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{{short description|Sauropod dinosaur genus from Late Jurassic-Early Cretaceous Period}}
{{automatic taxobox
| fossil_range = [[Late Jurassic]] to [[Early Cretaceous]] ([[Oxfordian (stage)|Oxfordian]] to [[Aptian]]), {{fossil range|161|114.4|latest=Early Cretaceous}} <small>Possible record during the [[Albian]]<ref name=Age/></small>
| image = Zigong_Dinosaur_Museum_Mamenchisaurus_hochuanensis.jpg
| image_caption = Mounted skeleton of ''M. hochuanensis''
| taxon = Mamenchisaurus
| authority = [[Yang Zhongjian|Young]], 1954
| type_species = {{extinct}}'''''Mamenchisaurus constructus'''''
| type_species_authority = Young, 1954
| subdivision_ranks = Other [[species]]
| subdivision =
* {{extinct}}'''''M. hochuanensis''''' <small>Young & Zhao, 1972</small>
* {{extinct}}'''''M. sinocanadorum''''' <small>[[Dale Russell|Russell]] & Zheng, 1993</small>
* {{extinct}}'''''M. youngi''''' <small>Pi, Ouyang & Ye, 1996</small>
* {{extinct}}'''''M. anyuensis''''' <small>He et al., 1996</small>
* {{extinct}}'''''M. jingyanensis''''' <small>Zhang, Li & Zeng, 1998</small>
* {{extinct}}'''''M. yunnanensis''''' <small>Fang et al., 2004</small>
}}
'''''Mamenchisaurus''''' ({{IPAc-en|m|ə|ˌ|m|ʌ|n|tʃ|i|ˈ|s|ɔː|r|ə|s}} {{respell|mə|MUN|chee|SOR|əs}},<ref name="Creisler2003">{{cite web |last1=Creisler |first1=Ben |url=http://www.dinosauria.com/dml/names/dinom.htm |title=Dinosauria Translation and Pronunciation Guide M |access-date=15 May 2025 |date=7 July 2003 |publisher=Dinosauria On-Line |archive-url=https://web.archive.org/web/20111110204457/http://www.dinosauria.com/dml/names/dinom.htm |archive-date=10 November 2011 |url-status=dead}}</ref> or [[spelling pronunciation]] {{IPAc-en|m|ə|ˌ|m|ɛ|n|tʃ|ɪ|ˈ|s|ɔː|r|ə|s}}) is an extinct genus of [[sauropod]] dinosaurs known for their remarkably long [[neck]]s<ref name="HDS97">{{cite book|last=Sues|first=Hans-Dieter|url=https://archive.org/details/isbn_9780253333490/page/274|title=The Complete Dinosaur|publisher=Indiana University Press|year=1997|isbn=0-253-33349-0|editor=James Orville Farlow|___location=Bloomington|pages=[https://archive.org/details/isbn_9780253333490/page/274 274]|chapter=Sauropods|editor2=M. K. Brett-Surman|url-access=registration}}</ref> which made up nearly half the total body length.<ref name="DBN04">{{cite book|last=Norman|first=David B.|url=https://archive.org/details/dinosauriandedit00weis|title=The Dinosauria|publisher=University of California Press|year=2004|isbn=0-520-24209-2|editor=Weishampel, D.B.|edition=2nd|___location=Berkeley|pages=[https://archive.org/details/dinosauriandedit00weis/page/n336 318]|chapter=Dinosaur Systematics|editor2=Dodson, P.|editor3=Osmólska, H.|url-access=limited}}</ref> 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|Yunnan Province]] in China. Several species from the [[Shaximiao Formation|Upper Shaximiao Formation]], whose [[Geologic time scale|geologic age]] is uncertain, have been described. However, evidence suggests this formation to be no earlier than the [[Oxfordian (stage)|Oxfordian stage]] of the [[Jurassic|Late Jurassic.]] ''M. sinocanadorum'' dates to the Oxfordian stage (161.2 to 158.7 [[Myr|mya]]), and ''M. anyuensis'' to the [[Aptian|Aptian stage]] of the [[Cretaceous|Early Cretaceous]] (around 114.4 mya).<ref name="Age">{{cite journal|last1=Wang|first1=J.|last2=Norell|first2=M. A.|last3=Pei|first3=R.|last4=Ye|first4=Y.|last5=Chang|first5=S.-C|year=2019|title=Surprisingly young age for the mamenchisaurid sauropods in South China|journal=Cretaceous Research|volume=104|article-number=104176|doi=10.1016/j.cretres.2019.07.006|bibcode=2019CrRes.10404176W |s2cid=199099072}}</ref> Most species were medium-large to large sauropods, measuring roughly {{convert|15|to|26|m|sp=us}} in length—possibly up to {{convert|35|m|sp=us}}, based on two undescribed vertebrae.<ref name="RussellZheng1993">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.</ref><ref name="paul2010">Paul, G.S. (2016). ''The Princeton Field Guide to Dinosaurs'', Princeton University Press.</ref><ref name=":7">{{Cite journal|last=Paul|first=Gregory S.|date=2019|title=Determining the largest known land animal: A critical comparison of differing methods for restoring the volume and mass of extinct animals|url=http://www.gspauldino.com/Titanomass.pdf|journal=Annals of the Carnegie Museum|volume=85|issue=4|pages=335–358|doi=10.2992/007.085.0403|bibcode=2019AnCM...85..335P |s2cid=210840060}}</ref>
==History and species==
[[File:Mamenchisaurus hochuanensis Field Museum.jpg|left|thumb|Mounted ''M. hochuanensis'' skeleton, [[Field Museum]]]]''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.<ref name="Age" /> The partial skeleton fossil was later studied and named ''Mamenchisaurus constructus'' in 1954 by the renowned Chinese paleontologist Professor [[Yang Zhongjian|C. C. Young]].
