November 17 (Reuters) – Criss-crossing the subtropical seas that lapped the coasts of the archipelago that made up Europe 83 million years ago, was one of the largest turtles on record, a reptile the size of a small car – a Mini Cooper to be precise – that braved treacherous waters.
Researchers on Thursday described the remains discovered in northeastern Spain of a turtle named Leviathanochelys aenigmatica which was around 3.7 meters long, weighed just under two tonnes and lived during the Cretaceous period – the final chapter of the dinosaur era. It is the most famous turtle in Europe.
It eclipsed today’s largest turtle – the leatherback turtle, which can reach 7 feet (2 meters) in length and is known for its marathon sea migrations. Leviathanochelys almost matched the largest turtle on record – Archelon, which lived around 70 million years ago and grew to around 15 feet (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 affiliated with the Universitat Autònoma de Barcelona.
It was good to be the size of a car, considering the dangerous traffic in the ancient Tethys Sea in which the Leviathanochelys swam. Huge marine reptiles with powerful jaws called mosasaurs were the largest predators – some exceeding 15 meters in length. Various sharks and rays as well as long-necked fish-eating marine reptiles called plesiosaurs were also lurking.
“Attacking an animal the size of Leviathanochelys could perhaps only have been done by large predators in the marine context. At that time, the large marine predators in the European area were mainly sharks and mosasaurs,” said said Oscar Castillo, student in a master’s program in paleontology at the Universitat Autònoma de Barcelona and lead author of the study published in the journal Scientific Reports.
“During the Cretaceous, sea turtles tended to increase in body size. Leviathanochelys and Archelon may represent the peak of this process. The reason for this increase in body size has been assumed to be predatory pressures, but there could be have other factors,” Castillo added.
Other large turtles from Earth’s past include Protostega and Stupendemys, both of which grew to around 13 feet (4 meters) in length. Protostega was a Cretaceous sea turtle that lived about 85 million years ago and, like its later cousin Archelon, inhabited the great inland sea that at the time divided North America in two. Stupendemys roamed the lakes and rivers of northern South America around 7 to 13 million years ago during the Miocene epoch.
Scientists have discovered the remains of Leviathanochelys near the village of Coll de Nargó in Alt Urgell county in Catalonia after fossils protruding from the ground were spotted by a hiker in the Southern Pyrenees mountains. So far, they have found parts of the posterior part of its carapace, or shell, and most of the pelvic girdle, but no skull, tail, or limbs.
Fossils indicated that it had a smooth carapace similar to that of leatherback turtles, with the carapace itself about 7.7 feet (2.35 meters) long and 7.2 feet (2.2 meters) wide. Leviathanochelys seems built for the open ocean, only rarely returning to land – for example to lay eggs.
The presence of a few bony bulges on the front side of the pelvis differs from any other known sea turtle, indicating that Leviathanochelys represents a newly discovered lineage. It shows that gigantism in sea turtles developed independently in separate Cretaceous lineages in North America and Europe.
Leviathanochelys aenigmatica means “enigmatic leviathan turtle” due to its large size and the curious shape of its pelvis which researchers suspect is related to its respiratory system.
“Some pelagic animals (living in the open ocean) show a modification of their respiratory system to maximize their breathing capacity at great depths,” Sellés said.
Reporting by Will Dunham in Washington, editing by Rosalba O’Brien
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