Fossils found in Spain reveal one of the largest turtles to have lived on Earth

More than 300 is the number of species of turtles that are currently listed throughout the world. And they show great diversity in size. Some barely reach ten centimeters while others are well over one meter. Tens of millions of years ago, however, much larger turtles roamed the Earth.

This is confirmed by a study published in November 2022. in the review Scientific Reports. This work reveals the existence of a new species of turtle that lived during the Cretaceous, more than 66 million years ago. Her name : Leviathanochelys aenigmatica. And she had something to impress since she was as big and heavy as a hippopotamus.

It was from fossils discovered near the village of Coll de Nargó in northeastern Spain that the species was described. The bones, exhumed between 2016 and 2021, include a fragmented but almost complete pelvis as well as pieces of carapace. So many elements that quickly made researchers understand that the creature was colossal.

Up to 3.7 m and three tons

From the remains, they determined that the turtle’s body could reach up to 3.7 meters in length with an estimated mass of more than three tons. So far, no European turtle – living or extinct – has shown a length greater than 1.5 meters. This species would thus constitute the greatest discovery in Europe and one of the largest turtles having ever lived on Earth.

She competes with Archon, an extinct genus of sea turtles identified on the North American continent that was estimated to grow to a size of 4.6 meters in length and weigh up to 3.2 tons. “We are used to finding dinosaur bones in the northeast of Spain and some are very large“, has explained at PopSci Albert G. Sellés, one of the co-authors of the study.

But until today, we had never found fossilized remains of a marine animal, let alone of such a colossal size.“, continued this researcher from the Autonomous University of Barcelona, ​​specifying that “the size of Leviathanochelys aenigmatica is probably its most surprising feature.”

The fossils of Leviathanochelys aenigmatica at their site near the village of Coll de Nargó in northeastern Spain. © Angel Galobart

According to the report, the species’ pelvis could reach a maximum width of 88.9 centimeters, which is slightly greater than the maximum estimates made for the best-known specimens ofArchelon, about 81 cm. The latter nevertheless displayed a slightly greater pelvic length of 46 cm against 39.5 estimated for Leviathanochelys.

Among its other features, the fossil exhibited an unusual bony growth on the front of the pelvis, which helped researchers determine that it represented a new group of extinct sea turtles. A taxon that they therefore decided to baptize Leviathanochelys in reference to Leviathan, a biblical sea monster.

The aenigmatic nomination […] refers to the particular anatomical features of its pelvis and carapace“, specify the authors in their report. According to the analyses, this immense turtle would have lived off the coast of Spain during the Campanian, between 72.1 and 83.6 million years ago. gender representatives Archelon.

A gigantism that arose independently in distinct lineages

These findings thus suggest that gigantism in sea turtles may have evolved independently in different lineages in both North America and Europe. For L. aenigmatica in particular, it could be a response to the unique conditions that prevailed in the oceans of the European archipelago during the Cretaceous.

Despite the rare and fragmentary nature of the individual, this new discovery not only increases the taxonomic diversity of Late Cretaceous sea turtles in Europe but also opens a new line of exploration and raises new questions.” on the evolution of the gigantism of sea ​​turtlesespecially during this period, support the authors.

Artist’s reconstruction of the tortoise species Leviathanochelys aenigmatica, as large and heavy as a hippopotamus. © CIFAR_Arts

The portrait of this newcomer among turtles is however far from complete. Further studies are needed, for example, to determine the diet of L. aenigmatica, as well as the predators that preyed on it despite its colossal size. “It is too early to say for sure but it is likely that the turtle was hunted by sharks“, noted Albert G. Sellés.

This hypothesis is based on the fact that the carapace has some particular marks which could be from bites, and that a shark tooth was found near the skeleton.“, he added. Nowadays, it is the Leatherback Turtle which, with an average length of 1.5 meters, takes the title of the largest turtle in the world.

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