Scientists Unearth a Prehistoric Marine Turtle the Size of a Car

Fragments of the creature’s pelvis and shell were discovered in the Pyrenees

a marine turtle
An illustrated reconstruction of Leviathanochelys aenigmatica. ICRA_Arts

Researchers have unearthed the remains of a new species of gigantic marine turtle in northern Spain. Weighing about two tons and measuring 12 feet long, the prehistoric creature is the largest of its kind ever discovered in Europe. 

The find was completely accidental: A hiker stumbled across some bone fragments while walking in the Pyrenees mountains, writes James Ashworth for London’s Natural History Museum. After that, a local museum and the Catalonian Department of Culture collected the remains, but no one studied them until 2021. Researchers began new excavations at the Pyrenees site and uncovered fragments of the turtle’s pelvis and carapace—the part of the shell that covers the creature’s back.

Scientists described the turtle, which they named Leviathanochelys aenigmatica, in a paper published Thursday in Scientific Reports. “Leviathan” is a nod to the animal’s large body size, and “chelys” means turtle. “Aenigmatica” translates to enigma—in reference to some of the creature’s strange characteristics, the authors write.

For example, the turtle has an “exceedingly large pelvis and shell reduction in the carapace,” Sandra Chapman, the Natural History Museum in London’s former curator of fossil reptiles and birds, tells the museum. It also has a unique bone bulging out from the side of its pelvis, which hasn’t been observed in any other living or dead turtle species. The structure appears to have connected to muscles, so the researchers believe it may have helped L. aenigmatica breathe in deep waters. 

Researchers estimate the animal lived during the Campanian Age of the Late Cretaceous Epoch, making it at least 72 million years old. 

“During the Cretaceous, there was a tendency in marine turtles to increase their body size… The reason for this increase in body size has been hypothesized to be predatory pressures, but there might be other factors,” lead author Oscar Castillo‑Visa, a paleontologist at the Autonomous University of Barcelona in Spain, tells Reuters’ Will Dunham. “At that time, the large marine predators in the European zone were mainly sharks and mosasaurs.” 

The largest turtle on record, called Archelon, lived some 70 million years ago and grew to be about 15 feet long, making it a bit bigger than the new species. “Leviathanochelys was as long as a Mini Cooper, while Archelon was the same size as a Toyota Corolla,” Castillo‑Visa tells Reuters. 

In comparison, the biggest turtle alive today is the leatherback, which weighs an average of 660 to 1,100 pounds and measures just 4 to 6 feet.

Previously, researchers thought gigantic marine turtles only lived in North America. But this new study suggests giant turtles developed independently in separate lineages in North America and Europe, per the authors.

“I think this specimen is a really good find which has been well researched,” Chapman tells the museum. “It adds another piece to the puzzle of trends in the evolution of turtles. It supports the idea that extreme sizes are more common prior to an extinction and smaller, but still substantial, sizes predominate afterwards.”

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