Open Paleo

Deinonychosauria

Colbert & Russell, 1969

Its genera lived 154.8–66.0 million years ago Late Jurassic–Late Cretaceous

Deinonychosauria is a clade of paravian theropod dinosaurs that lived from the Late Jurassic to the Late Cretaceous, with fossils recovered on nearly every continent, from North America and Europe to Asia, Africa, South America, and Antarctica. It traditionally unites the dromaeosaurids and the troodontids, two families whose members bore enlarged, sickle-shaped claws on the second toe. That claw was held clear of the ground in a hyperextended position, so that only the third and fourth toes carried the animal's weight while walking, an arrangement known as functional didactyly. Most deinonychosaurs were predators, though some of the smaller troodontids appear to have been at least omnivorous. The group has long been considered among the closest relatives of birds.

Under dispute

Whether dromaeosaurids and troodontids form a clade to the exclusion of birds is unresolved. Analyses on the Theropod Working Group matrix and its descendants usually recover Deinonychosauria, with low support (Turner and colleagues, 2012; Pei and colleagues, 2020; Freimuth and colleagues, 2026), as do Hartman and colleagues (2019), who find that moving troodontids closer to birds costs a single step. Analyses on Cau's matrix place troodontids closer to birds (Cau and Madzia, 2021; Lee and colleagues, 2022); Foth and colleagues (2025) place dromaeosaurids closer to birds; and Agnolín and colleagues (2019) leave the paravian clades in a polytomy. The clade is retained in its traditional, broadly used sense pending consensus.

Diagnosis

  1. Enlarged, retractable sickle-shaped ungual on pedal digit II
  2. Functionally didactyl foot with a raised second toe
  3. Elongate penultimate phalanx on pedal digit II
  4. Modified metatarsal II permitting hyperextension of the second toe

Clades within Deinonychosauria

Genera placed directly in Deinonychosauria

  • Changzhousaurus Xu, 2026 Aptian (121.4–113.2 Ma)Chinaincertae sedisunder dispute

References

  1. Colbert, E. H.; Russell, D. A. (1969). The small Cretaceous dinosaur Dromaeosaurus. American Museum Novitates 2380: 1-49. colbert1969a
  2. 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 Deinonychosauria with troodontids inside it, and found that placing troodontids closer to birds costs one step.

    hartman2019a
  3. Sereno, P. C. (1998). A rationale for phylogenetic definitions, with application to the higher-level taxonomy of Dinosauria. Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen 210: 41-83. doi:10.1127/njgpa/210/1998/41

    Gave the node-based definition, with Troodon and Velociraptor as reference taxa.

    sereno1998a
  4. 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 Deinonychosauria with low jackknife support (GC 3); collapsing the node costs one step.

    turner2012a
  5. 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

    Recovered Deinonychosauria as the sister of Avialae, with low group support.

    pei2020a
  6. Freimuth, W. J.; Lively, J. R.; Zanno, L. E. (2026). Reassessment of the Early Cretaceous North American "troodontid" Geminiraptor suarezarum as a therizinosaurian and mosaic evolution of coelurosaurian maxillae. PLOS ONE 21(9): e0356471. doi:10.1371/journal.pone.0356471

    Recovered Deinonychosauria as the sister of Avialae on the Pei and colleagues (2020) dataset.

    freimuth2026a
  7. 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 troodontids closer to birds; the traditional Deinonychosauria costs 12 steps.

    cau2021a
  8. Lee, S.; Lee, Y. N.; Currie, P. J.; Sissons, R.; Park, J. Y.; Kim, S. H.; Barsbold, R.; Tsogtbaatar, K. (2022). A non-avian dinosaur with a streamlined body exhibits potential adaptations for swimming. Communications Biology 5(1). Springer Science and Business Media LLC. doi:10.1038/s42003-022-04119-9

    Recovered Dromaeosauridae as the sister of Troodontidae plus Avialae.

    lee2022a
  9. 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 Dromaeosauridae, not Troodontidae, as the sister of Avialae.

    foth2025a
  10. Agnolín, F. L.; Motta, M. J.; Brissón Egli, F.; Lo Coco, G.; Novas, F. E. (2019). Paravian Phylogeny and the Dinosaur-Bird Transition: An Overview. Frontiers in Earth Science 6: 252. doi:10.3389/feart.2018.00252

    Recovered the paravian clades in a polytomy at the base of Pennaraptora.

    agnolín2019a