Deinonychus’ claws were hookers, not rippers

From Austin, Texas, at a meeting of the Society of Vertebrate Paleontology

Deinonychus and its relatives, a group of bipedal, meat-eating dinosaurs collectively known as raptors, gained a fearsome reputation because of the enlarged, sicklelike claw they had on each foot. Many paleontologists have presumed that the claw enabled the lithe predators to disembowel victims with a single slash, but two analyses suggest that the claws were instead used to grip and climb large prey.

Deinonychus’ claw was about 10 centimeters long and curved through an arc of about 160°, almost a semicircle. In a previous study, Phillip L. Manning, a paleontologist at the University of Manchester in England, and his colleagues built a detailed model of the dinosaur’s foot, equipping it with a claw made of aluminum sheathed in Kevlar and carbon-fiber composite. The researchers plunged the foot into a fresh pig carcass at speeds comparable to those expected during Deinonychus attacks.

Despite having a sheath 40 times as strong as the keratin that likely enveloped a Deinonychus claw, the model claw didn’t rip a gash through the flesh. Instead, says Manning, the claw pierced the carcass and gripped the flesh but generated injuries no more than 40 millimeters deep. Those would be fatal for small prey, but trying to subdue a large dinosaur with such wounds “would be like trying to kill a person by stabbing them with plastic spoons,” says Manning.

Manning’s team has now developed a computer model of a Deinonychus claw that combines information gleaned from computerized tomography scans of fossils with data about the strength of bone and keratin. Results suggest that the claw could support the dinosaur’s full 40-kilogram weight.

Manning and his colleagues suggest that raptors used their claws as climbing crampons. While latched onto the side of a large herbivore, the raptors could have used their teeth to inflict mortal wounds, they say. Lions today sometimes use a similar technique, hanging on to large prey by their claws while clamping their jaws around the victim’s windpipe.