Nov 17 (Reuters) – Wandering the subtropical seas that washed the shores of the archipelago that formed Europe 83 million years ago, it was one of the largest recorded turtles, a small car-sized reptile – a Mini Cooper to be exact – braving dangerous waters.
On Thursday, researchers announced the remains of a turtle named Leviathanochelys aenigmatica, which was around 12 feet (3.7 meters) long, slightly less than two tons, and lived during the Cretaceous Period, the last chapter of the dinosaur era, discovered in northeastern Spain. It is the largest known tortoise in Europe.
It outshines the leatherback turtle, which can reach 2 meters (7 feet) in length and is known for its marathon sea migrations, the largest tortoise today. Leviathanochelys was almost a match for Archelon, the largest tortoise on record, which lived about 70 million years ago and reached a length of about 4.6 meters.
“While Leviathanochelys was as tall as a Mini Cooper, the Archelon was the same size as a Toyota Corolla,” said Albert Sellés, a paleontologist and co-author of the study from the Institut Català de Paleontologia (ICP), a research center affiliated with the Universitat Autònoma de Barcelona.
It was good that it was the size of a car, considering the dangerous traffic in the ancient Tethys Sea, in which Leviathanochelys swam. Giant marine reptiles with powerful jaws called mosasaurs were the biggest predators – some exceeding 15 meters in length. Various sharks and stingrays lurked, as well as long-necked fish-eating marine reptiles called plesiosaurs.
“Attacking an animal the size of Leviathanochelys could probably only have been done in a marine context by large predators. At that time, large marine predators in the European region were mostly sharks and mosasaurs,” said Oscar Castillo, a student. Master’s program in paleontology at the Universitat Autònoma de Barcelona and lead author of the study published in the journal Scientific Reports.
“There was a tendency for sea turtles to increase their body size during the Cretaceous. Leviathanochelys and Archelon may represent the culmination of this process. This increase in body size has been hypothesized to be due to predatory pressures, but there could be other factors,” Castillo added.
Other large turtles from Earth’s past include Protostega and Stupendemys, both reaching a length of about 13 feet (4 meters). Protostega was a Cretaceous sea turtle that lived about 85 million years ago, and like its later cousin Archelon, it lived in the great inland sea that then bisected North America. Stupendemys prowled the lakes and rivers of northern South America during the Miocene Period, about 7-13 million years ago.
Scientists have unearthed the remains of Leviathanochelys near the village of Coll de Nargó in Catalonia’s Alt Urgell county after fossils were identified protruding from the ground by a hiker in the Southern Pyrenees mountains. To date, they have found parts of its shell or the posterior part of its shell and most of its pelvic girdle, but no skull, tail or limbs have been found.
The fossils showed that its shell was about 7.7 feet (2.35 meters) long and 7.2 feet (2.2 meters) wide, with a smooth shell similar to leatherback turtles. Leviathanochelys seem to have been built for the open ocean, rarely returning to land—for example, to spawn.
The presence of a pair of bony prominences on the anterior aspect of the pelvis differs from all other known sea turtles, indicating that Leviathanochelys represents a newly discovered lineage. It shows that gigantism in sea turtles evolved independently in separate Cretaceous lineages in North America and Europe.
Leviathanochelys aenigmatica means “enigmatic sea turtle” because of its large size and interesting pelvis shape that researchers suspect is related to the respiratory system.
“Some pelagic (living in the open ocean) animals show a change in their respiratory system to maximize their respiratory capacity at great depths,” Sellés said.
By Will Dunham, Washington, Edited by Rosalba O’Brien
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