Open Paleo

Mamenchisaurus

Young, 1954 muh-MUN-chee-SOR-uhs, or spelling pronunciation /məˌmʌntʃiˈsɔːrəs/

Named after Mamenchi (a transliteration of the Chinese place name for a ferry crossing, Maming Creek), where the first fossils were found near Yibin, Sichuan, China, combined with Greek 'sauros' (lizard); meaning 'Mamenchi lizard'

161.5–143.1 million years ago Oxfordian–Tithonian, Late Jurassic
Late Jurassic stages

Mamenchisaurus is an extinct genus of sauropod dinosaurs known for their remarkably long necks, which made up nearly half the total body length. Numerous species have been assigned to the genus; however, the validity of these assignments has been questioned. Fossils have been found in the Sichuan Basin and Yunnan Province in China. Several species from the Upper Shaximiao Formation, whose geologic age is uncertain, have been described. However, evidence suggests this formation to be no earlier than the Oxfordian stage of the Late Jurassic. M. sinocanadorum dates to the Oxfordian stage (161.2 to 158.7 mya), and M. anyuensis to the Aptian stage of the Early Cretaceous (around 114.4 mya). Most species were medium-large to large sauropods, measuring roughly 15 to 26 meters (49 to 85 ft) in length-possibly up to 35 meters (115 ft), based on two undescribed vertebrae.

Under dispute

The composition of Mamenchisaurus is unsettled and the genus is poorly defined. Many species and fragmentary specimens have been referred to it over the years, several of them fragmentary and undiagnostic, and repeated analyses have failed to recover the genus as monophyletic (Moore and colleagues, 2020, 2023; Wang and colleagues, 2019). The type species, M. constructus, rests on fragmentary material that yields little character information: Moore and colleagues (2023) recovered no autapomorphies for it, found its phylogenetic position unstable, and regarded the forked mid-caudal chevrons long cited as diagnostic of the genus as possibly an artifact of reconstruction. It frequently falls outside the clade containing the other referred species (Dai and colleagues, 2025). Moore and colleagues (2023) placed M. sinocanadorum outside that clade as well, closest to Xinjiangtitan, but withheld taxonomic action pending a re-evaluation of the type species, and Dai and colleagues (2025) retained the generic name for their new species expressly to avoid further nomenclatural confusion. The referred species also span an implausible interval: Wang and colleagues (2019) dated the upper Suining Formation, the horizon of M. anyuensis, to 114.4 million years, some 30 million years younger than the Late Jurassic species, and called for a total re-evaluation of the genus. Moore and colleagues (2020) likewise failed to recover ZDM 0126 as sister to the M. hochuanensis holotype, casting doubt on that referral.

Diagnosis

  1. Cervical and dorsal vertebrae highly pneumatic and procoelous; cervical vertebrae very large with dorsal neural spines relatively straight and low
  2. Cervical ribs with a pronounced trough-like form and a broad, thin distal end
  3. Dorsal vertebrae with relatively concave lateral surfaces
  4. Anterior six or seven caudal vertebrae deeply procoelous; mid-caudal and posterior caudal vertebrae amphiplatyan
  5. Chevrons of the mid-caudal region markedly bifurcated but not massive, remaining connected above, unlike the open-topped chevrons of Diplodocus

Species (5)

Mamenchisaurus constructus Young, 1954

Type species

From Latin 'constructus' meaning 'constructed' or 'built', chosen because the holotype fossil was discovered during construction work on the Yitang Highway in Sichuan Province, China.

Holotype
IVPP V790 , Institute of Vertebrate Paleontology and Paleoanthropology
Material
Fourteen cervical vertebrae, five dorsal vertebrae, thirty caudal vertebrae with ribs and chevrons, fragmentary ilium, partial right femur, complete right tibia and fibula, right astragalus, and partial right pes.
Horizon
upper Shaximiao Formation, Oxfordian–Tithonian, Late Jurassic , 161.5–143.1 million years ago
Locality
Mamenchi Ferry, Yibin, Sichuan, China

Mamenchisaurus sinocanadorum Russell & Zheng, 1993

From sino- (China) and canad- (Canada) with the Latin genitive plural -orum, for the China-Canada Dinosaur Project that recovered the holotype.

