Yi is a genus of scansoriopterygid dinosaur from the Late Jurassic of China. Its own species, Yi Qi, is known from a single fossil specimen of an adult individual found in Middle or Late Jurassic Tiaojishan Formation of Hebei, China, approximately 159 million years ago. It was a small, possibly tree-dwelling animal. Yi is a genus of climbing and gliding dinosaurs from the Jurassic of China. Its only species, Yi qi is known from a single fossil specimen of an adult found in middle or late Jurassic of Hebei, China. It lived about 160 million years ago. Discovered by a farmer in rural China in 2007 and named Yi qi (“strange wing” in Mandarin) by researchers, it is the first dinosaur with strong evidence for having
a skin membrane for a wing, similar to a bat or flying squirrel. About the size of a large pigeon, it also had unusual feathers and a huge novel elongated bone that jutted out from its wrist called the styliform that helped support the wing membranes. These dinosaurs have adaptations to life in trees and for gliding or flapping flight and are among the smallest dinosaurs known. Yi qi and its family members did not have complex long feathers like modern birds and probably did not achieve powered flight like birds and pterosaurs but glided down from trees. Scientists once thought that vertebrates had two options to take to the air. You can use feathers like birds or you can use membranes like bats and pterosaurs, the flying reptiles that were contemporaneous with dinosaurs. There is no other way and we certainly weren’t prepared to find a mix of both. But Yi qi has both primitive feathers and a membrane, showing us that flight, or at least gliding, has evolved so many times in a few different ways. Few people ever thought a dinosaur would be found with pterosaur-like wings.