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Long ago, gigantic sea turtles swam the Earth’s seas. Until recently, these prehistoric giants, which reached lengths of more than 10 feet (3 meters) from head to tail, were thought to only be found in the waters around North America.
Now scientists have discovered a previously unknown species: the largest European sea turtle ever identified.
Initially found by a hiker who stumbled upon the remains in 2016 in the Pyrenees mountains of northern Spain, the species was given the name Leviathanochelys aenigmatica. “Leviathan” is the Biblical term for a sea monster, an allusion to the creature’s large bodily size, while “chelys” translates to turtle and “aenigmatica” translates to enigma, referring to the turtle’s peculiar characteristics, wrote the authors of 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, according to the study.
Before discovery, the largest European species measured just 1.5 meters (5 feet) long, similar to today’s leatherbacks, which weigh an average of 300 to 500 kilograms (660 to 1,100 pounds) and measure from 1 to 2 meters (or between 3 and 6.5 feet), according to the Smithsonian Institution.
However, bone fragments from this newly identified species have led scientists to estimate that Leviathanochelys had a body that was 3.7 meters long (12.1 ft), almost as big as an average sedan.
“We never thought it was possible to find something like this. After quite a long study of the bone fragments, we realized that there were some features that were totally different, not present in any other fossil turtle species discovered so far,” said Albert Sellés, study co-author and postdoctoral student. Researcher at the Catalan Institute of Paleontology Miquel Crusafont of the Autonomous University of Barcelona in Spain.
Originally, the researchers believed the bones belonged to a different type of animal, according to Sellés.
“It is quite common to find bone fragments, many. But most of them are not informative,” said Sellés. “It’s quite rare to discover something that really tells you a little about life in the past.”
A local museum and the Catalan Ministry of Culture had originally collected the bone specimens, but they remained unstudied for almost five years. When Sellés and the other researchers began their work studying the bones in 2021, they realized they were dealing with a completely new species of sea turtle to science and quickly returned to the Pyrenees site for further excavation.
There, more fragments of the specimen were discovered, including pieces of the turtle’s pelvis and carapace, the part of the shell that covered the creature’s back. With these findings, the scientists observed more features than ever before seen in any species of turtle, living or dead.
“The main differences of this new fossil are related to the pelvic region. More specifically, to a pair of bony protuberances present in the anterior part of the pelvis, which we suspect are related to some type of muscle that controls the movement of the abdominal region of the turtle,” said Sellés.
This feature, or muscle, likely affected the turtles’ ability to breathe, allowing them to hold their breath longer than other species of turtles, to swim in the depths of the ocean to find food or escape predators, according to Sellés.
The research team estimated that the ancient animal lived during the Campanian Era of the Late Cretaceous Epoch, making it at least 72 million years old.
The largest recorded tortoise, named Archelon, lived about 70 million years ago and grew to be about 15 feet (4.5 meters) long. Prior to this recent discovery, all prehistoric giant sea turtle discoveries were part of the same lineage as Archelon.
“We are showing that tortoises can reach really gigantic proportions at different times and also in different families,” Sellés said. “For the first time, we found a (giant) tortoise that does not belong to this family.”
The researchers hope to return to the fossil site to search for more bones, as they are not sure that all the fragments of this specimen have been discovered, according to Sellés.
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