Whales, dolphins, and porpoises all belong to the same taxonomic order called cetaceans. Cetaceans are comprised of about 80 kinds of whales, dolphins, and porpoises. The word cetacean is derived from the Latin "cetus" (a large sea animal) and the Greek "ketos" (sea monster). Cetaceans use a magnificent way of communicating using ultrasound.
Dolphins are Cetaceans and belong to the family Delphinidae. The largest dolphin is the Killer whale, Orcinus Orca being 23 feet (7 meters) long; the smallest is the Heaviside’s dolphin, Cephalorhynchus heavisidii being 3.5 feet (1.2 meters) long. The Killer whale weighs up to 4.48 tons (4.55 tonnes); and the Heaviside’s dolphin up to 88 pounds (40 kilograms). Their life span can reach up to 100 years, depending on species. Gestation is usually 10 to 12 months for most species and they usually have one calf which weighs between 10 to 400 pounds (4.5 to 180 kilograms), depending on species and they reach their age of maturity at 6 to 15 years, depending on species.
Dolphins have an eye on each side of their head. Each eye moves independently of the other, so dolphins can see ahead, to the side, and behind them. They can also see very well both underwater and in the air.
Members of the dolphin, or Delphinidae family, usually have teeth in both jaws. We can find four different species of river-dolphins: Indian river-dolphin (Indus and Ganges river-dolphins), Amazon river-dolphin (Boto), Yangtse river-dolphin (Baiji), and the La Plata dolphin. The Baiji Yangtze Dolphin is with all probability gone extinct in December 2006. There are only two species in the Monodontidae family, the Narwhale and the Beluga (white whales).
Long live the Dolphins!