Deinonychus antirrhopus

Deinonychus antirrhopus was a medium-sized predatory dinosaur from Early Cretaceous North America. Its enlarged second-toe claw, long grasping hands, lightly built skeleton and tail stiffened by elongated bony processes formed a highly specialised predatory body plan. Although no feather impressions are known from Deinonychus itself, feathers are strongly supported by its position among feathered dromaeosaurids and close bird relatives. John Ostrom's 1969 descriptions challenged the then-common image of dinosaurs as uniformly slow reptiles and became central to the dinosaur renaissance and renewed study of the dinosaur–bird relationship.

Its fossils occur between approximately 115 and 108 million years ago. Values shown here are approximate and reflect the current curated seed dataset.

The holotype, YPM 5205, is limited to a complete left foot and part of the right foot. Much of the broader reconstruction comes from numerous referred bones recovered from the same quarry, so the familiar skeleton represents a species-level composite rather than one articulated individual. The enlarged claw on pedal digit II was held clear of the ground. Its shape and foot mechanics are consistent with gripping and pinning prey, while the reinforced tail provided balance without being completely rigid.

• Enlarged, strongly curved claw on the second toe
• Second toe capable of being raised clear of the ground
• Long three-fingered hands with recurved claws
• Low, lightly built skull with serrated teeth
• Tail reinforced by elongated vertebral processes and tendons
• Long hind limbs adapted for active terrestrial movement
• Feathered body inferred from close dromaeosaurid relatives

Barnum Brown collected the first recognised Deinonychus material in Montana in 1931, but his proposed name 'Daptosaurus' was never formally published. In 1964 John H. Ostrom led a Yale Peabody Museum expedition to the Cloverly Formation near Bridger, Montana, where the team recovered abundant remains from several individuals. Ostrom named Deinonychus antirrhopus in February 1969 and followed it with a detailed osteological monograph later that year. Deinonychus means 'terrible claw'; antirrhopus refers to the tail's counterbalancing role.

Discovery credit: John H. Ostrom, Yale Peabody Museum field team.

Naming authors: John H. Ostrom.

Deinonychus inhabited river floodplains and seasonally variable lowlands represented by the Cloverly and Antlers formations. The landscape supported conifers, ferns and other low vegetation around channels and wetter areas. Tenontosaurus, the armoured Sauropelta, small ornithopods, crocodilians, turtles, mammals and several other theropods shared parts of this ecosystem.

Bite marks and shed teeth associated with Tenontosaurus provide direct evidence that Deinonychus fed on this much larger herbivore, although a particular association cannot always distinguish hunting from scavenging. Foot mechanics support using the enlarged toe claw to grip and restrain prey rather than slicing it open. Stable-isotope differences between smaller and larger teeth suggest diet changed during growth and do not support a modern wolf-like pack structure. Individuals may still have gathered at carcasses or interacted socially; the fossils do not reveal one fixed social system.

• The Jurassic Park 'Velociraptors' were largely inspired by the much larger Deinonychus body plan.
• The holotype is mainly a pair of feet, not the complete skeleton often imagined for such a famous dinosaur.
• Its tail was reinforced for balance but still retained more movement than a rigid rod.
• John Ostrom's work on Deinonychus helped revive the scientific case that birds evolved from small theropod dinosaurs.
• Direct bite marks show that large individuals could puncture bone, but modelled bite forces depend on how the marks and jaw mechanics are interpreted.

A research repository is not necessarily a public exhibit. Loan and display status can change, so check with the institution before visiting.

1. 01
   The Paleobiology Database

   Open source
2. 02
   A new theropod dinosaur from the Lower Cretaceous of Montana

   John H. Ostrom · Postilla · 1969

   Open source
3. 03
   Osteology of Deinonychus antirrhopus, an unusual theropod from the Lower Cretaceous of Montana

   John H. Ostrom · Bulletin of the Peabody Museum of Natural History · 1969

   Open source
4. 04
   A description of Deinonychus antirrhopus bite marks and estimates of bite force using tooth indentation simulations

   Paul M. Gignac, Peter J. Makovicky, Gregory M. Erickson, Robert P. Walsh · Journal of Vertebrate Paleontology · 2010

   Open source
5. 05
   The predatory ecology of Deinonychus and the origin of flapping in birds

   Denver W. Fowler, Elizabeth A. Freedman, John B. Scannella, Robert E. Kambic · PLOS ONE · 2011

   Open source
6. 06
   Ontogenetic dietary shifts in Deinonychus antirrhopus: insights into the ecology and social behavior of raptorial dinosaurs through stable isotope analysis

   Joseph A. Frederickson, Michael H. Engel, Richard L. Cifelli · Palaeogeography, Palaeoclimatology, Palaeoecology · 2020

   Open source
7. 07
   Deinonychus

   Yale Peabody Museum

   Open source