Deinonychus antirrhopus
Pronounced dye-NON-ih-kus an-tee-ROH-pus
Eudromaeosauria · Dromaeosauridae
A wolf-sized dromaeosaurid with a large sickle claw from the Early Cretaceous of Montana. Its 1969 description started the "dinosaur renaissance" and the idea that birds descend from dinosaurs; it was the model for the films' "raptors".
- Feathered
- Bipedal
- Sickle claw
- Possible pack behavior
- Eggs known
- Movie icon
- Period
- Cretaceous· Aptian
- Diet
- Carnivore
- Length
- 3.3–3.4 m
- Mass
- 60–100 kg
- Location
- Montana, Wyoming
Quick answers
- How big was Deinonychus antirrhopus?
- Deinonychus antirrhopus was about 3.3–3.4 m long. It stood about 0.8–1 m tall at the hips. It weighed about 60–100 kg. (Ostrom 1969; Paul 2010)
- When did Deinonychus antirrhopus live?
- Deinonychus antirrhopus lived during the Early Cretaceous, about 121.4–100.5 million years ago. (Cohen et al. 2023; Ostrom 1969)
- Where have Deinonychus antirrhopus fossils been found?
- Fossils of Deinonychus antirrhopus have been found in Cloverly Formation (Montana) and Wyoming. (Ostrom 1969; Ostrom 1969)
- What did Deinonychus antirrhopus eat?
- Deinonychus antirrhopus was a carnivore. (Ostrom 1969; Ostrom 1969)
- Who named Deinonychus antirrhopus, and when?
- Deinonychus antirrhopus was described by John H. Ostrom in 1969. (Ostrom 1969; Ostrom 1969)
On this page
dye-NON-ih-kus an-tee-ROH-pus
- Period
- Cretaceous121.4–100.5 Ma
- Diet
- Carnivore
- Length
- 3.3–3.4 m
- Mass
- 0.1–0.1 t
- Classification
- Eudromaeosauria · Dromaeosauridae
- Described
- 1969, John H. Ostrom
Overview
Deinonychus antirrhopus lived in western North America in the Early Cretaceous, about 115 to 108 million years ago. John Ostrom and Grant Meyer found its remains in the Cloverly Formation of Montana in 1964, and Ostrom named it in 1969.
It was a light, agile predator about 3 m long, with a stiffened tail, grasping hands and an enlarged, raised claw on the second toe of each foot. Ostrom argued that such an animal must have been active and warm-blooded, and noticed its many similarities with Archaeopteryx and birds. This work revived the idea that birds are living dinosaurs.
Several Deinonychus have been found with skeletons of the plant-eater Tenontosaurus, which led to the idea of pack hunting. Roach and Brinkman (2007) argued instead for mobbing behaviour like that of modern crocodiles or Komodo dragons. The "Velociraptor" of Jurassic Park was modelled largely on Deinonychus.
Name meaning
From Greek deinos ("terrible") and onyx ("claw"); antirrhopus, "counterbalancing", for the stiff tail (Ostrom 1969).
Biology & evidence
What scientists think about how this animal lived, and how strong the evidence for each idea is.
Feathers
Deinonychus had feathers.
Evidence level: Strong evidenceNo feathers are preserved with Deinonychus, but its close relatives had them, some with quill knobs on the arm; it is bracketed on both sides by feathered animals.
Evidence for / against · 1
Evidence for
Phylogenetic inference · Dromaeosaur quill knobs and feathered relatives
Close relatives are preserved with feathers, and Velociraptor shows quill knobs; Deinonychus sits inside this feathered group.
Reproduction
Deinonychus laid hard-shelled eggs and may have brooded them like birds.
Evidence level: HypothesisAn egg found against the belly ribs of a Deinonychus suggests it was brooding or about to lay. The link between egg and skeleton is not certain.
Evidence for / against · 1
Evidence for
Specimen · Deinonychus egg with gastralia
An egg associated with a Deinonychus skeleton, with shell structure like other maniraptorans.
Specimen: AMNH 3015-egg
Biomechanics
Deinonychus used its sickle claws to pin down prey.
Evidence level: HypothesisComparisons with hawks and eagles suggest the claw held struggling prey down while the animal fed, rather than slashing it.
