What is "pygostyle"

Pygostyle \Py"go*style\, n. [Gr. pygh` the rump + ? a pillar.] (Anat.) The plate of bone which forms the posterior end of the vertebral column in most birds; the plowshare bone; the vomer. It is formed by the union of a number of the last caudal vertebr[ae], and supports the uropigium.

n. The plate supporting the tail-feathers in birds, formed from fused vertebrae.

Pygostyle describes a skeletal condition in which the final few caudal vertebrae are fused into a single ossification, supporting the tail feathers and musculature. In modern birds, the rectrices attach to these. The pygostyle is the main component of the uropygium, a structure colloquially known as the parson's nose, pope's nose, or sultan's nose. This is the fleshy protuberance visible at the posterior end of a bird (most commonly a chicken or turkey) that has been dressed for cooking. It has a swollen appearance because it also contains the uropygial gland that produces preen oil.