Mamenchisaurus ( , or spelling pronunciation ) is an extinct genus of sauropod dinosaurs known for their remarkably long necks, which made up nearly half the total body length. Numerous species have been assigned to the genus; however, the validity of these assignments has been questioned. Fossils have been found in the Sichuan Basin and Yunnan Province in China. Several species from the Upper Shaximiao Formation, whose geologic age is uncertain, have been described. However, evidence suggests this formation to be no earlier than the Oxfordian stage of the Late Jurassic. M. sinocanadorum dates to the Oxfordian stage (161.2 to 158.7 mya), and M. anyuensis to the Aptian stage of the Early Cretaceous (around 114.4 mya). Most species were medium-large to large sauropods, measuring roughly in length—possibly up to , based on two undescribed vertebrae.Russell, D.A., Zheng, Z. (1993). "A large mamenchisaurid from the Junggar Basin, Xinjiang, People Republic of China." Canadian Journal of Earth Sciences, (30): 2082-2095.Paul, G.S. (2016). The Princeton Field Guide to Dinosaurs, Princeton University Press.
History and species Mamenchisaurus was first discovered in 1952 on the construction site of the Yitang Highway in Sichuan Province, China. The fossil site belonged to the Upper Shaximiao Formation, dating to at least the Late Jurassic. 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.Young, C. C. (1954), On a new sauropod from Yiping, Szechuan, China. sinica, III(4), 481-514.
Mamenchisaurus means 'Mamenchi lizard', from the Chinese Pinyin mǎ (马 'horse') and mén (门 'gate'), while chi is an alternative 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').Origin of the Mamenchisaurus name (in Chinese), Beijing Museum of Natural History website The fact that the first Mamenchisaurus fossil was found during construction work led Young to name the type species as Mamenchisaurus constructus.
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. In 1972, one of these specimens was reassigned to M. hochuanensis.
Mamenchisaurus hochuanensis
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, above the Fu River on the slope of a mountain.Young, C. C., and Zhao, X.-J. (1972). "Mamenchisaurus hochuanensis sp. nov." Institute of Vertebrate Paleontology and Paleoanthropology Monographs, A, 8:1-30. The M. hochuanensis fossil site also belonged to the Upper Shaximiao Formation, very close to the location of the M. constructus type specimen, dating to at least the Late Jurassic. Locals first discovered the remains sometime before the Chinese Communist Revolution. However, the remains were ultimately abandoned and left to weather in situ. Excavation of the specimen did not begin until 1957, when a team from the Sichuan Provincial Museum was dispatched to the site. Preparation, reconstruction, mounting, and description of the skeleton were completed in 1965.
The holotype specimen (CCG V 20401) consisted of an almost complete and articulated vertebral column, including 19 elongated cervical vertebrae, which were almost entirely preserved, 12 dorsal vertebrae, four sacral vertebrae, and 35 caudal vertebrae, with only the last several missing. Also missing from the skeleton were most of the forelimbs and the skull. When M. hochuanensis was first described, it was the largest sauropod known from China.
In 1958, Young described a mamenchisaur specimen (IVPP V. 946) from the Haishiwan region of Yongdeng, Gansu Province. This specimen was initially assigned to M. constructus. However, in 1972 it was reassigned to M. hochuanensis as a paratype. This specimen was slightly smaller than the holotype and consisted of less material overall. However, it contained some anatomical details missing in the type specimen.
In 2001, another specimen (ZDM0126) was described and referred to M. hochuanensis. It was found in 1995 at a construction site in Huidong New District, Zigong City, Sichuan Province. This specimen was nearly complete and mostly articulated, preserving features missing from the holotype, such as the skull, pectoral girdle, and forelimb material. However, a 2020 phylogenetic analysis by Moore and colleagues cast doubt on the referral of this specimen to M. hochuanensis.
Mamenchisaurus sinocanadorum
In August 1987, Z.-M. Dong observed a cervical rib projecting out of a cliff during an expedition by the China-Canada Dinosaur Project. The fossil site was located in the Junggar Basin, Xinjiang, from the upper part of the Shishugou Formation, making it one of the few mamenchisaurs known from outside the Sichuan basin. The locality is thought to date to around 162.2 million years ago. The location of the quarry where the specimen was found was originally reported as being north of an abandoned town, Jiangjunmiao. However, the original authors reported incorrect coordinates for the quarry that were later corrected by a subsequent study. The coarse and weak sandstone in which the specimen was preserved in, alongside the large and fragile nature of the bones, impeded excavation, leading to only the most anterior vertebrae being recovered despite more neck material being present. The specimen was named as a new species of Mamenchisaurus, coined M. sinocanadorum, in 1993 by Dale Russell and Zhong Zheng. The specific name refers to the China-Canada Dinosaur Project.
