However, this is not how we’ve always envisioned members of this dinosaur family, called scansoriopterygids. In 2002 and 2008, paleontologists announced the discovery of the first two members of this family: Scansoriopteryx and Epidexipteryx respectively. Having seen no evidence that these creatures had wings, they were instead described as having bizarre, lengthy fingers, extending from their hands like spindly spider legs capped with claws.
An old reconstruction of Scansoriopteryx with a typical theropod dinosaur's feathered wings. Image by Nathan E. Rogers.
This interpretation was generally accepted as the most accurate that artists could come up with at the time. It was so striking that it made it into National Geographic’s “Bizarre Dinosaurs,” a series including a magazine cover story, a TV series, and a book describing the strangest bodies of the dinosaur world. Aside from the tall sails and spines of Spinosaurus and Amargasaurus and the strange headgear of Dracorex, an artist depicts a scansoriopterygid as one of the weirdest. The reconstruction of Epidendrosaurus, now considered a synonym of Scansoriopteryx, shows it reaching out its spindly, caliper-like fingers like some sort of sinister movie monster.
At the time, paleontologists suspected that the animals used their long fingers to climb trees, or to grasp food like the long-fingered modern primate, the aye-aye.
“This was actually a good hypothesis, brought up in 2002 when the first scansoriopterygid had been found,” said Dr. Wang Min, lead author of the Ambopteryx study and vertebrate paleontologist at the Chinese Academy of Sciences. “Back then, we didn’t find any dinosaurs with such a long digit. So we have to draw some reference from other living animals like the primates.”
However, not everyone was sold on this interpretation. Way back in 2008, vertebrate paleontologist Andrea Cau discussed the concept of winged scansoriopterygids with paleo artist Lukas Panzarin, who agreed that the idea was plausible. Cau published a blog post about the idea, as well as a speculative drawing of the animal, on his paleontology blog Theropoda.
“I am not sure if my hypothesis was taken seriously by other paleontologists before the discovery of Yi,” Cau said. “I mean, I never published such ideas in a peer-reviewed paper, and they were just plausible speculations in a blog...I've always assumed that only the discovery of actual fossils like Yi and Ambopteryx could validate such speculations.” In 2012, the book All Your Yesterdays included a reference to Cau’s interpretation, and a drawing of "A Scansoriopterygid with Wings." The authors described the illustration as “a truly bizarre beast, and this pterosaur-mimic reconstruction has to be appreciated as food for thought rather than a genuine hypothesis."
A new reconstruction of Ambopteryx with its bat-like wings. Image by Nathan E. Rogers.
The fossils of Scansoriopteryx and Epidexipteryx didn’t include any evidence that they flew, but, Wang explains, that doesn’t mean that they didn’t. Because the animals were not as well-preserved as Yi and Ambopteryx, the first discovered members of the family didn’t show the flaps of skin between their fingers and arms. Furthermore, they were so young when they died that the rod protruding from the wrist hadn’t yet turned to bone. Thus, the evidence of their wings was not preserved. Still, the wings of Yi and Ambopteryx suggest that the entire family had similar characteristics. “I would say that for this whole clade, the scansoriopterygids,” Wang explains, “It’s likely that those dinosaurs all had membrane wings.”
Now, Cau’s interpretation is vindicated as the most likely reality for this family. “As a paleontologist, it is a great emotion when you [suggest] an intriguing explanation for a very bizarre fossil, an explanation that you see as ‘working’ very well and fitting with several enigmatic elements of that creature,” Cau says. “And then, many years later, new fossils confirm your ideas. It was an amazing day for me, when Yi was published.”
Nathan E. Rogers