Meeting Abstract
Batoids (skates and rays) are a diverse clade of flat cartilaginous fishes that occur primarily in benthic marine habitats. They typically use their flexible pectoral fins for feeding and propulsion via undulatory swimming. However, two clades of rays have adopted a pelagic or bentho‐pelagic lifestyle and utilize oscillatory swimming—the Myliobatidae and Gymnuridae. Oscillatory swimming is associated with changes in pectoral fin morphology, including lateral elongation, a redistribution of pectoral fin rays, and the evolution of modified anterior pectoral fin domains called cephalic lobes- anteriorly extended appendages used for feeding in the Myliobatidae. Variation in the number of fin rays in batoid pectoral fins has not been characterized in a comparative or phylogenetic context. To better understand how the batoid body plan was modified in association with a shift in feeding and swimming modes, we quantified fin rays that articulate with the three primary cartilages of pectoral fins and cephalic lobes in myliobatids and their relatives. Additionally, we analysed how morphology of the anterior primary cartilage varies in relation to dual-functionality. While most undulatory swimmers exhibit symmetry, we found a posterior shift in the distribution of fin rays arose twice independently. The shape and segmentation patterns of the anterior primary cartilage varies among batoid genera and is linked to feeding and swimming mode. Further, we described a derived skeletal feature in anterior pectoral fins of the Myliobatidae. Overall, this research has implications for morphological evolution associated with invasion of the pelagic environment, and the biomechanics of underwater flight.
