DOLPHIN TEETH SKIN

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. They are related to the Indohyus, an extinct chevrotain-like ungulate, from which they split approximately 48 million years ago. Main article: Evolution of cetaceans Dolphins display convergent evolution with fish and aquatic reptiles.ĭolphins are descendants of land-dwelling mammals of the artiodactyl order (even-toed ungulates). Male dolphins are called 'bulls', females called 'cows' and young dolphins are called 'calves'. Ī group of dolphins is called a 'school' or a 'pod'. Although the terms 'dolphin' and 'porpoise' are sometimes used interchangeably, 'porpoise' usually refers to the Phocoenidae family, which have a shorter beak and spade-shaped teeth and differ in their behavior. There are six species of dolphins commonly thought of as whales, collectively known as blackfish: the orca, 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. The name 'dolphin' is used casually as a synonym for bottlenose dolphin, the most common and familiar species of dolphin. 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'. This term has often been applied in the US, mainly in the fishing industry, to all small cetaceans (dolphins and porpoises) are considered to be porpoises, while the fish dorado is called dolphin fish. The term 'dolphin' can be used to refer to most 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). The term mereswine (that is, 'sea pig') has also historically been used. 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 'Dol phin'. The animal's name can therefore be interpreted as meaning 'a 'fish' with a womb'. The name is originally from Greek δελφίς ( delphís), 'dolphin', which was related to the Greek δελφύς ( delphus), 'womb'. The most common dolphin species in captivity is the bottlenose dolphin, while there are around 60 orcas in captivity.

Dolphins are sometimes kept in captivity and trained to perform tricks. Dolphins have been depicted in various cultures worldwide. Besides drive hunting, they also face threats from bycatch, habitat loss, and marine pollution. Dolphins produce a variety of vocalizations, usually in the form of clicks and whistles.ĭolphins are sometimes hunted in places such as Japan, in an activity known as dolphin drive hunting. Mothers of some species fast and nurse their young for a relatively long period of time. Calves are typically born in the spring and summer months and females bear all the responsibility for raising them. Male dolphins typically mate with multiple females every year, but females only mate every two to three years. Dolphins feed largely on fish and squid, but a few, such as the orca, feed on large mammals such as seals. Most species prefer the warm waters of the tropic zones, but some, such as the right whale dolphin, prefer colder climates.

DOLPHIN TEETH SKIN

They have a layer of fat, or blubber, under the skin to keep warm in the cold water.ĭolphins are widespread. Some species are well adapted for diving to great depths. It is so well developed that some can survive even if they are blind. They have well-developed hearing which is adapted for both air and water. Dolphins use their conical teeth to capture fast-moving prey. Though not quite as flexible as seals, some dolphins can briefly travel at speeds of 29 kilometres per hour (18 mph) or leap about 9 metres (30 ft). They have streamlined bodies and two limbs that are modified into flippers. Various species of dolphins exhibit sexual dimorphism where the males are larger than females. There are 40 extant species named as dolphins.ĭolphins range in size from the 1.7-metre-long (5 ft 7 in) and 50-kilogram (110-pound) Maui's dolphin to the 9.5 m (31 ft) and 10-tonne (11-short-ton) orca. Dolphin species belong to the families Delphinidae (the oceanic dolphins), Platanistidae (the Indian river dolphins), Iniidae (the New World river dolphins), Pontoporiidae (the brackish dolphins), and possibly extinct Lipotidae (baiji or Chinese river dolphin).

For other uses, see Dolphin (disambiguation).Ī common bottlenose dolphin ( Tursiops truncatus)Ī dolphin is an aquatic mammal within the infraorder Cetacea.

Dolphin teeth