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''Mamenchisaurus'' (

or spelling pronunciation ) is a genus of
sauropod Sauropoda (), whose members are known as sauropods (; from '' sauro-'' + '' -pod'', ' lizard-footed'), is a clade of saurischian ('lizard-hipped') dinosaurs. Sauropods had very long necks, long tails, small heads (relative to the rest of their ...
dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23  million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is ...
known for their remarkably long
neck The neck is the part of the body on many vertebrates that connects the head with the torso. The neck supports the weight of the head and protects the nerves that carry sensory and motor information from the brain down to the rest of the body. I ...
s which made up nearly half the total body length. Numerous species have been assigned to the genus; however, many of these might be questionable. Fossils have been found in the
Sichuan Basin The Sichuan Basin (), formerly transliterated as the Szechwan Basin, sometimes called the Red Basin, is a lowland region in southwestern China. It is surrounded by mountains on all sides and is drained by the upper Yangtze River and its tribut ...
and
Yunnan Province Yunnan , () is a landlocked province in the southwest of the People's Republic of China. The province spans approximately and has a population of 48.3 million (as of 2018). The capital of the province is Kunming. The province borders the C ...
in China. Several species are from the
Upper Shaximiao Formation The Shaximiao Formation () is a Middle to Late Jurassic aged geological formation in Sichuan, China, most notable for the wealth of dinosaurs fossils that have been excavated from its strata. The Shaximiao Formation is exposed in and around th ...
whose geologic age is uncertain. However, evidence suggests that this be no earlier than the Oxfordian stage of the
Late Jurassic The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 163.5 ± 1.0 to 145.0 ± 0.8 million years ago (Ma), which is preserved in Upper Jurassic strata.Owen 1987. In European lithostratigraphy, the nam ...
. ''M. sinocanadorum'' dates to the Oxfordian stage (158.7 to 161.2 mya) and ''M. anyuensis'' to the Aptian stage of the
Early Cretaceous The Early Cretaceous ( geochronological name) or the Lower Cretaceous ( chronostratigraphic name), is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 145  Ma to 100.5 Ma. Geology Pr ...
around 114.4 mya. Most species were medium- to large-size sauropods in length.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. Two as-yet-undescribed
cervical vertebrae In tetrapods, cervical vertebrae (singular: vertebra) are the vertebrae of the neck, immediately below the skull. Truncal vertebrae (divided into thoracic and lumbar vertebrae in mammals) lie caudal (toward the tail) of cervical vertebrae. ...
, which might belong to ''M. sinocanadorum,'' suggest one of the largest dinosaurs known; estimated at in length and possibly weighed .


Description

It's not certain that all the species assigned to ''Mamenchisaurus'' should belong to the genus. 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 Quadrupedalism is a form of locomotion where four limbs are used to bear weight and move around. An animal or machine that usually maintains a four-legged posture and moves using all four limbs is said to be a quadruped (from Latin ''quattu ...
, large bodies, small heads, and long tails. The most distinctive feature of mamenchisaurids is their exceptionally long necks which approach half their total length. Complete necks are known in ''M. youngi and M. hochuanensis'', consisting of 18 and 19 vertebrae, respectively.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. ''Mamenchisaurus'' cervical vertebrae are elongated, lightly constructed and highly
pneumatic Pneumatics (from Greek ‘wind, breath’) is a branch of engineering that makes use of gas or pressurized air. Pneumatic systems used in industry are commonly powered by compressed air or compressed inert gases. A centrally located and el ...
. The neural spines on their posterior cervical and anterior dorsal vertebrae are bifurcated. Their shoulders were somewhat higher than the hips. The different species vary in length, from around to at least , and maybe up to based on two undescribed vertebrae. The neck posture of sauropod dinosaurs is a controversial topic. Andreas Christian and colleagues analysed the neck of ''Mamenchisaurus youngi''. They found the neck was nearly straight with a slight upward bend at the base and a slight downward bend towards the head when articulated in a neutral posture. 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 on the intervertebral joint
cartilage Cartilage is a resilient and smooth type of connective tissue. In tetrapods, it covers and protects the ends of long bones at the joints as articular cartilage, and is a structural component of many body parts including the rib cage, the neck a ...
. Their results suggest the neck was kept mostly straight, with the possible exception of the neck base and near the head. ''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.
Gregory S. Paul Gregory Scott Paul (born December 24, 1954) is an American freelance researcher, author and illustrator who works in paleontology, and more recently has examined sociology and theology. He is best known for his work and research on theropod di ...
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 pelvises of Mamenchisaurs are retroverted (tilted), which may have allowed slow walking whilst bipedal. A large ulna (GPIT SGP 2006/10) measuring less than in length, referred to ''Mamenchisaurus'' sp. from the
Shishugou Formation The Shishugou Formation () is a geological formation in Xinjiang, China. Its strata date back to the Late Jurassic period. Dinosaur remains are among the fossils that have been recovered from the formation.Weishampel, David B; et al. (2004). "D ...
, 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.


