An additional bone in the carpal region of raptorial birds.

In a series of 4 species of owls and 12 species of diurnal raptors, an additional bone was present bilaterally in the area of the carpus. Designating the bone as an "additional bone of the raptorial carpal region" is suggested pending appropriate embryological studies to determine the origin of the bone. Generally, the bone was present in owls and in diurnal raptors with relatively short, rounded wings, but was absent in species with longer, more tapered wings. The bone lies at the cranial edge of the carpal area near the radial carpal bone, and is fixed to the surrounding skeleton by ligaments. The tendon of the tensor patagium longus muscle has one slip that attaches to the additional bone and another that passes over its craniodorsal surface en route to insertion. Awareness of the occurrence of this bone in some raptors, but not others, is essential in clinical evaluation of wing injuries, as well as in forming a prognosis for the return to soundness, the potential for release, and, therefore, the life of an injured raptor.