Coelurosauria
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- For the prehistoric gliding reptile, see Coelurosauravus.
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Coelurosauria is a diverse group of theropod dinosaurs that includes tyrannosaurs, ornothomimosaurs, and maniraptors, including the birds, the only coelurosaurs alive today. All feathered dinosaurs discovered so far have been coelurosaurs; in fact, some scientists believe that most members of coelurosauria bore some kind of feathers.
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[edit] Description
Most coelurosaurs were bipedal predators. The group includes some of the largest (Tyrannosaurus) and smallest (Microraptor, Parvicursor) carnivorous dinosaurs ever discovered. Characteristics that distinguish coelurosaurs include:
- a sacrum (series of vertebrae that attach to the hips) longer than in other dinosaurs
- a tail stiffened towards the tip
- a bowed ulna (lower arm bone).
- a tibia (lower leg bone) that is longer than the femur (upper leg bone)
[edit] Feathers: A Coelurosaurian Trait
Because fossilized traces of feathers have been identified (so far) only among coelurosauria, Prum and Brush hypothesize that feathers "originated in a lineage of coelurosaurian theropod dinosaurs including both Sinosauropteryx and birds". Moreover, feathers probably did not exist in theropod groups outside of coelurosauria, such as the "allosauroids, ceratosaurids, and coelophysids."[1]
In fact, feathers of some type have been found in fossils of at least one species in almost every coelurosaur subgroup—compsognathids, tyrannosauroids, oviraptorosaurians, therizinosaurians, alvarezsaurids, troodontids, dromaeosaurids, and birds. (Modern birds are classified as coelurosaurs by nearly all palaeontologists[2], though not by a few ornithologists[3].) To date, the ornithomimosaurians are the only group of coelurosaurs without direct evidence of feathers, and based on phylogenetic bracketing, most paleontologists agree that they were feathered as well.
[edit] Classification
For many years, coelurosauria was a 'dumping ground' for all small theropods. (Large theropods were classified in the complementary group "Carnosauria".) However, during the 1980s and 1990s, paleontologists discovered that many small theropods were not 'coelurosaurs' at all (notably the coelophysids are actually theropods more primitive than coelurosauria), and that some large theropods, such as the tyrannosaurids, were not carnosaurs but actually giant coelurosaurs. Even more drastically, the therizinosaurs, once not even regarded as theropods, have turned out to be non-carnivorous coelurosaurs.
[edit] Phylogeny
The following cladogram is taken, in abbreviated form, from Weishampel, Dodson, and Osmólska, 2004. They define Coelurosauria as those dinosaurs sharing a more recent common ancestor with the House Sparrow than with Allosaurus fragilis.[4]
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[edit] Taxonomy
After the 1960s, when several distinctive lineages of coelurosaurs were recognized, a number of new infraorders were erected, including the Ornithomimosauria, Deinonychosauria, Oviraptorosauria, and Segnosauria (a name which has since been replaced with the unranked clade Therizinosauria). Most modern studies follow phylogenetic nomenclature and avoid assigning ranks. However, when rankings are used, such as in the taxonomy below (after Benton 2004), exclusive individual families are favored over the traditional coelurosaur infraorders. (Note: Benton places the order Oviraptorosauria within the class Aves; others place the oviraptorids elsewhere.)[5]
- Division Coelurosauria
- Family Coeluridae (including Compsognathidae)
- Subdivision Maniraptoriformes
- Family Tyrannosauridae
- Family Ornithomimidae
- Infradivision Maniraptora
- Family Alvarezsauridae
- Family Therizinosauridae
- Cohort Deinonychosauria
- Family Dromaeosauridae
- Family Troodontidae
- Class Aves (including Family Oviraptorosauria)
[edit] "Coelurosaurus"
"Coelurosaurus" is an informal generic name, attributed to Friedrich von Huene, 1929 (sometimes incorrectly given as 1914), that is sometimes seen in lists of dinosaurs. It is probably a typographical error; von Huene intended to assign indeterminate remains to Coelurosauria incertae sedis, but at some point in the process of publication, the text was revised to make it appear that he was creating a new generic name "Coelurosaurus" (as described by George Olshevsky in a 1999 post to the Dinosaur Mailing List).[6] The name is undescribed and has not been used seriously, although it has appeared in works of fiction.
[edit] See also
[edit] References
- ^ Prum, R., and Brush, A.H. (2002). "The evolutionary origin and diversification of feathers". The Quarterly Review of Biology, 77: 261-295.
- ^ Mayr, G., B. Pohl & D.S. Peters (2005). "A well-preserved Archaeopteryx specimen with theropod features". Science, 310(5753): 1483-1486.
- ^ Feduccia, A. (1993).
- ^ Weishampel, D.B., Dodson, P., and Osmólska, H. (eds.) (2004). The Dinosauria, Second Edition. University of California Press., 861 pp.
- ^ Benton, M.J. (2004). Vertebrate Palaeontology, Third Edition. Blackwell Publishing, 472 pp.
- ^ Olshevsky, G. Re: What are these dinosaurs. Retrieved on 2007 January 29.
[edit] External links
- Coelurosauria at DinoData.
- Lark Quarry, Queensland, Australia. Lark Quarry.
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