Mamenchisaurus
Mamenchisaurus (/məˌmʌntʃiˈsɔːrəs/ mə-MUN-chee-SOR-əs,[1] or spelling pronunciation /məˌmɛntʃɪˈsɔːrəs/) is a genus of sauropod dinosaur known for their remarkably long necks[2] which made up nearly half the total body length.[3] Numerous species have been assigned to the genus; however, many of these might be questionable. Fossils have been found in the Sichuan Basin and Yunnan Province in China. Several species are from the Upper Shaximiao Formation whose geologic age is uncertain. However, evidence suggests that this be no earlier than the Oxfordian stage of the Late Jurassic. M. sinocanadorum dates to the Oxfordian stage (158.7 to 161.2 mya) and M. anyuensis to the Aptian stage of the Early Cretaceous around 114.4 mya.[1] Most species were medium to large size sauropods, around 15 to 26 meters (49 to 85 ft) in length and possibly up to 35 meters (115 ft) based on two undescribed vertebrae.[4][5][6]
Mamenchisaurus was first discovered in 1952 on the construction site of the Yitang Highway in Sichuan Province of China. The fossil site belonged to the Upper Shaximiao Formation, dating to at least the Late Jurassic.[1] The partial skeleton fossil was later studied and named Mamenchisaurus constructus in 1954 by the renowned Chinese paleontologist Professor C. C. Young.
The type specimen (IVPP V. 790) was fragmentary, disordered, and not excavated in a technical way. Material included five dorsal vertebrae, 30 caudal vertebrae, rib fragments, dorsal neural spines, and chevrons. Fourteen neck vertebrae were preserved, but none were complete. Young noted that some neck vertebrae might have been missing. Limb material included; two pieces of a femur, a complete tibia, fibula, astragalus, metatarsals, phalanges, and claws. The skull, forelimbs, and pelvic girdle were missing.[7]
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'). The intention was to name the genus after the place where its fossil was first found. 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').[8] The fact that the first Mamenchisaurus fossil was found due to construction work led to Young's naming the type species as Mamenchisaurus constructus.[7]
In 1958, Young described additional sauropod remains collected from Gansu Province. The remains consisted of various partial specimens (IVPP V. 945, V. 946, V. 947, V. 948) most of which were assigned to M. constructus.[9] In 1972, one of these specimens was reassigned to M. hochuanensis.[10]
In 1972, Young and Xijin Zhao described a second species, Mamenchisaurus hochuanensis. The fossils were found near a village in Hechuan, north of Chongqing (originally part of the Sichuan Province), China; 200 meters (660 ft) above the Fu River on the slope of a mountain.[10] The M. hochuanensis fossil site also belonged to the Upper Shaximiao Formation, very close to the M. constructus type specimen's location, dating to at least the Late Jurassic.[1] Locals first discovered the remains sometime before the Chinese Revolution. However, the remains were ultimately abandoned and left to weatherin situ. Excavation did not begin on the site until 1957.
