SCHAEFER, J.S.; Univ. of California, Irvine: Batoid wing skeletons: a comparison of oscillatory and undulatory swimmers

The skeleton of the wings of skates and rays consists of a series of radially oriented cartilaginous fin rays fanning out from the pectoral girdle. Each fin ray is segmented into longitudinally oriented skeletal elements, traditionally represented as simple cylindrical building blocks. High-resolution radiography reveals the pattern of calcification in batoid wing elements and their organization within the fin ray to be considerably more complex and phylogenetically variable than previously thought. Morphological variations include varying degrees of calcification in skeletal elements between families of batoids, as well as among different areas of the wing in the same species. Oscillatory swimmers have interconnections between fin rays in the medial area of the wing. Variations may be directly linked to the locomotive strategy employed, with oscillatory swimmers needing stiffer wing skeletons than undulatory swimmers. Wing bending stiffness of a variety of batoids was tested at several points along the wing axis. Mathematical calculations of second moment of area of individual skeletal elements were also performed, allowing a theoretical comparison of stiffness between different calcification patterns.