The [[type specimen]] (IVPP V. 790) was fragmentary, disordered, and not excavated in a technical way. Material included five [[Glossary of dinosaur anatomy#dorsals|dorsal vertebrae]], 30 [[Glossary of dinosaur anatomy#caudals|caudal vertebrae]], rib fragments, dorsal neural spines, and [[Haemal arch|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.<ref name="young1954">Young, C.C. (1954), ''On a new sauropod from Yiping, Szechuan, China.'' sinica, III(4), 481-514.</ref>
''Mamenchisaurus'' means 'Mamenchi lizard', from the [[Chinese language|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 [[Ancient Greek|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 [[Yang Zhongjian|Young]], the ___location name ''Mǎmíngxī'' (马鸣溪 'horse-neighing brook') was mistaken as ''Mǎménxī'' (马门溪 'horse-gate brook').<ref>[http://www.bmnh.org.cn/web/cn/kppd/dekt/dektnr/1968/20040806/25176.html Origin of the ''Mamenchisaurus'' name] {{webarchive|url=https://web.archive.org/web/20070927091006/http://www.bmnh.org.cn/web/cn/kppd/dekt/dektnr/1968/20040806/25176.html |date=2007-09-27 }} (in Chinese), Beijing Museum of Natural History website</ref> The fact that the first ''Mamenchisaurus'' fossil was found due to construction work led to Young's naming the [[type species]] as ''Mamenchisaurus constructus''.<ref name="young1954" />
In 1958, Young described additional sauropod remains collected from [[Gansu|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.''<ref name=":10">{{Cite journal|last=Young|first=C. C.|date=1958|title=New Sauropods from China|url=|journal=Vertebrata PalAsiatica|volume=2|issue=1|pages=}}</ref> In 1972, one of these specimens was reassigned to ''M. hochuanensis.''<ref name="young&zhao1972" />
=== ''Mamenchisaurus hochuanensis'' ===
[[File:Memenchisaurid-Skulls--SVG--Steveoc86.svg|upright|thumb|The holotype skulls of ''M. youngi,'' ''M. jingyanensis,'' and ''M. sinocanadorum,'' and a skull referred to ''M. hochuanensis'']]
In 1972, Young and Xijin Zhao described a second species, ''Mamenchisaurus hochuanensis''. The fossils were found near a village in [[Hechuan District|Hechuan]], north of [[Chongqing]] (originally part of the Sichuan Province), China; {{convert|200|m|sp=us}} above the [[Fu River (Sichuan)|Fu River]] on the slope of a mountain.<ref name="young&zhao1972">Young, C.C., and Zhao, X.-J. (1972). "''Mamenchisaurus hochuanensis'' sp. nov." ''Institute of Vertebrate Paleontology and Paleoanthropology Monographs'', A, 8:1-30.</ref> 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.<ref name="Age" /> Locals first discovered the remains sometime before the [[Chinese Communist Revolution]]. However, the remains were ultimately abandoned and left to [[Weathering|weather]] in situ. Excavation did not begin on the site until 1957.{{cn|date=August 2025}}
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 was the majority of the forelimbs and skull. When ''M. hochuanensis'' was first described, it was the largest sauropod known from China.<ref name=":6">{{Cite book |last=Glut |first=Donald F. |title=Dinosaurs: The Encyclopedia: Supplement 1 |publisher=Jefferson: McFarland & Company |year=2000 |isbn=0786405910 |___location=North Carolina |pages=}}</ref>
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.<ref name="young&zhao1972" />
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.''<ref name="moore2020" />
=== ''Mamenchisaurus sinocanadorum'' ===
[[File:Xinjiang_regions.png|thumb|left|Location of [[Xinjiang]] province in China, where ''M. sinocanadorum'' is found; the Junggar Basin is seen in yellow.]]
In August 1987, a [[Glossary of dinosaur anatomy#cervical rib|cervical rib]] was seen projecting out of a cliff by Z-M. Dong on 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;<ref name="Age" /><ref name="RussellZheng1993" /><ref name="moore2023">{{cite journal |last1=Moore |first1=Andrew J. |last2=Barrett |first2=Paul M. |last3=Upchurch |first3=Paul |last4=Liao |first4=Chun-Chi |last5=Ye |first5=Yong |last6=Hao |first6=Baoqiao |last7=Xu |year=2023 |title=Re-assessment of the Late Jurassic eusauropod Mamenchisaurus sinocanadorum Russell and Zheng, 1993, and the evolution of exceptionally long necks in mamenchisaurids |url=https://www.tandfonline.com/doi/full/10.1080/14772019.2023.2171818 |journal=Journal of Systematic Palaeontology |volume=21 |issue=1 |doi=10.1080/14772019.2023.2171818|bibcode=2023JSPal..2171818M |url-access=subscription }}</ref> the locality is thought to date to around 162.2 million years ago. The ___location of the quarry the specimen was found in was originally reported as being {{Convert|22|km|miles|abbr=off}} north of an abandoned town, Jiangjunmiao. However, the original authors reported incorrect coordinates for the quarry that were later corrected by a subsequent study.<ref name=moore2023/> The coarse and weak sandstone 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.<ref name="moore2023" /><ref name="RussellZheng1993"/> 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.<ref name="RussellZheng1993" />
[[File:Mamenchisaurus in Japan.jpg|thumb|Mounted reconstruction of ''M. sinocanadorum'' in [[Japan]]]]
Overall, the specimen, IVPP V10603, consists of a complete left {{dinogloss|mandible}}, a right {{dinogloss|dentary}}, a {{dinogloss|vomer}}, a right {{dinogloss|pterygoid}}, a possible {{dinogloss|ectopterygoid}}, a right {{dinogloss|quadrate}}, portions of the second through fourth {{dinogloss|cervical vertebrae}}, and an intact left {{dinogloss|cervical rib}}. 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]] and eventually buried.<ref name="RussellZheng1993" /> 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.<ref name="moore2023" />
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 sizes and origin. However, these vertebrae have yet to be formally described. Paul has suggested these may represent one of the [[Dinosaur size#Sauropodomorphs|largest dinosaurs known]].<ref name="paul2010" /><ref name=":13">{{Cite journal|last=Paul|first=Gregory|date=2019-12-31|title=Determining the Largest Known Land Animal: A Critical Comparison of Differing Methods for Restoring the Volume and Mass of Extinct Animals|url=http://dx.doi.org/10.2992/007.085.0403|journal=Annals of Carnegie Museum|volume=85|issue=4|pages=335|doi=10.2992/007.085.0403|bibcode=2019AnCM...85..335P |s2cid=210840060|issn=0097-4463|url-access=subscription}}</ref> 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 so cannot be compared for diagnosis. They also noted an undescribed specimen on display at the [[China University of Geosciences (Beijing)|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.<ref name="moore2023" />
