Avisauridae
Avisauridae | |
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Skeletal reconstruction of Mirarce | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Clade: | Dinosauria |
Clade: | Saurischia |
Clade: | Theropoda |
Clade: | Avialae |
Clade: | †Enantiornithes |
Clade: | † Euenantiornithes
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Family: | †Avisauridae Brett-Surman and Paul, 1985 |
Genera | |
Synonyms | |
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Avisauridae is a
Description
Avisaurids were among the largest and last enantiornithines to have lived, although they are also among the most poorly preserved. The majority of them are known primarily from fossilized tarsometatarsal bones, the part of a bird's leg formed by fused metatarsals (the bones which comprise the foot in humans). As a result, members of this family are distinguished from other enantiornithines exclusively by features of the tarsometatarsal and pedal phalanges (toe bones).
Unlike in some prehistoric birds, avisaurid tarsometatarsals were not completely fused, with the distal (outer) parts of the metatarsals being separate from each other. The proximal (near) half of metatarsal III (the long bone in the middle of the tarsometatarsus) is convex from the front. The inside edge of this bone's trochlea (toe joint) has a bony tab which points downward, known as a plantar projection. The innermost bone of the tarsometatarsus, metatarsal I, is small, laterally compressed (flattened from side-to-side), and J-shaped from the side. It is connected to a reversed hallux sporting a very large and curved claw.[4][2]
Chiappe and Calvo (1994) found that the Avisauridae shared adaptations of the foot — including a fully reversed and distally placed
History and classification
Avisauridae was erected as a family by Michael Brett-Surman and Gregory S. Paul in 1985. At that time the family consisted of a few fossils that they believed belonged to small non-avian dinosaurs. They doubted that these fossils belonged to birds due to the presence of several features of the tarsometatarsus. In Avisaurus (the only avisaurid known at that time), only the proximal parts of the metatarsals were fused, the proximal part of metatarsal III was wide, and the hypotarsus (a wide ridge extending down the back of the tarsometatarsus) was poorly developed.[6]
However, Chiappe later reassigned the Avisauridae to the
Chiappe in 1993 defined the family as the common ancestor of
The following is a cladogram based on Cau and Arduini (2008):[2]
References
- doi:10.1002/gj.1209.
- ^ a b c d e f g Cau, A. & Arduini, P. (2008). "Enantiophoenix electrophyla gen. et sp. nov. (Aves, Enantiornithes) from the Upper Cretaceous (Cenomanian) of Lebanon and its phylogenetic relationships". Atti della Societa Italiana di Scienze Naturali e del Museo Ivico di Storia Naturale in Milano. 149 (2): 293–324.
- hdl:11336/60953.
- ^ a b c Chiappe, Luis M. (1992) "Enantiornithine (Aves) Tarsometatarsi from the Cretaceous Lecho Formation of Northwestern Argentina" Journal of Vertebrate Paleontology. September, 1992. 12 (3): 344-350
- ^ Chiappe, Luis M., Calvo, Jorge O. (1994) "Neuquenornis volans, a New Late Cretaceous Bird (Enantiornithes: Avisauridae) from Patagonia, Argentina". Journal of Vertebrate Paleontology. June 22, 1994 Volume 14 No. 2 pp.230-246.
- JSTOR 4523037.
- ^ L.M. Chiappe. 1993. "Enantiornithine (Aves) tarsometatarsi from the Cretaceous Lecho Formation of northwestern Argentina". American Museum Novitates. 3083, 39 pp
- ^ Mortimer, Mickey (2013-01-03). "The Theropod Database Blog: Martyniuk's (2012) new definitions and clades". The Theropod Database Blog. Retrieved 2018-02-03.
- .