Cetacea (order)

Order containing around 80 species in extant 10 families, the living members characterized by being nearly fully adapted to aquatic life with a fusiform (streamlined) body, forelimbs modified into flippers, tiny vestigial hindlimbs that do not attach to the backbone and are hidden within the body, a tail with horizontal flukes, being nearly hairless, insulation provided by a thick layer of blubber, and typically a high level of intelligence.