Open Paleo

Scansoriopterygidae

Czerkas & Yuan, 2002 Type genus Scansoriopteryx

Its genera lived 168.2–121.4 million years ago Middle Jurassic–Early Cretaceous

Scansoriopterygidae is a family of small, unusual maniraptoran theropod dinosaurs from the Middle to Late Jurassic of China, known from a handful of well-preserved fossils recovered from the Tiaojishan Formation of Liaoning and Hebei. The group includes Scansoriopteryx, Epidexipteryx, Ambopteryx, and Yi, and counts among the smallest non-avian dinosaurs known. Its members are set apart by an extremely long third finger, longer than the first and second digits, the reverse of the usual theropod hand in which the second finger is longest. In at least Yi and Ambopteryx, this elongated finger paired with a long styliform bone at the wrist to support a bat-like membranous wing used for gliding, making scansoriopterygids the only known dinosaurs to develop true membranous wings. They also share short, deep skulls with down-turned jaws and large front teeth, long arms, and a body covering of simple feathers. Their placement among coelurosaurs remains contentious, in part because much of the material is fragmentary or juvenile.

Under dispute

The position of Scansoriopterygidae within Coelurosauria is unresolved. Recent analyses recover it within Oviraptorosauria, as basal members (Cau and Madzia, 2021; Foth and colleagues, 2025) or as the basalmost oviraptorosaurs under Bayesian inference (Cau, 2018). Others recover it as the sister group of Oviraptorosauria outside Avialae (Agnolín and Novas, 2013), or, for Epidexipteryx alone, at the base of Paraves (Turner and colleagues, 2012), or within Avialae as an early-branching avialan clade (Zhang and colleagues, 2008; Hartman and colleagues, 2019) — the last also recovered by the parsimony analysis of Cau (2018), whose two methods disagree, and by Cau (2024), who places it crownward of a paraphyletic anchiornithid grade. The fragmentary and often juvenile nature of much of the material contributes to the instability.

Diagnosis

  1. Greatly elongate third manual digit, longer than the first two
  2. Membranous wing supported by an ossified styliform wrist element in some members
  3. Short, deep skull with procumbent anterior teeth
  4. Small body size with a proportionally large head

Genera placed directly in Scansoriopterygidae

  • Ambopteryx Wang et al., 2019 Callovian (165.3–161.5 Ma)China
  • Epidexipteryx Zhang et al., 2008 Bathonian–Callovian (168.2–161.5 Ma)Chinaunder dispute
  • Scansoriopteryx Czerkas & Yuan, 2002 Barremian (125.8–121.4 Ma)Chinaunder dispute

References

  1. Czerkas, S. A.; Yuan, C. (2002). An arboreal maniraptoran from northeastern China. Feathered Dinosaurs and the Origin of Flight 1: 63-95. The Dinosaur Museum, Blanding, UT. czerkas2002a
  2. Zhang, F.; Zhou, Z.; Xu, X.; Wang, X.; Sullivan, C. (2008). A bizarre Jurassic maniraptoran from China with elongate ribbon-like feathers. Nature 455(7216): 1105-1108. Springer Science and Business Media LLC. doi:10.1038/nature07447

    Gave Scansoriopterygidae its phylogenetic definition and recovered it at the base of Avialae.

    zhang2008a
  3. Cau, A.; Madzia, D. (2021). The phylogenetic affinities and morphological peculiarities of the bird-like dinosaur Borogovia gracilicrus from the Upper Cretaceous of Mongolia. PeerJ 9: e12640. PeerJ. doi:10.7717/peerj.12640

    Recovered Scansoriopterygidae within Oviraptorosauria, consistently across the unweighted and all implied-weighting analyses.

    cau2021a
  4. Cau, A. (2018). The assembly of the avian body plan: a 160-million-year long process. Bollettino della Società Paleontologica Italiana 57(1): 1-25. doi:10.4435/BSPI.2018.01

    Parsimony analysis recovers scansoriopterygids among basal avialans, the Bayesian analysis as the basalmost oviraptorosaurs.

    cau2018a
  5. Agnolín, F. L.; Novas, F. E. (2013). Avian Ancestors. SpringerBriefs in Earth System Sciences. Springer Netherlands. doi:10.1007/978-94-007-5637-3

    Recovered scansoriopterygids as non-paravian maniraptorans, sister group to Oviraptorosauria.

    agnolín2013a
  6. Pei, R.; Pittman, M.; Goloboff, P. A.; Dececchi, T. A.; Habib, M. B.; Kaye, T. G.; Larsson, H. C. E.; Norell, M. A.; Brusatte, S. L.; Xu, X. (2020). Potential for Powered Flight Neared by Most Close Avialan Relatives, but Few Crossed Its Thresholds. Current Biology 30(20): 4033-4046.e8. Elsevier BV. doi:10.1016/j.cub.2020.06.105

    Included scansoriopterygids in its analysis and refers to them as non-paravian pennaraptorans, leaving Yi out of its flight-parameter estimates.

    pei2020a
  7. 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 Scansoriopterygidae within Avialae as the first-branching avialan clade.

    hartman2019a
  8. Turner, A. H.; Makovicky, P. J.; Norell, M. A. (2012). A Review of Dromaeosaurid Systematics and Paravian Phylogeny. Bulletin of the American Museum of Natural History 371: 1-206. doi:10.1206/748.1

    Recovered Epidexipteryx as the basalmost paravian; Scansoriopterygidae was not recovered, and constraining it costs four steps and places it basally in Avialae.

    turner2012a
  9. 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 Scansoriopterygidae within Avialae, crownward of a paraphyletic anchiornithid grade; no support values are reported.

    cau2024a
  10. Foth, C.; van de Kamp, T.; Tischlinger, H.; Kantelis, T.; Carney, R. M.; Zuber, M.; Hamann, E.; Wallaard, J. J. W.; Lenz, N.; Rauhut, O. W. M.; Frey, E. (2025). A new Archaeopteryx from the lower Tithonian Mörnsheim Formation at Mühlheim (Late Jurassic). Fossil Record 28(1): 17-43. doi:10.3897/fr.28.131671

    Recovered Scansoriopterygidae as basal members of Oviraptorosauria rather than within Paraves.

    foth2025a