To bend a dolphin: Convergence of force transmission designs in cetaceans and scombrid fishes

The similarity in swimming style and external body shape between dolphins a nd scombrid fishes, especially tunas, is a textbook example of evolutionary convergence. I identify additional morphological features of the musculosk eletal system shared by dolphins and tunas. Specifically, these swimmers sh are a pattern of force transmission through a complex, three-dimensional sy stem of collagenous fabrics, which are stiffened by muscular hydrostatic pr essure. This force transmission system increases both the displacement adva ntage and moment arm of contracting axial muscle. These features represent a functionally significant design for steady swimming vertebrates.