Discovery and species

''Mamenchisaurus'' was first discovered in 1952 on the construction site of the Yitang Highway in
Sichuan Sichuan (; zh, c=, labels=no, ; zh, p=Sìchuān; alternatively romanized as Szechuan or Szechwan; formerly also referred to as "West China" or "Western China" by Protestant missions) is a province in Southwest China occupying most of t ...
Province of
China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's List of countries and dependencies by population, most populous country, with a Population of China, population exceeding 1.4 billion, slig ...
. 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 In biology, a type is a particular specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to anchor or centralizes ...
(IVPP V. 790) was fragmentary, disordered, and not excavated in a technical way. Material included five dorsal vertebrae, 30
caudal vertebrae The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic ...
, 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, and estimated the whole neck at . 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. ''M. constructus'' has been estimated around in length with a mass of .Paul, G.S. (2016). ''The Princeton Field Guide to Dinosaurs'', Princeton University Press.Young, C.C. (1954), ''On a new sauropod from Yiping, Szechuan, China.'' sinica, III(4), 481-514. ''Mamenchisaurus'' means 'Mamenchi lizard', from the
Chinese Chinese can refer to: * Something related to China * Chinese people, people of Chinese nationality, citizenship, and/or ethnicity **''Zhonghua minzu'', the supra-ethnic concept of the Chinese nation ** List of ethnic groups in China, people of v ...
Pinyin Hanyu Pinyin (), often shortened to just pinyin, is the official romanization system for Standard Mandarin Chinese in China, and to some extent, in Singapore and Malaysia. It is often used to teach Mandarin, normally written in Chinese f ...
''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 Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...
''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'). The fact that the first ''Mamenchisaurus'' fossil was found due to construction work led to Young's naming the
type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen( ...
as ''Mamenchisaurus constructus''. In 1958, Young described additional sauropod remains collected from
Gansu Province Gansu (, ; alternately romanized as Kansu) is a province in Northwest China. Its capital and largest city is Lanzhou, in the southeast part of the province. The seventh-largest administrative district by area at , Gansu lies between the Tibet ...
. 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, a second species Young and Xijin Zhao described ''Mamenchisaurus hochuanensis''. The fossils were found near a village in
Hechuan Hechuan () is a district in the northern part of Chongqing Municipality, People's Republic of China, located at the meeting point of the Jialing, Fu and Qu rivers, with a history of 1,500 years. Hechuan is away from downtown Chongqing's Yuz ...
, north of
Chongqing Chongqing ( or ; ; Sichuanese pronunciation: , Standard Mandarin pronunciation: ), alternately romanized as Chungking (), is a municipality in Southwest China. The official abbreviation of the city, "" (), was approved by the State Co ...
(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 ''M. constructus'' type specimen's location, dating to at least the Late Jurassic. Locals first discovered the remains sometime before the Chinese Revolution. However, the remains were ultimately abandoned and left to
weather Weather is the state of the atmosphere, describing for example the degree to which it is hot or cold, wet or dry, calm or stormy, clear or cloudy. On Earth, most weather phenomena occur in the lowest layer of the planet's atmosphere, the ...
in situ. Excavation didn't begin on the site until 1957. 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, twelve 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. The total length of ''M. hochuanensis'' is about with a neck. When ''M. hochuanensis'' was first described, it was the largest sauropod known from China. Young and Zhao estimated the mass of ''M. hochuanensis'' at . However, later volumetric mass estimates are lower at . 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 A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...
, such as the skull, pectoral girdle and forelimb material. Four fused tail vertebra from the tip of the tail have expanded neural arches and taller
neural spines The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic i ...
. It's thought that these could be a weapon, such as a
tail club In zoology, a club is a bony mass at the end of the tail of some dinosaurs and of some mammals, most notably the ankylosaurids and the glyptodonts, as well as meiolaniid turtles. It is thought that this was a form of defensive armour or weapon th ...
, or a sensory organ. Other Chinese sauropods, ''
Shunosaurus ''Shunosaurus'', meaning "shu lizard", is a genus of sauropod dinosaur from Late Jurassic ( Oxfordian) beds in Sichuan Province in China, approximately 159±2 million years ago. The name derives from "Shu", an ancient name for the Sichuan ...
'' and ''
Omeisaurus ''Omeisaurus'' (meaning "Omei lizard") is a genus of sauropod dinosaur from the Middle Jurassic Period (Bathonian-Callovian stage) of what is now China. Its name comes from Mount Emei, where it was discovered in the lower Shaximiao Formation o ...
'', are also known to have had 'tail clubs', but they differ in shape to that of ''M. hochuanensis''. Phylogenetic analyses have cast doubt on the referral of this specimen to ''M. hochuanensis.''


