A Blog by Ed Yong

Chinese Dinosaur Had Bat-Like Wings and Feathers

Since most dinosaur names consist of long, polysyllabic gargles—Parasaurolophus, Therizinosaurus, Pachycephalosaurus—it is refreshing that the latest addition to the family has the shortest one yet.

It is simply Yi.

In full, it is Yi qi, which comes from the Mandarin for “strange wing” and can be roughly butchered as “ee chee”. The name hints at this pigeon-sized animal’s most remarkable feature. Each of its hands had a long bony rod extending from the wrist. This rod seemed to support a membrane, much like that of a flying squirrel or bat.

Yi was a dinosaur with bat-like wings! What an astonishing find!

The Yi qi fossil. Credit: Zang Hailong/IVPP
The Yi qi fossil. Credit: Zang Hailong/IVPP

Until now, the assumption was that prehistoric reptiles took to the skies in one of two different ways. The dinosaurs did so with feathers. Many species were covered in downy insulating fuzz, and some small predatory species elaborated these into true, flight-capable feathers—long, flat vanes that protruded from their arms (and sometimes their legs). These winged creatures gave rise to the first birds. Meanwhile, the pterosaurs evolved a very different type of wing, by greatly lengthening their fourth fingers to support a membrane of skin and muscle. (Pterosaurs are often lumped with dinosaurs but belonged to a totally separate group.)

These wings were mutually exclusive: dinosaur or pterosaur, feathery or leathery. But Yi went for both options! It had membrane wings with a feathery covering on the leading edge. It shows that at least some dinosaurs had independently evolved the same kind of wings as pterosaurs—an extraordinary example of convergent evolution.

“This is refreshingly weird,” says Daniel Ksepka from the Bruce Museum, who was not involved in the study. “Paleontologists will be thinking about Yi qi for a long time, and we can surely expect some interesting research into the structure and function of the wing.”

There’s only one known fossil of Yi. A farmer in China’s Hebei Province found it around eight years ago., and the Shandong Tianyu Museum of Nature bought it shortly after. Xing Xu and Xioating Zheng from Linyi University, who discovered the creature, first laid eyes on it in 2009 and started working on it in 2013. “It looked special to me,” Xu recalls.

As the team exposed and analysed the specimen, they worked out that it was a scansoriopterygid—a group of small, feathered dinosaurs with very long third fingers. These species were reputedly good climbers (their name means “climbing wing”) but there was no evidence that their feathers were good enough for flight.

The same applied to Yi—its feathers, covering its skull, neck and limbs, were stiff filaments that ended in paintbrush-like tips. They were very different to the flight-capable plumes of birds.

Then, the team noticed the weird rod. It stuck out from each of the dinosaur’s wrists and was longer than its forearm. It’s not a finger, but its chemical composition revealed that it is indeed a bone, or perhaps a piece of hardened cartilage. The team had no idea what it was. “When I saw the bone, I was really confused,” says Xu. “There is nothing comparable in any other dinosaur.”

But, as Corwin Sullivan from the Chinese Academy of Sciences realised, there is something comparable in flying squirrels. These rodents glide from tree to tree by expanding a membrane that stretches from their wrists to their ankles. They deploy this membrane by splaying their limbs and extending a long piece of cartilage (called the styliform process) that protrudes from their wrists. Bats have a similar piece of cartilage (the calcar) on their feet, and pterosaurs had a similar bone (the pteroid) on their arms.

All of these structures do the same thing: they support a membrane that keeps their owner in the air. Yi’s wrist rod was almost certainly fulfilling the same role. “As far as i know, this is the only plausible interpretation,” says Xu. He even found several patches of what look like sheet-like membranes, surrounding the rods and fingers of both hands. Again, they’re unlike anything seen in other dinosaurs.

“The ‘bone’ seems to be what they say it is, and they have made appropriate studies to show it isn’t something else,” says Michael Benton from the University of Bristol. “So, yes, it seems real, and, my goodness, what a further broadening of flight capabilities in paravians!” (That’s the group of dinosaurs that includes the scansoriopterygids, celebrities like Velociraptor, and all birds.)

