The embryology of cetaceans documents features that elucidate the interaction between form and function in modern species, as well as their evolution from extinct ones. Prenatal specimens of the dolphin Stenella attenuata demonstrate critical aspects of the embryonic and fetal development of cetaceans, the pharyngeal arches, ear ossicles, nasal opening, teeth, forelimb, hind limb, and flukes. In addition, specimens of the bowhead whale (Balaena mysticetus) illustrate the development of baleen and hair.