Open Paleo

Haplocheirus

Choiniere et al., 2010 HAP-lo-KY-ruhs /ˌhæplʊuˈkəirəs/

Simple hand; from Ancient Greek haplós (simple) and kheír (hand)

165.3–154.8 million years ago Callovian–Oxfordian, Middle Jurassic–Late Jurassic
Middle Jurassic and Late Jurassic stages

Haplocheirus is an extinct genus of theropod dinosaur from the Middle Jurassic Shishugou Formation of Xinjiang in China. It is generally considered to be an alvarezsauroid, although some researchers have questioned this assignment. The genus contains a single species, H. sollers, which is known from a mostly complete skeleton including the skull.

Under dispute

Haplocheirus sollers is recovered as the basalmost alvarezsauroid by the dedicated alvarezsaur analyses (Choiniere and colleagues, 2010, 2014; Xu and colleagues, 2018; Qin and colleagues, 2019; Meso and colleagues, 2024), but its alvarezsauroid affinity is contested. The maniraptoromorph analysis of Hartman and colleagues (2019) recovered it as a compsognathid, and Agnolín and colleagues (2021) argued on cranial evidence that Haplocheirus and the other Jurassic Chinese "alvarezsauroids" resemble ornithomimosaurs and may fall outside Alvarezsauroidea.

Diagnosis

  1. Ventral edge of the distal end of the paroccipital processes twisted posteriorly
  2. Metacarpal III one-half the length of metacarpal II
  3. Dorsally expanded distal end of the jugal process of the maxilla (unique among alvarezsauroids)
  4. Heterodont dentary tooth row with an enlarged tooth in the fourth alveolus
  5. Alveolar margin at the anterior end of the dentary dorsally convex
  6. Maxillary and dentary teeth with serrations on the distal carinae

Species

Haplocheirus sollers Choiniere et al., 2010

Type species

From Latin 'sollers' meaning 'skillful'.

Holotype
IVPP V15988 , Institute of Vertebrate Paleontology and Paleoanthropology
Material
Nearly complete skeleton missing only distal caudal vertebrae and dorsal aspects of ilia.
Horizon
middle Shishugou Formation, Callovian–Oxfordian, Middle Jurassic–Late Jurassic , 165.3–154.8 million years ago
Locality
Wucaiwan, Xinjiang, China Choiniere and colleagues (2010) gave the horizon as "Lower orange mudstone beds in the upper part of the Shishugou Formation"; their 2014 redescription places it in the "Middle beds", between tuffs dated 162.2 and 159.7 Ma, which on the ICS chart v2024/12 straddle the base of the Oxfordian. Qin and colleagues (2019) put it about 40 m above the lower tuff.

References

  1. Choiniere, J. N.; Xu, X.; Clark, J. M.; Forster, C. A.; Guo, Y.; Han, F. (2010). A Basal Alvarezsauroid Theropod from the Early Late Jurassic of Xinjiang, China. Science 327(5965): 571-574. American Association for the Advancement of Science (AAAS). doi:10.1126/science.1182143 choiniere2010a
  2. Choiniere, J. N.; Clark, J. M.; Norell, M. A.; Xu, X. (2014). Cranial osteology of Haplocheirus sollers Choiniere et al., 2010 (Theropoda: Alvarezsauroidea). American Museum Novitates (3816): 1-44. American Museum of Natural History. doi:10.1206/3816.1

    Detailed cranial redescription of the holotype with a revised diagnosis; retracts the second mandibular fenestra as a preservational artifact and adds cranial autapomorphies.

    choiniere2014a
  3. Paul, G. S. (2024). The Princeton Field Guide to Dinosaurs (3rd ed.). Princeton University Press.

    Source of the appearance features.

    paul2024a
  4. 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

    Included Haplocheirus in an alvarezsaurian phylogenetic analysis.

    qin2019a
  5. 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 Haplocheirus as a compsognathid in a maniraptoromorph analysis.

    hartman2019a
  6. 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

    Included Haplocheirus in analysis of early alvarezsaurian forelimb evolution

    xu2018c
  7. Agnolín, F. L.; Lü, J. C.; Kundrát, M.; Xu, L. (2021). Alvarezsaurid osteology: new data on cranial anatomy. Historical Biology 34(3): 443-452. doi:10.1080/08912963.2021.1929203

    Argued on cranial evidence Haplocheirus resembles ornithomimosaurs, possibly falling outside Alvarezsauroidea

    agnolín2021b
  8. 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

    Bearing on the contested alvarezsauroid affinity of Haplocheirus.

    meso2024a