But Yi “is not necessarily as weird as it might first seem, in an evolutionary sense,” says Michael Habib from the University of Southern California. “Living birds actually have membranes around their forelimbs, including a well-developed membrane in front of the elbow called a propatagium. Feathers cover [these] parts of the wing, obscuring the soft tissues.” Yi simply extended these membranous parts with the help of their weird extra bone.

Yi-qi-reconstructionFor the moment, the team can’t work out how it held its wrist rods, and so can’t reconstruct the true shape or capabilities of the extended wing. This is crucial. A broad membrane, Habib says, would have kept Yi qi stable in the air, and allowed it to launch and land safely. With a narrower membrane, it would have needed to fly or flap very fast to stay airborne, and to take off at high speeds.

Yi might have moved through the air with a combination of flapping and gliding flight, though it probably relied more on gliding,” says Xu, who is planning to search for more specimens. “There are many questions remaining to answer about this bizarre dinosaur.”

For now, this discovery reminds us that the evolution of flight among birds and other dinosaurs was not a simple story. In the late Jurassic period, when Yi lived, there were all manner of dinosaurs with varying shapes, sizes, and numbers of wings. It was a world of not-quite-birds and just-about-birds—and now bat-winged dinosaurs, too! “What a grand age of experimentation!“ says Ksepka.

“This may also be evidence that flight evolved multiple times within dinosaurs—perhaps three or more times,” adds Habib.

Reference: Xu, Zheng, Sullivan, Wang, Xing, Wang, Zhang, O’Connor, Zhang & Pan. 2015. A bizarre Jurassic maniraptoran theropod with preserved evidence of membranous wings. Nature http://dx.doi.org/10.1038/nature14423

PS: Here’s another odd thing about Yi. Its feathers preserve traces of melanosomes—small sacs of coloured pigments. That’s not unusual in itself; several scientists have used melanosomes to reconstruct the colours of fossil feathers. But Yi has some of the largest melanosomes ever seen. “I had to double-check to make sure I did not misread the measurements,” says Ksepka.

26 thoughts on “Chinese Dinosaur Had Bat-Like Wings and Feathers

  1. I repeat: where there are environmental pressures to diverse and take to the air, return to the sea, change diat, or even go back to laying eggs it will have been accomplished many times. Will ostriches eventually “return to the air”?

  2. Wow, a ‘new’, middle–upper Jurassic dinosaur – er, start of 3rd paragraph should be Yi. Thanks, great write-up.

  3. Awesome. The world of dinosaur research always manages to produce some intriguing discoveries. One wonders what other secrets the strata from the Mesozoic, particularly in China, still hold.

  4. Funny…those myths of Chinese dragons came from somewhere, and I am not referring to ancient people making up stories about buried fossils. Ironic how science is helping solidify ancient beliefs and traditions.

  5. It is actually called Qi Yi (or Qi Yi Long, Long = dinosaur/dragon) by Chinese usage, with Qi meaning strange and Yi meaning wing(s) so that Qi Yi = strange wing(s). But I can understand why it appeared as Yi Qi in an English language journal, as is in the case of first name and last name.

  6. The generic name tends to be a name while the species name should be an adjective describing it… That’s why the name changes from proper Chinese qi yi (qiguai de yizi, 奇怪的翼子,strange wing), to Yi qi (and why I didn’t get the etymology till now)

    Really , what a curious animal this is…

  7. This is a wonderful transitional between pterosaur and bird.

    [It is not. Those two evolved their wings indepedently. – Ed]

  8. Doug, it’s not related to pterosaurs…scansors evolved their gliding membranes independently, which is even more amazing!

  9. NO, there is no ‘transition’ between pterosaurs and birds (avian dinosaurs.) Pterosaurs are a different branch from dinosaurs, the same way the ancient marine reptiles are. Birds (avian dinos) descended from theropod ancestors.

