The Collaborative International Dictionary of English v.0.48:

Tibiotarsus \Tib`i*o*tar"sus\, n.; pl. 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.
   [1913 Webster]