After over a century and a half of discovery, you'd think dinosaurs would start getting a little mundane. Paleontologists have already described over 500 different genera of the prehistoric celebrities, and the shape of the dinosaur family tree is well known. But almost on a monthly basis, paleontologists describe new saurians that set social media afire with cries of “What is that thing?” The unexpectedly herbivorous Chilesaurus did so earlier this week, and now, hot on its scaly heels, comes Yi qi—the “strange wing”.
The 163-million-year-old dinosaur was about the size of a sparrow and was covered in fluffy feathers. But unlike previous fossil dinosaurs with aerodynamic appendages, Yi has thin rods of bone jutting from each wrist. “When I saw the rod-like bone, I was really confused,” says paleontologist Xing Xu of the Chinese Academy of Sciences. “There is nothing comparable in any other dinosaur.”
According to Xing and his team, the bony rods on the dinosaur’s wrist likely supported bat-like wings. The discovery, reported today in Nature, joins a growing body of evidence that the direct ancestors of birds weren’t the only dinosaurs taking to the air, and it may add to our understanding of the evolution of flight. Not to mention that a dinosaur that may have swooped around like Batman is just plain cool.
From beautifully preserved fossils, paleontologists have been able to confirm that the wings of birds are just the slightly modified, feathery arms of Velociraptor-like dinosaurs. Some, such as Microraptor, even had long feathers attached to their legs to create a second set of wing-like appendages—although how such a creature might have moved through the air is hotly debated.
Yi is different, and it took a long path into the scientific spotlight. Like many feathered dinosaur fossils, Yi was uncovered by a farmer working in China's Hebei Province. From there, the fossil made its way to the Shandong Tianyu Museum in 2007, says Xing. That’s where he first saw it, and it was special enough that he sent a fossil preparator to carefully clean up the fragile remains.
The dinosaur turned out to belong to a strange, recently discovered group of theropod dinosaurs called scansoriopterygids, a group closely related to the dinosaurs that gave rise to birds. In addition to those weird rods of bone, Yi was found with a thin membrane attached to the spikes. Putting these clues together, study co-author Corwin Sullivan suggested that these were adaptations for gliding or flying.
“This new specimen is fantastically strange compared to other theropod dinosaurs like Allosaurus and Tyrannosaurus, says University of Southern California paleontologist Michael Habib. But compared to dinosaurs that are closely related to the earliest birds, Yi isn’t quite as bizarre as it might initially seem. Living birds actually have a membrane around their wings called the propatagium, Habib points out. It’s just that the feathers of today’s avian dinosaurs obscure this part of the wing, while Yi has a more expanded membrane that Habib describes as “a wing using the same basic parts as a bird, but in reverse of how bird wings are built.”
Could Yi flap these little wings? From that dinosaur’s skeletal anatomy and what has been proposed for other dinosaurs of the same group, Xing suspects that Yi lived up in the trees rather than on the ground. Perhaps the little dinosaur was some kind of Jurassic BASE jumper, Xing suggests, using a combination of flapping and gliding to make it to its next perch.
But Habib cautions that there’s still much to learn about how the wing of Yi was arranged and what the strange wrist bone actually was. For starters, as Xing and coauthors point out in the paper, it’s not clear whether Yi had an expanded wing or a narrow one. If Yi had a large, bat-like wing, then it probably could have launched, flown and landed safely, Habib says. But if Yi had a slimmer wing profile, the dinosaur would need to launch at great speed to get into the air and likely would have been unstable while flying.
Determining exactly how Yi moved through the air will rely on future studies and discoveries. But it’s apparent that the dinosaur had some sort of aerodynamic ability. This means that at least three different lineages of dinosaurs independently evolved flight, each with different wing shapes and aerial capabilities, Habib notes. Yi is one of the more unusual reminders that dinosaurs didn’t just stomp around on the ground—a feathery variety fluttered, flapped and flew, too.