Injuries in deep time: interpreting competitive behaviours in extinct reptiles via palaeopathology

For over a century, palaeopathology has been used as a tool for understanding evolution, disease in past communities and populations, and to interpret behaviour of extinct taxa. Physical traumas in particular have frequently been the justification for interpretations about aggressive and even competitive behaviours in extinct taxa. However, the standards used in these interpretations have been inconsistent and occasionally questionable, and knowledge of extant reptile pathology is limited. Interpretations about the timelines and causes of unhealed bone damage are unreliable, and so behavioural implications from these marks are dubious. Even in the case of tooth marks, perimortem damage can be difficult to distinguish from postmortem alteration. In this review, methods from the anthropological sciences are adapted for the purposes of palaeontology, especially in establishing a new framework to distinguish antemortem traumatic damage from other similarly presenting features like sediment encrustation, postmortem damage/taphonomic features, variants of anatomical features, and non-traumatic palaeopathologies. Even in cases where traumatic palaeopathologies are accurately macroscopically identified, noting isolated incidences may not provide sufficient evidence to interpret behaviour at any taxonomic level. Future research directions in modern reptile pathology are proposed to improve the efficacy of traumatic palaeopathologies as a tool in interpreting extinct reptile behaviours.