Cetacea is derived from the Greek word meaning whale. There are two suborders of whales, the baleen whales (Mysticeti) and the toothed whales (Odonticeti). The two subgroups have been distinct since the late Eocene. Both are fully aquatic, have fusiform bodies and tails flattened dorsoventrally as flukes. Posterior limbs are absent externally, and the anterior limbs are enclosed in flippers. The baleen in the Baleen whales filter out plankton in their buccal cavities, water being filtered through the comblike baleen plates, having been scooped up in huge mouthfuls. Toothed whales capture fish or small marine mammals. Most toothed whales are relatively small. All whales are sensitive to acoustic signals and the toothed whales are unusual in their use of echolation to identify the location and character of food, other objects, as well each other. Most whales are highly social. They breath periodically through their blowholes as they rise to the surface. The nasal, maxilla and frontal bones of the skull are telescoped to permit the blowholes to exit dorsally rostral to the cranium. The neck is very short in all species. The pinnae are absent, the thick skin is virtually hairless and is underlain by considerably thick layers of fat (blubber). As fully marine, airbreathing mammals the Cetacea dwell in all oceans of the planet earth.

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SUBORDER ODONTOCETI
Family Delphinadae

• Bottlenose Dolphin (Tursiops truncatus)