Giraffe-necked dinosaur: fossil mystery solved

Since 1852 paleontologists have speculated about the way of life of this 242 million year old dinosaur. (Image: Beat Scheffold, PIMUZ, UZH)

The neck of the giraffe-necked dinosaur Tanystropheus was three times as long as its body. But did this strange creature from the Triassic age live on land or in water and were there two species? The first reconstruction of his skull now shows that Tanystropheus was a water dweller. However, the lack of efficient fins suggests that the giraffe-necked dinosaur, over five meters long, was a lurker. In addition, smaller fossils that were previously thought to be his young have now turned out to be a separate dwarf.

Tanystropheus has been a headache for paleontologists for over 150 years: There have even been assumptions that this creature was a pterosaur, because the strange long and hollow bones were thought to be wing structures. But then it became clear that they had formed a strangely oversized neck of a dinosaur that lived 242 million years ago. The first dinosaurs were just emerging on land and giant reptiles ruled the sea. Therefore, scientists have not yet been sure whether Tanystropheus lived on land or in water – his bizarre body features did not allow any clear conclusions. In addition, fossils about one meter in size were discovered at sites in the Alps, and it remained unclear whether they were young animals of Tanystropheus or another species.

3D reconstruction reveals characteristic features

The main problem with characterizing the dinosaur so far has been that no well-preserved skulls have been found – just badly shattered remains. But now an international team of researchers has reconstructed a skull of Tanystropheus using such fragments in a previously unknown wealth of detail. The scientists used the so-called SRμCT method (synchrotron radiation micro-computed tomography), an extremely powerful form of computer tomography. For the first time, they were able to draw well-founded conclusions about his lifestyle and development.

Tanystropheus was probably lying in wait in the water, waiting for prey. (Image: Emma Finley-Jacob)

The 3D reconstruction made it clear: The skull of Tanystropheus shows several adaptations to life in the water. As the researchers report, the nostrils are on the top of the snout – similar to today’s crocodiles. The teeth are long and curved, making them perfectly adapted to catch slippery prey such as fish and other marine animals, the researchers explain.

However, there is a lack of recognizable adaptations to the limbs and tail for efficient locomotion in the water. This suggests that Tanystropheus was not a particularly good swimmer. “He probably hunted by moving slowly through the murky water and secretly approaching his prey,” says first author Stephen Spiekman from the University of Zurich. “His small head and very long neck helped him stay hidden for as long as possible,” says the paleontologist.

Big and small kind

The researchers also clarified the mystery of the fossils of different sizes as part of the study. Previously, they were considered to be young and adults of the same species. The current study refutes this interpretation. Because the newly reconstructed skull, which comes from a large specimen, differs significantly from the remains of smaller skulls, especially in the features of the dentition. In order to specifically determine whether the small specimens could have been juveniles, the scientists also examined cross-sections of the bones of some fossils.

They were able to uncover characteristic growth rings that form when bone growth is drastically slowed down. “Based on the number and distribution of the growth rings, we conclude that the smaller type was not a young but an adult,” says co-author Torsten Scheyer from the University of Zurich. “The small fossils are therefore a separate, smaller species of Tanystropheus”.

As the scientists explain, the two closely related species were able to evolve in the same environment because they occupied different niches. “The different sizes of the animals, along with the conical teeth on the large species and the crown-shaped teeth on the small, means they are unlikely to compete for the same prey: the small ones likely fed on small shellfish such as crabs while the large ones Species hunted fish and squid, ”explains Scheyer.

In conclusion, co-author Olivier Rieppel of the Field Museum in Chicago says:
“I’ve been studying Tanystropheus for over thirty years, so it is extremely satisfying to see how this creature has finally been demystified,” said the paleontologist.

Source: FieldMuseum, University of Zurich, specialist article: Current Biology, doi: 10.1016 / j.cub.2020.07.025

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