Closer examination does not support infection as cause for enigmatic Tyrannosaurus rex mandibular pathologies

Many tyrannosaurid specimens preserve unusual pathologies in the caudal half of the mandible that are of uncertain origin. The two main hypotheses put forth to date both suggest these pathologies are lesions resultant from infection either due to bacteria or protozoans. In light of this controversy, we provide a comparative anatomical study to characterize the pathophysiology of these enigmatic pathologies in order to elucidate their underlying cause. Human individuals that had been subjected to cranial trepanation and specimens of the late Triassic reptile Stagonolepis exhibiting healing fractures provide phylogenetic bracketing for investigating bone surface alterations induced by trauma in dinosaurs. Examination of mandibular pathologies in Tyrannosaurus rex FMNH PR2081 reveals all the characteristics of wound healing in the absence of infection. Additional evidence that refutes the previous hypothesis that these pathologies result from infection by the protozoan, Trichomonas gallinae, is discussed. Behavioral evidence suggests that these pathologies may be wounds induced through intraspecific combat.