=== ''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.<ref name="Heal1996">{{cite journal|last=He|first=Xinlu|author2=Yang, Suihua|author3=Cai, Kaiji|author4=Li, kui|author5=Liu, Zongwen|year=1996|title=''A new species of sauropod, Mamenchisaurus anyuensis sp. nov.''|url=http://www.paleoglot.org/files/He&_96.pdf|journal=Papers on Geosciences Contributed to the 30th Geological Congress|pages=83–86}}</ref> ''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.<ref name="Age" />
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.<ref name="Heal1996" />
=== ''Mamenchisaurus youngi'' ===
Also described in 1996 was ''Mamenchisaurus youngi'' from the Upper Shaximiao Formation.<ref name="Age" /><ref name=":0" /> A local quarrying stone near a village in Zigong, [[Sichuan]] Province, found the remains in 1987. The species was named in honour of C. C. Young.<ref name=":0" />
The holotype specimen (ZDM 0083) was very complete and mostly articulated, preserving all the vertebrae from the head down to the 8th tail vertebra. Also preserved were the pectoral girdle, pelvic girdle, and material from all four limbs. This specimen also preserved a nearly complete skull.<ref name=":0" />
=== ''Mamenchisaurus jingyanensis'' ===
[[File:Mamenchisaurus at the Beijing Museum of Natural History.jpg|upright|thumb|''M. jingyanensis'' skeleton, [[Beijing Museum of Natural History]]|227x227px]]''M. jingyanensis'' was described in 1998 by Yihong Zhang, Kui Li, and Qinghua Zeng. The type specimen (CV00734) was located {{Convert|200|m|sp=us}} away from the administrative headquarters of the town of Meiwang, [[Jingyan County|Jingyan county]]. Another specimen (JV002) was found in the village of Sanjiang approximately {{Convert|10|km|0|sp=us}} from Meiwang and became the paratype. A third specimen (CV00219) found near the village of Dujia, about 10 kilometers from Sanjiang.<ref name="Zhangetal1998">{{cite journal |last=Zhang |first=Yihong |author2=Li, kui |author3=Zeng, Qinghua |year=1998 |title='A new species of sauropod from the Late Jurassic of the Sichuan Basin (''Mamenchisaurus jingyanensis'' sp. nov.)' |journal=Journal of the Chengdu University of Technology |volume=25 |issue=1 |pages=61–68}}</ref> The fossils were located in the Sichuan basin, from the Upper Shaximiao Formation.<ref name="Age" /><ref name="Zhangetal1998" /> The species name refers to Jingyan County from which the majority of specimens were excavated.<ref name="Zhangetal1998" />
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, various caudal vertebrae including a nearly articulated column, 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.<ref name="Zhangetal1998" />
=== Other ''Mamenchisaurus'' species and material ===
Other species of ''Mamenchisaurus'' have been named over the years. In some cases, species from other genera have been transferred to ''Mamenchisaurus,'' but there is disagreement with the referral's validity''.'' Some of these species are based on fragmentary remains and have been considered undiagnostic. Others are considered as invalid or as [[Nomen nudum|''nomina nuda'']].<ref name="Age" /><ref name="Xingetal2009">{{cite journal |last=Xing |first=L |author2=Ye, Y |author3=Shu, C |author4=Peng, G |author5=You, H |year=2009 |title=Structure, orientation and finite element analysis of the tail club of Mamenchisaurus hochuanensis. |journal=Acta Geologica Sinica (English Edition) |volume=83 |issue=6 |pages=1031–1040 |doi=10.1111/j.1755-6724.2009.00134.x |bibcode=2009AcGlS..83.1031L |s2cid=129309522}}</ref>
In 1976, Hou, Chao and Chu named a new genus, ''[[Zigongosaurus fuxiensis]].''<ref name=":6" /><ref>{{Cite journal|last1=Hou|first1=Lianhai|last2=Zhou|first2=Shiwu|last3=Cao|first3=Youshu|date=1976|title=New discovery of sauropod dinosaurs from Sichuan|url=http://www.ivpp.cas.cn/cbw/gjzdwxb/xbwzxz/200905/W020090813376971757825.pdf|journal=Vertebrata PalAsiatica|language=zh, en|volume=14|issue=3|pages=160–165}}</ref> Known from at least four specimens from the Upper Shaximiao Formation. The type specimen (CV 02501<ref>{{Cite journal |last1=Peng |first1=G.Z. |last2=Ye |first2=Y. |last3=Gao |first3=Y.H. |last4=Shu |first4=C.K. |last5=Jiang |first5=S. |date=2005 |title=Jurassic dinosaur faunas in Zigong |url=https://www.yumpu.com/en/document/view/11867570/jurassic-dinosaur-faunas-in-zigong- |journal=Zigong Dinosaur Museum, Zigong.}}</ref>) included skull material; maxilla, dentary, and [[Basilar part of occipital bone|basioccipital]]. Additional material includes dorsal vertebrae, pubis, and ischium. Since ''Zigongosaurus'' was described, other researchers have disagreed on whether the genus is valid. In 1983, Dong, Zhou and Zhang assigned some of the remains to the similarly named ''Omeisaurus fuxiensis'', and the rest to ''Omeisaurus junghsiensis''. Zhang and Chen assigned the remains to ''Mamenchisaurus'' as ''M. fuxiensis'' in 1996.<ref name="ZC962">{{cite book|last=Zhang|first=Y.|title=The Continental Jurassic|author2=W. Chen|publisher=Museum of Northern Arizona|year=1996|editor=Morales, M.|series=Museum of Northern Arizona Bulletin, '''60'''|pages=97–107|chapter=Preliminary research on the classification of sauropods from Sichuan Basin, China}}</ref> Li and Cai considered it a ''nomen nudum'' in 1997.<ref name=":6" /> In 1999, Valérie Martin-Rolland considered ''Zigongosaurus'' a valid genus. Wang and colleagues considered it undiagnostic in 2019.<ref name="Age" /><ref name=":3" /><ref name="Xingetal2009" />
Another species, "Mamenchisaurus guangyuanensis", has [[list of informally named dinosaurs|not been formally described]], making it a ''nomen nudum''. It is known from the remains of several individuals, ranging from juvenile to adult, from the Upper Shaximiao Formation.<ref name="LiCai1997"/> The largest individuals were estimated to have a length of {{convert|16|m|ft}}<ref name="LiCai1997"/> It was originally described by Zhang Suping in her 1981 thesis as "Omeisaurus guangyuanensis",<ref name=":1"/> but in 1997, Li and Cai listed it as a species of ''Mamenchisaurus''.<ref name="LiCai1997"/> Like ''Mamenchisaurus'', but unlike ''Omeisaurus'', it shows bifurcated neural spines and procoelous caudal vertebrae.<ref name=":1"/> It was considered non-diagnostic by Wang and colleagues in 2019.<ref name="Age" />
