Long-necked marine reptiles were decapitated in the age of dinosaurs

Many different lineages of marine reptiles that lived before and during the age of dinosaurs had extremely long necks, usually more than twice its body length. This particular body morphology even seems to have inspired the legend of “Nessie”, the Loch Ness monster.

For over 200 years, paleontologists have speculated that these long-necked marine reptiles were especially vulnerable to attack by large predators, but no fossils have been found to support this idea. Until now.

Now, paleontologists Stephan Spiekman, from the State Museum of Natural History in Stuttgart (SMNS, Germany) and Eudald Mujal, from that museum, and a researcher associated with the Institut Català de Paleontologia Miquel Crusafont (ICP) have found two fossil specimens of the triassic marine reptile Tanystropheus, 242 million years.

They observed that the necks of these two animals were completely separated from the body and showed bite marks by predators. These fossils represent the first clear evidence that, despite the enormous evolutionary success of these long necks – common in many species of marine reptiles – this anatomical peculiarity was also a weakness that made them vulnerable. O investigation was published in the magazine current biology.

“Of the various forms of marine reptiles, Tanystropheus is perhaps one of the strangest examples: it had a neck three times as long as its torso, but with only 13 extremely elongated vertebrae. This made its neck particularly long, thin and rigid. Most likely, he used it to capture his prey through an ambush strategy,” he explains. Spiekmanspecialist in Triassic reptiles and co-author of the research paper.

Two species are known Tanystropheus from behind 242 million years they lived in a shallow sea on the border between what is now Switzerland and Italy. One of the species was no more than 1.5 meters long and probably fed on crustaceans and other invertebrates. The other species could reach 6 meters in length and fed on fish and cephalopods.

Skull and neck of the large species of Tanystropheus (Tanystropheus hydroides). The specimen is located at the Paleontological Institute of the University of Zurich, Switzerland. / Stephan Spiekman

Decapitation of long-necked marine reptiles

Finding evidence of predator-prey interactions in the fossil record is very rare. “The fossils we studied are direct evidence of decapitation by predation in long-necked marine reptiles. The specimens represent the two species of Tanystropheus and, in both cases, the neck was completely severed”, comments Eudald Mujalco-author of the study and specialist in taphonomy and trophic interactions.

“The type of abrupt fracture of the bones together with the disposition of the bite marks suggest that the necks were severed with a single bite”, explains the researcher. The fact that these lesions have been documented in specimens from different species suggests that the long neck may represent a functional weakness in this group of animals on certain occasions.

The absence of the body in both specimens suggests that the predators that hunted them probably fed on it, leaving behind the neck and head. The excellent preservation of the remains and the absence of bite marks allow us to rule out that the animals were eaten by scavengers, but that they were actively hunted.

“The small species of Tanystropheus it could have been decapitated by any number of predators, from a large fish to another marine reptile. On the other hand, for large species, there are fewer possible candidates,” explains Spiekman. The investigators suspect Nothosaurus giganteus, a great ancestor of plesiosaurs as responsible for their demise.

Tanystropheus It was a species with relative evolutionary success. It lived for at least 10 million years, and fossil remains have been found in Europe, the Middle East, China, North America and possibly South America.

The fossils used are deposited at the University of Zurich (Switzerland) and come from the deposit Mount San Giorgio, close to that country’s border with Italy, surrounded to the north by Lake Lugano. It is one of the most important deposits of marine fossils from the Middle Triassic and has been declared a World Heritage Site by UNESCO.

Paleontologists Eudald Mujal (left) and Stephan Spiekman (right), in the reserves of the Natural History Museum in Stuttgart. / Liliana Reinohl / SMNS