The specimen was first displayed in 1995, but collected in 1931 by a team headed by legendary dinosaur collector, Barnum Brown, (including Peter Kaisen). This mount of Deinonykus contains mostly real bones, unlike all other displays around the world. The bones were collected from the Cloverly formation, Buster Creek, Cashen Ranch, Crow Indian Reservation, Montana. The sediments date from the early Cretaceous, about 107 million years ago.

Barnum Brown called the specimen Daptosaurus but never published his work. It was a medium-sized theropod with hollow bones. In 1964, John Ostrom, of Yale University, investigated the Cloverly Formation and discovered a curved claw and then other bones. His investigations revealed similarities to avian (bird) morphology, especially in one of the wrist bones which had a half-moon shape (semi-lunate carpal). He named it Deinonychus antirrhopus, the terrible claw. The type specimen resides in the Peabody Museum, New Haven, Connecticut.

Deinonychus's terrible claw is on an extensible second toe (pedal ungual). Long boney extensions (prezygopophysis) on the caudal vertebrae kept the tail straight, counter-balancing the body. Similar features are present in Velociraptor and Bambiraptor. The extensible second toe found in Troodon exhibits anatomical differences from the previous dinosaurs, and is thought to represent convergence.