A limping dinosaur in the Late Jurassic: Pathologies in the pes of the neornithischian Othnielosaurus consors from the Morrison Formation (Upper Jurassic, USA)

Abstract

The study of palaeopathology provides valuable information about injury and behaviour in extinct organisms. Appendicular pathologies are interesting as they directly affect mobility and therefore the ability of an animal to survive. Here, the injuries recorded in the left pes of the neornithischian Othnielosaurus consors are described. The implications of these injuries in its behaviour are also discussed. Othnielosaurus shows pathological features in all its pes digits, with three types of pathologies have been identified: calcium pyrophosphate deposition disease (CPPD), and pilon and impact fractures. Calcium pyrophosphate deposition disease is visible on the articular surface of phalange II-3 as a small osseous plaque. A pilon fracture is evidenced by the growth of callus tissue on the shaft of the phalange I-1 and demonstrates healing before death. The impact fractures are identified as a focal subsidence on the articular surfaces of phalanges III-1 and IV-4, which are partially healed. Perhaps the suite of palaeopathologies encountered would generate pain and discomfort when walking, which probably resulted in a limp that would have impacted on its lifestyle. Finally, the fact that the fractures are in different stages of healing would suggest that impact fractures could have contributed to the death of the individual.