Pygostylia

Pygostylia
Left: the reptile-like tail of Archeopteryx . Right: the tail of a modern bird. The last caudal vertebrae are fused into a pygostyle.
Temporal occurrence
Lower Cretaceous to this day
130 to 0 million years
Systematics
Trunk : Chordates (chordata) Sub-stem : Vertebrates (vertebrata) Superclass : Jaw mouths (Gnathostomata) Row : Land vertebrates (Tetrapoda) Class : Birds (aves) without rank: Pygostylia
Scientific name
Pygostylia
Chatterjee , 1997

Skeleton of a giant petrel with an upright pygostyle at the tail end

The taxon Pygostylia describes a group within the birds (class Aves), which is distinguished from other birds such as Archeopteryx by a shortened bony tail and the fusion of the last caudal vertebrae to a pygostyle . Further features for diagnosing the group are a number of seven or more pelvic vertebrae ( sacralia ), which are fused together in the so-called synsacrum , and elongated raven bones ( coracoid ).

The Pygostylia include all recent bird groups as well as most fossil ones . The affiliation of the oviraptorosaurs is under discussion : In some species the last caudal vertebrae were fused into a pygostyle-like structure. Some paleontologists see this feature as an indication that oviraptorosaurs were flightless descendants of early (airworthy) birds. Others doubt that the "pygostyle" of the oviraptorosaurs is homologous to that of the birds and place this group among the "non-avian dinosaurs " (a term used by cladisticians that means dinosaurs in the traditional sense, i.e. exclusively their descendants, the birds).

Systematics of birds taking into account fossil groups of birds

The systematics of the birds is as follows, including the group Pygostylia and new findings on the relationships among Mesozoic birds:

Aves ("Avialae" after Fastovsky and Weishampel 2005)	Pygostylia    Confuciusornithidae      ? Oviraptorosaur (not to birds according to Fastovsky and Weishampel 2005)   Ornithothoraces    Enantiornithes   Ornithuromorpha    Patagopteryx      Vorona   Ornithurae    Hesperornithiformes   Carinatae    Ichthyornithiformes      Neornithes ("Aves" after Fastovsky and Weishampel 2005)      Archeopterygidae      Rahonavis      Jeholornis

See also

• Bird skeleton , paleornithology , Confuciusornis

Individual evidence

1. ↑ Michael J. Benton : Vertebrate Palaeontology. 3. Edition. Blackwell, Malden MA 2005, ISBN 0-632-05637-1 .
2. ↑ ^{a b c d} David E. Fastovsky , David B. Weishampel : The Evolution and Extinction of the Dinosaurs. 2nd Edition. Cambridge University Press, Cambridge 2005, ISBN 0-521-01046-2 .
3. ↑ Zhonghe Zhou : The origin and early evolution of birds: discoveries, disputes and perspectives from fossil evidence. In: The natural sciences . Vol. 91, No. 10, 2004, pp. 455-471, doi: 10.1007 / s00114-004-0570-4 .