@dolphin @DolphinersOfficial

DolphinSea Animal

Dolphin is a common name of aquatic mammals within the infraorder Cetacea. The term dolphin usually refers to the extant families Delphinidae, Platanistidae, Iniidae, and Pontoporiidae, and the extinct Lipotidae. There are 40 extant species named as dolphins.

Speed: Short-beaked common dolphin: 60 km/h

Phylum: Chordata

Lifespan: Killer whale: 29 years, Striped dolphin: 55 – 60 years, MORE

Mass: Killer whale: 3,600 – 5,400 kg, MORE Encyclopedia of Life

Length: Killer whale: 6 – 8 m, MORE Encyclopedia of Life

Gestation period: Killer whale: 15 – 18 months,

Dolphins are small-toothed cetaceans easily recognizable by their curved mouths, which give them a permanent “smile.” There are 36 dolphin species, found in every ocean.

Most dolphins are marine and live in the ocean or brackish waters along coastlines. There are a few species, however, like the South Asian river dolphin and the Amazon river dolphin, or boto, that live in freshwater streams and rivers.

The largest dolphin, the orca, can grow to be over 30 feet long. The smallest, the Maui dolphin, is just five feet long.

Dolphins feed chiefly on fish and squid, which they track using echolocation, a built-in sonar that bounces sound waves off prey and reveals information like

Biology Of Dolphin
Etymology
The name is originally from Greek δελφίς (delphís), "dolphin", which was related to the Greek δελφύς (delphus), "womb". The animal's name can therefore be interpreted as meaning "a 'fish' with a womb".

The name was transmitted via the Latin delphinus (the romanization of the later Greek δελφῖνος – delphinos), which in Medieval Latin became dolfinus and in Old French daulphin, which reintroduced the ph into the word. The term mereswine (that is, "sea pig") has also historically been used.

The term 'dolphin' can be used to refer to, under the parvorder Odontoceti, all the species in the family Delphinidae (oceanic dolphins) and the river dolphin families Iniidae (South American river dolphins), Pontoporiidae

(La Plata dolphin), Lipotidae (Yangtze river dolphin) and Platanistidae (Ganges river dolphin and Indus river dolphin).

This term has often been misused in the US, mainly in the fishing industry, where all small cetaceans (dolphins and porpoises) are considered porpoises, while the fish dorado is called dolphin fish.

In common usage the term 'whale' is used only for the larger cetacean species, while the smaller ones with a beaked or longer nose are considered 'dolphins'.

The name 'dolphin' is used casually as a synonym for bottlenose dolphin, the most common and familiar species of dolphin. There are six species of dolphins commonly thought of as whales, collectively known as blackfish: the killer whale,

the melon-headed whale, the pygmy killer whale, the false killer whale, and the two species of pilot whales, all of which are classified under the family Delphinidae and qualify as dolphins.

Evolution
Dolphins are descendants of land-dwelling mammals of the artiodactyl order (even-toed ungulates). They are related to the Indohyus, an extinct chevrotain-like ungulate, from which they split approximately 48 million years ago.

The primitive cetaceans, or archaeocetes, first took to the sea approximately 49 million years ago and became fully aquatic by 5–10 million years later.

Archaeoceti is a parvorder comprising ancient whales. These ancient whales are the predecessors of modern whales, stretching back to their first ancestor that spent their lives near (rarely in) the water.

Likewise, the archaeocetes can be anywhere from near fully terrestrial, to semi-aquatic to fully aquatic, but what defines an archaeocete is the presence of visible legs or asymmetrical teeth.

Their features became adapted for living in the marine environment. Major anatomical changes include the hearing set-up that channeled vibrations from the jaw to the earbone which occurred with Ambulocetus 49 million years ago, a

streamlining of the body and the growth of flukes on the tail which occurred around 43 million years ago with Protocetus, the migration of the nasal openings toward the top of the cranium and the modification of the forelimbs

into flippers which occurred with Basilosaurus 35 million years ago, and the shrinking and eventual disappearance of the hind limbs which took place with the first odontocetes and mysticetes 34 million years ago.

The modern dolphin skeleton has two small, rod-shaped pelvic bones thought to be vestigial hind limbs. In October 2006, an unusual bottlenose dolphin was captured in Japan; it had small fins on each side of its genital slit, which scientists believe to be an unusually pronounced development of these vestigial hind limbs.

Anatomy
Dolphins have torpedo-shaped bodies with generally non-flexible necks, limbs modified into flippers, a tail fin, and bulbous heads.

Dolphin skulls have small eye orbits, long snouts, and eyes placed on the sides of its head; they lack external ear flaps.