Fossils of a car-sized dinosaur-era sea turtle unearthed in Spain

Fossils of a car-sized dinosaur-era sea turtle unearthed in Spain

An illustrated reconstruction of the large Cretaceous sea turtle Leviathanochelys aenigmatica, which lived about 83 million years ago and whose fossils were found in the Catalan county of Alt Urgell in northeastern Spain, can be seen in this undated handout image. Reuters

Traversing the subtropical seas that lapped the coasts of the archipelago that made up Europe 83 million years ago was one of the greatest turtles on record a reptile the size of a small car – a Mini Cooper, to be precise – that defied danger bodies of water.

Researchers on Thursday described remains of a turtle called Leviathanochelys aenigmatica, discovered in northeastern Spain, which was about 3.7 meters long, weighed just under two tons and lived during the Cretaceous Period – the final chapter in the age of dinosaurs. It is Europe’s largest known turtle.

It dwarfed today’s largest turtle – the leatherback, which can grow up to 2 meters long and is known for marathon sea migrations. Leviathanochelys almost equaled the largest tortoise of all time – Archelon, which lived about 70 million years ago and grew to about 4.6 meters in length.

“Leviathanochelys was as long as a Mini Cooper, while Archelon was the same size as a Toyota Corolla,” said paleontologist and study co-author Albert Sellés of the Institut Català de Paleontologia (ICP), a research center of the Universitat Autònoma de Barcelona.

Being the size of a car was good given the dangerous traffic in the ancient Tethys Sea where Leviathanochelys swam. Huge marine reptiles with powerful jaws called mosasaurs were the largest predators – some were over 15 meters long. Various sharks and rays as well as long-necked, fish-eating marine reptiles called plesiosaurs also lurked.

“Attacking an animal the size of Leviathanochelys could possibly only be accomplished by large predators in a marine context. At that time, the large marine predators in the European zone were mainly sharks and mosasaurs,” said Oscar Castillo, a graduate student in paleontology at the Universitat Autònoma de Barcelona and first author of the study published in the journal Scientific Reports.

“During the Cretaceous period, sea turtles tended to increase in body size. Leviathanochelys and Archelon may represent the culmination of this process. The reason for this increase in height has been suggested to be predatory pressure, but there may be other factors,” Castillo added.

Other large tortoises from Earth’s past include Protostega and Stupendemys, both of which grow to around 4 meters in length. Protostega was a Cretaceous sea turtle that lived about 85 million years ago and, like its eventual cousin Archelon, inhabited the great inland sea that then divided North America in two. Stupendemys roamed the lakes and rivers of northern South America about 7-13 million years ago during the Miocene.

Scientists discovered the remains of Leviathanochelys near the village of Coll de Nargó in the Catalan county of Alt Urgell after a hiker discovered fossils sticking out of the ground in the southern Pyrenees. To date they have found parts of the rear part of its carapace or carapace and most of the pelvic girdle, but no skull, tail or limbs.

The fossils showed that it had a smooth carapace resembling leatherback turtles, with the carapace itself measuring about 2.35 meters long and 2.2 meters wide. Leviathanochelys seems to be built for the open ocean and rarely returns to land – for example to lay eggs.

The presence of some bony protrusions on the front of the pelvis differs from all other known sea turtles, suggesting that Leviathanochelys represents a newly discovered lineage. It shows that gigantism in sea turtles evolved independently in separate chalk lines in North America and Europe.

Leviathanochelys aenigmatica means “enigmatic leviathan tortoise” because of its size and the odd shape of its pelvis, which researchers suspect is related to its respiratory system.

“Some pelagic (open ocean) animals show a modification in their respiratory system to maximize their breathing capacity at great depths,” Sellés said.

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