ABSTRACT
This chapter focuses on crucial topics in developmental and evolutionary biology, such as the origin of pelvic vs. pectoral appendages and of paired vs. median appendages. The muscles of the fins are described together because they share a similar pattern. The appendicular musculature of the first dorsal fin located on the back of sharks is usually described as a "lateral" dorsal fin muscle or "radial" muscle (Lingham-Soliar 2005)—present on the right and left sides of the fin. The composition of the dorsal and anal fin musculature in the Acipenser brevirostrum and Polyodon spathula specimens seems to be paedomorphic. The musculature of the dorsal and anal fins of Lepisosteus oculatus is rather similar to that of teleosts such as the zebrafish Danio rerio. Unlike the pectoral and the other median fins (anal and dorsal), which are locally connected to the body, the caudal fin is a posterior continuation of the trunk.
