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Deinonychus antirrhopus

Some discoveries in science completely change our ideas. This was the case with the discovery of Deinonychus ("terrible claw"). Most people believed that extinct dinosaurs were like giant, sluggish lizards. Then, in 1969, John H. Ostrom of Yale University described Deinonychus, a fossil skeleton he had unearthed some 5 years earlier in Montana. This animal was a totally new kind of dinosaur--obviously fast, agile and intelligent, and it was armed with fiercesome claws. The description of this animal sparked a controversy that caused scientists to rethink the lazy-lizard image of dinosaurs. The athletic, intelligent images of dinosaurs that we see today in movies and on television have their origins in the discovery and description of Deinonychus. Not only was Deinonychus a very active predator, it shared some important characteristics with todays living dinosaurs, birds. Imagine the excitement of being the first to discover this vital connection between the extinct dinosaurs, such as Deinonychus, and the living, flying dinosaurs we see today.

Discovery
Deinonychus antirrhopus is only definitely known from the Early Cretaceous Cloverly Formation of Montana and Wyoming. There are a minimum of six individuals known from reasonably complete skeletons. Two of these skeletons were collected from the Crow Indian Reservation in Montana by Barnum Brown of the American Museum of Natural History in 1931 and 1932, but they wee not described. One skeleton (AMNH 3015) was consists of much of a headless skeleton whereas the second (AMNH 3037) is mainly fragments of a manus (hand) and pes (foot).

The largest collection of Deinonychus remains was found by John Ostrom while leading expeditions to collect Cloverly vertebrates from 1962-1966. The Yale Deinonychus quarry was found late in 1964 by Grant E. Meyer and Ostrom near Bridger, Montana. Most of the bones from this quarry were disarticulated. However, a left pes and manus and parts of three tails were found articulated. The Yale quarry yielded a minimum of three individuals. Ostroms' field parties also found many isolated teeth of Deinonychus in the Cloverly Formation of both southern Montana and northern Wyoming.

In July 1984, Steven Orzack found another skeleton of Deinonychus near the American Museum of Natural History quarries. This skeleton (MCZ 4371) was collected by a field party from Harvard University led by Farish A. Jenkins. Importantly, the Harvard skeleton included several bones of Deinonychus which were not preserved, or not well-preserved, in the other skeletons including the femur (thigh bone), pubes (front hip bones) and ilium (top hip bone).

Taxonomy
The taxonomic relationships of dinosaurs are a complicated arrangement full of long Greek and Latin words. This complex system helps us understand which dinosaurs are related to one another as well as the characteristics they have in common. The systematics of a specimen tell the story of its lineage and evolutionary relationships. Deinonychus is a theropod. This large group (Suborder) includes most of the well known meat-eating dinosaurs. Theropods are further divided into at least three smaller groups: ceratosaurs, carnosaurs, and coelurosaurs. Deinonychus falls into the coelurosaur group and the dromaeosaur family. The other two main coelurosaur families are ornithomimosaurs and oviraptorosaurs.

Anatomy
Deinonychus antirrhopus, the specimen you are holding, is related to other dromaeosaurs like Velocoraptor from Asia and Utahraptor from the American West. The meat-eating lifestyle of dromaeosaurs is easy to see from their curved and serrated teeth. Typical characteristics of the dromaeosaurs include: a relatively large head; numerous serrated teeth; long forelimbs with three-fingered hands; posteriorly directed pubic bone; a rigid tail; and an enormous killing claw on the second toe of each foot. Deinonychus skeletons exhibit all of these traits.

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