behavior since injuries to the feet could be obtained while running or migrating. The researchers concluded that contact with struggling prey is the likely cause of a tendon avulsion found in the forelimb of the Tyrannosaurus specimen Sue. The authors concluded that the presence of stress fractures in theropods provide evidence for "very active" predation-based diets rather than obligate scavenging. Saurornitholestes preyed upon by juvenile tyrannosaur A. R. Jacobsen published a description of a dentary referred to Saurornitholestes with tooth marks. The dentary is about 12 cm long and preserves fifteen tooth positions; ten of these have teeth, with five of those teeth fully erupted and intact, two broken but functional as evidenced by the presence of wearfacets, and three only partially erupted. Three toothmarks were visible on the lingual surface of the dentary. Two of the three marks are series of grooves made by the serrations on the maker's teeth. The first consists of 6-7 parallel grooves within a 4 × 1.3 mm area beneath the alveolus of the third tooth and angled at 45° to the dentary's longitudinal axis. The striations are between .37 mm and .40 mm thick with cuboidal cross-sections. The second tooth mark lies between the fifth and sixth alveoli and consists of two smaller grooves separated 1.8 and 1.6 mm respectively from a larger central groove, with a V-shaped groove beneath it at an angle of 60° to the longitudinal axis of the jaw. The third mark consists of four parallel grooves in a 2 × 2 mm area on the seventh tooth oriented at 90° to the longitudinal axis of the tooth. The shapes of the preserved serrations are too different from those of Saurornitholestes for the marks to be the result of injuries incurred during intraspecific face biting behaviors. Although the right shape for Dromaeosaurus tooth serrations, the preserved marks are too coarse to have been left by that genus. Although a specific identification cannot be made, the most likely perpetrator would be a juvenile individual of one of the Dinosaur Park Formation's tyrannosaurids, like Gorgosaurus, Daspletosaurus, or Aublysodon. Jacobsen determined that all of the marks on the jawbone were left by the same animal because the serration marks all share the same morphology. Dromaeosauridae Saurornitholestes An ornithomimid caudal vertebra has been discovered that has tooth drag marks attributed to Saurornitholestes. Deinonychus Deinonychus, along with other similar dromaeosaurs, were suggested to kill