Mamenchisaurus is a sauropod dinosaur 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 Oxfordian to Tithonian ages of the late Jurassic Period of China, and the largest species may have reached 35 m (115 ft) in length and possibly weighed 50 to 75 tons.
The longest neck of any animal known to us from any time belonged to Mamenchisaurus. It made up half the animal’s total length. Reaching perhaps 49 feet (15 m) long, this incredible structure was supported by 19 vertebrae – no other dinosaur had as many neck vertebrae. Because these vertebrae were hollow – and in places the bone was as thin as egg shells – the neck was very light. Long bony struts running between the neck vertebrae would have limited its flexibility, and many reconstructions of Mamenchisaurus show it with the neck held straight as a ramrod. Some of these bony struts would have overlapped three or four vertebrae.
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.
Only a few skull fragments have been found of Mamenchisaurus. These suggest that it had a relatively short snout with robust, blunt teeth in the front and along the sides of the mouth. The particularly heavy teeth give a clue to its diet. These teeth could have dealt with the coarser, harder parts of plants and would have been especially good for shredding cycads and other fibrous fronds.
Although superficially Mamenchisaurus looks similar to North American sauropods such as Diplodocus and Apatosaurus, we now think that it was part of a group of sauropods unique to Asia. By the late Jurassic, the early Atlantic Ocean had become wide enough to restrict the flow of animals between North America and Europe and, although Europe and Asia were connected by land, there were deserts and mountain ranges that would have restricted the movement of large land animals from east to west.
- M. anyuensis He, Yang, Cai, Li & Liu, 1996. Approximately 21 meters (69 ft) in length. Known from both the Suining Formation and Penglaizhen Formation.
- 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.
- M. jingyanensis Zhang, Li & Zeng, 1998. Known from Shaximiao Formation and estimated between 20 to 26 metres (66 to 85 ft) in length.
- 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.
- M. youngi Pi, Ouyang & Ye, 1996: Mamenchisaurus youngi (pronunciation YOUNG-eye) 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 (52 ft) long with a 6.5-meter (21 ft) neck, is relatively small among various species of Mamenchisaurus.