Fossilised shell of a turtle the size of a car discovered in South America

A graphic reconstruction of the giant turtle Stupendemys geographicus which was the size of a modern-day car (PA)

The fossilised remains of a gigantic turtle shell have been uncovered in South America.

Scientists have concluded it belonged to the biggest species of turtle that has ever lived – weighing over a tonne and roaming the waters off modern-day Colombia 10 million years ago.

Named Stupendemys geographicus and twice as big as the largest turtle alive today, it may even have weaponised its eight-foot long shell in fights to the death with rivals.

At the time the continent was a ‘lost world’ of bizarre oversized creatures – including enormous rats and alligators.

Stupendemys was unearthed at an animal graveyard known as the La Venta archaeological site in the Tatacoa Desert of Colombia.

The beast described in is based on an analysis of several new shell specimens and a lower jaw – the first discovery of its kind in the fossil record.

Lead author Professor Edwin Cadena said ‘The now-extinct animal is the largest land turtle of all time. The remains include the biggest complete turtle shell ever identified.

Colombian and Venezuelan paleontologists work together during the excavation of the giant turtle Stupendemys geographicus (Reuters)

‘The enormous carapace is 2.4 metres (8ft)-long and may have housed a 1,145-kilo turtle. It is almost 100 times the size of its closest living relative, the Amazon river turtle Peltocephalus dumerilianus, and twice that of the largest turtle today, the marine leatherback Dermochelys coriacea.’

The findings, published in the journal Science Advances, significantly expand the known range of Stupendemys which plodded around northern South America during the late Miocene.

They also indicate it was the lone giant species in the northern Neotropics.. It was first identified in 1976 from remains discovered in Venezuela.

Prof Cadena, a palaeontologist at at the University of Rosario in Bogota, said knowledge of these reptilian giants has stalled due to a lack of full specimens.

To uncover more information about the turtle’s prehistoric life, his team conducted detailed anatomical analyses on specimens dating from 1994 expeditions, as well as from more recent finds.

They found males of this species sported unique horn-like shells at the front of their hard upper shells.

Venezuelan Palaeontologist Rodolfo Sanchez and a male carapace of the giant turtle Stupendemys geographicus (University of Zurich/Edwin Caden)

Prof Cadena said: ‘This is a feature that may have served to protect their massive skulls when engaged in combat with other males.’

The authors also suggest Stupendemys may have achieved such unparalleled size due to the presence of warm, extensive wetland and lake habitats.

Prof Cadena said: ‘Massive crocodiles may also have influenced the turtle’s evolution, with bite marks on some specimens – including a lone crocodile tooth protruding from a carapace.

‘This suggests they needed protection from other lurking giants.’

The largest specimen of the giant turtle Stupendemys geographicus, a male individual found in Venezuela, is seen in this picture (Reuters)

When Stupendemys inhabited South America, carnivorous mammals had not yet arrived on the continent, since the Isthmus of Panama was not yet formed and there was no terrestrial connection with Antarctica.

It was isolated, like a giant island. The apex predators were giant crocodiles and alligators, up to 40 feet long. Prof Cadena added: ‘Bite marks and punctured bones on Stupendemys indicate interactions with large caimans that also inhabited the marshy environment.’

Some extinct South American animals of the time reached giant proportions because of these unique conditions during the Late Miocene, some 10 million years ago.