Open Paleo

Yuxisaurus

Yao et al., 2022 YOO-she-SOR-us

Named after Yuxi, a city in Yunnan Province, China (the type locality), combined with Greek sauros ('lizard'), meaning 'Yuxi lizard'

192.9–184.2 million years ago Pliensbachian, Early Jurassic
Early Jurassic stages

Yuxisaurus is an extinct genus of early thyreophoran dinosaur from the Early Jurassic (Sinemurian-Toarcian) Fengjiahe Formation of southwestern China. The genus contains a single species, Yuxisaurus kopchicki, known from a partial skeleton and many osteoderms.

Diagnosis

  1. Deep, subtriangular, dorsoventrally elongated depression on either side of the nuchal crest
  2. V-shaped notch on the dorsal margin of the paroccipital process
  3. Basal tubera considerably ventrally offset with respect to the occipital condyle, clearly visible in posterior view
  4. Basipterygoid processes ventrally offset with respect to the basal tubera, creating a dorsoventrally deep, stepped basicranial profile in lateral view
  5. Cultriform process ventrally offset with respect to the occipital condyle in lateral view
  6. Angular with elongate, dorsally deflected posterior process that almost reaches the posterior margin of the retroarticular process
  7. Atlas intercentrum with symmetrical anterolaterally directed low ridges and associated arrow-like depressions on its ventral surface
  8. Relatively short anterior cervical centra (length/height ratio less than 1.5)
  9. Cervical centra lack ventral keels
  10. Border of the medial condyle of the distal femur invaginated to form a broad, U-shaped trough

Species

Yuxisaurus kopchicki Yao et al., 2022

Type species

Named for John J. Kopchick, a biologist honored by the describers of the genus.

Holotype
CVEB 21701 , Centre for Vertebrate Evolutionary Biology, Yunnan University
Material
Partial skeleton with cranial and associated postcranial elements including skull bones (maxilla, lacrimal, nasal, prefrontal, jugal, supraorbitals), braincase, partial skull roof, hemimandible fragments, four cervical and five dorsal vertebrae, scapulae, humerus, femur, and more than 120 osteoderms
Horizon
upper Fengjiahe Formation, Pliensbachian, Early Jurassic , 192.9–184.2 million years ago
Locality
Jiaojiadian village, Yunnan, China

References

  1. Yao, X.; Barrett, P. M.; Yang, L.; Xu, X.; Bi, S. D. (2022). A new early branching armored dinosaur from the Lower Jurassic of southwestern China. eLife 11: e75248:1-37. doi:10.7554/eLife.75248

    Named Yuxisaurus and recovered it as an early-diverging thyreophoran near Emausaurus, outside Eurypoda.

    yao2022a
  2. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Ornithischians. Princeton University Press.

    Treats Yuxisaurus as an early-diverging thyreophoran.

    jones2026a
  3. Fonseca, A. O.; Reid, I. J.; Venner, A.; Duncan, R. J.; Garcia, M. S.; Müller, R. T. (2024). A comprehensive phylogenetic analysis on early ornithischian evolution. Journal of Systematic Palaeontology 22: 2346577. doi:10.1080/14772019.2024.2346577

    Recovered Yuxisaurus outside Eurypoda.

    fonseca2024a
  4. Sánchez-Fenollosa, S.; Cobos, A. (2025). New insights into the phylogeny and skull evolution of stegosaurian dinosaurs: an extraordinary cranium from the European Late Jurassic (Dinosauria: Stegosauria). Vertebrate Zoology 75: 165-189. doi:10.3897/vz.75.e146618

    Recovered Yuxisaurus outside Eurypoda.

    sánchez-fenollosa2025a