Yi

Phylogeny: Dinosauria > Saurischia > Theropoda > Neotheropoda > Tetanurae > Avetheropoda > Coelurosauria > Maniraptora > Pennaraptora > Scansoriopterygidae

Overview: The full scientific name of this genus’s type species is Yi qi, meaning “strange wing” in Mandarin Chinese. On top of being one of the shortest binomial names of any dinosaur, this was also a very fitting name for this creature – its wings were indeed very bizarre. Wings and wing-like forelimbs were common among maniraptoran dinosaurs, as they were very closely related to birds, often possessing long pennaceous feathers on the lower arms and hands. In birds, these feathers act as the surface enabling flight. Yi, however, had wings that were almost more similar to those of bats. Fossil evidence shows that it had feathers over much of its body, but its wings were formed by membranes stretching from its fingers to the sides of its torso, supported in the middle by a long, rod-like bone extending from the wrist. These membranes probably allowed it to glide from tree to tree, similar to a modern flying squirrel, its long clawed fingers allowing it to scale the sides of tree trunks and branches. Yi was the first dinosaur ever found with such wings, showing us that flight or similar behavior evolved independently and in wildly different forms between dinosaur lineages.

Dinosaurs related to Yi were actually known prior to its 2015 description, but only its holotype was so well preserved at that time, with evidence of its membranous wings. Scansoriopteryx is one such example, originally reconstructed simply with elongated fingers, used to climb. Said genus acts as the namesake of this dinosaur’s family – the Scansoriopterygidae. These tiny and unusual creatures flourished for a brief time in the Middle to Late Jurassic, seemingly only in China. Their phylogeny is debated. Some classify Yi and its kin as close relatives of the Oviraptorosauria, but others find the family to have been closer to true birds, in the clade Paraves, though as basal members. Members of the Scansoriopterygidae usually had tiny, needle-like teeth, suggesting an omnivorous diet of insects, seeds, and other such things. Fossils of Yi are known from China’s Tiaojishan Formation, in what is today the province of Hebei. Fossil preservation in the Tiaojishan is quite remarkable, so it’s little surprise that the type specimen of Yi was found with impressions of its membrane, as well as a set of long, trailing feathers growing out from its short tail.