Researchers uncover fossil remains of world's largest known turtle

Stupendemys geographicus

Fossils shed new light on car-sized turtle that once roamed South America

The tropical region of South America is one of the world's hot spots when it comes to animal diversity.

Stupendemys is the second-largest known turtle, behind seagoing Archelon, which lived roughly 70m years ago at the end of the age of dinosaurs and reached about 15ft (4.6 meters) in length.

Only one turtle in history was thought to be larger: the Archelon, an ocean-dwelling behemoth that measured 4.6 metres (15 feet) long and lived almost 70 million years ago.

Colombian and Venezuelan paleontologists work together during the excavation of the giant turtle Stupendemys geographicus in northern Venezuela, in an undated picture released February 12, 2020. For millions of years, the South American rainforest has fostered unique fauna, including some of the most wonderful extinct giant rodents and crocodilians, including crocodiles, alligators, caimans, and gavials.

One of the largest turtles that ever lived prowled the lakes and rivers of northern South America from about 13 million years ago to 7 million years ago - and this car-sized freshwater beast was built for battle. Credit: Produced by Rio Verde for Edwin Cadena.

Thanks to the recovery and analysis of several exceptionally preserved Stupendemys geographicus specimens, scientists have gained new insights into the physiology and anatomy of the giant turtle. The turtle had an estimated body mass of 1,145 kg - nearly one hundred times that of its closest living relative, the big-headed Amazon river turtle.

In some individuals, the complete carapace showed a peculiar and unexpected feature: horns. Researchers revealed that these horns were used as weapons during male to male combat.

"This is the first time that sexual dimorphism in the form of horned shells has been reported for any of the side-necked turtles, one of the two major groups of turtles worldwide".

The turtle's impressive size may make it 'one of the largest, if not the largest turtle that ever existed, ' said lead researcher Marcelo Sánchez, director of the Paleontological Institute and Museum at UZH.

The stupendous turtle was massive by modern standards, but not when compared to some of the big crocodile ancestors that occupied the same prehistoric swamps of its era. In many areas, the occurrence of Stupendemys coincides with Purussaurus, the largest caimans. Bite marks and punctured bones in fossil carapaces of Stupendemys support the notion that the turtle was subjected to predation.

They think the giant turtle lived at the bottom of lakes and rivers alongside giant crocodile eating a diverse diet of small animals, vegetation, fruit and seeds.

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