ABSTRACT

The most comprehensive comparative analyses of the muscles of the pectoral and pelvic appendages of bony fishes based on a direct observation of members of a wide range of taxa rather than on previous literature were performed many decades ago. This chapter provides an updated review of the homologies and evolution of the pectoral and pectoral fin muscles of actinopterygians. The plesiomorphic condition for living actinopterygians and for living bony fishes seems to be that there were six muscles related to the movements of the pectoral fins. These include the abductor superficialis and abductor profundus, the adductor superficialis and adductor profundus, a preaxial muscle, and a postaxial muscle. These two arrector muscles, the adductor superficialis and profundus and the abductor superficialis and profundus, are present in one of the model organisms that is most studied among actinopterygians as well as among osteichthyan fishes in general, the zebrafish Danio rerio.