Mamenchisauridae is a family of sauropod 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.
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.
[Young, C.C. and Zhao, X. (1972). " Mamenchisaurus hochuanensis sp. nov.". Institute of Vertebrate Palaeontology and Palaeoanthropology Monographs Series A 8: 1-30.]
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 , as relatives of mamenchisaurids, mirroring earlier conceptions about the family.
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:
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 , reached sexual maturity at 20 years and died at age 31.
[Griebeler EM, Klein N, Sander PM (2013) Aging, Maturation and Growth of Sauropodomorph Dinosaurs as Deduced from Growth Curves Using Long Bone Histological Data: An Assessment of Methodological Constraints and Solutions. PLoS ONE 8(6): e67012. doi:10.1371/journal.pone.0067012]
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.
Fossils of
Tonganosaurus date to even earlier, from the (
Pliensbachian) Early Jurassic.
The Tendaguru Formation taxon
Wamweracaudia from Tanzania extends the geographic distribution of Mamenchisauridae into Africa,
while fossil remains from the
Itat Formation in Russia suggest they also reached Siberia.
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.
Sources
