More than 300 is the number of turtle species currently listed worldwide. And they show a great diversity of sizes. Some reach just ten centimeters while others well exceed one metre. 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 journal Scientific reports. This work reveals the existence of a new species of turtle that lived during the Cretaceous period, more than 66 million years ago. His name : Leviathanochelys aenigmatica. And he had something to impress as he 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 nearly complete pelvis and pieces of carapace. So many elements that soon made the 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 have reached 3.7 meters in length with an estimated mass of over three tons. So far, no European tortoise – living or extinct – has shown a length exceeding 1.5 metres. This species would therefore constitute the largest discovery in Europe and one of the largest turtles ever to live on Earth.
She competes with Archon, an extinct genus of sea turtle identified on the North American continent that has been estimated to grow to a size of 4.6 meters long and weigh up to 3.2 tons. “We are used to finding dinosaur bones in northeastern Spain and some are very large“explained a 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 striking feature.”
According to the report, the pelvis of the species could reach a maximum width of 88.9 centimeters, slightly higher than the maximum estimates made for the best-known specimens ofArchelon, about 81cm. However, the latter showed a slightly greater pelvic length of 46 cm against the 39.5 estimated for Leviathanchelys.
Among its other features, the fossil showed 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 have therefore decided to baptize Leviathanchelys in reference to Leviathan, a biblical sea monster.
“The enigmatic name […] refers to the particular anatomical characteristics of the 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 Campano, between 72.1 and 83.6 million years ago. Genus representatives Archelon.
A gigantism that arose independently in distinct lineages
These results therefore 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 may be a response to the unique conditions that prevailed in the European archipelago oceans 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 up a new line of exploration and raises new questions.“on the evolution of sea turtle gigantism, particularly in this period, argue the authors.
The portrait of this turtle newcomer, however, is far from complete. More studies are needed, for example, to determine the diet of L. aenigmatica, as well as predators that preyed on it despite its colossal size. “It’s too early to tell for sure, but the turtle was likely hunted by sharks“, observed Albert G. Sellés.
“This hypothesis is based on the fact that the carapace has particular signs that 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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