Infectious spondylitis with pathology mimicking that of tuberculosis in a cervical vertebra of a plesiosaur from the Upper Cretaceous of Patagonia, Argentina

Abstract

Paleopathological studies have been used to understand the history of injury and disease in extinct populations, their putative causes and, on this basis, to infer paleoecology and behavioral aspects. The most common pathologies reported in the zoological/paleontological record are traumatic injuries, post-traumatic malformations, inflammatory arthritis, infection and congenital defects. Although pathologies in plesiosaurs are recognized since the 1870s, reports of infectious disease are comparatively scarce. Here we report the pathological cervical vertebra of a plesiosaur recovered from the Upper Cretaceous of Argentina. The anterior external surface shows an elliptical, subchondral erosion with new bone formation and slight adjacent filigree reaction. The right anteroventral surface of the centrum bears erosive processes with bone reaction and alterations that have the appearance produced by space-occupied masses. On the left anteroventral surface of the centrum, there are abnormal vascular channels, associated with a groove just ventral to the articular surface. The combination of these features indicates that the pathological aspect of the vertebra is due to an infection. The pattern of bone abnormalities is compatible with those described in Pleistocene mammals affected by the granulomatous tuberculosis infection and with the abnormal ribs and cervical vertebrae of an eosauropterygian from the Triassic. The case reported herein represents the first record of tuberculosis-like infection in a plesiosaur. As the vertebra was not part of an associated skeleton, we cannot infer if the cause of death could have been related to the compromised hunting ability (due to limited neck mobility) or the result of infection-related organ failure.