Shoulder to shoulder: comparative functional morphology of the scapula across therians

The scapula (shoulder blade) in therian mammals is highly variable in its morphology, and understanding how this variation relates to biomechanical function can inform research in many fields, such as within palaeontology, where anatomical correlates are used to infer behaviours and ecology of extinct mammals. While the relationship between scapular morphology and function has been investigated across all major extant therian clades, taxonomic constraint and discrepancies in methodology make it near-impossible to synthesise this research into generalisable evidence of form-function relationships, especially in the context of locomotion behaviour. This thesis begins by quantifying locomotion behaviour in high resolution using a multivariate scoring system, producing both a data matrix and a mathematically-defined categorical variable, greatly surpassing traditional behavioural quantification methods. Next, scapula morphology across 201 species of extant therians (covering all extant orders) is quantified in 3D using 71 landmarks via geometric morphometric methods, and this is related to locomotion behaviour, allometry and clavicle presence within a phylogenetic framework, using a suite of multivariate statistics. The results demonstrate clear morphological correlates associated with allometry, clavicle loss, and certain locomotion behaviours (particularly climbing/aerial movement and running ability). Finally, these results are validated in the functionally-representative order, Rodentia, which demonstrates consistencies in the form-function relationships, and supports rodents as a suitable model order in the context of scapular functional morphology. The findings of this thesis provide a clade-wide investigation of scapular morphology in therians, which shows robust evidence of generalisable links between scapular form and function across therians based on the highest resolution shape and function datasets thus far in the field.