Long-necked reptiles, Tanystropheus, were easily decapitated by dinosaur predators

During the era when dinosaurs roamed the Earth, a myriad of marine reptiles, such as Tanystropheus, were extraordinarily long-necked. They looked very much unlike their modern-day counterparts.

For years, paleontologists hypothesized that these elongated necks, despite proving beneficial for survival, also exposed these marine creatures to a greater risk from predators. Today, nearly two centuries of persistent research have led to the discovery of direct fossil evidence substantiating this theory.

This landmark finding, published in the journal Current Biology on June 19, sheds light on the curious neck structure of two Triassic species of Tanystropheus. This was a reptile species distantly related to crocodiles, birds, and dinosaurs.

Tanystropheus species had very unique necks

The necks of these Tanystropheus species were unique. They comprised 13 highly extended vertebrae and rib-like struts. The stiffened necks allowed these marine creatures to lay in ambush for their prey. However, this unusual feature also presented an irresistible opportunity for predators to attack.

Recent meticulous study of the fossilized bones of these species revealed something dramatic. Two specimens, each from a different species, had their necks severed.  Distinct bite marks were evident at the break. These findings present compelling and macabre evidence of predator-prey interactions dating back more than 240 million years, according to the researchers.

“Paleontologists speculated that these long necks formed an obvious weak spot for predation, as was already vividly depicted almost 200 years ago in a famous painting by Henry de la Beche from 1830,” remarked Stephan Spiekman from the Staatliches Museum für Naturkunde Stuttgart, Germany.

He went on to add, “Nevertheless, there was no evidence of decapitation—or any other sort of attack targeting the neck—known from the abundant fossil record of long-necked marine reptiles until our present study on these two specimens of Tanystropheus.”

Two Tanystropheus species lived in the same habitat

Spiekman, who conducted extensive research on these reptiles as part of his doctoral work at the Paleontological Museum of the University of Zurich, Switzerland, made some intriguing discoveries. He found that two species of Tanystropheus, one small and one considerably larger, inhabited the same environment.

The smaller species, measuring about a meter and a half, probably fed on soft-shelled animals like shrimp. The larger six-meter species subsisted on fish and squid. An investigation into the skull shape revealed that Tanystropheus most likely spent the majority of its life underwater.

Even though it was known that two specimens of these species had well-preserved heads and abruptly ending necks, no detailed study on these necks had been conducted.

How the Tanystropheus study was conducted

Spiekman joined forces with Eudald Mujal, a fellow researcher at the Stuttgart Museum and a research associate at the Institut Català de Paleontologia Miquel Crusafont, Spain, to address this gap.

After an afternoon spent meticulously examining the two specimens in Zurich, they arrived at a conclusive finding. The necks had clearly been bitten off by predators.

Something that intrigued the researchers was the condition of the skull and the preserved part of the neck. Mujal noted, “Only the neck and head are preserved; there is no evidence whatsoever of the rest of the animals. The necks end abruptly, indicating they were completely severed by another animal during a particularly violent event, as the presence of tooth traces evinces.”

Mujal further theorized that when these creatures were buried, their bones were still covered by soft tissues like muscle and skin. He conjectured that the predator was likely more interested in the meatier parts of the body than the skinny neck and small head.

According to Mujal, this suggested that the animals were more likely hunted and decapitated rather than scavenged. However, he admitted that scavenging could not be entirely ruled out due to the fossils’ ancient age.

Long necks of Tanystropheus are an evolutionary mystery

Interestingly, the same violent decapitation scenario was seen in specimens of two different Tanystropheus species. This, despite their different sizes and potential lifestyles. Spiekman found this quite remarkable.

These findings reinforce the notion that the necks of these ancient reptiles constituted an utterly unique evolutionary structure. They were more slender and stiffer than those of long-necked plesiosaurs.

The researchers noted that the long necks posed potential risks for these sea reptiles. This is a puzzling fact, despite being a prevalent evolutionary trait that lasted over 175 million years.

“In a very broad sense, our research once again shows that evolution is a game of trade-offs,” stated Spiekman.

“The advantage of having a long neck clearly outweighed the risk of being targeted by a predator for a very long time. Even Tanystropheus itself was quite successful in evolutionary terms, living for at least 10 million years and occurring in what is now Europe, the Middle East, China, North America, and possibly South America.”

More about Tanystropheus

Tanystropheus is a fascinating reptile known primarily from the Triassic period, which spanned from about 251 million to 199 million years ago.

The genus Tanystropheus is most renowned for its unusually long neck, which was made up of extremely elongated vertebrae. These neck vertebrae could make up over half of the animal’s total length, which is an exceptional characteristic among vertebrates.

Description

Tanystropheus had a long, thin neck, with up to 13 elongated vertebrae. The body was short, with a small head and large, robust jaws. It also had long, slender teeth, which suggest that it might have been a specialist fish eater. The tail was also long, which may have aided in swimming. Its total body length is estimated to range from 1.5 to 6 meters, depending on the species.

Ecology

There has been some debate over whether Tanystropheus was aquatic or terrestrial. Given its long neck and tail, and short, stubby body, many paleontologists believe it was likely a semi-aquatic animal, spending much of its time in the water. The large species of Tanystropheus was probably a pursuit predator, feeding on fish and squid, while the smaller species probably fed on shellfish and other small marine animals.

Distribution

Fossils of Tanystropheus have been found in Europe, the Middle East, China, and North America, suggesting that this genus had a wide geographic distribution.

Evolutionary success

Despite the apparent vulnerability of its long neck to predation, Tanystropheus was evolutionarily successful, surviving for at least 10 million years. Its long neck was a distinguishing adaptation, allowing it to potentially ambush prey, although it also provided a clear target for predators.

Research

Much of what we know about Tanystropheus comes from spectacularly preserved fossils found in the Monte San Giorgio locality on the border between Switzerland and Italy. The site has been called the “most important locality in the world for understanding marine life” during the Triassic period.

Classification

Tanystropheus is a member of the order Protorosauria, a group of early archosauromorphs, which includes the ancestors of crocodiles, birds, and dinosaurs.

Tanystropheus continues to be an active area of study, with new discoveries and interpretations helping us to further understand its unique biology and ecology.