What About the Wings

There is something about the forelimbs of Yi qi that seems unnatural or even a bit downright creepy. Yi qi had feathers preserved with its skeleton. Those feathers are stiff and cover almost the entirety of the body. However, there are no flight feathers associated with this dinosaur. Instead, the elongate digits (Digit III being the longest digit) are spanned by a preserved membrane that lacks avian-like feathering altogether. Evidence for this membrane stretching to the torso is not preserved in the fossil, though it has been interpreted as extending that far medially in order to complete a wing structure. The inclusion of a styliform bone, debated as misidentified radius and ulna by some (David Peters for example), was proposed to have expanded the wing caudally from the wrist and past the range of the digits. This gliding wing would have been substantial with this addition but obviously becomes somewhat smaller and less expansive without the added distance from the wrist.

From Xu et al. 2015