abundance in the fossil record. In 2001, Bruce Rothschild and others published a study examining evidence for stress fractures in theropod dinosaurs and the implications for their behavior. Since stress fractures are caused by repeated trauma they are more likely to be a result of the animal's behavior than fractures obtained during a single injurious event. The distribution of stress fractures also has behavioral significance. Stress fractures to the hand are more likely to result from predatory behavior since injuries to the feet could be obtained while running or migrating. In order to identify stress fractures occurring in the feet of Allosaurus specifically due to predatory behavior, the researchers checked to see if the toes which bore the greatest stress while in motion also had the greatest percentage of stress fractures. Since the lower end of the third metatarsal would contact the ground first while a theropod was running it would have borne the most stress and should be most predisposed to suffer stress fractures. The lack of such a bias in the examined fossils indicates an origin for the stress fractures from a source other than running, like interaction with prey. They suggested that such injuries could occur as a result of the allosaur trying to hold struggling prey with its feet. Contact with struggling prey is also the likely cause of tendon avulsions found in the forelimbs of Allosaurus and Tyrannosaurus. The authors concluded that the presence of stress fractures provide evidence for "very active" predation-based diets rather than obligate scavenging. Tyrannosauridae Tyrannosaur tooth marks are the most commonly preserved feeding traces of carnivorous dinosaurs. They have been reported from ceratopsians, hadrosaurs and other tyrannosaurs. Tyrannosaurid bones with tooth marks represent about 2% of known fossils with preserved tooth marks. Tyrannosaurid teeth were used as holdfasts for pulling meat off a body, rather than knife-like cutting functions. Tooth wear patterns hint that complex head shaking behaviors may have been involved in tyrannosaur feeding. In 2001, Bruce Rothschild and others published a study examining evidence for stress fractures and tendon avulsions in theropod dinosaurs and the implications for their behavior. Since stress fractures are caused by repeated trauma they are more likely to be a result of the animal's behavior than fractures obtained during a single injurious event. The distribution of stress fractures also has behavioral significance. Stress fractures to the hand are more likely to result from predatory