Histology and morphology of sauropod cervical ribs: Implications for neck posture

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The long neck of sauropod dinosaurs is probably the most distinctive feature of their anatomy and one of the key evolutionary innovations, permitting their unique gigantism by reducing the energy spent feeding. However, the position in which the neck was held is controversial, with either a nearly horizontal or a distinctly raised neck favored by different workes. Arguments put forth have centered on the constraints imposed by the cardiovascular system, the mobility of the intervertebral joints, and on biomechanical considerations. Surprisingly, the distinctive and sometimes extremely elongated cervical ribs (different sauropod taxa have different configurations) have not been studied in this regard although a bracing function has been hypothesized for the cervical ribs. We intend to study the bone histology and microanatomy of sauropod cervical ribs with the aim of reconstructing the soft tissue parts of the musculoskeletal system involving the ribs and the vertebrae in order to test the bracing hypothesis. This is possible because insertions of tendons, ligaments, and muscles leave a trace in the bone tissue, the Sharpey`s fibres. These can be seen in thin sections but we also intend to visualize them using a non-destrcutive method, micro-CT scanning. Ventral or dorsal bracing by the cervical ribs would have resulted in a stiff neck with restricted mobility. On the other hand, a lack of a bracing function together with an auxilliary muscle and tendon system would suggest highly flexible necks, at least in some taxa.