Nemegtosauridae

Live reconstruction of the head of Nemegtosaurus

• Asia
• Africa
• South America

The Nemegtosauridae are a group of sauropod dinosaurs within the Titanosauria. While it originally only included the genera Nemegtosaurus and Quaesitosaurus, you have been attributed to other genera in recent years - but these associations vary depending on the author. The validity of the Nemegtosauridae is not generally accepted as the name of many researchers is not used. As a group derived ( advanced ) Titanosauria the Nemegtosauridae often contrasted with the Saltasauridae, another derived Titanosauria group, which includes, for example Saltasaurus and Opisthocoelicaudia.

History of Research

The taxon Nemegtosauridae was set up in 1995 by Barrett and Upchurch to summarize the genera Nemegtosaurus and Quaesitosaurus. Both genera are known only by the skull, their morphology shows strong similarities with that of the Diplodocoidea. In fact, the Nemegtosauridae was initially filed together with all other titanosaurs within the Diplodocoidea. Only Salgado and colleagues ( 1997) and Wilson and Sereno (1998 ) showed that Titanosaurier were actually closer related to Brachiosaurus -like shapes. Although both studies suggest reasoned that the Nemegtosauridae is classified within or as relatives of Titanosaurier, held several other researchers found in a classification within the Diplodocoidea. For example, lead Upchurch and colleagues ( 2004) as representative of the Nemegtosauridae Diplodocoidea, while they represent the Titanosauria in the closer relationship of Brachiosaurus -like shapes. With the discovery of Rapetosaurus first time Titanosaurier became known, is obtained from the complete skull material in conjunction with the rest of the skeleton: This discovery shows that Titanosaurier actually had a Diplodocoideen -like skull. This skull shape must therefore at Diplodocoideen and titanosaurs evolved independently of one another ( convergent evolution ). Today the classification of Nemegtosauridae is generally accepted consensus within the Titanosauria.

Definition and common features derived

The first definition of the group comes from Upchurch and colleagues ( 2004), which, however, classified the Nemegtosauridae within the Diplodocoidea: According to these authors, the Nemegtosauridae is a stem line based taxon ( steam -based definition) that all taxa including with closer with Nemegtosaurus were used as with Diplodocus. Wilson ( 2005) sees the Nemegtosauridae representing the Titanosauria and changed the definition: For the Nemegtosauridae are a stem -based taxon line, the mechanism involves all taxa that were more closely related than Nemegtosaurus with Saltasaurus. Wilson suggested the following, various shared derived characteristics ( synapomorphies ) against which to distinguish the group from other groups: For example, the lacrimal bone ( lacrimal ) showed an extension on the front; In addition, the crowns had a thin cross-section. The teeth of the dentary had a smaller diameter than that of the premaxillary bone ( premaxilla ) and the upper jaw ( maxilla ), as in Diplodocus.

Genera

While the group originally consisted of only Nemegtosaurus and Quaesitosaurus until today other genera of the group were attributed. So is Wilson (2005 ) that the group in addition at least Rapetosaurus should be assigned. Other genres he performs as a possible further Nemegtosauriden, including Opisthocoelicaudia, Antarctosaurus wichmannianus, cf " Antarctosaurus " septentrionalis, Mongolosaurus, Phuwiangosaurus and Bonita aura. Zaher and colleagues ( 2011) write the newly discovered genus Tapuiasaurus also the Nemegtosauridae to.