The bird hand is thought to derive from the second, third and fourth digits of an ancestral five-digit hand. However, the three-fingered hand of theropod dinosaurs, which are the closest extinct relatives of birds, are thought to derive from the first, second and third digits. The discovery of a small, primitive herbivorous theropod from the Jurassic period of China with a stub of the first digit alongside more developed second, third and fourth digits, sheds light on this problem.
- Xing Xu
- James M. Clark
- Yu Guo
