First mass grave discovered by pterosaurs

A storm killed 120 million years ago a whole pterosaur colony, including eggs

For example, the pterodactyl Hamipterus tianshanensis could have looked during his lifetime. © Chuang Zhao
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Sensational fossil find: Paleontologists have discovered a whole colony of fossil pterosaurs in northwestern China for the first time. So far, relics of these dinosaurs were rare and were found at most isolated. Among the 120 million year old fossils are also the first well-preserved and not flattened eggs of such winged lizards. This find gives for the first time an insight into the hitherto almost unknown way of life and reproduction of the pterosaurs.

They were the primeval rulers of the skies - and the first vertebrates that could fly: pterosaurs dominated the airspace of our planet for more than 150 million years. With wing spans of up to twelve meters, light bones and wing-like thin skins, they were perfectly adapted to flying. However, little is known about the way of life of these flying lizards until today, because fossils are only sporadically, relics of juveniles or eggs even rarer.

"So far, only four single, flattened eggs of pterosaurs have been known, " said Xiaolin Wang from the Chinese Academy of Sciences in Beijing and his colleagues. But they were so poorly preserved that details of their construction were barely recognizable. And even about how the pterosaurs raised their offspring, betrayed this single finds nothing.

Fossils of males, females and eggs of pterosaurs were found close together. © Chuang Zhao

Thousands of bones and many eggs

But that has now changed the sensational find in Xinjiang province in northwestern China. In the sedimentary rocks of the Turpan-Hami Basin, paleontologists discovered a true treasure: hundreds, probably even thousands of fossil skeletons of a previously unknown species of pterosaur. Close together lie the well-preserved remains of males and females, juveniles and even eggs.

"It was absolutely exciting to find them all in one place, " says Wang. The skeletons show that the pterosaur males were slightly larger and had a more pronounced head crest. In females, the head crest started farther back and was smaller. This is especially exciting because today's reptiles are often females and because there were hardly any findings on the gender differences in pterosaurs. display

A little bit shredded, but well: first three-dimensionally preserved egg of a pterodactyl. Maurilio Oliveira

Eggs in the sand nest

The five previously excavated eggs are not only largely preserved, they are also not flattened, so that for the first time the original, three-dimensional form of such pterosaur eggs is visible. The eggs are about 6 inches long and 3.4 inches wide and slightly asymmetrical oval. Instead of a solid calcareous shell, they only have a gossamer, flexible limestone shell, which rests on a thicker, firm skin. They are similar to the eggs of today's snakes and lizards, as the researchers explain.

From the situation and the somewhat different sizes of the eggs, palaeontologists conclude that they do not have to be a clutch, but must come from different females. Probably the pterosaurs buried their eggs in the moist sand of the lake shore to protect them from drying out, much like many sea turtles do today. Obviously, they did not leave the nests to themselves, but formed a large colony on the beach.

Common death in the storm

"Our findings prove that these pterosaurs behave sociably, " say the palaeontologists. Most likely, the primeval lizards died together:

Selected sediments in the same layer as the bones indicate that at least one strong storm swept over the shallow, sandy shores of the lake 120 million years ago. Probably this storm triggered a mass extinction, which fell victim to a large part of the pterosaur colony.

From the remnants of this colony, palaeontologists hope to gain further insights into the way of life and social behavior of these primeval giants of the Lungs. (Current Biology, 2014; doi: 10.1016 / j.cub.2014.04.054)

(Cell Press / Current Biology, 06.06.2014 - NPO)