Dolphin fins are composed of dense connective tissue, muscle, and bone. The bones in the fin are called phalanges, and they are similar to the bones in human fingers. The phalanges are connected to each other by muscles and tendons, which allow the dolphin to move its fins in a variety of ways. The muscles in the fin are responsible for providing the power for swimming, and the blubber in the fin helps to keep the dolphin warm.