Quaesitosaurus
| Quaesitosaurus | ||||||||||||
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| Temporal occurrence | ||||||||||||
| Upper Cretaceous (middle to late Campanium ) | ||||||||||||
| 80.6 to 72 million years | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Quaesitosaurus | ||||||||||||
| Kurzanov , Bannikov , 1983 | ||||||||||||
| Art | ||||||||||||
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Quaesitosaurus is a genus of sauropod dinosaur from the group of Titanosauria from the Upper Cretaceous (middle to late Campanium ) of Asia.
So far, only a single, fragmentary skull is known, which comes from the Barun-Goyot Formation in the Mongolian Aimag Ömnö-Gobi . With the closely related Nemegtosaurus , also known only from a skull find , Quaesitosaurus is often combined in a group called Nemegtosauridae .
The genus was first described in 1983 with the only species Quaesitosaurus orientalis by Sergei Kurzanov and Alexander Bannikov . The name Quaesitosaurus ( Lat. Quaesitus - "extraordinary", Greek sauros - "lizard") indicates the unusual anatomy of the skull. The bones obtained include the intermaxillary bone (premaxillary), parts of the upper jaw (maxillary), lower jaw, cranium and wing bone (pterygoid).
Characteristics and differentiation from Nemegtosaurus
Quaesitosaurus is, besides Nemegtosaurus and Rapetosaurus, the only titanosaur for which relatively complete skull material is known. As with Nemegtosaurus and Rapetosaurus , the skull was elongated and sloping forward, with the nostrils high up on the skull at the level of the eye sockets. The tooth crowns were long and thin.
Wilson (1997) suspects that Quaesitosaurus and Nemegtosaurus could have been one and the same species. The Kurzanov and Bannikov gave eight characteristics in their first description, which should distinguish Quaesitosaurus from Nemegtosaurus . However, many of these differences are actually due to skull deformation and inadequate description, as later studies showed. For example, according to Kurzanov and Bannikov, the skull of Quaesitosaurus was wider and showed a shorter scaly bone (squamosum) without contact with the quadratojugale, while the occipital condyle (the articular knot of the occiput that forms the head joint) was rounded. Furthermore, these authors wrote that the side of the upper jaw of Quaesitosaurus had nine teeth, while there were only eight in Nemegtosaurus . The row of teeth in the lower jaw was also longer, the authors stated. However, later studies found that some of the morphological differences were due to subsequent deformations of the skull. The skull of Quaesitosaurus is compressed dorso-ventrally (vertically), while the skull of Nemegtosaurus is compressed at an angle. Other of the features listed by Kurzanov and Bannikov, such as the shorter scaly bone and the smaller number of teeth, could not be confirmed or refuted by later studies due to poor preservation. Still other features, such as the occipital condyle, are too insignificant to be used as diagnostic features and can also be traced back to individual variations.
Wilson (2005) published an extensive new description of the Nemegtosaurus skull and found additional features ( autapomorphies ) that support the status of a genus of its own for Quaesitosaurus . So shows quaesitosaurus example, unlike Nemegtosaurus pits in the front square leg while a comb at the back postorbital was not available.
Systematics
Originally, Quaesitosaurus and Nemegtosaurus were considered close relatives of Diplodocus and Dicraeosaurus , as the skulls have strong analogies to these genera. While Kurzanov and Bannikov (1983) and a number of later authors saw Quaesitosaurus as a representative of the Dicraeosaurinae , Carroll (1988) classified him within the Diplodocidae . Upchurch (1995) established a new group within the Diplodocoidea , which should include Quaesitosaurus and Nemegtosaurus - the Nemegtosauridae . Only when complete Titanosauria skull material in direct association with the residual skeleton (postcranium) became known with the discovery of Rapetosaurus , the position of the Nemegtosauridae within the Titanosauria could be confirmed. The status of the Nemegtosauridae is currently controversial, the group is only accepted by some researchers.
Individual evidence
- ^ Gregory S. Paul: The Princeton Field Guide To Dinosaurs. , 2010, ISBN 978-0-691-13720-9 , p. 212. (online)
- ↑ a b c d e Jeffrey A. Wilson: Redescription of the Mongolian Sauropod Nemegtosaurus mongoliensis Nowinski (Dinosauria: Saurischia) and comments on Late Cretaceous Sauropod diversity . In: Journal of Systematic Palaeontology . tape 3 , no. 3 , 2005, p. 283-318 , doi : 10.1017 / S1477201905001628 .
- ↑ a b c d Upchurch, Barrett, Dodson: Sauropoda . In: Weishampel, Dodson, Osmólska (eds.): The Dinosauria . 2nd edition. University of California Press, 2004, ISBN 0-520-24209-2 , pp. 259-322 .
- ↑ SM Kurzanov, AF Bannikov: A new sauropod from the Upper Cretaceous of Mongolia. In: Paleontological Journal. Volume 2, 1983, pp. 91-97.
- ↑ Ben Creisler: Dinosauria Translation and Pronunciation Guide ( Memento of October 13, 2011 in the Internet Archive )
- ↑ Quaesitosaurus. In: The Paleobiology Database. Retrieved December 20, 2010 .
- ↑ Paul Sereno: Nemegtosauridae. (No longer available online.) In: Taxon Search. Archived from the original on July 17, 2011 ; Retrieved December 20, 2010 . 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.