  10. In regards to the rod-like bone and the wing membrane, there is no transition from ANY dinosaur to Yi.
    “Most surprisingly, Yi has a long rod-like bone extending from each wrist, and patches of membranous tissue preserved between the rod-like bones and the manual digits. Analogous features are unknown in any dinosaur but occur in various flying and gliding tetrapods*”.

    * A pterosaur is of course a flying and gliding tetrapod.

  11. Doug, the authors relate the feature to the pterosaur pteroid (among various other tetrapods). Do you think the pterosaur pteroid represents the structure homologous to the styliform in Yi qi?

  12. No. The pterosaur wing finger (outermost finger) first phalange represents the structure homologous to the styliform in Yi qi.

  13. How can this be? The styliform was a single bone originating from the wrist, and the animal already has a long finger that forms the leading edge of the wing. That is even more unfeasible than considering it a modified pteroid.
    It doesn’t matter though, since Yi qi is firmly nested within theropod dinosaurs, as the authors find. And that is hardly a surprise.

  14. The Yi rod-like bone (“styliform element”) is positioned and functions like the wingfinger (outermost finger) in the ptersosaur.
    Take a look at a pterosaur wing and see where it is positioned. It is not complicated.

  15. Alternately
    The pterosaur wing finger (outermost finger) METACARPAL represents the structure homologous to the styliform in Yi qi.

  16. It’s not complicated, it’s wrong. The styliform does not form the leading edge of the wing in Yi qi, the elongated third finger does that. No reconstruction of the styliform shows it forming the edge, and it’s no wonder since then you would have a very long finger facing forwards and not taking part in the formation of the wing.

  17. Compared to what? Please describe the evolution of the Yi qi wing from a dinosaur. Any dinosaur.
    Please keep in mind:
    “Most surprisingly, Yi has a long rod-like bone extending from each wrist, and patches of membranous tissue preserved between the rod-like bones and the manual digits. Analogous features are unknown in any dinosaur but occur in various flying and gliding tetrapods*”.

  18. Why are you turning the question around? I am commenting on the specific claim you made about the styliform being homologous to the “wing” finger of pterosaurs. I explained to you that it would be highly unlikely since there is already a “wing” finger in Yi qi. I take it you understand that now.
    Anyway, as in the way of the possible evolution from a theropod arm to the Yi qi wing, I would say that (perhaps) the elongation of the third finger facilitated the formation of the membranous wing surface, then a neomorphic bone or maybe a modified carpal bone (much like the pterosaur pteroid) developed to help in widening and strengthening the wing surface (and perhaps maintaining the curvature). This is off the top of my head, of course, but it certainly doesn’t involve the wing finger in pterosaurs turning into a styliform in a wing that already has a wing finger.
    But let’s not forget the most important thing: Yi qi is a theropod dinosaur. It is therefore not a descendant of pterosaurs. That does not change.
    See the cladogram in the supplementary data.

  19. Doug, the problem is that Yi qi is a maniraptor theropod close to the origin of birds–it has nothing to do with pterosaurs. Theropods lost their fourth fingers at the base of Tetanurinae, so they were long gone by the time Yi qi came long. The styliform element is probably ossified cartilage, analogous to (but not homologous with) the wrist-spur of modern flying squirrels–but obviously larger. It’s not the remnant of a finger bone.

    It’s entirely possible that its relatives, Scansoriopteryx and Epidexipteryx, also had styliforms but they were not preserved or simply unossified.

  20. [Okay, I’ve deleted everything in this thread from the point when it descends into back-and-forth gibberish. This isn’t a schoolyard. – Ed]

  21. The feathers on the leading edges serve a very valid purpose. They are anti-stall turbulence generators as are the feathers on the legs and head. I think this thing flew with the body more upright than we are used to seeing, with legs bent up underneath, not streaming out back.Another reason it needed microturbulance feather generators, to reduce dirty air friction. Whipe I have not read all through the existing 25 comments yet and dont want to join in the wrist bone argument, I do think the wrist bone angle is correct the way it is shown most, straight back, to in effect move the CG forward on the wings, for the same stall reasons the article mentions. FASCINATING! Thanks for the article and video.

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