14 Vertebrate Paleontology II

Thursday, 2 April 2009
1:00 PM - 5:00 PM

INFERRING JUVENILE TYRANNOSAUR BEHAVIOR BASED ON EVIDENCE OF INTRASPECIFIC AGGRESSION

Paper number: 14-9
Program: Theme Sessions
Time: 3:40 PM – 4:00 PM

Authors

Abstract

The juvenile tyrannosaur specimen BMR P2002.4.1 (Burpee Museum of Natural History, Rockford, IL) possesses a series of at least four partially healed oblong punctures along the left maxilla and nasal bones. The morphology of the punctures and their positioning and orientation are compatible with the jaws of the specimen, suggesting that the punctures may have been the result of a bite from an attacker of similar size and species as the bite victim. Partial healing is evident by cicatrisation of the punctures, demonstrating 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, however a majority of documented injuries are in adults. The presence and nature of these wounds suggests that juvenile tyrannosaur behavior included intraspecific aggression among similar sized individuals, as has been observed in modern crocodilians.

From these observations we can only speculate regarding the reason for the aggression. As a juvenile animal, it is less likely that the behavior directly reflects sexual competition or conflict, though it may represent learning behavior for later conflict as competing adults or territoriality over food or spatial resources.