Evidence for / against · 1
Evidence for
Comparative anatomy · Raptor prey restraint model
Comparison of dromaeosaur feet with those of living birds of prey: the sickle claw pinned prey down rather than slashing it open.
Social life
Deinonychus hunted in cooperative packs.
Evidence level: DisputedSeveral Deinonychus were found with a Tenontosaurus, suggesting group attacks. Critics argue that living relatives rarely cooperate, and that these sites fit a free-for-all mob better than a coordinated pack.
Evidence for / against · 2
Evidence for
Specimen · Deinonychus found with Tenontosaurus skeletons
Deinonychus teeth and skeletons found at several Tenontosaurus sites, at one quarry with several Deinonychus individuals.
Specimen: AMNH 3015
Evidence against
Comparative anatomy · Theropod group-behaviour review
Comparison with living archosaurs: birds and crocodiles rarely hunt cooperatively; the Deinonychus-Tenontosaurus sites fit mobbing and cannibalism better than a coordinated pack.
Size
- Length
- 3.3–3.4 m
- Height
- 0.9 mpublished range 0.8–1 m
- Mass
- 60–100 kg
(11.2 ft)
(3 ft)
Based on YPM 5205 and referred (femur c. 0.34 m)
Timeline
Periods: Aptian (121.4–113 Ma), Albian (113–100.5 Ma), Early Cretaceous (145–100.5 Ma)
Ages are the ICS 2023/09 bounds of the Aptian and Albian, the stage(s) the fossils are assigned to; they bracket the record and are not dated first/last appearances. The Cloverly beds with Deinonychus are usually dated to about 115-108 Ma.
Location
Formations
- Cloverly Formation · Montana
- Cloverly Formation near Bridger, Carbon County, Montana · Cloverly Formation · Montana · position approximate
These are the places where fossils have been found, not the full area where the animal lived.
Ecosystem
Lived in: Antlers
120–112 million years ago · floodplain, river system, coastal plain
Early Cretaceous plains of the Trinity Group in Oklahoma, Arkansas and north-east Texas.
Same ecosystem
Lived in: Cloverly
115–108 million years ago · floodplain, river system, forest
Early Cretaceous river floodplains of Montana and Wyoming, with seasonal climate and conifer forests; the plant-eater Tenontosaurus was the commonest large dinosaur.
Classification
- cladeDinosauria
- cladeSaurischia
- cladeTheropoda
- cladeCoelurosauria
- cladeManiraptora
- familyDromaeosauridae
- cladeEudromaeosauria
- genusDeinonychus
- speciesDeinonychus antirrhopus
Taxonomic status: Valid
Fossil record
| Catalog number | Status | Institution | Found |
|---|---|---|---|
| YPM 5205 | Holotype | Yale Peabody Museum (YPM) | 1964 |
| AMNH 3015 | Referred specimen | American Museum of Natural History (AMNH) | 1931 |
| AMNH 3015-egg | Specimen | American Museum of Natural History (AMNH) | — |
What has been found
Holotype: YPM 5205
- Preserved
- Partial
- Reconstructed
- Unknown / not recorded
Holotype: YPM 5205
Region by region (table)
| Region | State |
|---|---|
| Skull | Unknown / not recorded |
| Mandible | Unknown / not recorded |
| Teeth | Unknown / not recorded |
| Cervical vertebrae | Unknown / not recorded |
| Dorsal vertebrae | Unknown / not recorded |
| Sacrum | Unknown / not recorded |
| Caudal vertebrae | Unknown / not recorded |
| Ribs | Unknown / not recorded |
| Gastralia | Unknown / not recorded |
| Scapula / shoulder girdle | Unknown / not recorded |
| Humerus | Unknown / not recorded |
| Forearm (radius / ulna) | Unknown / not recorded |
| Hand (manus) | Unknown / not recorded |
| Pelvis | Unknown / not recorded |
| Femur | Unknown / not recorded |
| Tibia / fibula | Unknown / not recorded |
| Foot (pes) | Preserved · Left foot with sickle claw. |
Referred specimen: AMNH 3015
Region by region (table)
| Region | State |