''Mamenchisaurus sinocanadorum''

In 1993, ''M. sinocanadorum'' was described by Dale Russell and Zhong Zheng. The remains were found in 1987 when a cervical rib was seen projecting out of a cliff. The fossil site was located in the Junggar Basin,
Xinjiang Xinjiang, SASM/GNC: ''Xinjang''; zh, c=, p=Xīnjiāng; formerly romanized as Sinkiang (, ), officially the Xinjiang Uygur Autonomous Region (XUAR), is an autonomous region of the People's Republic of China (PRC), located in the northwes ...
; from the upper part of the Shishugou Formation (between 161.2 Ma and 158.7 Ma in age). The specimen (IVPP V10603) consisted of an articulated series of the first four cervical vertebrae, a well-preserved
mandible In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bon ...
, and other skull material. The mandible was 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. The neural arches of the vertebrae were well fused to the centra suggesting that the animal was mature. This species possessed the longest
cervical rib A cervical rib in humans is an extra rib which arises from the seventh cervical vertebra. Their presence is a congenital abnormality located above the normal first rib. A cervical rib is estimated to occur in 0.2% to 0.5% (1 in 200 to 500) of the ...
of any described
sauropod Sauropoda (), whose members are known as sauropods (; from '' sauro-'' + '' -pod'', ' lizard-footed'), is a clade of saurischian ('lizard-hipped') dinosaurs. Sauropods had very long necks, long tails, small heads (relative to the rest of their ...
dinosaur, measuring . For comparison, a ''
Sauroposeidon ''Sauroposeidon'' ( ; meaning "lizard earthquake god", after the Greek god Poseidon) is a genus of sauropod dinosaur known from several incomplete specimens including a bone bed and fossilized trackways that have been found in the U.S. states ...
'' cervical rib measures . 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 . The neck has been estimated at in length. The species name refers to the
China-Canada Dinosaur Project The China-Canada Dinosaur Project ( Chinese: 中国-加拿大恐龙计划; Pinyin: ''Zhōngguó-jiānádà kǒnglóng jìhuà''; also known as ''Sino-Canadian Dinosaur Project'') was a six-year series of palaeontological expeditions carried ou ...
. The authors noted that the teeth are fully erupted but unworn, 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 Decomposition or rot is the process by which dead organic substances are broken down into simpler organic or inorganic matter such as carbon dioxide, water, simple sugars and mineral salts. The process is a part of the nutrient cycle and is ...
. The head and part of the neck then drifted downstream until they came to rest in shallow water on a
point bar A point bar is a depositional feature made of alluvium that accumulates on the inside bend of streams and rivers below the slip-off slope. Point bars are found in abundance in mature or meandering streams. They are crescent-shaped and located ...
and eventually buried. Two large cervical vertebrae have since been found from the same formation as ''M. sinocanadorum'' and might belong to the species. However, these vertebrae have yet to be formally described. Gregory S. Paul has suggested these may represent one of the largest dinosaurs known, with an estimated length of and .


