Venezuela and Colombia, slinking along at 9m, snout to tail. Among their prey: the Stupendemys geographicus, a colossal turtle.
New research, published last week in the journal Science Advances, reveals important findings about the Stupendemys, a now-extinct freshwater turtle, and details the discovery of one of its shells — the largest known turtle shell found, at nearly 3m long. The animal would have resembled, in length and weight, a midsized car.
The hulking reptile was about 100 times the size of its closest living relative, the Amazon river turtle, and twice the size of the largest living turtle, the marine leatherback. The new findings provide the most thorough accounting yet of the Stupendemys, helping answer crucial questions about what might have been the largest turtle.
“For almost four decades, we didn’t have new and excellently preserved fossils of this turtle,” Edwin Cadena, a Universidad del Rosario, Colombia, paleontologist and one of the study’s lead researchers, told The Washington Post.
“Many questions — about its diet, if there were differences between males and females, and even if we were dealing with one or more giant turtle species — were completely unknown.”
But thanks to the recently unearthed fossils, dug up in northern Venezuela and Colombia’s Tatacoa Desert, Cadena and his co-authors have filled in some of the blanks, which had lingered since the 1970s, when the animal was first described. It now was likely Stupendemys (“stupendous turtle”) geographicus was the lone species of giant turtle in the region at that time, he said, there were differences between the sexes and their diet was diverse and omnivorous.
Among the most surprising discoveries, Cadena said, was the presence of sturdy, frontfacing horns on the shells of the males. The researchers suggest the horns were used as “weapons” in male-male combat. Deep scrapes in the horn of one fossil indicated they might have been used by turtles tangling over territory.
Cadena’s team found more marks, too, some that told of their fearsome fights with the Purussaurus, the giant caimans that roamed the northern Neotropics in the Miocene epoch at the same time. The scars from their skirmishes are still visible.
Some of the Stupendemys fossils had bite marks and punctured bones, and one shell had a tooth embedded in it.
Earth’s landscape at the time bore little resemblance to today’s topography.
The turtle’s habitat has turned to desert, but it was humid and swampy then. The Andes weren’t yet fully formed and the Orinoco and Amazon rivers cut different paths.
A sprawling wetland and lake system meant plenty of room for massive animals — especially the Stupendemys, which spent most of its days at the bottom of freshwater streams and small lakes, Cadena said.
They probably lived across the whole northern part of South America.
But those ideal conditions did not last. Over time, plate tectonics pushed the Andes higher, disrupting the water systems and drastically reducing the scope of their habitat, the researchers say.
At some point, their huge size was no longer enough to keep them alive.
In the early Pliocene, about five million years ago, they became extinct.