
Pygostyle describes a skeletal condition in which the final few
caudal
Caudal may refer to:
Anatomy
* Caudal (anatomical term) (from Latin ''cauda''; tail), used to describe how close something is to the trailing end of an organism
* Caudal artery, the portion of the dorsal aorta of a vertebrate that passes into the ...
vertebra
The spinal column, a defining synapomorphy shared by nearly all vertebrates, Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characterist ...
e are fused into a single
ossification
Ossification (also called osteogenesis or bone mineralization) in bone remodeling is the process of laying down new bone material by cells named osteoblasts. It is synonymous with bone tissue formation. There are two processes resulting in ...
, supporting the tail
feathers and musculature. In modern
bird
Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...
s, the
rectrices
Flight feathers (''Pennae volatus'') are the long, stiff, asymmetrically shaped, but symmetrically paired pennaceous feathers on the wings or tail of a bird; those on the wings are called remiges (), singular remex (), while those on the tai ...
attach to these. The pygostyle is the main component of the uropygium, a structure colloquially known as the bishop's nose, parson's nose, pope's nose, or sultan's nose. This is the fleshy protuberance visible at the posterior end of a
bird
Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...
(most commonly a
chicken
The chicken (''Gallus gallus domesticus'') is a domestication, domesticated junglefowl species, with attributes of wild species such as the grey junglefowl, grey and the Ceylon junglefowl that are originally from Southeastern Asia. Rooster ...
or
turkey
Turkey ( tr, Türkiye ), officially the Republic of Türkiye ( tr, Türkiye Cumhuriyeti, links=no ), is a list of transcontinental countries, transcontinental country located mainly on the Anatolia, Anatolian Peninsula in Western Asia, with ...
) that has been dressed for
cooking
Cooking, cookery, or culinary arts is the art, science and craft of using heat to prepare food for consumption. Cooking techniques and ingredients vary widely, from grilling food over an open fire to using electric stoves, to baking in vari ...
. It has a swollen appearance because it also contains the
uropygial gland
The uropygial gland, informally known as the preen gland or the oil gland, is a bilobed sebaceous gland possessed by the majority of birds used to distribute the gland's oil through the plumage by means of preening. It is located dorsally at th ...
that produces
preen oil
The uropygial gland, informally known as the preen gland or the oil gland, is a bilobed sebaceous gland possessed by the majority of birds used to distribute the gland's oil through the plumage by means of preening. It is located dorsally at t ...
.
Evolution
Pygostyles probably began to
evolve very early in the
Cretaceous
The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...
period, perhaps 140 – 130 million years ago. The earliest known
species
In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of ...
to have evolved a pygostyle were members of the
Confuciusornithidae
Confuciusornithidae is an extinct family of pygostylian avialans known from the Early Cretaceous, found in northern China. They are commonly placed as a sister group to Ornithothoraces, a group that contains all extant birds along with their cl ...
. The structure provided an evolutionary advantage, as a completely mobile tail as found in species such as ''
Archaeopteryx
''Archaeopteryx'' (; ), sometimes referred to by its German name, "" ( ''Primeval Bird''), is a genus of bird-like dinosaurs. The name derives from the ancient Greek (''archaīos''), meaning "ancient", and (''ptéryx''), meaning "feather" ...
'' is detrimental to its use for flight control. Modern birds still develop longer caudal vertebrae in their
embryo
An embryo is an initial stage of development of a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male sperm ...
nic state, which later fuse to form a pygostyle.
There are two main types of pygostyle: one, found in Confuciusornithidae,
Enantiornithes
The Enantiornithes, also known as enantiornithines or enantiornitheans in literature, are a group of extinct avialans ("birds" in the broad sense), the most abundant and diverse group known from the Mesozoic era. Almost all retained teeth and cl ...
, and some other
Mesozoic
The Mesozoic Era ( ), also called the Age of Reptiles, the Age of Conifers, and colloquially as the Age of the Dinosaurs is the second-to-last era of Earth's geological history, lasting from about , comprising the Triassic, Jurassic and Creta ...
birds, as well as in some
oviraptorosaur
Oviraptorosaurs ("egg thief lizards") are a group of feathered maniraptoran dinosaurs from the Cretaceous Period of what are now Asia and North America. They are distinct for their characteristically short, beaked, parrot-like skulls, with or w ...
s like ''
Nomingia
''Nomingia'' is a genus of oviraptorid theropod dinosaur hailing from the Late Cretaceous Bugin Tsav Beds of Mongolia.
Discovery and naming
The remains, consisting of most of the vertebral column, pelvic girdle and left tibio-tarsus, holoty ...
'', 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
down
Down most often refers to:
* Down, the relative direction opposed to up
* Down (gridiron football), in American/Canadian football, a period when one play takes place
* Down feather, a soft bird feather used in bedding and clothing
* Downland, a ty ...
y fuzz and sometimes 2–4 central "streamers" such as those found in some specimens of ''Confuciusornis'' or in ''
Paraprotopteryx
''Paraprotopteryx'' is a genus of enantiornithean birds from the Mesozoic of China.Zheng, X. Zhang, Z. & Hou, L. (2007) A new enantiornithine bird with four long rectrices from the Early Cretaceous of northern Hebei, China. ''Acta Geologica Sin ...
''.
[Clarke ''et al.'' (2006)]
By contrast, the function of the pygostyle in the
terrestrial
Terrestrial refers to things related to land or the planet Earth.
Terrestrial may also refer to:
* Terrestrial animal, an animal that lives on land opposed to living in water, or sometimes an animal that lives on or near the ground, as opposed to ...