Holotype
IVPP V10603 , Institute of Vertebrate Paleontology and Paleoanthropology
Material
Partial skull (left vomer, right pterygoid, possible ectopterygoid, right quadrate), right dentary and complete left mandible; partial cervical vertebrae 2–4; a nearly intact left cervical rib
Horizon
upper Shishugou Formation, Callovian–Oxfordian, Middle Jurassic–Late Jurassic , 165.3–154.8 million years ago
Locality
22 km north of Jiangjunmiao, Xinjiang, China Moore and colleagues (2023) place the holotype 3 m above a tuff at Jiangjunmiao that is probably equivalent to the T-1 tuff at Wucaiwan, making it "no older than 162.4 Ma", a floor below the base of the Oxfordian on the ICS chart v2024/12.
Diagnosis
  1. Exceptionally elongate external mandibular fenestra (length:height ratio in lateral view of 3.7)
  2. Ventral surface of the axis bears a deep, trough-like depression containing several pneumatic foramina anteriorly
  3. Large, irregularly developed, paramedian pneumatic foramina flush with the surrounding ventral surface of cervical vertebra 3
  4. Parallel-sided tooth crowns in labial view combined with a distolingual boss on some dentary teeth
  5. Anterior surangular foramen at least twice as large in greatest diameter as the posterior surangular foramen
  6. Essentially straight axial spinopostzygapophyseal lamina combined with a relatively low neural spine (neural spine:neural arch height ratio <0.45)

Mamenchisaurus hochuanensis Young & Zhao, 1972

Named for Hechuan (Hochuan) County, Sichuan, China, where the holotype was discovered

Holotype
CCG V 20401 , Chengdu University of Technology
Material
Nearly complete vertebral column (cervical-caudal series), ilium, ischium, partial pubis, tibia, fibula, right distal femur, astragali, partial pes, fragmentary sternum, and proximal humerus
Horizon
upper Shaximiao Formation, Oxfordian–Tithonian, Late Jurassic , 161.5–143.1 million years ago
Locality
Mt. Gushushan, Sichuan, China
Diagnosis
  1. 19 cervical vertebrae, more numerous than in other known species of the genus
  2. Cervical ribs bear dagger-shaped rib heads, unlike the spoon-shaped heads of the type species
  3. Anterior three sacral neural spines fused, unlike the unfused condition in the type species
  4. 16 anterior caudal vertebrae procoelous, more than in the type species
  5. Astragalus relatively low, compared to a higher astragalus in the type species

Mamenchisaurus youngi Pi et al., 1996

Honors C. C. Young, the Chinese vertebrate paleontologist.

Holotype
ZDM 0083 , Zigong Dinosaur Museum
Material
Nearly complete skeleton with skull; presacral through eighth caudal vertebrae articulated; pectoral girdle, pelvic girdle, and all four limbs nearly complete and in articulation
Horizon
upper Shaximiao Formation, Oxfordian–Tithonian, Late Jurassic , 161.5–143.1 million years ago
Locality
Xinmin, Zigong, Sichuan, China
Diagnosis
  1. About two-thirds the size of M. hochuanensis, with 30 presacral vertebrae (vs. 32) and 5 sacral vertebrae (vs. 4).
  2. Cervicals only moderately elongated; longest cervical about twice the longest dorsal, versus more than three times in M. hochuanensis.
  3. Mid-series cervical rib capitula bifurcated and dorsal pleurocoels well developed, versus dagger-shaped capitula and poorly developed pleurocoels in M. hochuanensis.
  4. Tibia longer than fibula, lacking an expanded distal end and without the distomedial fibular inflation seen in M. constructus.
  5. Cervical ribs slender and elongated, versus relatively short in M. constructus.
  6. Axis/third cervical vertebra length index of 1.4 (vs. 1.71 in M. sinocanadorum); mandibular dentition of 22-24 teeth exceeds the Xinjiang specimen's count.

Mamenchisaurus sanjiangensis Dai et al., 2025

From Chinese Pinyin 'sanjiang' (three rivers), for the type locality at the confluence of the Jialing, Fu, and Qu Rivers in Hechuan District.

Holotype
CIP V0001 , Chongqing Institute of Paleontology
Material
Two cervical vertebrae, twelve dorsal vertebrae, five sacral vertebrae, four caudal vertebrae, left and right ilia, pubes and ischia, and the left femur, tibia, and fibula.
Horizon
upper Shaximiao Formation, Oxfordian, Late Jurassic , 161.5–154.8 million years ago
Locality
Hechuan District, Chongqing, China
Diagnosis
  1. Additional fossa on the base of the prezygodiapophyseal lamina of the posterior cervical and anterior dorsal vertebrae (autapomorphy)
  2. Accessory lamina extending from the prezygapophysis to the diapophysis on the anterior dorsal vertebrae (autapomorphy)
  3. Several accessory laminae divide the spinodiapophyseal fossa of the dorsal vertebrae, and the spinodiapophyseal lamina is bifurcated dorsally from the third to seventh dorsal, the two branches forming the lateral margins of a secondary deep fossa (autapomorphy)
  4. Epipophyseal-prezygapophyseal lamina preserved on the posterior cervical and anterior dorsal vertebrae
  5. Height of the neural arch relative to the posterior centrum articular surface increases prominently from the anterior to the posterior dorsal series
  6. Five sacral vertebrae completely fused, the distal portion of the neural spines platform-shaped, with lateral excavation on the sacrals
  7. Dorsal margin of the ilium semicircular; femoral head dorsoventrally projected, with a transverse width to anteroposterior length ratio of about 2.6 at the femoral mid-shaft

Notable specimens

  • ZDM0126

    Zigong Dinosaur Museum Found 1995 complementary

    Nearly complete, mostly articulated specimen referred to M. hochuanensis that preserves the skull, pectoral girdle, and forelimb material missing from the holotype. It uniquely shows four fused distal caudal vertebrae possibly forming a tail club. A 2020 analysis cast doubt on its referral.

