Shanag

• Mongolia ( Öösh )

• Shanag ashile

Shanag is a genus theropod dinosaur from the group of Dromaeosauridae. So far, only the jaw bone are known to originate from the Lower Cretaceous of Mongolia. The only way Shanag ashile, was founded in 2007 by Turner et al. described. It was a very small, bipedal running predator.

Features

The only fund consists of the right upper jaw (maxilla ), the dentary ( the tooth-bearing part of the lower jaw ) and a fragmentary Splenial that were discovered in the anatomical network.

Shanag was a very small theropod: comparisons with the better-known Microraptor zhaoianus suggest that the specimen found during his lifetime was about 45 cm long and 200 g in weight.

Autapomorphies, ie qualities enabling the genus from other Dromaeosauriden be distinguished clearly, are the lack of a Promaxillarfensters and chambers between the alveoli ( alveoli ). However, these chambers were not part of the air bag system, but were surrounded on all sides by a thin bone wall - they are only visible in the fossil found, because the lateral surface of the maxilla is decomposed. Shanag shows a mosaic of features that are typical of Dromaeosauriden or birds. Typical features bird show, for example, on the upper jaw, which is triangular, as in most birds and tapers to the rear. The large reduction antorbitale ( fossa ) extends over the major part of the lateral surface of the upper jaw. The Maxillarfenster is oval and relatively large and is similar to other Dromaeosauriden pretty high on the upward extension ( ramus ) of the maxilla. The dentary is straight, long and thin, with the height of only 12% of the length.

The found right maxilla shows at least nine alveoli, six of which contain teeth. A special feature is the very long roots of the three middle teeth of the upper jaw, which account for about 70 % of the total tooth length. The roots of two teeth are exposed in the fossil finds. Showed at least 15 of the mandibular teeth, which were packed closely and smaller than the teeth of the upper jaw.

System

While Turner et al. Shanag initially described as a close relative of Sinornithosaurus, they assign the genus in a later study, the group Unenlagiinae ( Buitreraptor, Rahonavis, Unenlagia ). According to the researchers form the Unenlagiinae together with the Dromaeosauriden the Jehol Group ( Microraptor, Graciliraptor, Sinornithosaurus ) a sister group to the more advanced Dromaeosauriden, which include the Velociraptorinen and related forms.

Fund and naming

The only Fund, a skull fragment ( specimen number IGM 100/1119 ), was discovered in 1999 by a joint expedition of the Mongolian Academy of Sciences and the American Museum of Natural History in Öösh, a locality in the Altai region of Central Mongolia. The deposits are from the Lower Cretaceous and thus have approximately the same age as the rich, known for their feathered dinosaur formations of the Jehol Group in China, although the exact age is not known. Öösh is known for rich finds of Ceratopsiers Psittacosaurus mongoliensis and of sauropods. Remains of theropods are rare in Öösh - at the time the description of Shanag was the only described theropod find from Öösh " Prodeinodon " ( Osborn, 1924), based on large but not diagnosable teeth.

The name of the genus refers to the Shanag, schwarzhütige dancers of the Buddhist Tsamfestes. The Artepitheth ashile refers to the old name of Öösh locality, as it was used by Henry Fairfield Osborn.