New evidence of decapitations points to this Triassic predator’s fatal flaw

Science

The prehistoric reptile Tanystropheus had a neck that stretched longer than its body, allowing it to sneak up on prey in the water—and making it a target for even bigger hunters.

ByRiley Black

Published July 6, 2023

• 6 min read

An ancient marine reptile had a sneaky way of catching its prey, grabbing meals with a small, needle-toothed head at the end of its long, slender neck. Tanystropheus, which lived about 240 million years ago, likely used its elongated neck to keep the rest of its body hidden as it snatched unsuspecting fish and squid as it swam the Triassic seas.

But that neck, recent research shows, could have been Tanystropheus’s undoing.

Two fossils of the long-necked marine reptile on display at the University of Zurich in Switzerland intrigued paleontologists for including complete skulls and a few attached vertebrae—but nothing else. This wasn’t just an accident of preservation. The long-necked creatures had been decapitated, their spines bitten through.

“There was always the idea that the necks of these two specimens, and especially the big one, were bitten off,” says paleontologist Stephan Spiekman of the State Museum of Natural History in Stuttgart, Germany. But the idea was little more than an impression until Spiekman began discussing the fossils with colleague Eudald Mujal, who had previously studied bite marks on Triassic animals. The collaboration uncovered new clues as to what happened to the unfortunate Tanystropheus more than 242 million years ago, detailed in a study in the journal Current Biology.

Discovered in 1852, Tanystropheus has been a longtime favorite among fossil fans and paleontologists for its extraordinary neck. The living animal could reach lengths of about 20 feet, and most of that was neck. The reptile had evolved 13 ludicrously long vertebrae to support its 10-foot neck, longer than its torso and tail together.

Even though Tanystropheus was far from the only prehistoric reptile to evolve a long neck, its proportions and anatomy always seemed unusual. The reptile did not appear to be as at home in the water as the swimming plesiosaurs, which over time would evolve necks more than 22 feet long. For a time experts hypothesized that Tanystropheus stood on the shore, dipping its neck in the water to snatch fish or squid like some birds do today.

More recent analyses have indicated that Tanystropheus was a skilled swimmer and likely hunted in the water. Such a stupendous neck came at a cost, however. Tanystropheus had evolved to be a sneaky hunter, but the reptile also lived among predators that were hunting it.

Prehistoric bite marks

The way the Tanystropheus fossils seemed to end abruptly wasn’t the only thing that suggested some Triassic trauma. The researchers spotted “some evidence for bite marks that we have previously never confidently identified,” Spiekman says. A visit back to the fossils in Zurich turned up even more clues: punctures, scrapes, and fractures that must have been made in life and not as part of the fossilization process.

“The case that these injuries came from a bite is strong,” says paleontologist and fossil bite mark expert Stephanie Drumheller-Horton of the University of Tennessee, Knoxville, who was not involved in the new study. Teeth that hit bone leave particular kinds of damage—from scratches to punctures and breaks—that are readily visible on the bones.

The Triassic bite marks do more than indicate that a prehistoric creature was bitten. Spiekman and Mujal were able to use the markings to reconstruct how they think the two Tanystropheus were attacked and decapitated.

“It is of course always difficult to say something with certainty when talking about a predator-prey scenario that occurred 242 million years ago,” Spiekman says. But the damage on the bones offers some indication of what must have happened. “The way in which the two tooth punctures open posteriorly shows that this is where and when the neck broke, and then the scratch on the bone surface that widens backwards and upwards really shows that this was the direction in which the tooth was pulled away,” he says. Together, the evidence suggests the attacking animals came from above and behind, chomping into the exposed neck and pulling back as they bit through.

Drumheller-Horton is less certain about the angle of attack. The scenario in the paper is certainly plausible, she notes, but some reptilian carnivores like crocodiles bite and then lash their prey from side-to-side or even roll, motions that could have also created the damage pattern seen on Tanystropheus.

A susceptible nape

Even though other marine reptiles such as plesiosaurs evolved long necks, Tanystropheus was uniquely vulnerable. Instead of being made up of many compact vertebrae that might better withstand bites, the neck vertebrate of Tanystropheus were fewer and longer than those of other animals, making them more fragile.

“These vertebrae were almost completely hollow,” Spiekman says, “so all in all they have the shape of a thin, elongated tube or cylinder.” Even though Tanystropheus evolved a biomechanical solution to having a long, lightweight neck, the way in which Tanystropheus did so made them more vulnerable to the bigger aquatic reptiles prowling the same waters.

Precisely which reptile bit the two Tanystropheus—if the species has even been discovered—is unclear. “Many predators could have inflicted the trauma,” the researchers note in their study.

The spacing between the tooth marks narrowing down the possible attackers to another long-necked reptile Nothosaurus, the dolphin-like ichthyosaur Cymbospondylus, and the almost lizard-like Helveticosaurus. To find two fossils of decapitated Tanystropheus from the same rock layers is a rarity, however, suggesting that such moments of “nature red in tooth and claw” must have transpired relatively often.

Now that decapitated fossil reptiles have been identified, researchers can begin looking for more. Even with different skeletal constructions, Drumheller-Horton says, it’s surprising that similar damage hasn’t been seen on plesiosaurs or other long-necked marine reptiles.

Other bones in museum collections may bear the marks of deadly prehistoric bites, but paleontologists simply haven’t conducted a close inspection. “I think some of those fossils might warrant another look,” Drumheller-Horton says.

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