Austrocheirus
- Santa Cruz, Argentina ( Pari Aike Formation)
- Austrocheirus isasii
Austrocheirus is a genus theropod dinosaur from the group of Abelisauroidea. So far, a very fragmentary specimen handed down it is only known that from the Late Cretaceous (Lower Maastrichtian ) of Argentina is derived. This genus was first described in 2010 by Ezcurra and colleagues with the only kind Austrocheirus isasii scientifically.
The name Austrocheirus ( gr austros - "south "; cheirus - "hand" ) means something like " southern hand" and is intended to indicate the hand as a stand-out feature of this genus. The specific epithet, isasii, Marcelo Isasi honors for his years of work as a taxidermist paleontological discoveries as well as for the discovery of Austrocheirus - fossil.
Features
Austrocheirus was a medium sized theropod with an estimated length of the body 7 to 8 m. While derived representatives of Abelisauridae how Majungasaurus, Aucasaurus and Carnotaurus, proportional exhibited very short, reduced arms, the arms were not regressed from Austrocheirus. This is in Austrocheirus to the previously only known medium-sized, late Cretaceous Abelisauroidea with not shortened arms. The researchers conclude that the reduction of the arms is not related at Abelisauriden derived directly related to their larger body size, but that it is an apomorphy of this group.
Based on the bone structure of the third metacarpal bone can be the approximate age of the individual estimate. Thus the outermost cortex shows some very closely spaced lines of arrested growth - this is known as External fundamental system characteristic indicates that it was a full-grown individual. Since the cortex is not yet fully transformed by secondary osteons, it probably was not a question a very old individual.
This genus can be distinguished based on a number of unique anatomical features of other genres: for example, shows the third metacarpal bone ( metacarpal III) a dorsoventrally narrowed shaft, while the toe bones ( phalanges ) have a longitudinal ridge.
System
Austrocheirus is a basal (original ) Representatives of Abelisauroidea, a group within the Ceratosauria. However, by Ezcurra and colleagues ( 2010) conducted phylogenetic analysis can not resolve the exact phylogenetic relationships to other basal Abelisauroidea; in this analysis is a Austrocheirus Polytomie with the genera Noasaurus, Ligabueino, Masiakasaurus, Elaphrosaurus and the group Abelisauridae.
Discovery
The so far only find was discovered in March 2002 in the reference Hoyada Arroyo Seco, near the west bank of the Río La Leona in the southwestern Santa Cruz. The finding comes from the Pari Aike Formation ( Lower Maastrichtian ). Other dinosaur finds of this formation include the basal ornithopod Talenkauen, the Titanosaurier Puertasaurus, as well as the basal Tetanurae Orkoraptor with a.
The Fund ( holotype, specimen number MPM - PV 10003 ) consists of incomplete caudal vertebrae, a left third metacarpal bone, a left finger bones of the third finger, the lower end of the tibia (tibia ) and the fragmentary left third metatarsal. The bones were found on an area of 2 m². Since the bones correspond in size and no other remains were found for terrestrial vertebrates, all bones can be attributed to a single individual.
Documents
Used literature
- Martin Ezcurra, Federico Agnolin, Fernando Novas: An abelisauroid dinosaur with a non- atrophied manus from the Late Cretaceous Pari Aike Formation of southern Patagonia. In: Zootaxa. No 2450, 2010 ISSN 1175-5334, pp. 1-25.