Survey of tooth-marked hadrosaurid (Dinosauria, Ornithischia) jugals from the Late Cretaceous of Alberta: implications for feeding behavior

Abstract Paleopathologies and tooth marks observed on bones have long been used for behavioral interpretations of extinct organisms, including non-avian dinosaurs. However, our understanding of this behavior is limited by the rarity of large-scale surveys of recovered material. Here, we present a systematic survey of tooth marks across 148 hadrosaurid jugals from various Late Cretaceous formations of Alberta, Canada. Across 20 of the elements (13.6%), we observed 48 tooth marks, restricted to the lateral surface, 40% of which were located on the middle jugal body and showed no preferred orientation of the mark long axis. Across taphonomic modes, tooth marks are most common on isolated specimens, followed by bonebed specimens, with few articulated/semi-articulated/associated specimens showing marks. The proportion of tooth-marked to non-tooth-marked jugals is comparable to tooth-marking frequencies observed for modern mammalian carnivores. Although tooth marks were likely produced postmortem during feeding, it is unclear whether tooth marks were produced when the jugal was removed to access underlying adductor musculature or during the removal of extraoral tissues or a combination of these behaviors. Future large-scale surveys of hadrosaurid cranial elements could help clarify which of these explanations is more likely and elucidate Cretaceous carnivore carcass-processing behaviors. Our survey also identified an additional two specimens showing elongate healed marks extending anteroposteriorly across the lateral surface of the jugal body that are of unknown, but potentially the same, origin. Further specimens with similar paleopathologies could help decipher a likely mechanism of injury.