Mamenchisauridae

Mamenchisauridae is a family of sauropod dinosaurs belonging to the Eusauropoda known from the Jurassic and Early Cretaceous of Asia and Africa. Mamenchisaurids are characterized by their proportionately extremely long necks. Some members of the group reached gigantic sizes, amongst the largest of all sauropods.^[1]

Mamenchisauridae Temporal range: 184.5–114 Ma PreꞒ Ꞓ O S D C P T J K Pg N Possible Albian record
Mounted skeleton of Mamenchisaurus hochuanensis
Mounted skeleton of Omeisaurus tianfuensis
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Sarcopterygii
Clade:	Tetrapodomorpha
Clade:	Dinosauria
Clade:	Saurischia
Clade:	†Sauropodomorpha
Clade:	†Sauropoda
Clade:	†Eusauropoda
Family:	†Mamenchisauridae Young and Zhao, 1972
Genera
†Analong †Anhuilong †Chuanjiesaurus †Eomamenchisaurus †Huangshanlong †Hudiesaurus †Jingiella †Klamelisaurus †Mamenchisaurus †Omeisaurus †Qijianglong †Rhomaleopakhus †Tienshanosaurus †Tonganosaurus †Tongnanlong †Wamweracaudia †Xinjiangtitan †Yuanmousaurus †Zigongosaurus Possible mamenchisaurids †Bellusaurus †Daanosaurus †Datousaurus †Rhoetosaurus †Spinophorosaurus
Synonyms
Omeisauridae Wilson, 2002

Classification

The family Mamenchisauridae was first erected by Chinese paleontologists Yang Zhongjian ("C.C. Young") and Zhao Xijin in 1972, in a paper describing Mamenchisaurus hochuanensis.^[2]

A comprehensive analysis of Mamenchisauridae was presented by Moore et al., 2020, including several named species. Notably, some iterations of their analyses recovered Euhelopus and kin, usually considered somphospondylians, as relatives of mamenchisaurids, mirroring earlier conceptions about the family.^[3]

The 2023 redescription of Mamenchisaurus sinocanadorum incorporated updated versions of a matrix from Moore et al. (2020). These results are displayed in the cladogram below:^[4]

Mamenchisauridae	Tienshanosaurus Omeisaurus junghsiensis Wamweracaudia Qijianglong Mamenchisaurus constructus Bellusaurus Rhomaleopakhus Chuanjiesaurus Analong Mamenchisaurus youngi Mamenchisaurus hochuanensis (holotype) Shishugou cervicodorsals Phu Krandung taxon Klamelisaurus Mamenchisaurus sinocanadorum Xinjiangtitan Hudiesaurus Daanosaurus Mamenchisaurus hochuanensis (referred)

Paleobiology

Long-bone histology enables researchers to estimate the age that a specific individual reached. A study by Griebeler et al. (2013) examined long bone histological data and concluded that the unnamed mamenchisaurid SGP 2006/9 weighed 25,075 kilograms (27.6 short tons), reached sexual maturity at 20 years and died at age 31.^[5]

Paleoecology

Fossils of Mamenchisaurus and Omeisaurus have been found in the Shaximiao Formation, dating to the Oxfordian-Tithonian interval, around 159-150 Ma (million years ago). Chuanjiesaurus fossils date between 166.1 and 163.5 Ma, while those of Eomamenchisaurus were found in the Zhanghe Formation, believed to be around 175.6-161.2 million years old.^[6] Fossils of Tonganosaurus date to even earlier, from the (Pliensbachian) Early Jurassic.^[7] The Tendaguru Formation taxon Wamweracaudia from Tanzania extends the geographic distribution of Mamenchisauridae into Africa,^[8] while fossil remains from the Itat Formation in Russia suggest they also reached Siberia.^[9] Additionally, an indeterminate cervical vertebra from the Phu Kradung Formation of Thailand demonstrates survival of Mamenchisauridae into the Cretaceous combined with new radiometric dates for the Suining Formation that has yielded fossils of Mamenchisaurus anyuensis.^[10][11]