Sea turtle fossil found in Spain is one of the largest ever

The idea of ​​finding a giant sea turtle, almost 4 meters long, does not seem to fit with the scenery of rocky mountains located on the border of Spain and France.

These aquatic reptiles now live in tropical and subtropical waters, but they are not very fond of colder places. In a period between 83 and 76 million years ago, however, the Pyrenees region was made up of marine sediments, and the mountain chain occurred after the collision of the Iberian plate with the plate of the European continent. With that, the sediments from the sea floor were lifted. Several fossils of marine invertebrates are known from the region.

Now, scientists from the Autonomous University of Barcelona, ​​the Museum of Conca Dellá (also from Spain) and the Department of Geological Sciences at Masaryk University (Czech Republic), have described a fossil of a giant sea turtle, with an unusual size for the European continent, found near the town of Cal Torrades, in northern Spain.

The article describing the finding was published this Thursday (17) in the specialized journal Scientific Reports (from the Nature group).

From the fossilized animal, only a few bones of the pelvic basin remained, including pubis, ilium and ischium, and part of the carapace. The animal was named Leviathanochelys aenigmatica —the genus name comes from a mixture of “Leviathan”, the great sea monster of the Old Testament, and the suffix “chelys”, Greek for tortoise, while the epithet “aenigmatica” alludes to the reptile’s enigmatic characteristics.

In addition to the size, the anatomy of the new animal surprised the scientists, who identified similar characteristics with another European chelonian of much smaller size — the fossil Allopleuronestimated to be 1.5 meters long— and the leatherback (Dermochelys coriacea), which can reach 2.2 m, both part of the Chelonioidea group.

differently, Leviathanachelys shows an anterior extension of the acetabular process (which connects the head of the femur to the pelvis), ornamentation on the surface of the bones (which may indicate the presence of blood microvessels) and two accessory processes in the anterior region of the pelvis, a unique feature not found in any other sea turtle, fossil or otherwise.

Regarding size, paleontologist Albert Sellés, senior author of the study, explains that fossils of giant sea turtles are known from the Kansas region, in the United States, including the largest turtle genus to date, of the genus archelonwith individuals reaching up to 4.6 meters in length from the tip of the snout to the tail.

“The maximum length of the pelvis of Leviathanachelys was estimated at 88.9 cm, which would be slightly larger than that of archelon [81 cm]🇧🇷 Although there is no direct correlation between pelvis size and total length, the data suggest that the new fossil could have been as large as archelonreaching up to 3.74 m in length,” he said.

As the fossils are of different ages and, more importantly, lineages, it is likely that the so-called “gigantism” evolved several times in the group that gave rise to sea turtles, according to him. “We don’t know why exactly, but food availability, competition and pressure [seletiva] of predators may have acted in the selection of larger individuals and, consequently, led to the evolution of giant animals”, he adds.

Thus, the new species is different from current sea turtles and makes up the largest turtle fossil known on the European continent, and one of the largest in the world. As for its appearance in life, it is difficult to know what it would look like and whether it would have the “leathery” carapace characteristic of the leatherback turtle, but even that cannot be ruled out, says Sellés.

“The inspiration for the reconstruction [do fóssil] it may have been the leatherback based on an important criterion, the absence of bony markings on the outer carapace, which is only found in this species. But we cannot rule out that evolution would have led to the appearance of similar characteristics in different lineages, so it is not possible to know whether it had a leathery carapace or not”, he explains.