''M. yunnanensis was'' described by Fang and colleagues in 2004, from the [[Anning Formation]] in the Sichuan Basin, Yunnan. The type specimen consisted of disarticulated forelimb, hindlimb, and pelvic material.<ref>{{Cite journal|last1=FANG|first1=Xiaosi|last2=ZHAO|first2=Xijin|last3=LU|first3=Liwu|last4=CHENG|first4=Zhengwu|date=2004|title=Discovery of Late Jurassic Mamenchisaurus in Yunnan, southwestern China|url=|journal=Regional Geology of China Z|volume=23|pages=}}</ref> Wang and colleagues questioned the assignment to ''Mamenchisaurus'' in 2019.<ref name="Age" />
In 1988, He and colleagues considered ''Omeisaurus changshouensis'' to be closer to ''Mamenchisaurus'' based on features of the caudal vertebrae. In 2019, Tan and colleagues agreed with this assessment.<ref>{{Cite journal |last1=Tan |first1=Chao |last2=Dai |first2=Hui |last3=He |first3=Jian-Jun |last4=Zhang |first4=Feng |last5=Hu |first5=Xu-Feng |last6=Yu |first6=Hai-Dong |last7=Li |first7=Ning |last8=Wei |first8=Guang-Biao |last9=Peng |first9=Guang-Zhao |last10=Ye |first10=Yong |last11=Zhang |first11=Qian-Nan |last12=Ren |first12=Xin-Xin |last13=You |first13=Hai-Lu |date=2019 |title=Discovery of Omeisaurus (Dinosauria: Sauropoda) in the Middle Jurassic Shaximiao Formation of Yunyang, Chongqing, China |journal=Vertebrata PalAsiatica |pages=105–116}}</ref> In 1996, Zhang and Chen considered ''Omeisaurus changshouensis'' and ''Omeisaurus gongjianensis'' as referrable to ''Mamenchisaurus.''<ref name="ZC962" /> However, in 2004, Upchurch considered ''O. changshouensis'' undiagnosable.<ref name=":3" />
[[File:Moshi-Ryu.jpg|thumb|NSM PV17656]]
In 1978, an incomplete sauropod humerus (NSM PV17656) found in a layer of the [[Early Cretaceous]]-aged [[Miyako Group]] of [[Japan]] was considered to probably belong to ''Mamenchisaurus''. In 1991, it was referred to ''?Mamenchisaurus sp''. by Hasegawa and colleagues''.''<ref name=":12">{{Cite journal|last1=HASEGAWA|first1=Y.|last2=MANABE|first2=M.|last3=HANAI|first3=T.|last4=KASE|first4=T.|last5=OJI|first5=T.|date=1991|title=A diplodocid dinosaur from the Early Cretaceous Miyako group of Japan|url=|journal=Bulletin of the National Science Museum. Series C.|volume=17|issue=1|pages=}}</ref><ref name=":11">{{Cite book|last=Glut, Donald F.|title=Dinosaurs, the encyclopedia|date=1997|publisher=McFarland & Co|isbn=0-89950-917-7|___location=Jefferson, N.C.|oclc=33665881}}</ref> However, the humerus was reassessed by Azuma & Tomida in 1998, and Barrett and colleagues in 2002. These authors could not find any distinguishing features that could place the humerus into a specific sauropod group. They regarded it as an indeterminate sauropod.<ref>Azuma Y, Tomida Y. 1998. Japanese dinosaurs. In: Curie PJ, Padian K, eds. Encyclopaedia of dinosaurs. San Diego: Academic Press, 375–379.</ref><ref>{{Cite journal|last1=Barrett|first1=P.M.|last2=Hasegawa|first2=Y.|last3=Manabe|first3=M.|last4=Isaji|first4=S.|last5=Matsuoka|first5=H.|date=2002|title=Barrett, Paul M., et al. "Sauropod dinosaurs from the Lower Cretaceous of eastern Asia: taxonomic and biogeographical implications|journal=Palaeontology|volume=45|issue=6|pages=|doi=10.1111/1475-4983.00282|doi-access=free}}</ref> The remains were given an informal name "Moshi-ryu"; "Moshi" being the local name for the ___location it was discovered, and "ryu" being Japanese for [[Japanese dragon|dragon]]<ref name=":12" />—also referred to as "[[Moshisaurus]]".<ref name=":11" />
== Description ==
[[File:Mamenchisaurus Species Scale Steveoc86.svg|thumb|Size comparison of ''M. constructus, M. youngi, M. hochuanensis and M. sinocanadorum''|left]]There is uncertainty that all the species assigned to ''Mamenchisaurus'' should belong to the genus.<ref name="paul2010" /><ref name=":2" /><ref name=":3">{{Cite book|last1=Upchurch|first1=Paul|title=The Dinosauria|last2=Barrett|first2=Paul M.|last3=Dodson|first3=Peter|publisher=University of California Press|others=Weishampel, David B., Dodson, Peter., Osmólska, Halszka.|year=2004|isbn=978-0-520-94143-4|edition=2nd|___location=Berkeley, Calif.|pages=|chapter=Sauropoda|oclc=801843269}}</ref><ref name="moore2020" /> Some ''Mamenchisaurus'' species are almost completely known, and others are fragmentary. The species differ in overall size and specific features of the skull and skeleton but share typical sauropod traits, like [[quadrupedalism]], large bodies, small heads, and long tails. The most distinctive feature of mamenchisaurids is their exceptionally long necks which approach half their total length.<ref name="RussellZheng1993" /> The type specimens of ''M. youngi and M. hochuanensis'' preserve complete necks, which consist of 18 and 19 vertebrae, respectively.<ref name="young&zhao1972" /><ref name=":0">PI, L., OU, Y. and YE, Y. 1996. A new species of sauropod from Zigong, Sichuan, Mamenchisaurus youngi. 87–91. In DEPARTMENT OF SPATIAL PLANNING AND REGIONAL ECONOMY (ed.), Publication in Geoscience Contributed to the 30th International Geological Congress. China Economic Publishing House, Beijing.</ref> ''Mamenchisaurus'' cervical vertebrae are elongated, lightly constructed and highly [[Skeletal pneumaticity|pneumatic]].<ref name="moore2020" /> The neural spines on their posterior cervical and anterior dorsal vertebrae are bifurcated.<ref name="young&zhao1972" /><ref name="Zhangetal1998" /><ref name="Heal1996" /> Their shoulders were somewhat higher than the hips.<ref name="paul2010" />
The type species, ''M. constructus,'' is not particularly well preserved but has been estimated to be around {{convert|13|to|15|m|sp=us}} in length with a mass of around {{convert|5|t|ST}}. The neck of the type specimen was not completely preserved, but Young estimated the whole neck at {{convert|4.67|m|sp=us}}.<ref name="paul2010" /><ref name="young1954" />
