the world > animals > birds > parts of or bird defined by > [noun] > tail > bone in (3)
(a) Anatomy the vomer (now rare or disused); (b) Ornithology the pygostyle of a bird.
A triangular bony plate, formed of the fused caudal vertebrae, which supports the tail feathers in most birds.
Ornithology. The large terminal bone in the tail of most birds; the pygostyle.