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'''''Mamenchisaurus''''' ({{IPAc-en|m|ə|ˌ|m|ʌ|n|tʃ|i|ˈ|s|ɔː|r|ə|s}} {{respell|mə|MUN|chee|SOR|əs}}, [https://web.archive.org/web/20070928010631/http://www.dinosauria.com/dml/names/dinom.htm Dinosauria Translation and Pronunciation Guide M] or spelling pronunciation {{IPAc-en|m|ə|ˌ|m|ɛ|n|tʃ|ɪ|ˈ|s|ɔː|r|ə|s}}) is a genus of [[sauropod]] [[dinosaur]] 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 (158.7 to 161.2 [[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|pages=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|s2cid=210840060}}</ref>
==History and species==
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=== ''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 }}</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" />
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" />
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=== 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" />
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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 |pages=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" />
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== 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}}</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|issn=0077-7749}}</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"/>
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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"/>
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