Tail and pelvis pathologies of ankylosaurian dinosaurs

Ankylosaurid dinosaurs had modified distal caudal vertebrae (the handle) and large terminal caudal osteoderms (the knob), which together form the tail club. The tail club may have been used as a weapon. Ankylosaur pelvic and caudal elements were surveyed for evidence of healing wounds that may indicate traumatic injury, and which could support clubbing behaviour. No pathologies were found in the handle vertebrae, but several proximal caudal vertebrae show evidence of infection in the neural spines and transverse processes. One tail club knob has a lesion that may represent infection, and another knob has an unusual, furrowed texture of unknown aetiology. Two pelves each have large lesions at the junction of the fourth dorsosacral transverse process and the ilium, also of unknown aetiology. The cause of some lesions remains unknown and none of the pathologies can be used to support any hypothesised behaviour. If ankylosaurid tail clubs were used as weapons, then they were either well adapted for resisting fracture, or typical injuries were catastrophic and unlikely to heal.