• Webster's Revised Unabridged Dictionary
    • n Pygostyle (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 vertebræ, and supports the uropigium.
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Century Dictionary and Cyclopedia
    • n pygostyle In ornithology, the vomer or plowshare bone of a bird's tail, consisting of a number of caudal vertebraæ ankylosed together for the support of the tail-feathers, and possessed by nearly all birds. Since the oldest known birds (of Jurassic age) had no pygostyle, but a long tapering tail like a lizard's with a pair of large feathers to each vertebra (see cut under Archæopteryx), and since all modern birds have a pygostyle, upon which feathers are bunched in several pairs, it follows that, theoretically, a pygostyle includes or represents as many coalesced caudal vertebræ as there are pairs of feathers in the tail — namely, five or six in most birds, up to twelve or more in some. But this view does not rest upon observation. Whatever its morphological character, the pygostyle is always the last bone of the tail, and always conspicuous in size; in shape it is very variable in different birds.
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Chambers's Twentieth Century Dictionary
    • n Pygostyle pī′gō-stīl the vomer or ploughshare bone of a bird's tail
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Webster's Revised Unabridged Dictionary
Gr. pygh` the rump + a pillar
Chambers's Twentieth Century Dictionary
Gr. pygē, the rump, stylos, a column.


In literature:

The pygostyle is most modified in this subfamily.
"Phylogeny of the Waxwings and Allied Birds" by M. Dale Arvey
The last six or seven caudal vertebrae coalesce into the pygostyle, an upright blade which carries the rectrices.
"Encyclopaedia Britannica, 11th Edition, Volume 3, Slice 7" by Various