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.