Lijiangosaurus, new long-necked sauropterygian from Middle Triassic of China (free pdf)

[Ben Creisler]

Ben Creisler

bcre...@gmail.com

A new paper:

Free pdf:

Lijiangosaurus yongshengensis gen. et sp. nov.

Wei Wang, Qinghua Shang, Jiansheng Wang, Hongke Zi & Chun Li (2025)
Earliest long-necked sauropterygian Lijiangosaurus yongshengensis and plasticity of vertebral evolution in sauropterygian marine reptiles
Communications Biology 8: 1551
doi: https://doi.org/10.1038/s42003-025-08911-1
https://www.nature.com/articles/s42003-025-08911-1


A long neck is a morphological innovation in vertebrates, particularly iconic in many plesiosaurs, while the function of these long necks in plesiosaurs remains controversial. Here, we report Lijiangosaurus yongshengensis gen. et sp. nov. from a previously unknown early Middle Triassic locality in southwestern China. This taxon represents the earliest known sauropterygian evolving an exceptionally long neck with 42 cervical vertebrae, and is identified as a nothosaur rather than the immediate ancestors of plesiosaurs. Our discovery demonstrates that extreme cervical elongation developing more than 30 cervical vertebrae emerged in sauropterygians prior to the rise of plesiosaurs and their pistosaur ancestors. Furthermore, Lijiangosaurus possesses a unique type of accessory intervertebral articulation compared with other reptiles, and we attribute this structure to reducing body undulation. This discovery increases the known diversity of accessory intervertebral articulations in reptiles, and underscores the high plasticity of the vertebral column in the early evolution of sauropterygians.

[Mickey Mortimer]

This paper has a good example of how NOT to formulate a phylogenetic definition. Wang et al. write "Emended definition. Referred to the phylogenetic hypotheses recovered in this paper, the maximum clade definition of Nothosauria is reformulated as follows: all taxa more closely related to Brevicaudosaurus jiyangshanensis, Germanosaurus schafferi, and Nothosaurus species than Keichousaurus hui, Simosaurus gaillardoti, or Corosaurus alcovensis."

And here's their phylogeny-
https://media.springernature.com/full/springer-static/image/art%3A10.1038%2Fs42003-025-08911-1/MediaObjects/42003_2025_8911_Fig3_HTML.png

But why include Brevicaudosaurus and Germanosaurus at all? As the earliest diverging nothosaurs, they have the biggest chance to fall outside the clade in some other analysis and then their definition would be broken. This is actually the case for both of those genera in Liu et al. (2025), where Germanosaurus is closer to Corosaurus than to Nothosaurus, and Nothosaurus is closer to both of those than to Brevicaudosaurus. But if you just use "Nothosaurus mirabilis <- Keichousaurus hui, Simosaurus gaillardoti, Corosaurus alcovensis", Nothosauria works in both Wang et al.'s and Liu et al.'s topologies.

Reference-  Liu, Qiling; Cheng, Long; Stubbs, Thomas L.; Fang, Zichen; Tian, Li; Yan, Chunbo; Benton, Michael J. (2025-09-16). "Ontogenetic dietary partitioning in a Triassic sauropterygian: implications from a new juvenile specimen of Brevicaudosaurus jiyangshanensis (Reptilia: Diapsida)". Zoological Journal of the Linnean Society. 205 (1). doi:10.1093/zoolinnean/zlaf126

Mickey Mortimer