Mystery solved: Odd, giraffe-necked reptile lived in water

Paleontologists have finally solved the mystery of Tanystropheus, a bizarre giraffe-necked reptile that lived 242 million years ago.

It lived in water and was surprisingly adaptable, according to a new study.

For over 150 years, paleontologists have puzzled over the reptile that had a neck three times as long as its torso, but only had thirteen extremely elongated vertebrae, and whether it lived on land or in water.

Researchers have now reconstructed the reptile’s skull in unprecedented detail using synchrotron radiation micro-computed tomography (SRμCT), an extremely powerful form of CT scanning. In addition to revealing crucial aspects of its lifestyle, the scans also show that Tanystropheus had evolved into two different species.

Nostrils located on the top of the snout and curved teeth, perfectly adapted for catching slippery prey: The skull of Tanystropheus has several clear adaptations for life in water. (Credit: Emma Finley-Jacob)

The researchers were able to reconstruct an almost complete 3D skull from a severely crushed fossil. The reconstruction reveals that the skull of Tanystropheus has several very clear adaptations for life in water. The nostrils are located on the top of the snout, much like in modern crocodilians, and the teeth are long and curved, perfectly adapted for catching slippery prey like fish and squid.

“We expected the bizarre neck of Tanystropheus to be specialized for a single task, like the neck of a giraffe. But actually, it allowed for several lifestyles.”

However, the lack of visible adaptations for swimming in the limbs and tail also means that Tanystropheus was not a particularly efficient swimmer.

“It likely hunted by stealthily approaching its prey in murky water using its small head and very long neck to remain hidden,” says Stephan Spiekman, a paleontologist at the University of Zurich, and lead author of the paper in Current Biology.

Scientists have mainly found Tanystropheus remains at Monte San Giorgio on the border between Switzerland and Italy, a place so unique for its Triassic fossils that it was declared a UNESCO World Heritage Site.

Two types of Tanystropheus fossils were found at this location, one small and one large. Until now, these were believed to be the juveniles and adults of the same species. However, the new study disproves this assumption.

Reconstructions of the skeletons of Tanystropheus hydroides (large species, newly named) and Tanystropheus longobardicus (small species). The outline of a 170 cm (5.57 feet) tall diver serves as the scale. (Credit: Beat Scheffold/U. Zurich)

The reconstructed skull, belonging to a large specimen, differs greatly from the already known smaller skulls, particularly when it comes to its dentition.

In order to see whether the small fossils actually belonged to young animals, the researchers looked at cross sections of limb bones from the smaller type of Tanystropheus and found many growth rings that form when bone growth is drastically slowed down.

“The number and distribution of the growth rings tells us that these smaller types were not young animals, as previously considered, but mature ones,” says last author Torsten Scheyer. “This means that the small fossils belonged to a separate, smaller species of Tanystropheus.”

These two closely related species had evolved to use different food sources in the same environment, Spiekman says.

“The small species likely fed on small shelled animals, like shrimp, in contrast to the large species which ate fish and squid,” he says.

“We expected the bizarre neck of Tanystropheus to be specialized for a single task, like the neck of a giraffe,” the researchers say. “But actually, it allowed for several lifestyles.”

Source: University of Zurich

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