    Xing et al. (2009)Moore et al. (2020)

References

  1. Young, C. C. (1954). On a new sauropod from Yiping, Szechuan, China. Acta Paleontologica Sinica 2(4): 355-369.

    Original description of Mamenchisaurus constructus on the holotype IVPP V790; source of the genus diagnosis.

    young1954a
  2. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Sauropods. Princeton University Press.

    Source of the hip height estimate, and the appearance features.

    jones2026b
  3. Xing, L.; Ye, Y.; Shu, C.; Peng, G.; You, H. (2009). Structure, orientation and finite element analysis of the tail club of Mamenchisaurus hochuanensis. Acta Geologica Sinica (English Edition) 83(6): 1031-1040. doi:10.1111/j.1755-6724.2009.00134.x xing2009a
  4. Moore, A. J.; Upchurch, P.; Barrett, P. M.; Clark, J. M.; Xu, X. (2020). Osteology of Klamelisaurus gobiensis (Dinosauria, Eusauropoda) and the evolutionary history of Middle-Late Jurassic Chinese sauropods. Journal of Systematic Palaeontology 18(16): 1299-1393. doi:10.1080/14772019.2020.1759706 moore2020a
  5. Moore, A. J.; Barrett, P. M.; Upchurch, P.; Liao, C. C.; Ye, Y.; Hao, B.; Xu, X. (2023). Re-assessment of the Late Jurassic eusauropod Mamenchisaurus sinocanadorum Russell and Zheng, 1993, and the evolution of exceptionally long necks in mamenchisaurids. Journal of Systematic Palaeontology 21(1). doi:10.1080/14772019.2023.2171818

    Re-assessment of M. sinocanadorum on holotype IVPP V10603; recovers Mamenchisaurus as non-monophyletic but withholds taxonomic action pending re-evaluation of the type species.

    moore2023a
  6. Russell, D. A.; Zheng, Z. (1993). A large mamenchisaurid from the Junggar Basin, Xinjiang, People's Republic of China. Canadian Journal of Earth Sciences 30(10-11): 2082-2095. Canadian Science Publishing. doi:10.1139/e93-180

    Erects Mamenchisaurus sinocanadorum on holotype IVPP V10603 from the Shishugou Formation of Xinjiang.

    russell1993c
  7. Young, C. C.; Zhao, X. (1972). Mamenchisaurus hochuanensis sp. nov. Institute of Vertebrate Palaeontology and Palaeoanthropology Monographs, Series A 8: 1-30.

    Erects Mamenchisaurus hochuanensis on holotype CCG V 20401 from the Shaximiao Formation of Sichuan.

    young1972a
  8. Pi, L.; Ou, Y.; Ye, Y. (1996). A new species of sauropod from Zigong, Sichuan, Mamenchisaurus youngi. Papers on Geosciences Contributed to the 30th International Geological Congress 87-91.

    Erects Mamenchisaurus youngi on holotype ZDM 0083 from the Shaximiao Formation of Zigong, Sichuan.

    pi1996a
  9. Wang, J.; Norell, M. A.; Pei, R.; Ye, Y.; Chang, S. C. (2019). Surprisingly young age for the mamenchisaurid sauropods in South China. Cretaceous Research 104: 104176. Elsevier BV. doi:10.1016/j.cretres.2019.07.006

    Dates the upper Suining Formation, the horizon of M. anyuensis, to 114.4 million years, some 30 million years younger than the Late Jurassic species of the genus.

    wang2019c
  10. Dai, H.; Hu, X. F.; Tan, C.; Ren, X. X.; Ma, Q. Y.; Wei, G. B.; You, H. L. (2025). A new mamenchisaurid sauropod dinosaur from the Upper Jurassic of Southwest China reveals new evolutionary evidence from East Asian eusauropods. Scientific Reports 15(1). Springer Science and Business Media LLC. doi:10.1038/s41598-025-29995-z

    Erects Mamenchisaurus sanjiangensis on holotype CIP V0001 from the Shaximiao Formation of Chongqing; retains the generic name to avoid further nomenclatural confusion.

    dai2025b