''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 Jingyan () is a county of Sichuan Province, China. It is under the administration of Leshan Leshan, formerly known as Jiading or Jiazhou, is a prefecture-level city located at the confluence of the Dadu and Min rivers in Sichuan Province, Chi ...
. Another specimen (JV002) was found in the village of Sanjiang approximately from Meiwang and became the paratype. A third specimen (CV00219) 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. The type specimen includes a partial scapula and complete coracoid, forelimb material, a complete ischium, a relatively complete skull, and a
hyoid bone The hyoid bone (lingual bone or tongue-bone) () is a horseshoe-shaped bone situated in the anterior midline of the neck between the chin and the thyroid cartilage. At rest, it lies between the base of the mandible and the third cervical vert ...
. 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. The skull was restored at in length. There were four teeth in the premaxilla, 14–16 in the maxilla, and 17–19 in the dentary. Zhang and colleagues estimated this species between in length. Paul estimated it at with a mass of .


''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. This species shares a lot of morphological similarity to ''M. hochuanensis''. He and colleagues estimated the length of this species at . Paul estimated it longer at with a mass of .


''Mamenchisaurus youngi''

Also described in 1996 was ''Mamenchisaurus youngi'' from the Upper Shaximiao Formation. A local quarrying stone near a village in Zigong,
Sichuan Sichuan (; zh, c=, labels=no, ; zh, p=Sìchuān; alternatively romanized as Szechuan or Szechwan; formerly also referred to as "West China" or "Western China" by Protestant missions) is a province in Southwest China occupying most of t ...
Province, found the remains in 1987. The species was named in honour of C. C. Young. The holotype specimen (ZDM 0083) was very complete and mostly articulated, preserving all the vertebrae from the head down to the 8th tail vertebra; this species had 18 neck vertebrae. Also preserved was the pectoral girdle, pelvic girdle, and material from all four limbs. This specimen also preserved a nearly complete skull. There were four teeth in the premaxilla, 18 in the maxilla, and 22 to 24 in the dentary. 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. At long with a neck, ''M. youngi'' is one of the smaller species of ''Mamenchisaurus.''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. The mass of ''M. youngi'' was estimated at using volumetric techniques.


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 ''nomina nuda''. In 1976, Hou, Chao and Chu named a new genus, '' Zigongosaurus fuxiensis.'' Known from at least four specimens from the Upper Shaximiao Formation. The type specimen (CV 00261??) included skull material; maxilla, dentary, and basioccipital. Additional material includes dorsal vertebrae, pubis, and ischium. Since then other researchers have disagreed as to whether the genus is valid. Dong, Zhou and Zhang assigned the remains to the similarly named ''Omeisaurus fuxiensis'' in 1983. Zhang and Chen assigned the remains to ''Mamenchisaurus'' as ''M. fuxiensis'' in 1996. Li and Cai considered it a ''nomen nudum'' in 1997. In 1999, Valérie Martin-Rolland considered ''Zigongosaurus'' a valid genus. Wang and colleagues considered it undiagnostic in 2019. ''M. guangyuanensis'' was briefly mentioned by Zhang, Li, and Zeng in 1998 with the description of ''M. jingyanensis,'' but no details are given. Li and Cai considered it a ''nomen nudum''. Wang and colleagues considered it undiagnostic in 2019. ''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. Wang and colleagues questioned the assignment to ''Mamenchisaurus'' in 2019. ''M. yaochinensis'' is a ''nomen nudum''. In 1996, Zhang and Chen considered ''Omeisaurus changshouensis'' and ''Omeisaurus gongjianensis'' to be species of ''Mamenchisaurus.'' Upchurch considered ''O. changshouensis'' undiagnosable. In 1978, an incomplete sauropod humerus (NSM PV17656) found in a layer of the
Early Cretaceous The Early Cretaceous ( geochronological name) or the Lower Cretaceous ( chronostratigraphic name), is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 145  Ma to 100.5 Ma. Geology Pr ...
-aged Miyako Group of
Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...
was considered to probably belong to ''Mamenchisaurus''. In 1991, it was referred to ?''Mamenchisaurus'' sp. by Hasegawa and colleagues''.'' However, the humerus was reassessed by Azuma & Tomida in 1998, and Barrett and colleagues in 2002. They couldn't find any distinguishing features that could place the humerus into a specific sauropod group. They regarded it as an indeterminate sauropod. The remains were given an informal name "Moshi-ryu"; "Moshi" being the local name for the location it was discovered, and "ryu" being Japanise for
dragon A dragon is a reptile, reptilian legendary creature that appears in the folklore of many cultures worldwide. Beliefs about dragons vary considerably through regions, but European dragon, dragons in western cultures since the High Middle Ages hav ...
—also referred to as " Moshisaurus".


