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 vertebræ, and supports the uropigium.

The tail bone that supports the tail muscles and feathers.

Pygostyle refers to a number of the final few caudal vertebrae fused into a single ossification, to which the rectrices attach in birds. The pygostyle supports the tail feathers and musculature.