Mamenchisauridae is a family of sauropod dinosaurs belonging to Eusauropoda known from the Jurassic and Early Cretaceous of Asia and Africa.

Notably, some iterations of their analysis recover Euhelopus and kin, usually considered somphospondylians, as relatives of mamenchisaurids, mirroring earlier conceptions about the family.

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.

[7] 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.