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 expla...
• (n.) The large bone between the femur and tarsometatarsus in the leg of a bird. It is formed by the union of the proximal part of the tarsus with the tibia.
Tib`i·o·tar'sus noun ; plural Tibiotarsi (Anat.) The large bone between the femur and tarsometatarsus in the leg of a bird. It is formed by the union of the proximal part of the tarsus with the tibia. 
In Collembola, the fourth segment of the leg.
In birds, the tibiotarsus is the equivalent of the tibia, but it is fused at the lower end with some of the bones of the tarsus.
The top of the leg bone - like the human femur.
tibiotarsus The main bone of a bird's lower leg, formed by a fusion of the tibia and some of the bones of the tarsus.
Bone supporting the lower leg (crus) of birds; the tibiotarsus is formed by the fusion of the tibia with the proximal tarsal (ankle) bones.