Quaesitosaurus

• Mongolia, Barun Goyot Formation ( Omnö Gobi aimag )

• Quaesitosaurus orientalis

Quaesitosaurus is a genus of sauropod dinosaur from the group of Titanosauria from the Upper Cretaceous ( middle to late Campanian ) of Asia.

So far, a single, fragmentary skull is only known that originates from the Barun - Goyot lineup from the Mongolian Gobi Aimag Ömnö. With the closely related, also known only by a skull Fund Nemegtosaurus Quaesitosaurus is often summarized in a group designated as Nemegtosauridae.

The genus was first described in 1983 with the only kind Quaesitosaurus orientalis by Sergei Kurzanov and Alexander Bannikov. The name Quaesitosaurus (Lat. quaesitus - "extraordinary", gr sauros - " lizard" ) refers to the unusual anatomy of the skull. The bones obtained close the premaxillary bone ( premaxilla ), parts of the upper jaw ( maxilla ), mandible, skull and wing bone ( pterygoid ) with a.

Characteristics and differentiation Nemegtosaurus

Quaesitosaurus is next Nemegtosaurus and Rapetosaurus the only Titanosaurier from which relatively complete skull material is known. As with Nemegtosaurus and Rapetosaurus the skull was extended and fell forward from back, with the nostrils were at the level of the orbits near the top of the skull. The crowns were long and thin.

Wilson ( 1997) suggested that there might have been at Quaesitosaurus and Nemegtosaurus one and the same way. Although the Kurzanov and Bannikov gave in their first description of eight characteristics, which should be different from Quaesitosaurus Nemegtosaurus. Many of these differences are in fact due to a deformation of the skull and an inadequate description, as later studies showed. According Kurzanov and Bannikov example was the skull of Quaesitosaurus been broad and show a shorter squamosal ( squamosal ) without contact with the Quadratojugale while the occipital condyle ( of forming the head joint condyles of the occipital bone ) was rounded. Furthermore, these authors wrote that the side of the upper jaw of Quaesitosaurus had nine teeth, while there were only eight at Nemegtosaurus. The teeth of the lower jaw was longer, the authors said. Later studies, however, recognized that some of the morphological differences are formed by subsequent deformations of the skull. Thus, the skull of dorso- ventral Quaesitosaurus (vertical) is compressed while the skull is compressed obliquely from Nemegtosaurus. Another of the listed of Kurzanov and Bannikov features such as the shorter leg scales and the lower number of teeth, could not be confirmed or refuted by later studies due to poor preservation. Still other features, such as the occipital condyle in turn are too insignificant to be utilized as diagnostic features can, and can also be attributed to individual variations.

Wilson ( 2005) published an extensive redescribed Nemegtosaurus skull and found other features ( autapomorphies ) that support the status of a separate genus for Quaesitosaurus. So, for example, shows Quaesitosaurus unlike Nemegtosaurus pits in the front square leg, while a comb at the back postorbital was not available.

System

Originally were Quaesitosaurus and Nemegtosaurus as close relatives of Diplodocus and Dicraeosaurus because the skull have strong analogies to these genres. While the describer Kurzanov and Bannikov (1983) and a number of later authors Quaesitosaurus saw as a representative of Dicraeosaurinae, classified him Carroll (1988 ) within the Diplodocidae. Upchurch (1995 ) presented a new group within the Diplodocoidea, which should include Quaesitosaurus and Nemegtosaurus - the Nemegtosauridae. Only when it became known with the discovery of Rapetosaurus Titanosauria complete skull material in direct association with the rest of the skeleton ( Postkranium ), the position of the Nemegtosauridae within the Titanosauria could be confirmed. The status of the Nemegtosauridae is currently controversial, the group is accepted only by some researchers.