Dromaeosauridae

Australia: The Land Where Time Began

Dromaeosauridae

A small clade of theropod dinosaurs displaying highly derived characters shared by all of them, such as forelimb modifications that allow flexible grasping, which is seen in a modified form in the mechanism used in the flight stroke of birds. Birds are believed to have shared a common ancestor with dromaeosaurs, or may even have arisen from one of them, possibly at some time in the Jurassic. Assuming it was the common ancestor, and not the actual ancestral group, Dromaeosauridae would be a sister group of Aves, the birds.

According to the author¹ included among the dromaeosaurs are well-known animals such as Velociraptor and Deinonychus, as well as many other similar dinosaurs. The reason for the interest in the dromaeosaurs is the closeness of their skeletal anatomy to that of extant birds, this similarity being so great that it has led some to suggest that they are directly ancestral to birds.

Dromaeosaurs¹ have been found in the deposits at Liaoning Province, China, where the preservation conditions were so good that the skeletons are surrounded by what was a body covering in life, in same cases possibly filaments of keratin, a form of coarse hair, or in other cases feathers that were bird-like, emphasising their similarity to birds.

They varied in size from the size of a wolf to about 30 ft long, and had a highly specialised second toe that had an enormous claw on it. It was assumed it was a ripping claw, but others have suggested it was actually used like a grappling hook to climb onto the back of large prey where it could use its jaws on the neck or spine of the victim. They also had a stiffened tail that is believed to have been used as a dynamic stabiliser, and large grasping hands. The presence of the large claw on the second toe led to the suggestion that they were fast-moving, active predators.

Based on the large size of their femur, it is believed they may not have been as fast as other, more lightly built theropods, and it has been suggested they may have hunted in packs using ambush methods similar to lions, restricting their running to the short burst of speed to close in when the prey was in range.