New analyzes now confirm that Tanystropheus, an ancient reptile with a very long neck, lived in water and not on land. Additionally, we now know there was not one, but two distinct species.
Tanystropheus, who lived 242 million years ago in the Middle Triassic, has long baffled paleontologists. First described in 1852, its long, hollow bones first led scientists to believe they were phalanges to support the wing of a pterosaur-like reptile, such as a pterodactyl.
They later found out that they were the bones of a neck that once would have been very elongated. Based on these analyzes, they then imagined a reptile of six meters long, whose neck was about half that size.
If on the physical side, an animal was starting to take shape, researchers, on the other hand, have long wondered whether the latter lived on land or in water.
Another question: in the same region where the many large fossils of Tanystropheus, in present-day Switzerland, animal fossils of similar appearance but smaller (about 1.2 meters long) have also been found. Were they juveniles of the same species? Or did they represent a species in their own right?
New analysis techniques finally make it possible to close the debate. Details of the study are reported in the review Current Biology.
An aquatic reptile
The various skulls of the great fossils of Tanystropheus had all been crushed. Nevertheless, Olivier Rieppel and his team at the Field Museum in Chicago were able to take CT scans of these remains and generate 3D images allowing them to be exploited.
“The power of computed tomography allows us to see details that would otherwise be impossible to see in fossils, explain the researchers. From a heavily crushed skull, we were able to reconstruct an almost complete 3D skull, revealing crucial morphological details ”.
On these 3D models, the researchers were able to determine that the nostrils of these animals were placed above the muzzle – like those of a crocodile. According to the researchers, this characteristic alone makes it possible to imagine that Tanystropheus lived well in the water. He might have ventured out onto dry land to lay eggs, but generally speaking, it stayed in the ocean.
Olivier Rieppel was ultimately not surprised. “This neck, he said, does not make sense in a terrestrial environment. It would have been awkward to transport ”.
Two distinct species, no competition
To find out if the small specimens were juveniles or a separate species, the researchers looked at cross sections of their bones. They then isolated many growth rings. In other words, these animals were mature. They therefore represented a distinct species.
The researchers named the largest species Tanystropheus hydroides, after the long-necked hydras of Greek mythology. For their part, the smallest reptiles bear the original name, namely Tanystropheus longobardicus.
“For many years we have suspected the existence of two species of Tanystropheus, but until we could scan the larger specimens, we had no definitive evidencesays Nick Fraser, of the National Museum of Scotland and co-author of the article. It is now done “.
Finally, last point, it would seem that these two species which shared the same environment were not in direct competition for prey. The cone-shaped teeth of the larger ones suggest that they attacked fish or squid. The smaller ones, on the other hand, with their crown-shaped teeth, probably ate small shelled animals, such as shrimp.