The overall length of the ''M. hochuanensis'' type specimen is around {{convert|21|to|22|m|sp=us}} with a neck {{convert|9.3|m|sp=us}} long.<ref name="paul2010" /><ref name="young&zhao1972" /><ref name="paul19882">{{cite journal |last1=Paul |first1=G.S. |year=1988 |title=The brachiosaur giants of the Morrison and Tendaguru with a description of a new subgenus, ''Giraffatitan'', and a comparison of the world's largest dinosaurs |url= |journal=Hunteria |volume=2 |issue=3 |pages=1–14}}</ref> Young and Zhao estimated the mass of ''M. hochuanensis'' at {{convert|45|t|ST}}.<ref name="young&zhao1972" /> However, later volumetric mass estimates are lower at {{convert|14|to|18.2|t|ST|abbr=off}}.<ref name="paul2010" /><ref>{{Cite journal |last1=Sander |first1=P. Martin |last2=Christian |first2=Andreas |last3=Clauss |first3=Marcus |last4=Fechner |first4=Regina |last5=Gee |first5=Carole T. |last6=Griebeler |first6=Eva-Maria |last7=Gunga |first7=Hanns-Christian |last8=Hummel |first8=Jürgen |last9=Mallison |first9=Heinrich |last10=Perry |first10=Steven F. |last11=Preuschoft |first11=Holger |date=2011 |title=Biology of the sauropod dinosaurs: the evolution of gigantism |journal=Biological Reviews |language=en |volume=86 |issue=1 |pages=117–155 |doi=10.1111/j.1469-185X.2010.00137.x |pmc=3045712 |pmid=21251189 |doi-access=free}}</ref><ref name=":9">{{Cite journal |last1=Larramendi |first1=Asier |last2=Paul |first2=Gregory S. |last3=Hsu |first3=Shu-yu |year=2020 |title=A review and reappraisal of the specific gravities of present and past multicellular organisms, with an emphasis on tetrapods |journal=The Anatomical Record |language=en |volume=304 |issue=9 |pages=1833–1888 |doi=10.1002/ar.24574 |issn=1932-8494 |pmid=33258532 |s2cid=227243708|doi-access=free }}</ref> In 1972, Young and Chao described ''M. hochuanensis'' as having 19 cervical and 12 dorsal vertebrae. However, Paul Upchurch and colleagues suggested this vertebral count may be incorrect. The authors noted that the vertebra that is usually referred to as the second dorsal possessed a [[Hyposphene-hypantrum articulation|hyposphene]], a feature not usually seen until the third or fourth dorsal in sauropods. They provisionally proposed that the actual vertebral count might be 18 cervicals and 13 dorsals in ''M. hochuanensis''.<ref>{{Cite journal |last1=Upchurch |first1=Paul |last2=Mannion |first2=Philip D. |last3=Xu |first3=Xing |last4=Barrett |first4=Paul M. |date=2021-07-04 |title=Re-assessment of the Late Jurassic eusauropod dinosaur Hudiesaurus sinojapanorum Dong, 1997, from the Turpan Basin, China, and the evolution of hyper-robust antebrachia in sauropods |journal=Journal of Vertebrate Paleontology |volume=41 |issue=4 |pages=e1994414 |doi=10.1080/02724634.2021.1994414 |issn=0272-4634|doi-access=free |bibcode=2021JVPal..41E4414U }}</ref>
''M. sinocanadorum'' is known from fragmentary remains, but these suggest that it was a large species. The cervical vertebrae are on average 1.19 times longer than those of ''M. hochuanensis;'' based on this, Russel and Zheng estimated the type specimen at {{convert|26|m|sp=us}} in length.<ref name="RussellZheng1993" /> Taylor and Wedel estimated the neck around {{convert|12|m|sp=us}} in length based on comparison to ''M. hochuanensis''.<ref name=":14">{{Cite journal |last1=Taylor |first1=Michael P. |last2=Wedel |first2=Mathew J. |date=2013-02-12 |title=Why sauropods had long necks; and why giraffes have short necks |journal=PeerJ |language=en |volume=1 |article-number=e36 |doi=10.7717/peerj.36 |issn=2167-8359 |pmc=3628838 |pmid=23638372 |doi-access=free }}</ref> However, the 2023 redescription gave a longer estimate between {{convert|14.4|m|sp=us}} and {{convert|15.1|m|sp=us}} based on comparison to ''Xinjiangtitan'', though the authors stressed the level of uncertainty.<ref name=moore2023/> The type specimen possessed the longest cervical rib of any described sauropod dinosaur, measuring {{convert|4.2|m|sp=us}}.<ref name="moore2023" /> For comparison, a ''[[Sauroposeidon]]'' cervical rib measures {{convert|3.42|m|sp=us}}.<ref name="RussellZheng1993" /><ref name=":15">"Osteology, paleobiology, and relationships of the sauropod dinosaur ''Sauroposeidon''", by Mathew J. Wedel, Richard L. Cifelli, and R. Kent Sanders (''Acta Palaeontologica Polonica'' 45, pages 343–388, 2000).</ref> Based on CT imaging, Moore and colleagues estimated the cervical vertebrae of ''M. sinocandorum'' to be 69–77% air by volume, assuming complete removal of bone marrow.<ref name="moore2023" /> The mandible was {{convert|60.3|cm|in|sp=us}} in length and had 19 teeth. In contrast to the more squared-off jaws of diplodocids, the front of the mandibles met at an oblique angle.<ref name="RussellZheng1993" /> Two as-yet-undescribed cervical vertebrae possibly suggest one of the largest dinosaurs known. Gregory S. Paul suggested that these might belong to ''M. sinocanadorum'' and estimated a length {{convert|35|m|sp=us}} and possibly weighing {{convert|60|to|80|t|ST|abbr=off}}.<ref name="paul2010" /><ref name=":7" /> However, the referral of these vertebrae to ''M. sinocanadorum'' has been questioned.<ref name="moore2023" />
''M. anyuensis'' shares morphological similarities to ''M. hochuanensis''. He and colleagues estimated the length of this species at {{convert|21|m|sp=us}}.<ref name="Heal1996" /> Paul estimated it longer at {{convert|25|m|sp=us}} with a mass of {{convert|25|t|ST}}.<ref name="paul2010" />[[File:Mamenchisaurus_youngi_steveoc_86.jpg|thumb|Artist's impression of ''M. youngi'']]
''M. youngi'' is one of the smaller species of ''Mamenchisaurus'' and known from relatively complete remains''.'' The type specimen was around {{convert|16|m|sp=us}} long with a {{convert|6.5|m|ft|adj=on|sp=us}} neck.<ref name=":0" /><ref name=":1">Ouyang, H. and Ye, Y. 2002. ''The First Mamenchisaurian Skeleton with Complete Skull: Mamenchisaurus youngi'' (in Chinese with English summary). 111 pp + 20 plates. Sichuan Science and Technology Press, Chengdu.</ref> The mass of ''M. youngi'' was estimated at {{convert|7.87|t|ST}} using volumetric techniques.<ref name=":9" /> The holotype specimen preserves a nearly complete skull. There were four teeth in the premaxilla, 18 in the maxilla, and 22 to 24 in the dentary.<ref name=":0" /> An unusual part of the skeleton is the wedge-shaped sacrum; this causes the sacrum and the base of the tail to pitch up relative to the rest of the vertebral column.<ref name=":5" />
''M. jingyanensis'' was estimated by Zhang and colleagues to be between {{convert|20|and|26|m|sp=us}} in length.<ref name="Zhangetal1998" /> Paul estimated it at {{convert|20|m|sp=us}} with a mass of {{convert|12|t|ST}}.<ref name="paul2010" /> The skull was restored at {{convert|55|cm|sp=us}} in length. There were four teeth in the premaxilla, 14–16 in the maxilla, and 17–19 in the dentary.
