Nemegtosaurus

Nemegtosaurus (meaning "reptile from the Nemegt") was a sauropod dinosaur from the Late Cretaceous Period of what is now Mongolia. Measuring an estimated long and weighing , it was named after the Nemegt Basin in the Gobi Desert, where the remains — a single skull — were found. The skull resembles diplodocoids in being long and low, with pencil-shaped teeth. However, recent work has shown that Nemegtosaurus is in fact a titanosaur, closely related to animals such as Saltasaurus, Alamosaurus, and Rapetosaurus.

==Discovery and taxonomy== thumb|left|Vertebrae that may belong to Nemegtosaurus The skull of Nemegtosaurus comes from the same beds as the titanosaur Opisthocoelicaudia, which is known from a skeleton lacking the neck and skull. Originally, the referral of Nemegtosaurus to Diplodocoidea and Opisthocoelicaudia to Camarasauridae argued that the two represented different species. Both of these genera represent advanced titanosaurians, however, raising the possibility that the two are in fact the same animal. Relocation of the Nemegtosaurus type locality in Central Sayr and discovery of postcrania comparable to those Opisthocoelicauda holotype at the Nemegtosaurus holotype locality has discussed the possibility that Opisthocoelicauda is a junior synonym. Consequently, Opisthocoelicaudiinae would be a junior synonym of Nemegtosauridae. In 2019, Alexander O. Averianov and Alexey V. Lopatin in a paper describing new specimens of Nemegtosaurus reanalyzed the argument for synonymy and determined that the taxa were not synonymous because shared characters between the species were either difficult to determine or based on comparisons with a specimen which actually belonged to Nemegtosaurus.