New research from Montana State University’s Museum of the Rockies has revealed how dinosaurs like Velociraptor and Deinonychus used their famous killer claws. The finding has a bearing on the development of bird flight. In a paper published Dec. 14 in PLoS ONE, MSU researchers Denver W. Fowler, Elizabeth A. Freedman, John B. Scannella and Robert E. Kambic (now at Brown University in Rhode Island), describe how comparing modern birds of prey helped develop a new behavior model for sickle-clawed carnivorous dinosaurs like Velociraptor.
In a press release, Fowler wrote that the study focuses on dromaeosaurids; a group of small predatory dinosaurs that include the famous Velociraptor that are closely related to birds, and are most famous for possessing an enlarged sickle-claw on digit two (D-2 inside toe) of the foot.
Previous researchers suggested that this claw was used to slash at prey, or help climb up their hides, but the new study proposes a different behavior.
Reserachers showed that the enlarged D-2 claws are used as anchors, latching into the prey, preventing their escape, the same as the sickle claw of dromaeosaurids.
Other features of bird of prey feet gave clues as to the their ancient relatives; toe proportions of dromaeosaurids seemed more suited for grasping than running, and the metatarsus (bones between the ankles and the toes) is more adapted for strength than speed.
The study also has implications for the next closest relatives of troodontids and dromaeosaurids: birds. An important step in the origin of modern birds was the evolution of the perching foot.
A grasping foot was originally evolved for predation, but would also have been available for use in perching. The new study proposes that be responsible for the evolution of flight.
When a modern hawk has latched its enlarged claws into its prey, it can no longer use the feet for stabilization and positioning. It flaps its wings, instead. The researchers suggest that this ‘stability flapping’ uses less energy than flight, making it an intermediate flapping behavior that may be key to understanding how flight evolved.
Another group of researchers has proposed that understanding flapping behaviors is key to understanding the evolution of flight.
The researchers believe their new ideas will open new lines of investigation.
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