|---|---|
| Skull | Unknown / not recorded |
| Mandible | Unknown / not recorded |
| Teeth | Unknown / not recorded |
| Cervical vertebrae | Unknown / not recorded |
| Dorsal vertebrae | Partial |
| Sacrum | Unknown / not recorded |
| Caudal vertebrae | Unknown / not recorded |
| Ribs | Unknown / not recorded |
| Gastralia | Unknown / not recorded |
| Scapula / shoulder girdle | Unknown / not recorded |
| Humerus | Unknown / not recorded |
| Forearm (radius / ulna) | Unknown / not recorded |
| Hand (manus) | Partial |
| Pelvis | Unknown / not recorded |
| Femur | Unknown / not recorded |
| Tibia / fibula | Unknown / not recorded |
| Foot (pes) | Partial |
Specimen: AMNH 3015-egg
Region by region (table)
| Region | State |
|---|---|
| Skull | Unknown / not recorded |
| Mandible | Unknown / not recorded |
| Teeth | Unknown / not recorded |
| Cervical vertebrae | Unknown / not recorded |
| Dorsal vertebrae | Unknown / not recorded |
| Sacrum | Unknown / not recorded |
| Caudal vertebrae | Unknown / not recorded |
| Ribs | Unknown / not recorded |
| Gastralia | Partial |
| Scapula / shoulder girdle | Unknown / not recorded |
| Humerus | Unknown / not recorded |
| Forearm (radius / ulna) | Unknown / not recorded |
| Hand (manus) | Unknown / not recorded |
| Pelvis | Unknown / not recorded |
| Femur | Unknown / not recorded |
| Tibia / fibula | Unknown / not recorded |
| Foot (pes) | Unknown / not recorded |
Discovery
- Year described
- 1969
- Described by
- John H. Ostrom
- Type specimen
- YPM 5205
Discovery timeline
1931 · First material found
Barnum Brown collects an undescribed raptor
Brown collects a small theropod with a Tenontosaurus in Montana, informally called "Daptosaurus", but never publishes it.
People: Barnum Brown
1964 · Specimen recovered
Ostrom and Meyer find Deinonychus
A Yale expedition finds the claw and skeletons near Bridger, Montana.
People: John H. Ostrom, Grant E. Meyer
1969 · Formally described
Ostrom names Deinonychus antirrhopus
The description and the full osteology later the same year start the "dinosaur renaissance".
People: John H. Ostrom
2006 · Major study
Deinonychus egg described
An egg found with a Deinonychus is described.
Sources
- Cohen, K. M., Harper, D. A. T., Gibbard, P. L. & Car, N. (2023). International Chronostratigraphic Chart (v2023/09). International Commission on Stratigraphy. https://stratigraphy.org/ICSchart/ChronostratChart2023-09.pdf (opens in a new tab)
- Fowler, D. W., Freedman, E. A., Scannella, J. B. & Kambic, R. E. (2011). The predatory ecology of Deinonychus and the origin of flapping in birds. PLoS ONE 6(12): e28964. doi:10.1371/journal.pone.0028964 (opens in a new tab)
- Maxwell, W. D. & Ostrom, J. H. (1995). Taphonomy and paleobiological implications of Tenontosaurus-Deinonychus associations. Journal of Vertebrate Paleontology 15(4): 707-712. doi:10.1080/02724634.1995.10011256 (opens in a new tab)
- Ostrom, J. H. (1969). A new theropod dinosaur from the Lower Cretaceous of Montana. Postilla 128: 1-17.
- Ostrom, J. H. (1969). Osteology of Deinonychus antirrhopus, an unusual theropod from the Lower Cretaceous of Montana. Bulletin of the Peabody Museum of Natural History 30: 1-165.
- Paul, G. S. (2010). The Princeton Field Guide to Dinosaurs. Princeton University Press.
- Paul, G. S. (2016). The Princeton Field Guide to Dinosaurs (2nd edition). Princeton University Press.
- Roach, B. T. & Brinkman, D. L. (2007). A reevaluation of cooperative pack hunting and gregariousness in Deinonychus antirrhopus and other nonavian theropod dinosaurs. Bulletin of the Peabody Museum of Natural History 48(1): 103-138. doi:10.3374/0079-032X(2007)48[103:AROCPH]2.0.CO;2 (opens in a new tab)