Specimens of Tanystrophy can grow to over five meters (16 ft) in length, with its tail being about a third of its length and its body perhaps a quarter. The rest is all around the neck.
« Tanystrophy looked like a stocky crocodile with a very, very long neck, ”says paleontologist Olivier Rieppel of the Field Museum in Chicago.
Why this reptile evolved such expansive dimensions is a complete mystery. The fact that no one could tell if they would rather be submerged in water or wander around on land only made it harder to draw conclusions.
Part of its quirk is the shape of the neck bones. Unlike those of a snake or a lizard, the cervical vertebrae Tanystrophy the fossils are spread out like those of a giraffe. In fact, when its remains were first discovered in 1852, the scattered bones were believed to be the elongated wing bones of a flying pterosaur.
Not all of the individuals we have found are the size of a crocodile either. A number are much smaller, making paleontologists question whether any of the specimens in their records are juvenile or represent a completely different species.
This is a common problem in paleontology – the tiny fossil of a dwarf species can be almost identical to the immature bones of a young one. To separate them, you have to look for clues as to whether the skeleton has not yet reached its actual size or if it still has work to do.
Fortunately, such clues can be found deep in the fossils. Just as the rings inside a tree trunk show evidence of their age, so can bones.
To find them, Rieppel and his colleagues used x-rays on an assortment of Tanystrophy skeletons, transforming scans into 3D models using high-resolution computerized tomography (CT) technology.
“The power of CT scans allows us to see details that are otherwise impossible to see in fossils,” says lead author Stephan Spiekman, an expert in Triassic reptile evolution at the University of Zurich.
Growth rings revealed the smallest Tanystrophy the bodies did indeed belong to adults, which shows quite clearly that what the researchers had in their hands were two distinct species.
To distinguish them, the team named the largest T. hydroides, after the hydra in Greek mythology. Its little cousin has retained the original name of the species T longobardico.
Turning the scans into digital models also provided the researchers with a way to rearrange the crushed bones into a clearer configuration, which made it possible to see the entire anatomy of the creature well.
“From a heavily crushed skull, we were able to reconstruct an almost complete 3D skull, revealing crucial morphological details,” says Spiekman.
With all his bone fragments in their place, he looks like Tanystrophy would be nice at home in the water after all.
The reptile’s skull has its nostrils perched on top, much like a crocodile’s snout – just the thing for an ambush predator to keep a lung full of air while waiting for a meal to pass.
What had been a bunch of tangled sharp teeth can also be seen forming a fairly effective trap for catching a cephalopod, at least for large species.
“Smaller species probably ate small, shelled animals like shrimp, unlike fish and squid that larger species ate,” says Spiekman.
“It’s really remarkable, because we expected the bizarre neck of Tanystrophy be specialized for a single task, like the neck of a giraffe. But in fact, it enabled several ways of life. It completely changes the way we look at this animal. ”
The fact that the two very similar species have such different ways of using their long bodies made it much easier for them to exist in the same habitats, sharing their surroundings without competing for the same food sources.
We can now almost imagine the stocky body of the crocodile-shaped animal lying against the ground of a shallow coast about 242 million years ago, its head rising very high to the surface for that his nostrils could siphon air, his bristling mouth gaping slightly in anticipation. of a stray squid to trip over.
As familiar as the scene seems, Tanystrophy is still a strange creature.
This research was published in Current biology.