The dolphin's face is rather unexpressive. The eyes may widen and dart with excitement, or narrow abruptly in anger, but the perpetual smile of most species tells us nothing about their emotional state.
Some dolphin's have a well-defined beak... other's have none at all. There is no external ear, only a pinhole opening on either side of the head, which doesn't seem to be used for hearing. In front of these are the eyes, which function independently of one another.
In most species, the jaws are straight, elongated and narrow. Towards the back of the upper jaw sits an area of fatty tissue known as the 'melon'. The braincase is at the very rear of the skull. The lower jaw is hollow, and is filled with fatty tissue.
Most dolphins species have large numbers of teeth, some over 200. Two notable exceptions are the adult Risso's Dolphin, who has no teeth in the upper jaw and no more than 14 in the lower; and the male Narwhal, whose tusk is almost always it's only visible tooth. Unlike many mammals, toothed whales do not have milk teeth, but develop only a single set which are not replaced.
Situated behind the melon on top of the head is the blowhole, where the dolphin breathes. In most animals the hole is crescent- shaped, with the curve towards the back. In all species the hole is naturally closed and must be opened by muscular action. There are two nasal passages in the skull, which join into a single tube which then fits over the end of the trachea. The fact that the trachea and oesophagus are completely separate allows the animal to feed underwater without drowning.
Lost? Click here for the main index page.