- Pope's nose redirects here. It may also refer to the licence plate light on early Volkswagen Beetles.
The pygostyle is the main component of the structure colloquially known as 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.
Pygostyles probably started to evolve very early in the Cretaceous, maybe 140-130 million years ago. The earliest known species to have evolved a pygostyle were members of the Confuciusornithidae. The structure provided an evolutionary advantage, as a completely mobile tail like in Archaeopteryx is detrimental to its use for flight control. Modern birds still develop longer caudal vertebrae in their embryonal state, which later fuse to form a pygostyle.
There are two main types of pygostyle: one, found in Confuciusornithidae, Enantiornithes, and some other Mesozoic birds, as well as in some oviraptorosaurs like Nomingia, is long and rod- or dagger blade-like. None of the known fossils with such pygostyles show traces of well-developed rectrices. The tail feathers in these animals consisted of downy fuzz and sometimes 2-4 central "streamers" such as those found in some specimens of Confuciusornis or in Paraprotopteryx.
By contrast, the function of the pygostyle in the terrestrial Nomingia is not known. It is notable however that its older relative Caudipteryx had no pygostyle but a "fan" of symmetrical feathers which were probably used in social display. Perhaps such ornaments were widespread in Caenagnathoidea and their relatives, and ultimately the oviraptorosaurian pygostyle evolved to help support them. The related Similicaudipteryx, described in 2008, also had a rod-like pygostyle, associated with a fan of tail feathers.
The other pygostyle type is plowshare-shaped. It is found in Ornithurae (living birds and their closest relatives), and in almost all flying species is associated with an array of well-developed rectrices used in maneuvring. The central pair of these attach directly to the pygostyle, just as in Confuciusornis. The other rectrices of Ornithurae are held in place and moved by structures called bulbi rectricium (rectricial bulbs), a complex feature of fat and muscles located on either side of the pygostyle. The oldest known species with such a pygostyle is Hongshanornis longicresta.
As evidenced by the oviraptorosaurian cases, the pygostyle evolved at least twice, and rod-shaped pygostyles seem to have evolved several times, in association with shortening of the tail but not necessarily with a retractable fan of tail feathers. In other words, the pygostyles of oviraptorosaurs and Confuciusornis were likely weight-saving measures, and the specialized "true" pygostyles of ornithurans were adapted from these later to improve flight performance.
The bird clade Pygostylia was named in 1996, by Luis Chiappe, for the presence of this feature and roughly corresponds to its appearance in the bird family tree, though the feature itself is not included in its definition. In 2001, Jacques Gauthier and Kevin de Queiroz (2001) re-defined Pygostylia to refer specifically to the apomorphy of a short tail bearing an avian pygostyle.
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"Pygostyle" is of Ancient Greek origin, literally meaning "rump pillar".
The phrase "parson's nose", from the notion that an English parson may 'have his nose in the air', upturned like the chicken's rear end. The term must have been known as early as around 1400 AD, when a carpenter had been contracted to provide new choir stalls for St Mary's Church, Nantwich.[verification needed] The vicar was either slow to pay the artisan, or did not pay at all. In retaliation, on the last misericord in the stalls, the carpenter carved a bird with an image of that Vicar's face with protuberant nose as rump. The carving is still visible today.
- Clarke et al. (2006)
- Xu, X.; Zheng, X.; You, H. (2010). "Exceptional dinosaur fossils show ontogenetic development of early feathers". Nature 464 (7293): 1338–1341. doi:10.1038/nature08965. PMID 20428169.
- O'Connor, J.K.; Gao, K.-Q.; and Chiappe, L.M. (2010). "A new ornithuromorph (Aves: Ornithothoraces) bird from the Jehol Group indicative of higher-level diversity". Journal of Vertebrate Paleontology 30 (2): 311–321. doi:10.1080/02724631003617498.
- Chiappe, L. (1997). "The Chinese early bird Confuciusornis and the paraphyletic status of Sauriurae". Journal of Vertebrate Paleontology 17 (3): 37A.
- "The Building and Contents of St Mary’s Nantwich". St Mary's PCC, Nantwich. parsonsnose.jpg. Retrieved 2012-02-29.
- Clarke, Julia A.; Zhou, Zhonghe & Zhang, Fucheng (2006): Insight into the evolution of avian flight from a new clade of Early Cretaceous ornithurines from China and the morphology of Yixianornis grabaui. Journal of Anatomy 208 (3):287-308. doi:10.1111/j.1469-7580.2006.00534.x PMID 16533313 PDF fulltext Electronic Appendix
- He, T.; Wang, X.-L. & Zhou, Z.-H. (2008): A new genus and species of caudipterid dinosaur from the Lower Cretaceous Jiufotang Formation of western Liaoning, China. Vertebrata PalAsiatica 46(3): 178-189.