Mamenchisaurus hochuanensis (named after Hechuan County) was discovered by locals prior to the Chinese revolution. But under the leadership of the Chinese Guomindang reactionary party, it was ignored and allowed to weather away where it lay. It was rediscovered in 1957 by the Sichuan Petroleum Exploration corps in the Shaximiao Formation 200 meters above the Gaochufujiang River on the slope of Mt. Gushushan, 35 km from the village of Taihezhen (formerly Taiheba). In 1972 it was named by C.C Young (Zhongjian Yang) and Zhao Xijin, who believed it was "adapted for both terrestrial and aquatic life while subsisting on shoreline vegetation".
Dakang Zhu of the Sichuan Museum of Natural History, and Xuanmin Li and Yanwan Gong from the Chungking Museum of Natural History, later undertook a detailed excavation of the area and within three months had excavated China's largest and most complete sauropod skeleton. Mamenchisaurus hochuanensis includes remains from Haishiwan that C.C Young had assigned to Mamenchisaurus constructus in 1958. Four fused vertebrae at the tip of its tail suggest a weapon of some sort may have been attached. Estimated length: 22 meters. Mamenchisaurus anyuensis (named by He, Yang, Cai, Li and Liu in 1996 for Anyue County) was recovered from two localities (the Suining Formation at Longjiawa and Penglaizhen Formation at Matisi) near the town of Longchiaoxiang, Anyue County, in the centre of the Sichuan Basin, in 1987.
The holotype (AL001) is a relatively complete skeleton plucked from an assemblage of at least ten individuals. Estimated length: 21 meters. ?Mamenchisaurus fuxiensis was originally named Zigongosaurus by Hou, Zhao and Chu in 1976 based on a partial skull (holotype: CV 00261) and a plethora of body and limb bones from several individuals. It was re-named Mamenchisaurus fuxiensis by Zhang and Chen in 1996 after a tangle with Omeisaurus fuxiensis (Dong, Zhou, and Zhang, 1983) and a stint being synonymous with Omeisaurus junghsiensis (McIntosh, 1990). At least one palaeontologist believes it doesn't belong to Mamenchisaurus. Mamenchisaurus jingyanensis (named by Zhang, Li and Zeng in 1998 for "Jingyan": a Pinyin romanization of the county in which the holotype was excavated) was discovered in the Upper Shaximiao Formation, 200m from the administrative headquarters of the town of Meiwang, Jingyan County, Sichuan Province. The holotype (CV00734) is a relatively complete skull (including several loose teeth), a partial shoulder, a right upper arm bone, a left lower arm bone and a hip bone.
Estimated length: 20-26 metres. Mamenchisaurus sinocanadorum (named by Russell and Zheng in 1994 for the Sino-Canadian expedition that found its remains) was discovered in the upper part of the Shishugou Formation.
Initially known only from a partial skull and isolated bones, Mamenchisaurus sinocanadorum has the longest neck ribs of any known sauropod (4.1 m). A fairly complete but as-yet undescribed skeleton makes Mamenchisaurus sinocanadorum by far the largest species of Mamenchisaurus and one of the largest known sauropods.
Estimated length: 35-40 meters, with its neck accounting for 17 them. Mamenchisaurus youngi (named in 1996 by Lizhong Pi, Yanghui Ou, and Yong Ye for C.C Young) was discovered by Mr Renfa Song whilst quarrying stone near Xinminxiang village, Zigong, Sichuan Province, China, in 1989.
The holotype (ZDM0083) is a virtually complete skeleton, complete with skull. Mamenchisaurus youngi is the smallest species of Mamenchisaurus, with its 18-vertebrae neck being "only" six-and-a-half meters long.
Estimated length: 16 meters.