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Long ago, huge sea turtles swam in the seas of the Earth. Up until recently, these prehistoric giants, measuring more than 3 meters (10 feet) from head to tail, were thought to be found only in the waters surrounding North America.
Now, scientists discovered a previously unknown species – the largest European sea turtle ever described.
First found in 2016 by a hiker who came across the remains in the Pyrenees mountains of northern Spain, the species has been named Leviathanochelys aenigmatica. “Leviathan” is a biblical term for a sea monster, a reference to the creature’s large body size, “chelys” means turtle, and “aenigmatica” means enigma—referring to the turtle’s distinctive features, the authors wrote. An article published Thursday in the journal Scientific Reports.
The presence of the unusual animal in this part of the prehistoric world revealed that giant tortoises were more common than previously thought. study.
Before discovery, the largest species in Europe, weighed on average 300 to 500 kilograms (660 to 1,100 pounds) and weighed between 1 and 2 meters (or 3 to 6.5 feet), According to the Smithsonian Institution.
However, the bone fragments of this newly described species led scientists to estimate that Leviathanochelys had a body that was 3.7 meters (12.1 feet) long. almost as big as an average sedan.
“We never thought it would be possible to find something like this. After quite a long study of bone fragments, we realized that some features were completely different, not found in any other turtle species fossil ever discovered,” said study co-author and postdoctoral researcher Albert Sellés. Researcher at the Miquel Crusafont Catalan Paleontology Institute at the Autonomous University of Barcelona in Spain.
According to Sellés, researchers initially believed the bones belonged to a different animal species.
“It’s pretty common to find a lot of bone fragments. But most don’t provide information,” said Sellés. “It’s pretty rare to discover anything that really tells you even a little bit about the life of the past.”

A local museum and the Catalonian Ministry of Culture initially collected the bone samples, but these remained unexamined for about five years. When Sellés and other researchers began their work examining the bones in 2021, they realized they were looking at an entirely new species of sea turtle for science and quickly returned to the Pyrenees region to dig further.
More specimen fragments were discovered there, including the turtle’s pelvis and fragments of its shell, which is the part of the shell that covers the creature’s back. With these findings, the scientists observed more features not seen before in any species of living or dead turtle.
“The main differences with this new fossil relate to the pelvic region. More specifically to a pair of bone mounds in the anterior part of the pelvis that we suspect are related to a type of muscle that controls the movement of the turtle’s abdominal region,” said Sellés.
According to Sellés, this feature or muscle likely affected the turtles’ breathing capacity, allowing them to hold their breath longer than other turtle species to find food or escape predators in the depths of the ocean.
The research team estimates that the ancient animal lived during the Campanian Age of the Late Cretaceous and is at least 72 million years old.
The largest recorded tortoise, called Archelon, lived about 70 million years ago and reached a length of about 4.5 meters (15 feet). Prior to this latest discovery, all prehistoric giant sea turtle discoveries were part of the same lineage as Archelon.

“We’re proving that turtles can reach truly gigantic proportions at different times and also in different families,” Sellés said. Said. “This is the first time we have found a (giant) turtle that does not belong to this family.”
According to Sellés, the researchers hope to return to the fossil site to look for more bones, as they are not sure that all pieces of this specimen have been discovered.