Tsaagan

Tsaagan mangas, artistic life reconstruction

  • Ömnö Gobi Aimag, Mongolia ( Djadochta Formation)
  • Tsaagan mangas

Tsaagan is a genus theropod dinosaur from the group of Dromaeosauridae. The only known species is Tsaagan mangas.

So far only a find is known which consists of a complete skull and a series of cervical vertebrae and was discovered in Mongolia. This finding comes from the Djadochta lineup and is dated to the Late Cretaceous ( Campanian average ). Although no bones of the trunk or the limbs are known, this carnivore was probably like all Dromaeosauriden an enlarged sickle- claw on the second toe and proportionally long arms and big hands.

Features

The only fund consisting of a skull with pine and the front eight cervical vertebrae. All bones were found in the anatomical network. The skull is slightly crushed - so the skull is laterally flattened and the snout region shifted slightly. The total length of the head is estimated to be 20.1 cm. As the degree of fusion of the skull shows, it was probably an adult individual.

The skull is characterized by a long snout, which accounts for 59% of the total length of the skull. The jaws are massive and the braincase less pneumatized ( permeated with air-filled chambers ) than in the closely related Velociraptor. At the rear of the skull is an upward comb, which is larger than any other previously known Dromaeosauriden. On each half of the lower jaw 14 to 15 were curved teeth, similar to other Dromaeosauriden. The left upper jaw (maxilla ) of the discovery points to 13 teeth, while the front of the maxilla located Zwischenkieferbein ( premaxilla ) shows four teeth.

Various anatomical details ( autapomorphies ) limits Tsaagan from all other Dromaeosauriden. So the Paroccipitalprozess straight, and the Basipterygoid process is extended and aligned anteroventral. The large, located on the front edge of the antorbitalen fossa ( fossa ) located Maxillarfenster and the fact that the Jugale the squamosal ( squamosal ) touches so that the postorbital is excluded from the edge of the infra pace Ralf Sters: Originally two other features were also considered autapomorphies. However, a recent study from 2010 found exactly these features in the recently described Dromaeosauriden Linheraptor. Linheraptor comes from the Wulansuhai Formation of Inner Mongolia, the Chinese equivalent of the Djadochta lineup.

System

How to show common features skull was Tsaagan a close relative and the sister taxon of Linheraptor, which probably formed their own group late Cretaceous, Asian Dromaeosauriden. Both species were basal ( primitive ) as Velociraptor and were probably between phylogenetically basal and advanced Dromaeosauriden.

Before the discovery of Linheraptor the descriptor of Tsaagan ( Norell and colleagues, 2006) have assumed that Tsaagan a group together with Deinonychus, Velociraptor, Utahraptor, Dromaeosaurus, Achillobator, Adasaurus and Saurornitholestes within the Dromaeosauridae, and from the more primitive Microraptorinen is defined Unenlagiinen. Often this group will be divided into two or three subgroups that Dromaeosaurinae ( Dromaeosaurus, Utahraptor and Achillobator ), the Velociraptorinae ( Velociraptor, Deinonychus ) and sometimes the Saurornitholestinae ( Saurornitholestes, Bambi Raptor, Atrociraptor ), although the describer find no evidence for such a subdivision could. Long Rich and Currie (2009) classify Tsaagan within the Velociraptorinae together with Adasaurus, Velociraptor and Itemirus.

Fund, naming and paleoecology

The so far only Fund ( copy number IGM 100/1015 ) comes from Ukhaa Tolgod, a locality in the Mongolian Gobi Aimag Ömnö. Stratigraphy of the locality belongs to Djadochta formation that is dated to the middle Campanian. The find was described scientifically by Norell, Clark, tournament, Makovicky, bars Bold and Rowe 2006. The name Tsaagan mangas comes from the Mongolian and means as much as "white monster " ( цагаан мангас ).

Tsaagan is only the second Dromaeosauride described from the Djadochta lineup, that has taken many of the closely related Velociraptor skeletons were discovered mongoliensis. Velociraptor is completely missing from the Ukhaa Tolgod - reference, indicating that the Dromaeosauriden fauna within the Djadochta formation was not uniform but showed regional differences. Tsaagan shared its habitat probably with another undescribed Dromaeosauriden from the nearby Zos Wash locality. Common findings of both sites are the Ceratopsia andrewsi Protoceratops and the Alvarezsauride Shuvuuia deserti.

Documents

  • MA Norell, JM Clark, AH Turner, PJ Makovicky, R. bars Bold, T. Rowe: A new theropod from dromaeosaurid Ukhaa Tolgod ( Omnogov, Mongolia ). In: American Museum Novitates. 3545, 2006, pp. 1-51.
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