Classification

''Mamenchisaurus'' is sometimes referred to as a '
wastebasket taxon Wastebasket taxon (also called a wastebin taxon, dustbin taxon or catch-all taxon) is a term used by some taxonomists to refer to a taxon that has the sole purpose of classifying organisms that do not fit anywhere else. They are typically define ...
', with researchers questioning the number of species and fragmentary remains assigned to the genus. The genus is poorly defined with an increasingly confused taxonomy which makes understanding phylogenic relationships difficult. Several analyses have failed to show ''Mamenchisaurus'' as
monophyletic In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic grou ...
, suggesting the need to revise the genus. Additional research on the type species, ''M. constructus,'' is required to better understand the genus. When ''M. constructus'' was first described, Young noted that the chevron bones indicated an affinity with Diplodocidae, but was uncertain to its exact position. In 1958, Young assigned ''Mamenchisaurus'' to the Titanosauridae. With the description of ''M. hochuanensis'', Young and Zhao created the family
Mamenchisauridae Mamenchisauridae is a family of sauropod dinosaurs belonging to Eusauropoda known from the Jurassic and Early Cretaceous of Asia and Africa. Some members of the group reached gigantic sizes, amongst the largest of all sauropods. Classification T ...
in 1972. 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. An analysis by Upchurch found ''Mamenchisaurus'' in the family Euhelopodidae. Euhelopodidae, being named first, would take priority over Mamenchisauridae. Several later analyses found ''Euhelopus'' to be a more distantly related
macronaria Macronaria is a clade of sauropod dinosaurs. Macronarians are named after the large diameter of the nasal opening of their skull, known as the external naris, which exceeded the size of the orbit, the skull opening where the eye is located (henc ...
n, with ''Mamenchisaurus'' in Mamenchisauridae just outside of
Neosauropoda Neosauropoda is a clade within Dinosauria, coined in 1986 by Argentine paleontologist José Bonaparte and currently described as '' Saltasaurus loricatus'', ''Diplodocus longus'', and all animals directly descended from their most recent common ...
. 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 in their analyses.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. Moore and colleagues analyses found the position of ''M. constructus'' to be unstable, probably due to the limited character information in its original description. Depending on the dataset used, ''Euhelopus'' would either be within Macronaria, as other studies have found or outside
Neosauropoda Neosauropoda is a clade within Dinosauria, coined in 1986 by Argentine paleontologist José Bonaparte and currently described as '' Saltasaurus loricatus'', ''Diplodocus longus'', and all animals directly descended from their most recent common ...
in a more traditional position, grouped with other ''Mamenchisaurus-''like taxa. The latter scenario would make mamenchisaurids members of Euhelopodidae. The analyses of Sekiya (2011) and Moore and colleagues (2020) didn't recover ZDM 0126 as a sister taxon to the holotype of ''M. hochuanensis,'' questioning its referral to the species. The
cladogram A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to ...
below shows a possible phylogenetic position of the genus within Sauropoda, from Allain and Aquesbi, 2008: Below, two
phylogenetic tree A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree showing the evolutionary relationships among various biological sp ...
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. Topology A: Implied-weights analysis, Gonzàlez Riga dataset Topology B: Time-calibrated Bayesian analysis, Gonzàlez Riga dataset


Paleochronology

''Mamenchisaurus'' was originally thought to have ranged from the Middle to Late Jurassic. However, there isn't reliable dating for the Upper Shaximiao Formation, where many of the ''Mamenchisaurus'' species are found. 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. ''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. ''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.


References


External links


Dinosaur.net.cn
(in Chinese and English) {{Taxonbar, from=Q131038 Mamenchisaurids Late Jurassic dinosaurs of Asia Jurassic China Early Cretaceous dinosaurs of Asia Cretaceous China Fossils of China Paleontology in Xinjiang Fossil taxa described in 1954 Taxa named by Yang Zhongjian