Open Paleo

Aorun

Choiniere et al., 2013 AW-roon

From Mandarin Chinese, a shortened masculine name of Ao Run, the Chinese mythical deity and Dragon King of the West Sea in the epic Journey to the West. The species name honors Professor Zhao Xijin.

165.3–161.5 million years ago Callovian, Middle Jurassic
Middle Jurassic stages

Aorun (敖闰 pinyin Áo rùn) is a genus of carnivorous theropod dinosaur first discovered in 2006, with its scientific description published in 2013. It is generally considered one of the oldest known coelurosaurian dinosaurs and is estimated to have lived ~161.6 million years ago during the Late Jurassic Period, though some researchers consider it to be a carnosaurian instead.

Under dispute

Aorun zhaoi is based on a juvenile skeleton, and its affinities are highly unstable. It was originally described as a basal coelurosaur (Choiniere and colleagues, 2013) and recovered as an early-diverging alvarezsaurian by Xu and colleagues (2018), Qin and colleagues (2019), and — with weak support — Meso and colleagues (2024). Broad theropod analyses reject this: Hartman and colleagues (2019) recovered it as a compsognathid, and Cau (2024) recovered it as an early-diverging allosauroid, interpreting its coelurosaurian signal as an artifact of the holotype's juvenile ontogeny. Jones (2026) treats it as a basal coelurosaur.

Diagnosis

  1. Large maxillary fenestra occupying most of the antorbital fossa
  2. Maxillary teeth with very small, apically directed serrations restricted to the distal carinae
  3. Weakly opisthocoelous cervical centra
  4. Heterogeneous manual ungual morphology: large, recurved medial ungual and two smaller lateral unguals with linear (not curved) ventral surfaces
  5. Tibia with mediolaterally narrow, proximodistally tall articular groove for ascending process of astragalus developed only on anterolateral margin
  6. Ascending process of astragalus low and restricted to lateral side of tibia

Species

Aorun zhaoi Choiniere et al., 2013

Type species

Named for Professor Zhao Xijin, who led several important vertebrate paleontological expeditions to the Junggar Basin.

Holotype
IVPP V15709 , Institute of Vertebrate Paleontology and Paleoanthropology
Material
Skull and partially articulated skeleton: cervical, dorsal and caudal vertebrae, left ulna, left manus, distal pubes, articulated left and right tibiotarsi, metatarsi and pedes
Horizon
lower Shishugou Formation, Callovian, Middle Jurassic , 165.3–161.5 million years ago
Locality
Wucaiwan, Xinjiang, China

References

  1. Choiniere, J. N.; Clark, J. M.; Forster, C. A.; Norell, M. A.; Eberth, D. A.; Erickson, G. M.; Chu, H.; Xu, X. (2013). A juvenile specimen of a new coelurosaur (Dinosauria: Theropoda) from the Middle-Late Jurassic Shishugou Formation of Xinjiang, People's Republic of China. Journal of Systematic Palaeontology 12(2): 177-215. Informa UK Limited. doi:10.1080/14772019.2013.781067 choiniere2013a
  2. Cau, A. (2024). A Unified Framework for Predatory Dinosaur Macroevolution. Bollettino della Società Paleontologica Italiana 63(1): 1-19. doi:10.4435/BSPI.2024.08

    Recovered Aorun as an early-diverging allosauroid, reading its coelurosaurian signal as a juvenile-ontogeny artifact.

    cau2024a
  3. Qin, Z.; Clark, J.; Choiniere, J.; Xu, X. (2019). A new alvarezsaurian theropod from the Upper Jurassic Shishugou Formation of western China. Scientific Reports 9(1). Springer Science and Business Media LLC. doi:10.1038/s41598-019-48148-7

    New alvarezsaurian description recovering Aorun consistent with earlier alvarezsauroid placement.

    qin2019a
  4. Hartman, S.; Mortimer, M.; Wahl, W. R.; Lomax, D. R.; Lippincott, J.; Lovelace, D. M. (2019). A new paravian dinosaur from the Late Jurassic of North America supports a late acquisition of avian flight. PeerJ 7: e7247. PeerJ. doi:10.7717/peerj.7247

    Recovered Aorun as a compsognathid rather than an alvarezsauroid.

    hartman2019a
  5. Xu, X.; Choiniere, J.; Tan, Q.; Benson, R. B. J.; Clark, J.; Sullivan, C.; Zhao, Q.; Han, F.; Ma, Q.; He, Y.; Wang, S.; Xing, H.; Tan, L. (2018). Two Early Cretaceous Fossils Document Transitional Stages in Alvarezsaurian Dinosaur Evolution. Current Biology 28(17): 2853-2860.e3. Elsevier BV. doi:10.1016/j.cub.2018.07.057

    Recovered Aorun as an early-diverging alvarezsaurian theropod

    xu2018c
  6. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Theropods. Princeton University Press.

    Reports alvarezsauroid, basal coelurosaur and compsognathid placements for Aorun.

    jones2026c
  7. Meso, J. G.; Pol, D.; Chiappe, L.; Qin, Z.; Díaz-Martínez, I.; Gianechini, F.; Apesteguía, S.; Makovicky, P. J.; Pittman, M. (2024). Body size and evolutionary rate analyses reveal complex evolutionary history of Alvarezsauria. Cladistics 41(2): 135-155. Wiley. doi:10.1111/cla.12600

    Included Aorun in its analysis of alvarezsaurian relationships.

    meso2024a