ABSTRACT
The basis for learning to deal with the anatomy, physiology, and diseases of an unfamiliar animal species is the understanding of how that animal is phylogenetically related to other species more familiar to the observer. The evolutionary development of marine mammals is unclear, but they are known to have originated from one or more stocks of terrestrial mammals. The marine mammals in existence today are classified into three groups: cetaceans, pinnipeds, and sirenia. The gross and microscopic anatomy of marine mammals is generally similar to the higher land mammals. The body shape of marine mammals is generally long and slender. Cetacean skin is most adapted to the aqueous world. The lack of hair aids in reducing friction. The cetacean larynx is a highly modified and elongated structure that connects the trachea with the blowhole. The skeletal muscles of marine mammals are very dark red, due to a high content of myoglobin in the muscle.
