Open Paleo

Yunnanosaurus

Young, 1940 yoo-NAN-oh-SOR-uhs /juːˌnænoʊˈsɔːrəs/

Named for Yunnan Province, China, where the fossils were found, combined with Greek 'sauros' meaning 'lizard'.

201.4–192.9 million years ago Hettangian–Sinemurian, Early Jurassic
Early Jurassic stages

Yunnanosaurus is an extinct genus of sauropodomorph dinosaur that lived approximately 199 to 183 million years ago in what is now the Yunnan Province, in China, for which it was named. Yunnanosaurus was a large sized, moderately-built, ground-dwelling, quadrupedal herbivore, that could also walk bipedally, and ranged in size from 7 meters (23 feet) long and 2 m (6.5 ft) high to 4 m (13 ft) high in the largest species.

Under dispute

Yunnanosaurus huangi is most commonly recovered among non-sauropodan sauropodiforms: Sekiya and colleagues (2013) recovered the Yunnanosaurus clade as the sister taxon of Sauropoda, and Zhang and colleagues (2018) treated it among the uncontroversial non-sauropodan sauropodomorphs of the Lufeng Basin. Rauhut and colleagues (2020) instead recovered it within Massospondylidae, in a subclade with Jingshanosaurus and Seitaad.

Diagnosis

  1. Small external naris, about 10% of maximum skull length
  2. Robust, rostrocaudally expanded nasal process of the premaxilla
  3. Ventral projection from the caudal margin of the ascending maxillary process
  4. Nutritive foramina absent from the lateral surface of the maxilla
  5. Shallow, subcircular fossa on the lateral surface of the ventral lachrymal process
  6. Midline boss near the rostral end of the frontals
  7. Prominent midline boss on the parietals
  8. Rostrolateral process of the parietal rostrocaudally expanded relative to the width of the caudolateral process
  9. Maxillary teeth mesiodistally narrow and lacking denticles

Species (2)

Yunnanosaurus huangi Young, 1940

Type species

Named for Huang Chiching (T.K. Huang), the director of the National Geological Survey of China at the time the species was described.

Holotype
NGMJ 004546 , Nanjing Geological Museum
Formerly
V 20 (renumbered)NGMJ V0116 (renumbered)
Material
Almost complete skeleton with skull, atlas and axis, further cervical, dorsal and caudal vertebrae, haemal arches, left scapula, sternum, both humeri, right ulna, partial left manus, pelvic girdle, hindlimbs and two metatarsals
Horizon
Zhangjiawa Member, Lufeng Formation, Hettangian–Sinemurian, Early Jurassic , 201.4–192.9 million years ago
Locality
Huangchiatien, Yunnan, China Barrett and colleagues (2007) give the Dark Red Beds of the Lower Lufeng Formation, which Norman and colleagues (2007) and Zhang and colleagues (2018) equate with the Zhangjiawa Member.

Yunnanosaurus youngi Lü et al., 2007

Honors Professor C. C. Young, who first studied the Lufeng Basin dinosaurs and erected the family Yunnanosauridae.

Holotype
CXMVZA 185 , Chuxiong Prefectural Museum
Material
Partial postcranial skeleton: 10 cervical, 14 dorsal, 3 fused sacral, 17 caudal vertebrae, both pubes, ischia, and right ilium; no skull, pectoral girdle, forelimbs, or hindlimbs.
Horizon
Zhanghe Formation, Bajocian–Bathonian, Middle Jurassic , 170.9–165.3 million years ago
Locality
Banqing Houshanliangzi, Jiangyi, Yunnan, China
Diagnosis
  1. Sixth cervical vertebra the longest in the vertebral column.
  2. Neural spines of the posterior cervical vertebrae short, with an expanded distal end wider than its anteroposterior length.
  3. Three sacral vertebrae tightly fused, with a stout sacrocostal yoke contacting the inner surface of the ilium.
  4. Ventral margin of the postacetabular process of the ilium slightly concave (reversed V-shaped in Y. huangi).
  5. Ischium longer than the pubis, the latter with a rounded distal end (pubis longer than ischium in Y. huangi).

Notable specimens

  • ZMNH-M8739

    Zhejiang Museum of Natural History ontogeny

    Juvenile referred to Yunnanosaurus robustus with partial cranial material and an almost complete postcranial skeleton; comparison with adult Y. huangi reveals very distinctive growth changes and characteristic dentition suggesting a potentially unique feeding mechanism.

