Nemegtosaurus Temporal range: Late Cretaceous, | |
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Cast of the skull of Nemegtosaurus on a reconstructed Opisthocoelicaudia skeleton, Museum of Evolution of Polish Academy of Sciences, Warsaw | |
Scientific classification ![]() | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Clade: | Dinosauria |
Clade: | Saurischia |
Clade: | † Sauropodomorpha |
Clade: | † Sauropoda |
Clade: | † Macronaria |
Clade: | † Titanosauria |
Family: | † Nemegtosauridae |
Genus: | † Nemegtosaurus Nowinski, 1971 |
Species | |
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Nemegtosaurus (meaning 'Reptile from the Nemegt') was a sauropod dinosaur from the Late Cretaceous Period of what is now Mongolia. 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 , [1] Alamosaurus and Rapetosaurus .
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. [1] 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. [2] 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. [3]
The type species, Nemegtosaurus mongoliensis, was first described by Nowinski in 1971 on the basis of ZPAL MgD-I/9. A second species, N. pachi, was described by Dong in 1977 on the basis of the teeth IVPP V.4879, recovered from the Subashi Formation, but is a nomen dubium .
The cladogram below follows Franca et al. (2016): [4]
Lithostrotia |
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Like other titanosaurs, the teeth are slender pencil-like structures that are ground down at a sharp angle to produce a chisel-like tip. The diet of Nemegtosaurus is unknown, however. There are no plant fossils from the Gobi, but during the Late Cretaceous, flowering plants became increasingly diverse, although in many environments ferns and conifers were still more common. Neither is it clear whether Nemegtosaurus browsed high in the trees or grazed on low-growing plants; related titanosaurs include both long-necked browsing forms like Rapetosaurus and short-necked forms like Bonitasaura .
Comparisons between the scleral rings of Nemegtosaurus and modern birds and reptiles suggest that it may have been cathemeral, active throughout the day at short intervals. [5]
Nemegtosaurus is found in the Maastrichtian aged (66-72 Ma) Nemegt Formation, which makes it one of the last sauropods on earth. There, on a lush river delta flowing through the ancient sands of the Gobi Desert, Nemegtosaurus would have coexisted with animals like the ornithomimid Gallimimus , the alvarezsaurid Mononykus , the velociraptorine Adasaurus , and the giant, saber-clawed therizinosaur Therizinosaurus . It also lived alongside the tyrannosaur Tarbosaurus . With its possible body length of 12 metres (39 ft), [6] an adult Nemegtosaurus may have been able to defend against Tarbosaurus, but juveniles would have been vulnerable.
Tarbosaurus is a genus of large tyrannosaurid dinosaur that lived in Asia during the Late Cretaceous epoch, about 70 million years ago. It contains the single type species: Tarbosaurus bataar, which is known from the Nemegt Formation of Mongolia, with more fragmentary remains found further afield in the Subashi Formation of China. Tarbosaurus is represented by dozens of fossil specimens, including several complete skulls and skeletons. These remains have allowed studies focusing on its phylogeny, skull mechanics, and brain structure. Further fossil remains have been reported from other geologic formations of Asia, however, these remains are fragmentary and can not be confidentially assigned to Tarbosaurus or the type species.
Titanosaurs were a diverse group of sauropod dinosaurs, including genera from all seven continents. The titanosaurs were the last surviving group of long-necked sauropods, with taxa still thriving at the time of the extinction event at the end of the Cretaceous. This group includes some of the largest land animals known to have ever existed, such as Patagotitan, estimated at 37 m (121 ft) long with a weight of 69 tonnes, and the comparably-sized Argentinosaurus and Puertasaurus from the same region.
Nemegtosauridae is a family of titanosaurian sauropod dinosaurs based on their diplodocid-like skulls. Only three species are known: Nemegtosaurus, Quaesitosaurus and possibly Tapuiasaurus, each from the Cretaceous.
