Meeting Abstract
The semicircular canals of the inner ear sense positional information of the body and angular acceleration of the head during movement. In birds and mammals with agile and spatially complex movements, differences in canal shape, more specifically canal radius of curvature, are thought to enhance sensitivity to these behaviors. However, it is not understood whether these supposed functional changes in canal radius of curvature in mammals are broadly applicable across vertebrates, or if morphological responses to movement have evolved independently. Documentation of inner ear variation in caecilians and fossorial snakes indicates that both groups may have adopted novel morphological traits thought to enhance sensitivity to movement below ground. We present a survey of the morphological diversity of the semicircular canals of frogs across all extant families and investigate the influence of allometry, ecology, and phylogeny on canal morphology using 3-D geometric morphometrics and phylogenetic comparative methods. Inner ear endocasts were generated from high-resolution micro-computed tomography data, and we document substantial variation in the size and shape of the semicircular canals across species. A multivariate regression between shape and centroid size exhibited significant allometry, indicating there is a strong size-shape relationship in the inner-ear of anurans. Surprisingly, ecology and clade membership had an overall much weaker influence on semicircular canal shape. We lastly quantified the inner ear morphology of several extinct anurans, which were compared to modern taxa to estimate ecological and phylogenetic affinities.