    Sekiya et al. (2013)

References

  1. Young, C. C. (1940). Preliminary notes on the Lufeng vertebrate fossils. Bulletin of the Geological Society of China 20(3-4): 235-239. doi:10.1111/j.1755-6724.1940.mp203-4003.x young1940a
  2. Sekiya, T.; Jin, X.; Zheng, W.; Shibata, M.; Azuma, Y. (2013). A new juvenile specimen of Yunnanosaurus robustus (Dinosauria: Sauropodomorpha) from Early to Middle Jurassic of Chuxiong Autonomous Prefecture, Yunnan Province, China. Historical Biology 26(2): 252-277. doi:10.1080/08912963.2013.821702

    Recovered the Yunnanosaurus clade as the sister taxon of Sauropoda.

    sekiya2013a
  3. Zhang, Q. N.; You, H. L.; Wang, T.; Chatterjee, S. (2018). A new sauropodiform dinosaur with a 'sauropodan' skull from the Lower Jurassic Lufeng Formation of Yunnan Province, China. Scientific Reports 8(1). Springer Science and Business Media LLC. doi:10.1038/s41598-018-31874-9

    Treated Yunnanosaurus among the uncontroversial non-sauropodan sauropodomorphs of the Lufeng Basin.

    zhang2018a
  4. Rauhut, O. W. M.; Holwerda, F. M.; Furrer, H. (2020). A derived sauropodiform dinosaur and other sauropodomorph material from the Late Triassic of Canton Schaffhausen, Switzerland. Swiss Journal of Geosciences 113(1). Pensoft Publishers. doi:10.1186/s00015-020-00360-8

    Recovered Yunnanosaurus within Massospondylidae, in a subclade with Jingshanosaurus and Seitaad.

    rauhut2020a
  5. Paul, G. S. (2024). The Princeton Field Guide to Dinosaurs (3rd ed.). Princeton University Press.

    Source of the mass estimate.

    paul2024a
  6. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Sauropods. Princeton University Press.

    Treats Yunnanosaurus as near the base of Sauropodiformes.

    jones2026b
  7. Lü, J.; Li, T.; Zhong, S.; Azuma, Y.; Fujita, M.; Dong, Z.; Ji, Q. (2007). New yunnanosaurid dinosaur (Dinosauria, Prosauropoda) from the Middle Jurassic Zhanghe Formation of Yuanmou, Yunnan Province of China. Memoir of the Fukui Prefectural Dinosaur Museum 6: 1-15.

    Erects Yunnanosaurus youngi on skeleton CXMVZA 185 from the Middle Jurassic Zhanghe Formation of Yuanmou, Yunnan.

    lü2007d
  8. Zhang, Q. N.; Jia, L.; Wang, T.; Zhang, Y. G.; You, H. L. (2024). The largest sauropodomorph skull from the Lower Jurassic Lufeng Formation of China. PeerJ 12: e18629. PeerJ. doi:10.7717/peerj.18629 zhang2024a
  9. Barrett, P. M.; Upchurch, P.; Zhou, X. D.; Wang, X. L. (2007). The skull of Yunnanosaurus huangi Young, 1942 (Dinosauria: Prosauropoda) from the Lower Lufeng Formation (Lower Jurassic) of Yunnan, China. Zoological Journal of the Linnean Society 150(2): 319-341. doi:10.1111/j.1096-3642.2007.00290.x

    Redescribes the holotype skull and emends the diagnosis on cranial characters alone. Gives the type locality as Huangchiatien village, in the Dark Red Beds of the Lower Lufeng Formation.

    barrett2007a
  10. Young, C. C. (1942). Yunnanosaurus huangi Young (gen. et sp. nov.), a New Prosauropoda from the Red Beds at Lufeng, Yunnan. Bulletin of the Geological Society of China 22(1-2): 63-104. Wiley. doi:10.1111/j.1755-6724.1942.mp221-2005.x

    Young's full description of the genus and species, which later work cites as the original description.

    young1942b
  11. Norman, D. B.; Butler, R. J.; Maidment, S. C. R. (2007). Reconsidering the status and affinities of the ornithischian dinosaur Tatisaurus oehleri Simmons, 1965. Zoological Journal of the Linnean Society 150(4): 865-874. doi:10.1111/j.1096-3642.2007.00301.x

    Records that the Dull Purplish Beds and Dark Red Beds were formally designated the Shawan and Zhangjiawa members.

    norman2007a