''Mamenchisaurus'' have forked chevrons (or sled chevrons) starting around the middle of the tail, similar to those seen in diplodocids; these chevrons curve strongly backwards and add a forward projection.<ref>{{Cite journal|last1=Otero|first1=Alejandro|last2=Gallina|first2=Pablo Ariel|last3=Canale|first3=Juan Ignacio|last4=Haluza|first4=Alejandro|date=2012-06-01|title=Sauropod haemal arches: morphotypes, new classification and phylogenetic aspects|url=https://doi.org/10.1080/08912963.2011.618269|journal=Historical Biology|volume=24|issue=3|pages=243–256|doi=10.1080/08912963.2011.618269|s2cid=84286012|issn=0891-2963|url-access=subscription}}</ref><ref name=":4">{{Cite book|last1=Hallett|first1=Mark|title=The Sauropod Dinosaurs : Life in the Age of Giants|last2=Wedel|first2=Mathew J.|publisher=Johns Hopkins University Press|year=2016|isbn=978-1-4214-2028-8|___location=Baltimore|pages=|oclc=947074739}}</ref> Paul has argued that these types of chevrons are adaptations linked to rearing behaviour. In a tripodal stance, the tail acts as a prop, and the forked chevrons would help distribute the weight evenly. Paul also notes that the [[Glossary of dinosaur anatomy#pelvis|pelvises]] of Mamenchisaurs are retroverted (tilted), which may have allowed slow walking whilst bipedal.<ref name=":4" /><ref name=":5">{{Cite journal|last=Paul|first=Gregory S.|date=2017|title=Restoring Maximum Vertical Browsing Reach in Sauropod Dinosaurs|journal=The Anatomical Record|language=en|volume=300|issue=10|pages=1802–1825|doi=10.1002/ar.23617|pmid=28556505|issn=1932-8494|doi-access=free}}</ref>
ZDM0126, a specimen possibly referable to ''M. hochuanensis,'' possessed four fused caudal vertebrae near the tip of the tail. These vertebrae have expanded [[Neural arch|neural arches]] and taller [[Vertebra#General structure|neural spines]], possibly representing a [[tail club]]. A study by Lida Xing and colleagues performed a [[Finite element method|finite element analysis]] on the club. The authors concluded that the club would have a limited ability to perform as a defensive weapon but might have also functioned as a sensory organ. Other Chinese sauropods, ''[[Shunosaurus]]'' and ''[[Omeisaurus]],'' are also known to have had tail clubs, but they differ in shape to that of ZDM0126.<ref name="Yeetal2001">{{cite journal |last1=Ye |first1=Y. |last2=Ouyang, H. |last3=Fu, Q.-M. |year=2001 |title=New material of ''Mamenchisaurus hochuanensis'' from Ziging China |journal=Vertebrata PalAsiatica |volume=39 |issue=4 |pages=266–271}}</ref><ref name="Xingetal2009" />
The [[Sauropod neck posture|neck posture]] and feeding strategies of sauropod dinosaurs is a controversial topic. Andreas Christian and colleagues analysed the neck of ''M. youngi'' and found that when articulated in a neutral posture, the neck was almost straight, with a slight upward bend at the base and a slight downward bend towards the head. The base of the neck has comparatively high upward flexibility but limited downward flexibility. The region near the head had better downward flexibility and low upward flexibility. In the mid-region, downward flexibility was high, which led the authors to conclude that ''M. youngi'' frequently fed at low levels. Long overlapping cervical ribs may have limited flexibility. The authors also estimated the [[Stress (mechanics)|stress]] on the intervertebral joint [[cartilage]]. Their results suggest the neck was kept mostly straight, with the possible exception of the neck base and near the head.<ref>{{Cite journal |last1=Christian |first1=Andreas |last2=Peng |first2=Guangzhao |last3=Sekiya |first3=Toru |last4=Ye |first4=Yong |last5=Wulf |first5=Marco G. |last6=Steuer |first6=Thorsten |date=2013-10-30 |editor-last=Farke |editor-first=Andrew A. |title=Biomechanical Reconstructions and Selective Advantages of Neck Poses and Feeding Strategies of Sauropods with the Example of Mamenchisaurus youngi |journal=PLOS ONE |language=en |volume=8 |issue=10 |pages=e71172 |bibcode=2013PLoSO...871172C |doi=10.1371/journal.pone.0071172 |issn=1932-6203 |pmc=3812961 |pmid=24204557 |doi-access=free}}</ref>
A large ulna (GPIT SGP 2006/10) measuring less than {{convert|96|cm|sp=us}} in length, referred to ''Mamenchisaurus'' sp. from the Shishugou Formation, was used in a bone histology analysis. By sectioning the bone and counting the growth rings, the age at death was estimated at 43 years.<ref>{{Cite book |last1=SANDER |first1=P. MARTIN |title=Biology of the Sauropod Dinosaurs : Understanding the Life of Giants. |last2=KLEIN |first2=NICOLE |last3=STEIN |first3=KOEN |last4=WINGS |first4=OLIVER |publisher=Indiana University Press |others=Nicole Klein, Remes, Kristian., Gee, Carole T., Sander, Martin, Dr. |year=2011 |isbn=978-0-253-01355-2 |___location=Bloomington |pages= |chapter=Sauropod Bone Histology and Its Implications for Sauropod Biology |oclc=858764960}}</ref>
== Classification ==
''Mamenchisaurus'' is sometimes referred to as a '[[wastebasket taxon]]', with researchers questioning the number of species and fragmentary remains assigned to the genus.<ref name="paul2010"/><ref name=":2">{{Cite journal|last1=Xing|first1=Lida|last2=Miyashita|first2=Tetsuto|last3=Zhang|first3=Jianping|last4=Li|first4=Daqing|last5=Ye|first5=Yong|last6=Sekiya|first6=Toru|last7=Wang|first7=Fengping|last8=Currie|first8=Philip J.|date=2015-01-02|title=A new sauropod dinosaur from the Late Jurassic of China and the diversity, distribution, and relationships of mamenchisaurids|url=http://www.tandfonline.com/doi/full/10.1080/02724634.2014.889701|journal=Journal of Vertebrate Paleontology|language=en|volume=35|issue=1|pages=e889701|doi=10.1080/02724634.2014.889701|bibcode=2015JVPal..35E9701X |s2cid=86062974|issn=0272-4634|url-access=subscription}}</ref><ref name=":3"/><ref name="moore2020"/><ref>{{Cite journal|last1=Wings|first1=Oliver|last2=Schwarz-Wings|first2=Daniela|last3=Fowler|first3=Denver W.|date=2011-11-01|title=New sauropod material from the Late Jurassic part of the Shishugou Formation (Junggar Basin, Xinjiang, NW China)|url=http://www.schweizerbart.de/papers/njgpa/detail/262/76478/New_sauropod_material_from_the_Late_Jurassic_part_?af=crossref|journal=Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen|language=en|volume=262|issue=2|pages=129–150|doi=10.1127/0077-7749/2011/0183|bibcode=2011NJGPA.262..129W |issn=0077-7749|url-access=subscription}}</ref> The genus is poorly defined with an increasingly confused taxonomy which makes understanding phylogenetic relationships difficult. Several analyses have failed to show ''Mamenchisaurus'' as [[monophyletic]], suggesting the need to revise the genus.<ref name="moore2020"/> Additional research on the type species, ''M. constructus,'' is required to better understand the genus.<ref name=":3"/>
