Tibiotarsus
The tibiotarsus is the large bone between the femur and the tarsometatarsus in the leg of a bird. It is the fusion of the proximal part of the tarsus with the tibia.
A similar structure also occurred in the Mesozoic Heterodontosauridae. These small ornithischian dinosaurs were unrelated to birds and the similarity of their foot bones is best explained by convergent evolution.
File:Tibiotarsi of extinct birds.jpg|thumb|left|Tibiotarsi of Grus cubensis, Propelargus edwardsi, and Palaelodus gracilipes at the Museum für Naturkunde, Berlin