Bite Force and Feeding Traces of Tyrannosaurusthroughout Ontogeny: A Review

Abstract

Bite marks attributed to adult Tyrannosaurus rexare common in the fossil record and have been subject to numerous studies, though relatively few bite marks attributed to T. rexhave been traced to juveniles. However, a series of recent studies have contributed new information on bite force, behavior, and ecological interactions of juvenile Tyrannosaurus rex, providing insight into ontogenetic changes in lifestyle and ecological roles of juvenile tyrannosaurs in the late Cretaceous of North America. Recent bite force estimates for a juvenile Tyrannosaurus rexwere based on mechanical tests designed to replicate bite marks previously attributed to a T. rex of approximately 13 years old in the centrum of a caudal vertebra of Edmontosaurus(BMR P2007.4.1) and the left maxilla and nasal of a juvenile Tyrannosaurus (BMR P2002.4.1). Results indicate an estimated bite force of 5,641.19 N, and suggest that bite forces were increasing parallel to growth and were utilizing the same prey as adults. Additionally, evidence of intraspecific aggression in the form of lesions resulting from face biting are present in over 50% of juvenile and adult tyrannosaurs. The high frequency of facial scars positively correlates with the inferred onset of sexual maturity. Furthermore, lesions attributed to a Trichomonas gallinae‐like parasite are present on the dentaries and surangulars of adult tyrannosaurs. Presented here is the first evidence of similar pathologies on a juvenile Tyrannosaurus rex that also possesses facial scars from intraspecific aggression, supporting a cause‐and‐effect relationship between the two groups of facial pathologies. Collectively, these findings suggest tyrannosaurs increased interactions, aggressive bouts, and potential transmission of parasites at the onset of sexual maturity as they were moving into different ecological niches. Furthermore, the frequency and category of pathologies in late Cretaceous tyrannosaurs and late Jurassic theropods of North America are compared with the unique guild structures of tyrannosaurs in the late Cretaceous of North America, suggesting a possible relationship between theropod diversity, behavior, and parasitism.