Overall, the specimen, IVPP V10603, consists of a complete left , a right , a , a right , a possible , a right , portions of the second through fourth , and an intact left . The neural arches of the vertebrae were well fused to the centra, suggesting that the animal was mature. The authors noted that the teeth are fully erupted but unworn, possibly suggesting the animal starved. Due to the limited amount of bone at the cliff base, the authors proposed that the cervical vertebrae broke away before full decomposition. The head and part of the neck then drifted downstream until they came to rest in shallow water on a point bar, where they were eventually buried. In 2023, M. sinocanadorum was redescribed by Andrew Moore and colleagues. The authors could not locate the vomer, right pterygoid, the possible ectopterygoid, the right quadrate, and the right dentary for restudy. A phylogenetic analysis performed by the authors found it to be outside the clade of other Mamenchisaurus species, closely allied to Xinjiangtitan, but refrained from taxonomic action until the type species M. constructus received re-evaluation.
Two large cervical vertebrae, found from the same formation as M. sinocanadorum, were informally referred to the species by Gregory S. Paul in 2019 based on their large size and origin. However, these vertebrae have not yet been formally described. Paul has suggested these may represent one of the largest dinosaurs known. Moore and colleagues could not support the referral of these vertebrae to M. sinocanadorum in their redescription of the species because the vertebrae lack anatomical overlap with the known material of the type specimen, and cannot therefore be compared for diagnostic purposes. They also noted an undescribed specimen on display at the China University of the Geosciences in Beijing, labelled as belonging to the species, which has not been evaluated firsthand or mentioned in the scientific literature. Accordingly, they consider the referral to the species premature.
Mamenchisaurus anyuensis M. anyuensis was described in 1996 by Xinlu He and colleagues. The remains were discovered in 1987 from two locations near the town of Longchiaoxiang in the Sichuan Basin. At one quarry, at least five to six individuals were found. At a second quarry, four individuals were found. One of these became the holotype, AL001, representing two-thirds of an articulated skeleton. Other specimens were also reported, AL002, AL003, and AL101-106, which provide more skeletal information. The species name references Anyue County, where it was discovered. M. anyuensis is known from both the top of the Suining Formation and the bottom of the Penglaizhen Formation. Uranium–lead dating places M. anyuensis in the Suining Formation 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.
The holotype specimen preserved eight posterior cervical vertebrae, twelve dorsal vertebrae, five sacral vertebrae, several caudal vertebrae, and a complete pelvis. Another specimen (AL102) preserved five articulated cervical vertebrae from the middle of the neck. Except for the digit bones, the forelimb is completely known and represented by multiple individuals. Mamenchisaurus youngi Also described in 1996 was Mamenchisaurus youngi from the Upper Shaximiao Formation. A local resident quarrying stone near a village in Zigong, Sichuan Province, found the remains in December 1988. In January the following year, a team from the Zigong Dinosaur Museum was organised to collect the specimen. The species was named in honour of C. C. Young.
The holotype specimen (ZDM 0083) was very complete, with the vertebral column entirely articulated from the first cervical down to the 8th tail vertebra. Also preserved were the pectoral girdle, pelvic girdle, and material from all four limbs, also nearly in articulation. This specimen also preserved a nearly complete skull.
Mamenchisaurus jingyanensis
M. jingyanensis was described in 1998 by Yihong Zhang, Kui Li, and Qinghua Zeng. The type specimen (CV00734) was located away from the administrative headquarters of the town of Meiwang, Jingyan County. Another specimen (JV002) was found in the village of Sanjiang, approximately from Meiwang, and was assigned the paratype. A third specimen (CV00219) was found near the village of Dujia, about 10 kilometers from Sanjiang. The fossils were located in the Sichuan basin, from the Upper Shaximiao Formation. The species name refers to Jingyan County, from which the majority of specimens were excavated. M. jingyanensis has a femur length of .
The type specimen includes a partial scapula and complete coracoid, forelimb material, a complete ischium, a relatively complete skull, and a hyoid bone. The paratype specimen included three anterior cervical vertebrae, several weathered dorsal vertebrae, a column of nearly articulated caudal vertebrae, relatively complete hind and forelimbs, and isolated teeth. The third specimen preserved a column of cervical vertebrae with articulated ribs, four fused sacral vertebrae, several caudal vertebrae, a complete scapulocoracoid, various limb bones, and isolated teeth.
Mamenchisaurus sanjiangensis