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Temporal range: Lower Cretaceous
FMNH Deinonychus.JPG
Deinonychus skeleton at the Field Museum, Chicago.
Scientific classification
Binomial name
Deinonychus antirrhopus
Ostrom, 1969

Deinonychus [1] was a medium-sized predatory theropod dinosaur of the dromaeosaur family. It was a larger relative of the famous Velociraptor. This 3.4 meter (11 ft) long dinosaur lived during the Lower Cretaceous, about 115-108 million years ago. Fossils have been recovered from the U.S. states of Montana, Wyoming, and Oklahoma.

Restoration by Emily Willhoughby
Reconstructed foot bones, showing the sickle-claw

Deinonychus has been described as the single most important discovery of dinosaur paleontology in the mid 20th century.[2]

Ostrom's analysis[change | change source]

Paleontologist John Ostrom's study of Deinonychus in the late 1960s started the debate on whether dinosaurs were warm-blooded.[3] It is now accepted that all or most smaller theropods had feathers whose function was temperature regulation.Ostrom noted the small body, sleek, horizontal, posture, and—especially—the enlarged claws on the feet, which suggested an active, agile predator.[4] Before this, the popular idea of dinosaurs had been one of plodding, reptilian giants.[5][6]

Deinonychus means Terrible claw. This refers to the large, sickle-shaped claw bone on the second toe of each hind foot. In life, archosaurs have a horny sheath over this bone which extends the length. Ostrom reconstructed the claw as over 120 millimetres (4.7 in) long.[4]

The species name antirrhopus means “counter balance”, which refers to Ostrom's idea about the function of the tail. As in other dromaeosaurids, the tail vertebrae have a series of ossified (bony) tendons and super-long bone processes. These features seemed to make the tail into a stiff counterbalance. A fossil of the very closely related Velociraptor has an articulated tail skeleton that is curved laterally in a long S–shape. This suggests that, in life, the tail could swish to the sides with some flexibility.[7]

Paleoecology[change | change source]

Deinonychus remains have been found closely associated with those of the ornithopod Tenontosaurus. Teeth discovered associated with Tenontosaurus specimens imply it was hunted or at least scavenged upon by Deinonychus.

References[change | change source]

  1. pronounced:dei-ON-ike-US
  2. Fastovsky, D.E., Weishampel, D.B. 2005. "Theropoda I: Nature Red in Tooth and Claw". In Fastovsky, D.E., Weishampel, D.B.. The Evolution and Extinction of the Dinosaurs 2nd ed, Cambridge: Cambridge University Press. pp. 265–299. ISBN 0-521-81172-4.
  3. Desmond A.J. 1977. The hot-blooded dinosaurs. ISBN 0-8600-7494-3
  4. 4.0 4.1 Ostrom, J. H. (1970). "Stratigraphy and paleontology of the Cloverly Formation(Lower Cretaceous) of the Bighorn Basin area, Wyoming and Montana". Bulletin of the Peabody Museum of Natural History 35: 1–234. 
  5. Bakker, Robert T. 1975. Dinosaur Renaissance, in Scientific American, April issue.
  6. Bakker, Robert T. 1986. The Dinosaur heresies: new theories unlocking the mystery of the dinosaurs and their extinction. Zebra Books.
  7. Norell, Mark A.; & Makovicky, Peter J. (1999). "Important features of the dromaeosaurid skeleton II: information from newly collected specimens of Velociraptor mongoliensis". American Museum Novitates 3282: 1–45.