By Will Dunham
(Reuters) – Sailing the subtropical seas that washed the shores of the archipelago that formed Europe 83 million years ago was one of the largest turtles ever recorded, a reptile the size of a small car – a Mini Cooper to be exact – that braved dangerous waters.
Researchers on Thursday described the remains discovered in northeastern Spain of a turtle called Leviathanochelys aenigmatica that measured about 12 feet (3.7 meters) long, weighed just under two tons and lived during the Cretaceous Period — the last chapter in the age of dinosaurs. It is Europe’s largest known turtle.
It eclipsed today’s largest turtle – the leatherback, which can reach 2 meters in length and is known for its marathon sea migrations. Leviathanochelys almost matched the largest turtle ever recorded – 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 as tall as a Toyota Corolla,” says paleontologist and study co-author Albert Sellés of the Institut Català de Paleontologia (ICP), a research center affiliated with Universitat Autònoma de Barcelona .
It was good to be the size of a car, given the dangerous traffic in the ancient Tethys Sea in which Leviathanochelys swam. Huge marine reptiles with powerful jaws called mosasaurs were the largest predators – some more than 15 meters long. Several sharks and rays, as well as long-necked fish-eating marine reptiles called plesiosaurs, also lay in wait.
“Attacking an animal the size of Leviathanochelys could possibly only be done by large predators in the marine context. At that time, the large marine predators in the European zone were mainly sharks and mosasaurs,” said Oscar Castillo, a student in a master’s degree. paleontology at the Universitat Autònoma de Barcelona and lead author of the study published in the journal Scientific Reports.
“During the Cretaceous, there was a tendency for sea turtles to increase their body size. Leviathanochelys and Archelon could represent the apex of this process. The reason for this increase in body size has been thought to be predatory pressure, but there may be other factors,” Castillo added.
Other large turtles from Earth’s past include Protostega and Stupendemys, both of which grow to about 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 split North America in two at the time. Stupendemys roamed the lakes and rivers of northern South America about 7-13 million years ago during the Miocene.
Scientists unearthed the remains of Leviathanochelys near the village of Coll de Nargó in Catalonia’s Alt Urgell province after fossils protruding from the ground were spotted by a hiker in the mountains of the southern Pyrenees. To date, they have found parts of the posterior part of the carapace, or carapace, and most of the pelvic girdle, but no skull, tail, or limbs.
The fossils indicated it possessed a smooth carapace, similar to leatherback turtles, with the shell itself about 7.7 feet (2.35 meters) long and 7.2 feet (2.2 meters) wide. Leviathanochelys seems built for the open ocean and only rarely returns to land – to lay eggs, for example.
The presence of a pair of bony bulges at the front 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 of North America and Europe.
Leviathanochelys aenigmatica means “enigmatic leviathan tortoise” because of its large size and the curious shape of its pelvis that researchers suspect is related to its respiratory system.
“Some pelagic (living in the open ocean) animals show an alteration in their respiratory system to maximize their breathing capacity at great depths,” Sellés said.
(Reporting by Will Dunham in Washington, editing by Rosalba O’Brien)