Abstract

The juvenile tyrannosaurid specimen BMR P2002.4.1 possesses a series of four partially healed, oblong lesions along the left maxilla and nasal bones. The morphology of the lesions and their positioning and orientation are compatible with the jaws of the specimen, suggesting that the lesions may have been the result of a bite from an attacker of similar size and species as the bite victim. Bone remodeling of the lesions indicates partial healing and demonstrates that the injury was not fatal. The injury appears to have affected the growth of the skull, causing a slight warping of the left maxilla and a slight leftward curvature of the nasal. Previous examples of intraspecific behavior in theropods have noted various injuries on skulls; the majority of documented injuries are in adults. The presence and nature of these wounds suggests that juvenile tyrannosaurid behavior included intraspecific aggression among similar-sized individuals, as has been observed in modern crocodilians. Although it is not possible to unequivocally infer behavior from a fossil specimen, as a juvenile animal it is unlikely that the behavior directly reflects sexual competition or conflict, although it may represent learning behavior for later conflict as competing adults or territoriality over food or spatial resources.

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