These Long-Necked Marine Reptiles Were Decapitated

Having a long, stiff neck helped some Triassic reptiles stealthily hunt for fish and other animals in shallow lagoons. But their uniquely gangly necks also made them easy targets for other predators, according to a new paper published Monday in the journal Current Biology.

The study focuses on Tanystropheus, a genus of marine reptiles that lived during the Middle Triassic between 237 and 247 million years ago. To hunt, these creatures likely stood on the seafloor, heads held aloft. Then, they bided their time until unsuspecting prey swam by, much like crocodiles do today.

But on at least two separate occasions, while the long-necked reptiles were lying in wait, another predator attacked from above, decapitating them with one, swift bite. That’s what researchers have deduced from studying two sets of fossilized remains housed at the Paleontological Museum of the University of Zurich. One set belonged to a Tanystropheus hydroides, a large species that could be nearly 20 feet long. The other belonged to Tanystropheus longobardicus, a smaller, long-necked creature that could grow up to five feet long.

The neck bones of both animals were broken in a way that looked like “snapping a broomstick,” says study co-author Stephan Spiekman, a paleontologist at the State Museum of Natural History in Stuttgart, Germany, to the New York Times’ Asher Elbein.

However, fossil evidence for this hypothesis was never found until now. We describe two instances of decapitation in Tanystropheus, a Triassic archosauromorph (distant bird/croc relative) with a particularly slender and stiff neck, formed by only 13 hyperelongate vertebrae (4/10) pic.twitter.com/XTuyblrPDS

— Stephan Spiekman (@StephanSpiekman) June 19, 2023

Intrigued by this damage, researchers took an even closer look at the bones and found bite marks. They compared the bite marks to the teeth and jaws of various predators that would’ve co-existed with Tanystropheus and landed on several possible suspects: A nothosaur or an ichthyosaur probably chomped down on the larger species’ neck, while a marine reptile or large fish likely decapitated the smaller specimen.

Though the predators might have taken a few initial, injurious bites, it’s “very plausible” that they bit off the neck “in one go,” as Spiekman tells Live Science’s Hannah Osborne. Based on the location of the bites in the fossils—on the thin, lower part of the neck well below the head—Tanystropheus likely never saw the predators coming and didn’t have a chance to fight back or flee.

Since paleontologists only discovered the fossilized head and neck bones of the two Tanystropheus specimens, it seems likely that the predators targeted the creatures’ long necks in their attack, but then primarily consumed the meatier bodies.

“The torso and limbs were the main source of meat,” says Spiekman to Newsweek’s Jess Thomson. “Reptiles cannot chew, so they likely would have ripped up the body and swallowed the meatiest parts whole.”

Overall, the findings suggest that, while helpful in some aspects of life, the creatures’ long necks were “a weak spot” in others, as study co-author Eudald Mujal, also a paleontologist at the State Museum of Natural History in Stuttgart, tells New Scientist’s Christa Lesté-Lasserre.

But evolutionarily speaking, “the value of a long neck must have generally outweighed the costs,” as Edinburgh University paleontologist Steve Brusatte, who was not involved in the study, tells the Guardian’s Ian Sample. Several types of marine reptiles independently evolved long necks over the course of 175 million years, which suggests that this body type was incredibly handy. After all, it appears to have served Tanystropheus well: The creatures persisted for at least ten million years and spread across much of the world.

As Spiekman says in a statement, “evolution is a game of trade-offs.”

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Sarah Kuta is a writer and editor based in Longmont, Colorado. She covers history, science, travel, food and beverage, sustainability, economics and other topics.