Deinonychus
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? Deinonychus Conservation status: Fossil
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 Deinonychus antirrhopus by John Conway
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| Deinonychus antirrhopus Ostrom, 1969 |
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Deinonychus antirrhopus (pronounced /dai.ˈna.ni.kəs/, or approximately "dyn-ON-ik-us") meaning "terrible claw" ( Greek deinos = terrible + onyx, onychos = claw) was a jaguar-sized, carnivorous dromaeosaurid dinosaur species from the Early Cretaceous Clovery Formation of Montana. Its name refers to the huge, sickle-shaped talons on the second toe, which were probably held retracted while the dinosaur walked on the third and fourth toes. It was commonly thought that Deinonychus would kick with the sickle claws to slash at its prey, but recent tests on reconstructions of similar velociraptor talons suggest that the claw was used to stab, not slash. Like with all dromaeosaurids the tail was stiffened by a series of ossified tendons. This might have given Deinonychus greater balance and turning ability.
Discoveries
Based on the association of a number of Deinonychus skeletons in a single quarry — several hundred Deinonychus bones were discovered by paleontologist John Ostrom and Grant E. Meyer in 1964 in southern Montana — it has been speculated that Deinonychus lived in packs. This is quite possible, but it is impossible to prove or disprove this idea. Shed teeth of Deinonychus are often found alongside skeletons of the ornithopod dinosaur Tenontosaurus, indicating that it fed on them, and perhaps hunted them. John Ostrom named and described Deinonychus, and the discovery of this clearly active, agile predator did much to change the scientific (and popular) conception of dinosaurs and open the door to speculation that dinosaurs may have been warm-blooded.
Several years later, Ostrom noted similarities between the hand of Deinonychus and birds, which led him to revive the hypothesis that birds are descended from dinosaurs. Thirty years later, this idea is almost universally accepted. Finds of related dinosaurs from China, such as Sinornithosaurus and Microraptor indicate that this dinosaur probably bore feathers. Other relatives include Velociraptor, Utahraptor, and Dromaeosaurus.
A skeleton of Deinonychus can be seen on display at the American Museum of Natural History or the Harvard Museum of Comparative Zoology. The American Museum and Harvard specimens are from a different locality than the Yale specimens which Ostrom described, and the claws are different shapes (Ostrom 1976). This raises the possibility that the two are, in fact, different species or even different genera.
- Skull length: 410 mm (16 in)
- Total length: 3 m (10 ft)
- Hip height: 1.2 m (4 ft)
- Weight: 80 kg (175 lb)