Tsaagan
| Tsaagan | ||||||||||||
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Tsaagan mangas , artistic life reconstruction |
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| Temporal occurrence | ||||||||||||
| Upper Crayon (middle Campanium ) | ||||||||||||
| 80.6 to 76.4 million years | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Tsaagan | ||||||||||||
| Norell et al. , 2006 | ||||||||||||
| Art | ||||||||||||
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Tsaagan is a genus of theropod dinosaur from the group of Dromaeosauridae . The only known type is Tsaagan manga .
So far, only one find is known, which consists of a complete skull and a series of cervical vertebrae and was discovered in Mongolia . This find comes from the Djadochta Formation and is dated to the Upper Cretaceous (middle Campanium ). Although no bones of the trunk or limbs are known, this carnivore likely, like all dromaeosaurids, exhibited an enlarged sickle claw on the second toe and proportionally long arms and large hands.
features
The only find consists of a skull with jaws and the front eight cervical vertebrae. All bones were found in the anatomical network. The skull is slightly crushed - so the side of the skull is flattened and the region of the snout is slightly shifted. The total length of the skull is estimated to be 8 inches. As the degree of fusion of the skull bones shows, it was likely an adult individual.
The skull is characterized by a long snout that makes up 59% of the total length of the skull. The jaws are more massive and the cerebral skull less pneumatized (with air-filled chambers) than in the closely related Velociraptor . At the rear end of the skull there is an upwardly directed crest that is larger than any other dromaeosaurid known to date. There were 14 to 15 curved teeth on each half of the lower jaw, similar to other dromaeosaurids. The left upper jaw (maxilla) of the find indicates 13 teeth, while the intermaxillary bone (premaxillary) in front of the upper jaw shows four teeth.
Various anatomical details ( autapomorphies ) differentiate Tsaagan from all other dromaeosaurids. Thus the paroccipital process is straight, and the basipterygoid process is elongated and oriented anteroventrally . Originally, two other features were also considered to be autapomorphies: The large maxillary window located on the anterior edge of the antorbital cranial fossa and the fact that the jugale touches the scaly bone (squamosum), so that the postorbital is excluded from the edge of the infratemporal window . A more recent study from 2010 found exactly these characteristics in the recently described dromaeosaurid Linheraptor . Linheraptor comes from the Wulansuhai Formation of Inner Mongolia , the Chinese equivalent of Djadochta formation.
Systematics
As common skull features show, Tsaagan was a close relative and sister taxon of Linheraptor , which probably formed a separate group of Late Cretaceous, Asian dromaeosaurids. Both genera were basal (more primitive) than Velociraptor and phylogenetically probably stood between basal and more advanced dromaeosaurids.
Before the discovery of Linheraptor , the descriptors of Tsaagan (Norell and colleagues, 2006) assumed that Tsaagan, along with Deinonychus , Velociraptor , Utahraptor , Dromaeosaurus , Achillobator , Adasaurus and Saurornitholestes forms a group within the Dromaeosauridae and the more primitive Microraptoridae Unenlagiinen is delimited. Often this group is divided into two to three subgroups, the Dromaeosaurinae ( Dromaeosaurus , Utahraptor and Achillobator ), the Velociraptorinae ( Velociraptor , Deinonychus ) and sometimes the Saurornitholestinae ( Saurornitholestes , Bambiraptor , Atrociraptor ), although the descriptions do not find any clues for such a subdivision could. Longrich and Currie (2009) classify Tsaagan within the Velociraptorinae together with Adasaurus , Velociraptor and Itemirus .
Find, naming and paleoecology
The only find so far (specimen number IGM 100/1015) comes from Ukhaa Tolgod , a site in the Mongolian Aimag Ömnö-Gobi . Stratigraphically , the site belongs to the Djadochta Formation , which is dated to the middle Campanian . The find was scientifically described in 2006 by Norell, Clark, Tournament, Makovicky, Barsbold and Rowe . The name Tsaagan mangas comes from Mongolian and means something like "white monster" (цагаан мангас).
Tsaagan is only the second dromaeosaurid described from the Djadochta formation, although numerous skeletons of the closely related Velociraptor mongoliensis have already been discovered. Velociraptor is completely absent from the Ukhaa Tolgod site, which indicates that the dromaeosaurid fauna within the Djadochta formation was not uniform, but showed regional differences. Tsaagan probably shared its habitat with another, still undescribed dromaeosaurid from the nearby Zos Wash site. Frequent finds at both sites are the Ceratopsier Protoceratops andrewsi and the Alvarezsauride Shuvuuia deserti .
supporting documents
- Mark A. Norell , James M. Clark , Alan H. Turner, Peter J. Makovicky , Rinchen Barsbold : A New Dromaeosaurid Theropod from Ukhaa Tolgod (Ömnögov, Mongolia) (= American Museum Novitates. No. 3545, ISSN 0003-0082 ) . American Museum of Natural History, New York NY 2006, online .
Individual evidence
- ^ Alan H. Turner, Diego Pol, Julia A. Clarke, Gregory M. Erickson, Mark A. Norell : A Basal Dromaeosaurid and Size Evolution Preceding Avian Flight. In: Science . Vol. 317, No. 5843, 2007, pp. 1378-1381, doi : 10.1126 / science.1144066 , digitized version (PDF; 507.41 KB) , Supporting Online Material (PDF; 755.11 KB) .
- ↑ a b Xing Xu , Jonah N. Choiniere, Michael Pittman, Qingwei Tan, Dong Xiao, Zhiquan Li, Lin Tan, James M. Clark , Mark A. Norell , David WE Hone, Corwin Sullivan: A new dromaeosaurid (Dinosauria: Theropoda ) from the Upper Cretaceous Wulansuhai Formation of Inner Mongolia, China. In: Zootaxa . Vol. 2403, 2010, pp. 1–9, PDF - limited preview with images , PDF, full text, without images ( memento of the original from March 13, 2012 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked . Please check the original and archive link according to the instructions and then remove this notice. .
- ↑ Nicholas R. Longrich, Philip J. Currie : A microraptorine (Dinosauria – Dromaeosauridae) from the Late Cretaceous of North America. In: Proceedings of the National Academy of Sciences of the United States of America . Vol. 106, No. 13, 2009, pp. 5002-5007, doi : 10.1073 / pnas.0811664106 .
