Mamenchisaurus is a sauropoddinosaur genus including several species, known for their remarkably long necks which made up half the total body length. It is known from numerous species which ranged in time from 160 to 145 million years ago, from the Oxfordianage of late Jurassic Period in China. The largest species, which according to Gregory S. Paul was M. sinocanadorum, may have reached in length and possibly weighed 60-80 tonnes.
Discovery
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 vertebrae preserved and none of these were complete. M. constructus has been estimated around and in length. Mamenchisaurus means 'Mamenchi lizard', from the Chinese Pinyinmǎ and mén, while chi is a transliteration of xī, combined with the suffix -saurus. It was intended to name the reptile after the place where its fossil was first found—a construction site next to the Mǎmíngxī Ferry Crossing by the Jinsha River, near Yibin in SichuanProvince of China. However, due to an accentual mix-up by Young, the location nameMǎmíngxī was mistaken as Mǎménxī. 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. In 1972, a second species was described, named Mamenchisaurus hochuanensis, with a neck that reached up to in length. This species had a complete neck preserved which contained 19 vertebrae. 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. Another long-necked sauropod exceeding M. hochuanensis was Sauroposeidon which was discovered in 1994. Based on the Sauroposeidonholotype, which only preserved 4 neck vertebra, its neck was estimated to be between 11.25 and 12 meters long. 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. This is longer than the longest Sauroposeidon cervical rib, which measures. Additional remains attributed to this species, but not yet formally described, belong to one of the largest dinosaurs known—the restored skeleton measuring in length. 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.
Species
M. anyuensis He, Yang, Cai, Li & Liu, 1996. Approximately in length. Known from both the Suining Formation and Penglaizhen Formation. Uranium-lead dating places M. anyuensis at 114.4 Ma in age; as this would make it roughly 30 million years younger than the other Mamenchisaurus species, it is unlikely that M. anyuensis is actually a member of the genus.
M. hochuanensis Young & Zhao, 1972: Four partial skeletons. Known from Shaximiao Formation and in length.
M. jingyanensis Zhang, Li & Zeng, 1998. Known from Shaximiao Formation and estimated between in length.
M. sinocanadorum D. Russell & Zheng, 1993: Partial skull, isolated bones, referred, nearly complete skeleton. Known from the upper part of the Shishugou Formation, it may include one of the largest dinosaur specimens known, measuring in length.
M. youngi Pi, Ouyang & Ye, 1996: Mamenchisaurus youngi was unearthed in Xinmin County, Zigong City in Sichuan Province, China, in 1989. 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 long with a 6.5-meter neck, is relatively small among various species of Mamenchisaurus.
Classification
The cladogram below shows a possible phylogenetic position:
