Palaeontologist Rodolfo Sanchez lies alongside a carapace of the giant turtle Stupendemys geographicus, from Urumaco, Venezuela. The animal would have resembled, in length and weight, a midsized vehicle.
The giant turtles, from the species named Stupendemys geographicus first described in the 1970s, roamed a humid, swampy swath of the continent that was also home to giant rodents, crocodiles and alligators between five and ten million years ago.
The shell was discovered at the La Venta archaeological site in the Tatacoa Desert. Aside from their massive size, the male turtles had front-facing horns lining the sides of their shells.
According to Marcelo Sánchez, director of the Paleontological Institute and Museum at the University of Zurich, this indicates that two sexes of the creature existed - with males having horned shells and females having hornless ones. It is believed to be one of the largest turtles that lived in the lakes and rivers of Northern South America from about 13 million years ago to 7 million years ago.
Researchers in their study report revealed that the Stupendemys geographicus weighed nearly 1,145 kilograms, and it is nearly a hundred times the size of the Amazon river turtle, its closest relative.
The new research provided scientists an improved understanding of the species' position within the turtle family tree.
The researchers hypothesise that the horns were used as "weapons in male-male combat behaviours". Deep scars detected in the fossils indicated that these horns may have been used like a lance for fighting with other Stupendemys males over mates or territory.
An artist's illustration of the giant turtle Stupendemys geographicus. This was most likely a predator of the giant turtle, given not only its size and dietary preferences, but also as inferred by bite marks and punctured bones in fossil carapaces of Stupendemys.
Earth's landscape at the time of the Stupendemys bore little resemblance to today's topography. "Putting together all the anatomical features of this species indicates that its lifestyle was mostly in the bottom of large freshwater bodies including lakes and rivers". The massive reptile lived across the entirety of the northern part of South America. Over time, plate tectonics pushed the Andes higher, disrupting the water systems and drastically reducing the scope of their habitat, the researchers wrote. And it was the flawless environment for this giant turtle, likely allowing them to reach "unparalleled size". In the early Pliocene, around 5 million years ago, they went extinct.