''Nomingia'' is not known. It is notable however that its older relative ''
Caudipteryx
''Caudipteryx'' (which means "tail feather") is a genus of peacock-sized theropod dinosaurs that lived in the Barremian age of the early Cretaceous (about 124.6 million years ago). They were feathered and extremely birdlike in their overall app ...
'' had no pygostyle but a "fan" of symmetrical feathers which were probably used in social display. Perhaps such ornaments were widespread in
Caenagnathoidea
Caenagnathoidea ("recent jaw forms") is a group of advanced oviraptorosaurian dinosaurs from the Cretaceous Period of what are now Asia and North America. They are distinct for their characteristically short, beaked, parrot-like skulls, often w ...
and their relatives, and ultimately the oviraptorosaurian pygostyle evolved to help support them. The related ''
Similicaudipteryx
''Similicaudipteryx'', meaning "similar to ''Caudipteryx''" (which itself means "tail feather"), is a genus of theropod dinosaur of the family Caudipteridae.
Discovery and naming
In 2007 the find of a new caudipterid was reported. In 2008 the ...
'', described in 2008, also had a rod-like pygostyle, associated with a fan of tail feathers.

The other pygostyle type is
plowshare
In agriculture, a plowshare ( US) or ploughshare ( UK; ) is a component of a plow (or plough). It is the cutting or leading edge of a moldboard which closely follows the coulter (one or more ground-breaking spikes) when plowing.
The plowshare ...
-shaped. It is found in
Ornithurae
Ornithurae (meaning "bird tails" in Greek) is a natural group which includes the common ancestor of '' Ichthyornis'', '' Hesperornis'', and all modern birds as well as all other descendants of that common ancestor.
Classification
Ernst Haeckel c ...
(living birds and their closest relatives), and in almost all flying species is associated with an array of well-developed rectrices used in maneuvering. The central pair of these attach directly to the pygostyle, just as in ''
Confuciusornis
''Confuciusornis'' is a genus of basal crow-sized avialan from the Early Cretaceous Period of the Yixian and Jiufotang Formations of China, dating from 125 to 120 million years ago. Like modern birds, ''Confuciusornis'' had a toothless beak, b ...
''. 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
oviraptorosauria
Oviraptorosaurs ("egg thief lizards") are a group of feathered maniraptoran dinosaurs from the Cretaceous Period of what are now Asia and North America. They are distinct for their characteristically short, beaked, parrot-like skulls, with or w ...
n 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
Pygostylia is a group of avialans which includes the Confuciusornithidae and all of the more advanced species, the Ornithothoraces.
Definition
The group Pygostylia was intended to encompass all avialans with a short, stubby tail, as opposed to ...
was named in 1996, by
Luis Chiappe
Luis María Chiappe (born 18 June 1962) is an Argentine paleontologist born in Buenos Aires who is best known for his discovery of the first sauropod nesting sites in the badlands of Patagonia in 1997 and for his work on the origin and early evol ...
, 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
Jacques Armand Gauthier (born June 7, 1948 in New York City) is an American vertebrate paleontologist, comparative morphologist, and systematist, and one of the founders of the use of cladistics in biology.
Life and career
Gauthier is the s ...
and
Kevin de Queiroz
Kevin de Queiroz is a vertebrate, evolutionary, and systematic biologist. He has worked in the phylogenetics and evolutionary biology of squamate reptiles, the development of a unified species concept and of a phylogenetic approach to biological ...
(2001) re-defined Pygostylia to refer specifically to the
apomorphy
In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to have ...
of a short tail bearing an avian pygostyle.
Etymology
"Pygostyle" is formed from
Ancient Greek
Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic p ...
words, literally meaning "rump pillar".
The insulting equation of the pygostyle with the noses of dignitaries dates back to 18th century Britain where ''pope's nose'' first appears (in 1786). The form ''parson's nose'' appears much later, dated to 1839. The usage is somewhat dependent on either a Catholic or Protestant viewpoint.
The forms ''bishop's nose'' and ''sultan's nose'' are 20th century variants.
As food
Turkey tail or turkey butt has an international exportation market in places such as
Micronesia
Micronesia (, ) is a subregion of Oceania, consisting of about 2,000 small islands in the western Pacific Ocean. It has a close shared cultural history with three other island regions: the Philippines to the west, Polynesia to the east, and ...
,
Samoa
Samoa, officially the Independent State of Samoa; sm, Sāmoa, and until 1997 known as Western Samoa, is a Polynesian island country consisting of two main islands (Savai'i and Upolu); two smaller, inhabited islands (Manono Island, Manono an ...
, and
Ghana
Ghana (; tw, Gaana, ee, Gana), officially the Republic of Ghana, is a country in West Africa. It abuts the Gulf of Guinea and the Atlantic Ocean to the south, sharing borders with Ivory Coast in Ghana–Ivory Coast border, the west, Burkina ...
. The turkey tail is commonly exported from America because it is considered unhealthy and cut off the normal turkey.
After World War II, cheap imported turkey tails became popular in Samoa. Because the cut has a very high fat content, it was banned from 2007 to 2013 to combat obesity, only allowed back when Samoa joined the World Trade Organization. The meat is otherwise used in
pet food
Pet food is animal feed intended for consumption by pets. Typically sold in pet stores and supermarkets, it is usually specific to the type of animal, such as dog food or cat food. Most meat used for animals is a byproduct of the human food in ...
.
Footnotes
References
*
Electronic Appendix*
{{refend
Bird anatomy
Vertebrate anatomy
Ancient Greek