Dating a dinosaur bone
The fossil was compressed and is visible on a stone plate and a counterplate.
It is largely articulated, including the skull, lower jaws, neck and limb bones but lacking most of the backbone, pelvis and tail.
Its few teeth were present only in the tips of the jaws, with the four upper front teeth per side being the largest and slightly forward-pointing, and the front lower teeth being angled even more strongly forward.
Like other scansoriopterygid dinosaurs, the first finger was shortest and the third was the longest.Unlike all other known dinosaurs, a long, pointed wrist bone known as a "styliform element", exceeding both the third finger and the ulna in length, extended backward from the forelimb bones.Yi was a relatively small animal, estimated to weigh about 380 grams (0.84 lb).Like other scansoriopterygids, the head was short and blunt-snouted, with a downturned lower jaw.This modified wrist bone and membrane-based plane is unique among all known dinosaurs, and might have resulted in wings similar in appearance to those of bats.