Mamenchisaurus

Mamenchisaurus Temporal range: Late Jurassic, 160–145 Ma PreЄ Є O S D C P T J K Pg N
Mounted skeleton of M. sinocanadorum, Japan
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Dinosauria
Order:	Saurischia
Suborder:	†Sauropodomorpha
Family:	†Mamenchisauridae
Genus:	†Mamenchisaurus Young, 1954
Type species
†Mamenchisaurus constructus Young, 1954
Species
†M. constructus Young, 1954 †M. hochuanensis Young & Zhao, 1972 †M. sinocanadorum Russell & Zheng, 1994 †M. youngi Pi, Ouyang & Ye, 1996 †M. anyuensis He et al., 1996 †M. jingyanensis Zhang, Li & Zeng, 1998 †M. yunnanensis Fang et al., 2004[1]

Mamenchisaurus (/mɑːˈmʌntʃiˈsɔːrəs/ mah-MUN-chi-SAWR-əs, or spelling pronunciation /məˌmɛntʃiˈsɔːrəs/) is a sauropod dinosaur genus including several species, known for their remarkably long necks^[2] which made up half the total body length.^[3] It is known from numerous species which ranged in time from 160 to 145 million years ago, from the Oxfordian to Tithonian ages of the late Jurassic Period of China, and the largest species may have reached 35 m (115 ft) in length.^[4]

Discoveries

Mounted M. youngi skeleton, Zigong Museum

Mamenchisaurus was first discovered in 1952 on the construction site of the Yitang Highway in Sichuan, China. The partial skeleton fossil was then studied, and named Mamenchisaurus constructus in 1954, by the renowned Chinese paleontologist Professor C. C. Young. The type specimen had an incomplete neck with 14 vertebra preserved and none of these were complete. M. constructus has been estimated around 13 m (43 ft) and 15 m (49 ft) in length.^[4][5]

In 1972, a second species was described, named Mamenchisaurus hochuanensis, with a neck that reached up to 9.3 m (31 ft) in length.^[6] This species had a complete neck preserved which contained 19 vertebrae.^[7] This was the longest neck known until the description of Supersaurus, based on a single neck vertebra, BYU 9024, with an estimated neck length of about 14 meters (46 feet). Another long-necked sauropod exceeding M.hochuanensis was Sauroposeidon which was discovered in 1994. Based on the Sauroposeidon holotype, which only preserved 4 neck vertebra, its neck was estimated to be between 11.25 and 12 meters (36.9–39.4 feet) long.^[8]

In 1993, M. sinocanadorum was described, which consisted of skull material and the first four cervical vertebrae. This species possessed the longest cervical rib of any described sauropod dinosaur, measuring 4.1 m (13.5 ft). This is longer than the longest Sauroposeidon cervical rib, which measures 3.42 m (11.2 ft).^[9] Additional remains attributed to this species, but not yet formally described, belong to one of the largest dinosaurs known—the restored skeleton measuring 35 metres (115 ft) in length with a neck measuring 18 metres (59 ft) long.^[4]

In 2001, another M. hochuanensis specimen was described. It had skull, pectoral girdle and forelimb material preserved, all of which were missing from the holotype. It was also found with four fused tail vertebra, which have expanded neural arches and taller neural spines, that belong at the tip of the tail. It’s thought that these could be a weapon, such as a tail club, or a sensory organ. Other Chinese sauropods, Shunosaurus and Omeisaurus, are also known to have had ’tail clubs’ but they differ in shape to that of M. hochuanensis.^[10][11]

Naming

Artist's impression of M. youngi

Mamenchisaurus means 'Mamenchi lizard', from the Chinese Pinyin mǎ (马 'horse') and mén (门 'gate'), while chi is a transliteration of xī (溪 'stream' or 'brook'), combined with the suffix -saurus (from Greek sauros meaning 'lizard').

It was intended to name the reptile after the place where its fossil was first found — a construction site next to the Mǎmíngxī (马鸣溪) Ferry Crossing by the Jinsha River (金沙江, the westernmost major headwater stream of the Yangtze River), near Yibin (宜宾) in Sichuan Province of China. However, due to an accentual mix-up by Young, the location name Mǎmíngxī (马鸣溪 'horse-neighing brook') was mistaken as Mǎménxī (马门溪 'horse-gate brook').^[12] The fact that the first Mamenchisaurus fossil was found as the result of construction work led to Young's naming the type species as Mamenchisaurus constructus.^[5]

Species

Size comparison of M. constructus, M. youngi, M. hochuanensis and M. sinocanadorum

