Meeting Abstract

19.3  Saturday, Jan. 4 10:45  Macroevolutionary dynamics of scapula shape and locomotor behavior in Carnivora SLATER, GJ; Smithsonian Institution SlaterG@si.edu

The mammalian scapula is a large, flat bone, forming the proximal end of the forelimb. Because the scapula has no bony articulation with the axial skeleton, the forelimb attaches to and supports the trunk through muscular action only. As a result, the shape of the scapula should be strongly influenced by the mechanics of locomotion and forelimb use, making it an ideal predictor of ecology in species whose habits are unknown. Unfortunately, there have been few quantitative comparative studies of scapula shape in mammalian clades. I used a geometric morphometric approach to quantify shape variation among the scapulae of ~160 species of fissiped (i.e., non-pinniped) carnivorans, a clade with tremendous variation in locomotor behavior and forelimb use. Ordinations qualitatively demonstrate strong differentiation of scapula shape along both functional and phylogenetic axes. These observations are confirmed quantitatively by univariate and multivariate macroevolutionary models fitted to a phylogenetic comparative dataset. Taken together, these results suggest that carnivorans rapidly diversified to fill locomotor niches early in their evolutionary history. The gross morphology of the scapula, where preserved, should be a strong predictor of ecology in fossil carnivorans, and renewed focus on this understudied element would benefit future paleocological work.