This forms a more extensive rigid structure than the pelvis of a mammal, fulfilling requirements for flight, locomotion and respiration. Posterior to the synsacrum there are a few free caudal vertebrae, the last of which is the pygostyle to which the long, stiff tail feathers are attached. The central section of the synsacrum is swollen to accommodate the glycogen body, an organ whose function is as yet unclear but which may be associated with balance.
This forms a more rigid structure than the pelvic bone of a mammal, fulfilling requirements for flight, locomotion, and respiration. The posterior portion of the synsacrum contains a few free caudal vertebrae, with the last one being the pygostyle to which the long, stiff tail feathers are attached. The central section of the synsacrum is enlarged to accommodate the glycogen body, an organ whose function remains unknown but may be linked to balance.