Ambopteryx longibrachium was a tiny dinosaur with bat wings

An article published in the journal “Nature” reports the identification of a new species of dinosaur that lived around 163 million years ago, in the Late Jurassic period, which had some characteristics similar to those of birds but with wings more similar to those of pterosaurs or bats. A team of researchers coordinated by the Chinese Academy of Sciences named it Ambopteryx longibrachium and classified it in the family of scansoriopterygid, which could be close relatives of birds. This little dinosaur could provide important information about the development of flight among dinosaurs and therefore in birds.

Scansoriopterygids (Scansoriopterygidae) are a family of dinosaurs that lived in the Jurassic period still subject of discussions to understand the actual relationship with birds, to define the various relationships among the few species classified within it and their place among dinosaurs. For this reason, in 2015 the identification of the first species of this family with wings more similar to those of bats than to those of birds, named Yi qi, raised a certain skepticism, also because it was based on a single partial skeleton. These are common problems in the field of paleontology with the need to perform more studies on the available fossils with different techniques and always be ready to change conclusions in case of new discoveries.

Now a team led by paleontologist Min Wang of the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences identified a new dinosaur classified in the scansoriopterygid family with similar characteristics that show a rather close relationship with Yi qi. A nearly complete skeleton was discovered in 2017 near the Chinese village of Wubaiding, in the Liaoning province. The good preservation of the new dinosaur offers better evidence of the wings characteristics and more information on this type of dinosaurs. The specimen of the species later named Ambopteryx longibrachium was initially mistaken for a bird but in the course of preparations Wang realized that it was something different.

Ambopteryx longibrachium was 32 cm long for a weight estimated at just over 300 grams, it had elongated rod-like bones called styliform elements that start from the wrists and probably supported the wing membrane. Some traces found on a wing could be remains of that membrane and there are still also fossil feathers and a pygostyle, a bone consisting of fused tail vertebrae that in modern birds supports tail feathers.

Another interesting discovery concern the Ambopteryx longibrachium specimen’s stomach contents as it ate shortly before its death: there were gizzard stones, pebbles like those of today’s herbivorous birds, but also bone fragments that suggest that this dinosaur was omnivorous.

The top image (Courtesy Min Wang. All rights reserved) shows the Ambopteryx longibrachium fossil (a), a drawing of this dinosaur (b), the melanosomes of its membranous wings (c) and the contents of its stomach (d). The bottom image (Courtesy Chung-Tat Cheung. All rights reserved) shows artistic reproductions of this animal.

The researchers are still studying Ambopteryx longibrachium’s flight skills. They believe it was a dinosaur that adapted to a life among trees and evolved to leap among them similarly to flying squirrels. In essence, it’s possible that it could glide but not fly like birds.

At least for now no scansoriopterygids are known from the Cretaceous period, the one after the Jurassic, therefore it’s possible that they became extinct and that that type of adaptation perhaps only partial to flight ended with species such as Ambopteryx longibrachium. Other feathered dinosaurs with a different wing structure kept on diversifying and some of them became the ancestors of modern birds. The fossils discovered in China in recent decades are bringing new information on that transition but the findings of scansoriopterygids also suggest that there were other adaptations to flight that had less success.

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