Meeting Abstract
16.1 Tuesday, Jan. 4 Hips don’t lie: How the batoid pelvic girdle shape correlates with locomotion and phylogeny MACESIC, L.J.; Florida Atlantic Univ., Boca Raton, FL ljmacesic@gmail.com
Batoids (skates and rays) exhibit several forms of locomotion. To swim, they perform axial undulation, pectoral fin undulation, or pectoral fin oscillation. On the substrate, benthic batoids perform true punting using pelvic fins, or augmented punting, wherein pectoral fins are also employed. Past research has examined batoid pelvic girdle shapes in a phylogenetic context with no clear resolution. The goal for this study was to use geometric morphometrics to determine how the pelvic girdle shape correlates with i) Order, ii) Family, iii) Swim Mode, and iv) Punt Mode. Landmarks and semilandmarks were placed along outlines of dorsal views of 61 pelvic girdles (3/3 orders, 10/13 families, 35/72 genera). The first three Relative Warps explained 88.45% of the variation among individuals. Only Order and Punt Mode contained groups that were all significantly different from each other (p<0.01 for all). Based on Canonical Variates Analyses, the majority of variation within each category was due to the presence/absence of lateral and pre-pelvic processes and the puboischiadic bar angle. More than 60% of the original specimens and 55% of the cross-validated specimens were correctly classified. The neutral angle of the first radial, which articulates with the pelvic girdle was also measured. All punt modes (true=15.05º±2.715SE; augmented=29.54º±2.907SE; non=54.01º±2.991SE) were significantly different from each other (p<0.01 for all). Only pectoral fin oscillation was significantly different from other swimming modes (p<0.01). This study illustrates that the pelvic girdle shape correlates most strongly with the punting mode in batoids, although correlations with the swimming mode do exist. The shape of the pelvic girdle cannot reliable predict the Family to which a batoid belongs, however, it can be used to predict the Order.
