Nanshiungosaurus
| Nanshiungosaurus | |
|---|---|
| |
| Skeletal restoration of the holotype | |
Scientific classification 
| |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | Theropoda |
| Superfamily: | † Therizinosauroidea
|
| Family: | †Therizinosauridae |
| Genus: | †Nanshiungosaurus Dong, 1979 |
| Type species | |
| †Nanshiungosaurus brevispinus Dong, 1979
| |
Nanshiungosaurus (meaning "Nanxiong's lizard") is a
therizinosaurid that lived in what is now Asia during the Late Cretaceous of South China. The type species, Nanshiungosaurus brevispinus, was first discovered in 1974 and described in 1979 by Dong Zhiming
. It is represented by a single specimen preserving most of the cervical and dorsal vertebrae with the pelvis. A supposed and unlikely second species, "Nanshiungosaurus" bohlini, was found in 1992 and described in 1997. It is also represented by vertebrae but this species however, differs in geological age and lacks authentic characteristics compared to the type, making its affinity to the genus unsupported.
It was a large-sized therizinosaurid that is estimated to have cover nearly 5 m (16 ft) in length and to have weighed about 907 kg (2,000 lb). Nanshiungosaurus had a very pneumatized
toes
and large flattened claws.
Nanshiungosaurus is classified as a therizinosaurian dinosaur. Along with prosauropod dinosaurs.
History of discovery
In 1974, during a geological expedition at the
sauropod characterized by a shorter but thicker neck than other sauropods based on the pelvis structure.[1]
In 1997 Dong Zhiming and You Hailu named and described a supposed second species: "Nanshiungosaurus" bohlini, based on a skeleton found in 1992 near
synapomorphies, she considered that the supposed second species is unrelated to Nanshiungosaurus and might warrant its own genus. In addition, she corrected the number of sacral vertebrae from 5 to 6 and noted that the holotype pelvis from the latter has suffered damage since collection and has been reconstructed with painted plaster in the affected areas.[3] Moreover, the remains of "N". bohlini were recovered from the lower red beds of the Zhonggou Formation in the Gongpoquan Basin, a completely different geological context. As an overall consensus, this dubious specimen is no longer considered to be relatable to Nanshiungosaurus.[4]
Description
Nanshiungosaurus was a relatively large-bodied
Vertebral column
Most cervicals have relatively short
ribs. As for most cervicals, the neural arches and spines are short, the anterior articular processes are strongly developed in that direction, and the anterior lobes of the diapophyses (bony projections to the lateral sides) extend to the bottom and lateral directions to articulate with tubercles. Seventh and eighth cervicals are the longest with 18 cm (180 mm) long centra and posterior to them, the vertebral size slightly narrows. In most posterior cervicals, the centra are opisthocoelous with shallow posterior grooves.[1]
The
neural spines are very elongated, the articular processes are located within the ligaments of the centrum, the neural spines are stocky, side to side thickened, and the top regions have stout tuberosities. A prominent spiral-like ridge is present on the bottom surface that becomes more notable to the posterior direction. Though most dorsals are completely preserved, eighth through tenth dorsals have damaged centra. On the posterior series the centra become platycoelous, approaching the sacral vertebrae structure. The sacrum is composed by six (originally five) sacral vertebrae and they are fused into a single structure, indicating that the individual was an adult at the time of death. They are lightly more longer than the dorsals and have stocky, side to ide broadened neural spines with the top surfaces bearing small depressions. A single caudal vertebra is present after the sacral series and represents the first caudal. Its neural spine is broken and the centrum is slightly amphicoelous (concave on both ends) with sub-equal height and length.[1]
Pelvic girdle
The pelvis is represented by the well-preserved left side composed by the
taphonomical factors has been bent out of shape. Like other derived therizinosaurids, the pelvis has an opisthopubic condition where the pubis and ischium are fused and directed backwards. The ilium is stocky with an extremely well-developed and elongated preacetabular process (anterior expansion of the iliac blade), nevertheless, the postacetabular process (posterior expansion) is missing. Its pubic peduncle (a robust projection that connects to the pubis) is also well-developed, being straight and thick at the end. The acetabulum (hip socket in the middle) is large and relatively circular in shape. The pubic bone has lost its lower end and is well-fused to the ischial bone. The ischium is relatively thin, expanded, and the obturator process (a notably large projection at the end) is broken.[1]
Classification
Nanshiungosaurus was in 1979 by Dong assigned to the
junior synonym of the older name Therizinosauridae.[15] Segnosauria also became synonymous with Therizinosauria.[16] In 1997, with the description and naming of "N". bohlini, Dong and You placed the therizinosaurids Nanshiungosaurus and the former into a separate Nanshiungosauridae. They did not provide authentic traits or bases behind this new grouping.[2] In 2010, Zanno performed one of the most complete analyses of the Therizinosauria at that point and noted that these two species do not pertain to the same genus and therefore the use of the Nanshiungosauridae was invalid and represents a synonym of Therizinosauridae.[3]
Nanshiungosaurus features multiple therizinosaurid traits such as an ophisthopubic pelvis, elongated iliac blade and an expanded obturator process. In her
phylogenetic analysis, Zanno recovered this taxon as a derived therizinosaurid closer to Nothronychus and Segnosaurus.[3] The therizinosaurid placement of Nanshiungosaurus has been widely followed and corroborated by most cladistic analyses.[17][18] The extensive phylogenetic analysis conducted by Hartman and colleagues in 2019 based on Zanno's 2010 analysis, recovers Nanshiungosaurus in a more derived position than Neimongosaurus or Therizinosaurus. Below are the obtained results:[18]
| Therizinosauridae |
| ||||||||||||||||||||||||||||||||||||||||||
Paleoecology
Nanshiungosaurus was one of the last therizinosaurs to exist. The fossil remains were unearthed from the
ornithopod dinosaurs are locally abundant at the Nanxiong region.[23]
The therizinosaurid Nanshiungosaurus was a bulky
See also
References
- ^ a b c d e Dong, Z. (1979). "Cretaceous dinosaur fossils in southern China" [Cretaceous dinosaurs of the Huanan (south China)]. In Institute of Vertebrate Paleontology and Paleoanthropology; Nanjing Institute of Paleontology (eds.). Mesozoic and Cenozoic Redbeds in Southern China (in Chinese). Beijing: Science Press. pp. 342−350. Translated paper
- ^ a b Dong, Z.; You, H. (1997). "A new segnosaur from Mazhongshan Area, Gansu Province, China". In Dong, Z. M. (ed.). Sino-Japanese Silk Road Dinosaur Expedition. Beijing: China Ocean Press. pp. 90−95.
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- ^ Perle, A. (1979). "Segnosauridae — novoe semejstvo teropod iz pozdnego mela Mongolii" [Segnosauridae — a new family of theropods from the Late Cretaceous of Mongolia]. Transactions of the Joint Soviet-Mongolian Paleontological Expedition (in Russian). 8: 45−55. Translated paper
- ^ Gauthier, J. (1986). "Saurischian monophyly and the origin of birds". Memoirs of the California Academy of Sciences. 8: 45.
- JSTOR 4523276.
- ISBN 9780520067271.
- ISBN 3-540-52084-8.
- doi:10.1139/e93-183.
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