LAUSR

Abstract We describe infectious arthritis and spondyloarthropathy in a juvenile mosasaur recovered from the upper Maastrichtian of Antarctica, representing the first report of a skeletal pathology of a mosasaur from the southern hemisphere. Macroscopic examination of the scapula revealed a remodelled, deeply excavated and expanded gleno-humeral joint with adjacent linear disruption. X-ray examination revealed a deep excavation expanding the glenoid fossa, with disorganized subchondral bone and a focal spherical defect. The individual did not continue to grow for a long time after the appearance of the lesion. Although not directly related to the mosasaur death, this condition may have contributed to the demise of the animal by reducing its effectiveness at obtaining food or increasing susceptibility to fatal disease, additional injury, or even predation.