Inter-Vertebral Flexibility of the Dinosaurs neck

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The flexibility and posture of the neck in sauropod dinosaurs has long been contentious. Improved constraints on sauropod neck function will have major implications for what we know of their foraging strategies, ecology and overall biology. Several hypotheses have been proposed, based primarily on osteological data, suggesting different degrees of neck flexibility. This study attempts to assess the effects of reconstructed soft tissues on sauropod neck flexibility through systematic removal of muscle groups and measures of flexibility of the neck in a living analogue, the ostrich (Struthio camelus). The possible effect of cartilage on flexibility is also examined, as this was previously overlooked in osteological estimates of sauropod neck function. These comparisons show that soft tissues are likely to have limited the flexibility of the neck beyond the limits suggested by osteology alone. In addition, the inferred presence of cartilage, and varying the inter-vertebral spacing within the synovial capsule, also affect neck flexibility. One hypothesis proposed that flexibility is constrained by requiring a minimum overlap between successive zygapophyses equivalent to 50% of zygapophyseal articular surface length (ONP50). This assumption is tested by comparing the maximum flexibility of the articulated cervical column in ONP50 and the flexibility of the complete neck with all tissues intact. It is found that this model does not adequately convey the pattern of flexibility in the ostrich neck, suggesting that the ONP50 model may not be useful in determining neck function if considered in isolation from myological and other soft tissue data. The sauropods were the largest terrestrial animals ever to have existed. The clade Sauropoda, a group of saurischian dinosaurs, was immensely successful from the Late Triassic to the very end of the Cretaceous, in terms of both species-richness and numerical abundance, with representatives found on all continents. Whilst their general morphology is well understood, the issue of their neck posture is still contentious. Some recent studies have proposed that the long necks of sauropods evolved by sexual selection  however, the lack of evidence for this theory [4] reinforces the long held view that long necks evolved for maximising the feeding envelope, either for high browsin or a wider lateral range of low browsing. Species- or clade-specific variations in neck morphology have also been proposed as the basis for ecologically significant differences in foraging behaviour, mediated by changes in relative and/or absolute neck length as well as differences in neck flexion capabilities . Various theories on the posture and flexibility of the neck have been presented with differing approaches leading to various implications for overall biology.

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With Regards
Alex john
Editorial Assistant
Entomology, Ornithology & Herpetology: Current Research