Quaesitosaurus is a genus of nemegtosaurid sauropod containing only the type species, Q. orientalis, described in 1983. It lived from 72 to 71 million years ago during the Late Cretaceous epoch in the Barun Goyot Formation. With long, low and horse-like with frontally located peg-teeth, the skull of Quaesitosaurus is similar enough to the skull of Diplodocus and its kin to have prompted informed speculation that the missing body was built like those of diplodocids.
Deinocheirus is a genus of large ornithomimosaur that lived during the Late Cretaceous around 70 million years ago. In 1965, a pair of large arms, shoulder girdles, and a few other bones of a new dinosaur were first discovered in the Nemegt Formation of Mongolia. In 1970, this specimen became the holotype of the only species within the genus, Deinocheirus mirificus; the genus name is Greek for "horrible hand". No further remains were discovered for almost fifty years, and its nature remained a mystery. Two more complete specimens were described in 2014, which shed light on many aspects of the animal. Parts of these new specimens had been looted from Mongolia some years before, but were repatriated in 2014.
Saurolophus is a genus of large hadrosaurid dinosaur from the Late Cretaceous period of Asia and North America, that lived in what is now the Horseshoe Canyon and Nemegt formations about 70 million to 66 million years ago. It is one of the few genera of dinosaurs known from multiple continents. The type species, S. osborni, was described by Barnum Brown in 1912 from Canadian fossils. A second valid species, S. angustirostris, is represented by numerous specimens from Mongolia, and was described by Anatoly Konstantinovich Rozhdestvensky.
Alioramus is a genus of tyrannosaurid theropod dinosaurs from the Late Cretaceous period of Asia. It currently contains two species. The type species, A. remotus is known from a partial skull and three foot bones recovered from the Mongolian Nemegt Formation, which was deposited in a humid floodplain about 70 million years ago. These remains were named and described by Soviet paleontologist Sergei Kurzanov in 1976. A second species, A. altai, known from a much more complete skeleton also from the Nemegt Formation, was named and described by Stephen L. Brusatte and colleagues in 2009. Its relationships to other tyrannosaurid genera were at first unclear, with some evidence supporting a hypothesis that Alioramus was closely related to the contemporary species Tarbosaurus bataar. However, the discovery of Qianzhousaurus indicates that it belongs to a distinct branch of tyrannosaurs, namely the tribe Alioramini.
Opisthocoelicaudia is a genus of sauropod dinosaur of the Late Cretaceous Period discovered in the Gobi Desert of Mongolia. The type species is Opisthocoelicaudia skarzynskii. A well-preserved skeleton lacking only the head and neck was unearthed in 1965 by Polish and Mongolian scientists, making Opisthocoelicaudia one of the best known sauropods from the Late Cretaceous. Tooth marks on this skeleton indicate that large carnivorous dinosaurs had fed on the carcass and possibly had carried away the now-missing parts. To date, only two additional, much less complete specimens are known, including part of a shoulder and a fragmentary tail. A relatively small sauropod, Opisthocoelicaudia measured about 11.4–13 m (37–43 ft) in length. Like other sauropods, it would have been characterised by a small head sitting on a very long neck and a barrel shaped trunk carried by four column-like legs. The name Opisthocoelicaudia means "posterior cavity tail", alluding to the unusual, opisthocoel condition of the anterior tail vertebrae that were concave on their posterior sides. This and other skeletal features lead researchers to propose that Opisthocoelicaudia was able to rear on its hindlegs.
Bagaceratops is a genus of small protoceratopsid dinosaurs that lived in Asia during the Late Cretaceous, around 72 to 71 million years ago. Bagaceratops remains have been reported from the Barun Goyot Formation and Bayan Mandahu Formation. One specimen may argue the possible presence of Bagaceratops in the Djadochta Formation.
Tylocephale is a genus of pachycephalosaurid dinosaur, a group of dome-headed, herbivorous ornithischians, that lived during the Late Campanian stage of the Late Cretaceous in what is now Mongolia. It is known from a partial skull and associated mandible that were unearthed in 1971 by a Polish-Mongolian Expedition to the Barun Goyot Formation of the Gobi Desert. The specimen was described in 1974 by Polish paleontologists Teresa Maryańska and Halszka Osmólska as a new genus and species.