When ''M. constructus'' was first described, Young noted that the chevron bones indicated an affinity with Diplodocidae, but was uncertain to its exact position.<ref name="young1954"/> In 1958, Young assigned ''Mamenchisaurus'' to the [[Lithostrotia|Titanosauridae]].<ref name=":10"/> With the description of ''M. hochuanensis'', Young and Zhao created the family [[Mamenchisauridae]] in 1972.<ref name="young&zhao1972"/> In 1978, when no ''Mamenchisaurus'' skulls were known, Berman and McIntosh assigned the genus to Diplodocidae based on diplodocid-like vertebral features such as the forked chevrons. In 1990, McIntosh assigned ''Mamenchisaurus'' to a subfamily Mamenchisaurinae, which was placed inside Diplodocidae.<ref name=":11"/>
An analysis by Upchurch in 1995 found ''Mamenchisaurus'' in the family [[Euhelopodidae]]. Euhelopodidae, being named first, would take priority over Mamenchisauridae.<ref>{{Cite journal|last=Upchurch|first=Paul|date=1995|title=The evolutionary history of sauropod dinosaurs|url=http://doc.rero.ch/record/16651/files/PAL_E2783.pdf|journal=Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences|volume=349|issue=1330|pages=365–390|doi=10.1098/rstb.1995.0125|bibcode=1995RSPTB.349..365U}}</ref> Several later analyses found ''Euhelopus'' to be a more distantly related [[macronaria]]n, with ''Mamenchisaurus'' in Mamenchisauridae just outside of [[Neosauropoda]].<ref name=":2"/><ref name="moore2020"/>
Analyses by Sekiya in 2011 and Moore and colleagues in 2020 treated ''M. constructus, M. hochuanensis,'' ZDM 0126 ''(M. hochuanensis'' referred''), M. sinocandadorum, and M. youngi'' separately.<ref name="moore2020"/><ref name="sekiya2011">Sekiya, T. (2011). Re-examination of ''Chuanjiesaurus anaensis'' (Dinosauria: Sauropoda) from the Middle Jurassic Chuanjie Formation, Lufeng County, Yunnan Province, southwest China." ''Memoir of the Fukui Prefectural Dinosaur Museum'', '''10''': 1－54.</ref> Moore and colleagues analyses found the position of ''M. constructus'' to be unstable, probably due to the limited character information in its description. Depending on the dataset used, ''Euhelopus'' would either be within Macronaria, as other studies have found or outside [[Neosauropoda]] in a more traditional position, grouped with other ''Mamenchisaurus-''like taxa. The latter scenario would make mamenchisaurids members of Euhelopodidae.<ref name="moore2020"/> The analyses of Sekiya (2011) and Moore and colleagues (2020) did not recover ZDM 0126 as a sister taxon to the holotype of ''M. hochuanensis,'' questioning its referral to the species.<ref name="moore2020"/><ref name="sekiya2011"/>
The [[cladogram]] below shows a possible phylogenetic position of the genus within [[Sauropoda]], from Allain and Aquesbi, 2008:<ref name="allain_aquesbi_2008">{{cite journal |issn=1280-9659 |volume=30 |issue=2 |pages=403, 404 |last=Allain |first=Ronan |author2=Najat Aquesbi |title=Anatomy and phylogenetic relationships of Tazoudasaurus naimi (Dinosauria, Sauropoda) from the late Early Jurassic of Morocco |journal=Geodiversitas |year=2008 |url=http://cat.inist.fr/?aModele=afficheN&cpsidt=20435881 |access-date=2021-03-13 |archive-date=2013-09-25 |archive-url=https://web.archive.org/web/20130925110151/http://cat.inist.fr/?aModele=afficheN&cpsidt=20435881 |url-status=dead }}</ref>
{{clade| style=font-size:90%;line-height:90%
|label1=[[Sauropoda]]
|1={{clade
|1=''[[Antetonitrus]]''
|2={{clade
|1=''[[Gongxianosaurus]]''
|2={{clade
|1=''[[Isanosaurus]]''
|label2=[[Gravisauria]]
|2={{clade
|label1=[[Vulcanodontidae]]
|1={{clade
|1=''[[Vulcanodon]]''
|2=''[[Tazoudasaurus]]''
}}
|label2=[[Eusauropoda]]
|2={{clade
|1=''[[Barapasaurus]]''
|2=''[[Patagosaurus]]''
|3={{clade
|label1=[[Omeisauridae]]
|1={{clade
|1=''[[Omeisaurus]]''
|2='''''Mamenchisaurus'''''
}}
|2=[[Neosauropoda]]
}}
}}
}}
}}
}}
}}
}}
Below, two [[phylogenetic tree]]s show the internal relationships of Euhelopodidae/Mamenchisauridae in the two analyses Moore and colleagues deemed most favorable, the implied-weights and Bayesian analyses of the Gonzàlez Riga dataset.<ref name="moore2020">{{cite journal|last1=Moore|first1=A.J.|last2=Upchurch|first2=P.|last3=Barrett|first3=P.M.|last4=Clark|first4=J.M.|last5=Xing|first5=X.|year=2020|title=Osteology of ''Klamelisaurus gobiensis'' (Dinosauria, Eusauropoda) and the evolutionary history of Middle–Late Jurassic Chinese sauropods|journal=Journal of Systematic Palaeontology|volume=18|issue=16|pages=1299–1393|doi=10.1080/14772019.2020.1759706|bibcode=2020JSPal..18.1299M |s2cid=219749618|url=https://discovery.ucl.ac.uk/id/eprint/10101710/1/Mooreetal2020%28Klamelisaurus%20green%20OA%29.pdf}}</ref>
'''Topology A:''' Implied-weights analysis, Gonzàlez Riga dataset<ref name="moore2020"/>
{{clade|{{clade
|1=''[[Tienshanosaurus chitaiensis]]''
|2={{clade
|label2=Core ''Mamenchisaurus''-like taxa
|1=''[[Omeisaurus junghsiensis]]''
|2={{clade
|1=''[[Wamweracaudia keranjei]]''
|2={{clade
|1={{clade
|1=''[[Qijianglong guokr]]''
|2='''''Mamenchisaurus sinocanadorum'''''}}
|2={{clade
|1={{clade
|1=''[[Chuanjiesaurus anaensis]]''
