Name Meaning: Terrible Claw
Geologic Era: Early Cretaceous
Location Discovered: Near Billings, Montana (original specimen)
Estimated Range: Western United States, with possible remains also found in Maryland
Size: Up to 3.4 meters long
Extinction Date: 108 million years ago
Our specimen of Deinonychus is a cast of its killing claw and is a 1:1 scale replica. Deinonychus was a member of the dromaeosaur family, which also contained animals such as Velociraptor and the newly discovered Dakotaraptor. This group of dinosaurs is primarily known for the killing claw on one of their toes, and ranged in from chicken sized to over 6 meters long. Deinonychus could be considered “middle ground” in terms of size.
Deinonychus is important to the study of paleontology in that it helped revise the notion that dinosaurs were simply big, sluggish lizards. Up until the discovery of Deinonychus in 1931 to its more formal study in 1964, most of the dinosaurs discovered seemed to be exactly that: big, slow lizards. Deinonychus did not fit that description at all, being much more lightly boned, giving the impression of a very agile, active predator.
An interesting fact about Deinonychus is that it may have been a pack hunter. Deinonychus remains are sometimes found associated with another animal called Tenontosaurus, an mid-sized herbivore. A lone Deinonychus would have found it next to impossible to take on a fully grown Tenontosaurus, though bones of the latter are sometimes found with teeth that match Deinonychus, sometimes even with puncture marks. These puncture marks were used to estimate the bite force that Deinonychus was capable of inflicting, which turned out to be roughly as strong as a comparably sized alligator. While crunching through bone may not have been routine for Deinonycus, it was possible.
The number of remains found associated with Tenontosaurus do seem to indicate some level of group behavior, even if it only extended to mobbing a sick or injured animal. However, a trackway has been found that matches to a dromaeosaur type animal that shows some species did at least move in groups. From this, there does extend a possibility of cooperative group behavior.
You may notice that the killing claws pictured above do not look quite like the claw replica in our collection. The reason for this is that there appears to be considerable variation in claw appearance among individuals. This could possibly show differences between male and female, age variations, or simply individual variation. It is known that Deinonychus claws became less curved as the individual approached adulthood. A very curved claw like the one pictured above could have been useful for climbing trees, as young Deinonychus are thought to have done. As the animal grew older and spent more and more time on the ground, the claw took on a less curved structure.
The exact purpose of the kill claw is not exactly certain. Biomechanical models show that the claw was not structured in a way to inflict deep slashes, though it could puncture. It is also possible that the claw was used as a “pin” to restrain small prey items. It clearly had a use, however, as the dromaeosaur trackway indicates that it was held off the ground during walking.
Deinonychus may also not have been as fast as popular media would have a person believe, with a walking speed of about 6 miles per hour. This speed would still have been more than adequate to run down prey items. Its skull structure also indicates that it had very good stereoscopic vision, meaning it could gauge distance and size of prey very well. While Deinonychus would not have been the apex predator of its environment, it still would have been a terror to small and mid-sized animals.
Foot Bones: By Didier Descouens – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=15397846
Life Restoration: http://spinops.blogspot.com/2012/06/deinonychus-antirrhopus.html