Kuru is a genus of dromaeosaurid theropod from the Late Cretaceous Barun Goyot Formation of Mongolia. The genus contains only a single species, the type species Kuru kulla, which is known from a fragmentary skeleton including a partial skull.
The Barun Goyot Formation is a geological formation dating to the Late Cretaceous Period. It is located within and is widely represented in the Gobi Desert Basin, in the Ömnögovi Province of Mongolia.
The Nemegt Formation is a geological formation in the Gobi Desert of Mongolia, dating to the Late Cretaceous. The formation consists of river channel sediments and contains fossils of fish, turtles, crocodilians, and a diverse fauna of dinosaurs, including birds.
The Museum of Evolution of Polish Academy of Sciences is the display area of the natural history museum in Warsaw, Poland. It is the public front of the Muzeum i Instytut Zoologii or Zoology Museum and the Instytut Paleobiologii or Paleobiology Institute. It is based at the Palace of Culture and Science.
Ceratonykus is a monospecific genus of alvarezsaurid dinosaur from Mongolia that lived during the Late Cretaceous in what is now the Barun Goyot Formation. The type and only species, Ceratonykus oculatus, is known from a fragmentary skeleton, including an incomplete skull, of an adult individual. It was named and described in 2009 by Vladimir Alifanov and Rinchen Barsbold. Its describers questioned the traditional placement of alvarezsaurs in Theropoda, instead suggesting they were ornithischians, but this has not been accepted since. Ceratonykus has an estimated length of 75 centimetres and weight of 760 grams. It has been considered as a possible junior synonym of Parvicursor.
Diamantinasaurus is a genus of titanosaurian sauropod from Australia that lived during the early Late Cretaceous, about 94 million years ago. The type species of the genus is D. matildae, first described and named in 2009 by Scott Hocknull and colleagues based on fossil finds in the Winton Formation. Meaning "Diamantina lizard", the name is derived from the location of the nearby Diamantina River and the Greek word sauros, "lizard". The specific epithet is from the Australian song Waltzing Matilda, also the locality of the holotype and paratype. The known skeleton includes most of the forelimb, shoulder girdle, pelvis, hindlimb and ribs of the holotype, and one shoulder bone, a radius and some vertebrae of the paratype.
Opisthocoelicaudiinae is a subfamily of titanosaurian dinosaurs from the Late Cretaceous. It was named by John McIntosh in 1990. Opisthocoelicaudiines are known from Mongolia, Argentina, and the United States. Two genera were assigned to Opisthocoelicaudiinae by Gonzalez et al. (2009): Alamosaurus and Opisthocoelicaudia, a conclusion also found by Díez Díaz et al. (2018). The hands of opisthocoelicaudiines lacked wrist bones and phalanges.
Khulsanurus is an extinct genus of alvarezsaurid theropod dinosaur from the Late Cretaceous Barungoyot Formation of the Khulsan Locality in the Gobi Desert region of Mongolia. The type and only species is Khulsanurus magnificus.
Ondogurvel is a genus of alvarezsaurid dinosaur from the Late Cretaceous (Campanian) Barun Goyot Formation in southern Mongolia. The type and only species is O. alifanovi, known from a partial skeleton consisting of fragments of two last dorsal vertebrae, three anterior sacral vertebrae, right ilium, left and right pubis and ischium, articulated right tibia, fibula, metatarsals II and IV, and phalanges IV-1 and IV-2, right carpometacarpus, left and right manual phalanx II-1, right femur, left pedal phalanx II-1, and fragments of unidentified phalanges.
Natovenator is a genus of halszkaraptorine dromaeosaurid dinosaur from the Late Cretaceous Barun Goyot Formation of Mongolia. The genus is known from a single species, N. polydontus. Natovenator is crucial to the understanding of halszkaraptorines due to it providing more support for the semi-aquatic lifestyle that has been proposed for this clade. This discovery is important as the semi-aquatic lifestyles of halszkaraptorines was contested in early 2022.
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