Strange Wings Over The Jurassic

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A research letter in Nature reports a new bat-like dinosaur from the Middle to Upper Jurassic Tiaojishan Formation in Hebei, China. This formation has been dated to between 165 to 153 million years ago.

The fossil has been assigned to the scansoriopterygid theropods, where it joins Scansoriopteryx and Epidexipteryx. At this point, all the letters had been used up, so the new animal has been dubbed simply Yi qi, which means “strange wing” in Mandarin.

The name comes from the fossil’s most noteworthy feature: a long rod either of bone or possibly cartilage extending from each of its wrists which the authors dub the “styliform element.” This creates a wing which is completely unique in the animal kingdom. Flying squirrels are somewhat similar in terms of having their “wings” supported by a styliform element, but the Yi qi also had a greatly extended third finger to support the wing.

In addition to the bones, some soft tissue structures were preserved in the fossil. There were feathers on the head and down the neck. There were also feathers on the forelimb, but these puffy feathers did not form the wing. Indeed, it appears that the longer feathers have been partially or completely lost and the wing was made up of a membrane, similar to that in a bat or a pterosaur.

The exact structure of this wing isn’t preserved so the authors suggested three possibilities. In the “bat” model, the styliform element extends straight down and the membrane forms a complete wing extending down to the hip. The “maniraptoran” model places the element so that it’s running back towards the body and the wing is much more narrow. Their final suggestion is a “frog” model where, again the element extends downward but the membrane is only on the hand, like the parachutes of a gliding frog. It’s not clear whether it was a glider or actually capable of powered flight, but the lack of strong muscle attachments tilt the argument slightly towards being predominantly a glider.

It’s not a complete skeleton. It consists of the skull, neck, a few ribs and most of one arm and impressions of the other plus a few bones. Only a few traces of the lower body are preserved. Overall, it’s the size of a typical bird like a duck or crow. It’s relative Epidexipteryx has been found with long tail feathers like those in the artist’s interpretation of Yi qi.

"Yi qi restoration" by Emily Willoughby, (e.deinonychus@gmail.com, emilywilloughby.com) - Own work. Licensed under CC BY-SA 4.0 via Wikimedia Commons
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Scansoriopterigidae are classed as paravians, forming a sister group to the line that eventually leads to birds. They are not considered direct ancestors so this appears to have been a parallel experiment in flight among the theropods.

“Yi qi restoration” by Emily Willoughby, (e.deinonychus@gmail.com, emilywilloughby.com) – Own work. Licensed under CC BY-SA 4.0 via Wikimedia Commons