|2=''[[Analong chuanjieensis]]''}}
|2={{clade
|1='''''Mamenchisaurus hochuanensis''''' (holotype)
|2='''''Mamenchisaurus hochuanensis''''' (referred)
|3={{clade
|1='''''Mamenchisaurus youngi'''''
|2={{clade
|1=Shishugou cervicodorsals
|2={{clade
|1=Phu Kradung taxon
|2=''[[Klamelisaurus gobiensis]]''}} }} }} }} }} }} }} }} }}|style=font-size:90%; line-height:90%;|label1=[[Mamenchisauridae]]}}'''Topology B:''' Time-calibrated Bayesian analysis, Gonzàlez Riga dataset<ref name="moore2020"/>
{{clade|{{clade
|1={{clade
|1=''[[Omeisaurus junghsiensis]]''
|2={{clade
|1=''[[Cetiosauriscus|Cetiosauriscus stewarti]]''
|2={{clade
|1=''[[Omeisaurus maoianus]]''
|2=''[[Omeisaurus tianfuensis]]''}} }} }}
|2={{clade
|label2=Core ''Mamenchisaurus''-like taxa
|1=''[[Tienshanosaurus chitaiensis]]''
|2={{clade
|1={{clade
|1=''[[Chuanjiesaurus anaensis]]''
|2={{clade
|1=''[[Analong chuanjieensis]]''
|2={{clade
|1=''[[Qijianglong guokr]]''
|2={{clade
|1=Shishugou cervicodorsals
|2='''''Mamenchisaurus sinocanadorum'''''}} }} }} }}
|2={{clade
|1={{clade
|1={{clade
|1='''''Mamenchisaurus hochuanensis''''' (holotype)
|2='''''Mamenchisaurus constructus'''''}}
|2={{clade
|1=Phu Kradung taxon
|2=''[[Klamelisaurus gobiensis]]''}} }}
|2={{clade
|1='''''Mamenchisaurus hochuanensis''''' (referred)
|2='''''Mamenchisaurus youngi'''''
|3={{clade
|1=''[[Wamweracaudia keranjei]]''
|2={{clade
|1={{clade
|1=''[[Xianshanosaurus shijiagouensis]]''
|2=''[[Daxiatitan binglingi]]''}}
|2={{clade
|1=''[[Euhelopus zdanskyi]]''
|2=''[[Dongbeititan dongi]]''}} }} }} }} }} }} }} }}|style=font-size:90%; line-height:90%;|label1=[[Euhelopodidae]]}}
The 2023 redescription of ''M. sinocanadorum'' found a consistent sister taxon relationship between it and ''Xinjiangtitan'', with ''[[Hudiesaurus]]'' and referred material of ''M. hochuanensis'' (ZDM 0126) also found to be consistent relatives.<ref name=moore2023/>
{{clade|style=font-size:90%; line-height:90%;
|label1=[[Mamenchisauridae]]
|1={{clade
|1=''[[Tienshanosaurus]]''
|2={{clade
|1=''[[Omeisaurus junghsiensis]]''
|2={{clade
|1=''[[Wamweracaudia]]''
|2={{clade
|1=''[[Qijianglong]]''
|2={{clade
|1='''''Mamenchisaurus constructus'''''
|2=''[[Bellusaurus]]''
|3={{clade
|1={{clade
|1=''[[Rhomaleopakhus]]''
|2={{clade
|1=''[[Chuanjiesaurus]]''
|2=''[[Analong]]'' }} }}
|2={{clade
|1='''''Mamenchisaurus youngi'''''
|2={{clade
|1={{clade
|1='''''Mamenchisaurus hochuanensis''''' (holotype)
|2={{clade
|1=Shishugou cervicodorsals
|2={{clade
|1=Phu Krandung taxon
|2=''[[Klamelisaurus]]'' }} }} }}
|2={{clade
|1={{clade
|1='''''Mamenchisaurus sinocanadorum'''''
|2=''[[Xinjiangtitan]]'' }}
|2={{clade
|1=''[[Hudiesaurus]]''
|2={{clade
|1=''[[Daanosaurus]]''
|2='''''Mamenchisaurus hochuanensis''''' (referred) }} }} }} }} }}
}} }} }} }} }} }} }}
== Paleochronology ==
''Mamenchisaurus'' was originally thought to have ranged from the Middle to Late Jurassic.<ref>{{Cite journal|last1=Li|first1=Kui|last2=Liu|first2=Jian|last3=Yang|first3=Chunyan|last4=Hu|first4=Fang|date=2011|title=Dinosaur assemblages from the middle jurassic shaximiao formation and chuanjie formation in the sichuan-yunnan basin, China|url=|journal=Volumina Jurassica|volume=IX|pages=21–42}}</ref><ref name="Age"/> However, there is not reliable dating for the Upper Shaximiao Formation, where many of the ''Mamenchisaurus'' species are found.<ref name="Age"/>
A study published in 2018 used uranium–lead dating on the underlying ''Omeisaurus'' bearing beds of the Lower Shaximiao Formation, previously thought to belong to the Middle Jurassic. However, the radiometric dating found the Lower Shaximiao Formation dated to the Late Jurassic, Oxfordian Stage, around 159 million years ago (mya). This finding suggests a younger age for the overlying ''Mamenchisaurus'' bearing rocks of the Upper Shaximiao; implying them to be no older than the Oxfordian.<ref name="Age"/><ref name=":8">{{Cite journal|last1=Wang|first1=Jun|last2=Ye|first2=Yong|last3=Pei|first3=Rui|last4=Tian|first4=Yamin|last5=Feng|first5=Chongqin|last6=Zheng|first6=Daran|last7=Chang|first7=Su-Chin|date=2018-09-01|title=Age of Jurassic basal sauropods in Sichuan, China: A reappraisal of basal sauropod evolution|url=https://pubs.geoscienceworld.org/gsa/gsabulletin/article/130/9-10/1493/530045/Age-of-Jurassic-basal-sauropods-in-Sichuan-China-A|journal=GSA Bulletin|language=en|volume=130|issue=9–10|pages=1493–1500|doi=10.1130/B31910.1|bibcode=2018GSAB..130.1493W|issn=0016-7606|url-access=subscription}}</ref>
''M. sinocanadorum'' was found from the Middle to Upper Shishugou Formation. Radiometric dating suggests this formation dated to the Oxfordian, ranging from 158.7 to 161.2 mya.<ref name="Age"/><ref name=":8"/> ''M. anyuensis,'' was found in the Suining Formation, thought initially to be Middle to Late Jurassic. A 2019 study found these rocks belonged to the Early Cretaceous, Aptian Stage, with an average age of around 114.4 mya. This indicates that mamenchisaurids might have existed around 30 million years longer than previously thought.<ref name="Age"/>
==References==
{{Reflist|30em|refs=
<ref name="LiCai1997">{{Cite journal| volume = 24| pages = 102–107| last1 = Li| first1 = Kui| last2 = Cai| first2 = Kaiji| title = Classification and evolution of Mamenchisaurus| journal = Journal of Chengdu University of Technology| date = 1997 }}</ref>}}
== External links ==
{{Commons category|position=left|Mamenchisaurus}}
* [https://web.archive.org/web/20061008164638/http://www.dinosaur.net.cn/museum/Mamenchisaurus.htm Dinosaur.net.cn] (in Chinese and English)
{{Sauropodomorpha|B.}}
{{Taxonbar|from=Q131038}}
[[Category:Mamenchisauridae]]
[[Category:Dinosaur genera]]
[[Category:Late Jurassic dinosaurs]]
[[Category:Early Cretaceous dinosaurs]]
[[Category:Shaximiao Formation]]
[[Category:Fossil taxa described in 1954]]
[[Category:Taxa named by Yang Zhongjian]]
[[Category:Dinosaurs of China]]
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