Evidence for survival in a Middle Jurassic plesiosaur with a humeral pathology: What can we infer of plesiosaur behaviour?

[摘要] Studying bone pathology frequently provides insights into an animal’s life, not only in terms of aetiology, but also how resulting limitations affected its behaviour and giving insight into potential survival strategies. A pectoral girdle of the plesiosaur, Cryptoclidus eurymerus, with the left forelimb damaged provides an opportunity to study post-trauma survival in the Middle Jurassic. Landmark data and macroscopic examination of the limb and associated scapulocoracoid are used to show that the damage was the result of an injury and not due to developmental pathology. Loss of the proximal humeral surface was associated with filigree modelling and periosteal reaction, which would have resulted in disruption of the adjacent scapulocoracoid surface rendering it functionally ineffective. This would have precluded its use in a power stroke or in providing directional locomotion. Healing of the pathology shows that it was possible for the plesiosaur not only to survive, but somehow to compensate for the loss of its limb. It is likely to have either corrected using hind-limb propulsion with the forelimbs compromised, or that the hindlimbs took a more active role in propulsion. The pectoral girdle of this specimen is smaller than would be expected for an adult C. eurymerus and the bones are thinner, indicating that the diet of the animal may have been restricted. The existence of healed tooth impacts on the dorsal aspect of the humerus suggests that the exostosis at the joint resulted from a pliosauroid or large crocodilian attack on the left flipper.

[学科分类] 地质学

[关键词] Bruce M. Rothschild;Neil D.L. Clark;Clare M. Clark;pathology;plesiosaur;humerus;pectoral girdle;Middle Jurassic;Cryptoclidus