Artist's impression of M. hochuanensis

• M. anyuensis He, Yang, Cai, Li & Liu, 1996. Approximately 21 meters (69 ft) in length. Known from both the Suining Formation and Penglaizhen Formation.^[13]
• M. constructus Young, 1954: (Type species) The holotype specimen, represented by a partial skeleton that was 13 m (43 ft) long.
• M. hochuanensis Young & Zhao, 1972: Four partial skeletons. Known from Shaximiao Formation and 22 m (72 ft) in length.^[7]
• M. jingyanensis Zhang, Li & Zeng, 1998. Known from Shaximiao Formation and estimated between 20 to 26 metres (66 to 85 ft) in length.^[14]
• M. sinocanadorum D. Russell & Zheng, 1993: Partial skull, isolated bones (type), referred, nearly complete skeleton. Known from the upper part of the Shishugou Formation (about 160 Ma ago), it may include one of the largest complete dinosaur specimens known, measuring 35 metres (115 ft) in length.^[4][15]
• M. youngi Pi, Ouyang & Ye, 1996: Mamenchisaurus youngi (pronunciation YOUNG-eye) was unearthed in Xinmin County, Zigong City in Sichuan Province, China, in 1989.^[16] The species was named in honour of Young. It was a very complete and articulated specimen preserving all the vertebra from the head up until the 8th tail vertebra. It had 18 neck vertebra. At 16 meters (52 ft) long with a 6.5-meter (21 ft) neck, is relatively small among various species of Mamenchisaurus.

Classification

Mounted M. hochuanensis skeleton, Field Museum

The cladogram below shows a possible phylogenetic position:^[17]

Sauropoda	Melanorosaurus Camelotia Blikanasaurus   Lessemsaurus Antetonitrus Gongxianosaurus Gravisauria Vulcanodon Tazoudasaurus Isanosaurus Eusauropoda Shunosaurus Patagosaurus Omeisaurus Mamenchisaurus Barapasaurus unnamed Cetiosaurus Neosauropoda

References

1. Fang, X.; Zhao; Lu, L.; Cheng, Z. (2004). "Discovery of Late Jurassic Mamenchisaurus in Yunnan, southwestern China". Geological Bulletin of China 23 (9-10): 1005–1011.
2. Sues, Hans-Dieter (1997). "Sauropods". In James Orville Farlow and M. K. Brett-Surman (eds.). The Complete Dinosaur. Bloomington: Indiana University Press. p. 274. ISBN 0-253-33349-0.
3. Norman, David B. (2004). "Dinosaur Systematics". In Weishampel, D.B., Dodson, P., and Osmólska, H. (eds.). The Dinosauria (2nd ed.). Berkeley: University of California Press. p. 318. ISBN 0-520-24209-2.
4. Paul, G.S. (2010). The Princeton Field Guide to Dinosaurs, Princeton University Press.
5. Young, C.C. (1954), On a new sauropod from Yiping, Szechuan, China. sinica, III(4), 481-514.
6. Paul, G.S. (1988). "The brachiosaur giants of the Morrison and Tendaguru with a description of a new subgenus, Giraffatitan, and a comparison of the world's largest dinosaurs". Hunteria, 2(3): 1–14.
7. Young, C.C., and Zhao, X.-J. (1972). "Mamenchisaurus hochuanensis sp. nov." Institute of Vertebrate Paleontology and Paleoanthropology Monographs, A, 8:1-30.
8. Wedel, M.J., and Cifelli, R.L. (2005). "Sauroposeidon: Oklahoma’s native giant." Oklahoma Geology Notes, 65(2): 40-57.
9. "Osteology, paleobiology, and relationships of the sauropod dinosaur Sauroposeidon", by Mathew J. Wedel, Richard L. Cifelli, and R. Kent Sanders (Acta Palaeontologica Polonica 45, pages 343–388, 2000).
10. Ye, Y.; Ouyang, H.; Fu, Q.-M. (2001). "New material of Mamenchisaurus hochuanensis from Ziging China". Vertebrata PalAsiatica 39 (4): 266–271.
11. Xing, L; Ye, Y; Shu, C; Peng, G; You, H (2009). "'Structure, orientation and finite element analysis of the tail club of Mamenchisaurus hochuanensis.'". Acta Geologica Sinica (English Edition) 83 (6): 1031–1040. doi:10.1111/j.1755-6724.2009.00134.x.
12. Origin of the Mamenchisaurus name (in Chinese), Beijing Museum of Natural History website
13. He, Xinlu; Yang, Suihua,; Cai,, Kaiji; Li,kui; Liu, Zongwen (1996). "A new species of sauropod, Mamenchisaurus anyuensis sp. nov." (PDF). Papers on Geosciences contributed to the 30th Geological Congress: 83–86. Cite uses deprecated parameter |coauthors= (help)
14. Zhang, Yihong; Li, kui; Zeng, Qinghua (1998). "'A new species of sauropod from the Late Jurassic of the Sichuan Basin (Mamenchisaurus jingyanensis sp. nov.)'". Journal of the Chengdu University of Technology 25 (1): 61–68.
15. Russell, D.A., Zheng, Z. (1993). "A large mamenchisaurid from the Junggar Basin, Xinjiang, People Republic of China." Canadian Journal of Earth Sciences, (30): 2082-2095.
16. Ouyang, H. and Ye, Y. 2002. The First Mamenchisaurian Skeleton with Complete Skull: Mamenchisaurus youngi (in Chinese with English summary). 111 pp + 20 plates. Sichuan Science and Technology Press, Chengdu.
17. J.A. Wilson, 2002, "Sauropod dinosaur phylogeny: critique and cladistic analysis", Zoological Journal of the Linnean Society 136: 217-276

External links

• Dinosaur.net.cn (in Chinese and English)