An examination of the profile of modern dolphins shows the extent to how
mammals have actually evolved to become adapted to their aquatic
All dolphins have a similar streamlined, torpedo-shaped body - their bodies
are larger at the front than at the back. The dolphin has a short, stiff
neck. As with all the ceteceans, all visible traces of hind limbs have
disappeared. The forelimbs have developed into paddle-shaped flippers which
helps in steering through water. The tail of a dolphin (called the fluke) is
used for propulsion: it is therefore very muscular.
Many features of the former land-dwelling mammals have disappeared, for
example, dolphins do not have significant body hair, an external ear lobe
(pinna), a projecting nose, and externally projecting genitals or mammary
glands. All their protruding parts are reduced or tucked away, so as to
improve hydrodynamic efficiency.
Their body shape differs very little in comparison with other ceteceans
(whales and porpoises). Sometimes, dolphins are even mistaken for sharks.
It is easy to distinguish between a dolphin and a shark on the surface; the
latter has a vertical tail fin which projects out of the water behind the
dorsal fin. Comparatively speaking, dolphins have a smaller head and shorter
body than whales. Dolphins have a beak and but porpoises do not and dolphins
usually have dorsal fins.