Evolutionary morphology of the theropod scapulocoracoid

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The theropod scapulocoracoid is an integral component of the avian flight apparatus, and its evolution is investigated using a combination of systematically based comparative anatomical and morphometric analyses. The morphological trends revealed via comparisons of theropod taxa are subsequently compared to the results of thin-plate spline analysis, allowing for a more objective assessment of shape changes observed in the scapulocoracoid. Thin-plate splines also permit graphical reconstruction of hypothetical ancestral forms situated at the internal nodes within a cladogram. The transformations inferred for the hypothetical ancestors, which represent more accurately the true line of descent, are compared to the transitions between the terminal taxa. In order to evaluate changes in the size and performance of the shoulder girdle musculature during this transition, theropod shoulder girdle musculature is reconstructed, based upon phylogenetic and functional inferences. Identification and comparison of osteological correlates of theropod shoulder musculature across theropod groups, and areas of shape change in the scapulocoracoid as revealed by anatomical comparisons, allow muscular changes to be mapped onto structural intermediates leading up to birds.
Bibliography: p. 384-411
Jasinoski, S. C. (2003). Evolutionary morphology of the theropod scapulocoracoid (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/19998