Paleontologists have identified a new species of sauropod dinosaur, Mamenchisaurus sanjiangensis, from a partial skeleton discovered near Chongqing in southwest China, a find that sheds fresh light on sauropod evolution in East Asia.
The dinosaur lived during the Early Oxfordian age of the Jurassic, around 160 million years ago. The bones were recovered from purplish‑red silty mudstones in the middle portion of the Upper Shaximiao Formation, a well-known fossil‑bearing stratum of that region.
Despite being known only from a single partial skeleton, the researchers classify M. sanjiangensis as a “diverged mamenchisaurid,” closely related to other species within the Mamenchisaurus genus. According to the study’s lead author Hui Dai and colleagues at the Chongqing Institute of Paleontology, this discovery underscores a peak in sauropod diversity during the Late Jurassic, when many non‑neosauropodan eusauropod lineages, like the mamenchisaurids, thrived globally alongside emerging neosauropods.
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The dominance of mamenchisaurids in Late Jurassic Asian fossil records appears markedly different from the sauropod faunas of contemporaneous European, North- and South-American formations. This suggests that Asia, particularly what is now southwestern China, was a hotspot for sauropod diversity, especially near the middle-late Jurassic transition.
Beyond enriching the taxonomy of early-diverging sauropods, M. sanjiangensis provides critical data for reconstructing the evolutionary history and paleobiogeography of Jurassic‑era eusauropods in East Asia. The authors note, however, that many gaps remain in the fossil record, and further reexamination of existing specimens is needed to better understand the early branching events that shaped sauropod evolution across ancient continents.
The findings were published on November 25, 2025 in the journal Scientific Reports
