Dolphin Taxonomy Evolution Of Dolphins Dolphin Anatomy

There are almost 40 species of dolphin in 17 genera. They vary in size from 1.2 metres and 40 kg ( Heaviside's DolphinHeaviside's Dolphin : Animalia : Chordata : Mammalia : Eutheria : Cetacea : Odontoceti : Delphinidae Cephalorhynchus heavisidii Binomial name Cephalorhynchus heavisidii Heaviside's Dolphin Cephalorhynchus heavisidii is a small dolphin that is found off th), up to 9.5 metres and 10 tonnes (the Orca). Most species weigh between about 50 and about 200 kg. They are found worldwide, mostly in the shallower seas of the continental shelves, and all are carnivores, mostly taking fish and squid.

The familyIn biology, family is one of the levels of taxonomic classification of organisms. It lies between the less-specific order and the more-specific genus; ie, an order will contain one or more families, and a family will contain one or more genera. Humans, fo Delphinidae is the largest in the Cetacea, and relatively recent: dolphins evolved about 10 million years ago, during the MioceneThe Miocene Epoch is a period of time that extends from about 5 million to 24 million years before the present. As with other older geologic periods, the rock beds that define the start and end are well identified, but the exact dates of the start and end.

1 Taxonomy

SuborderIn biology, a suborder is a subdivision of an order. Scientific classification. Odontoceti, toothed whales
- Family Delphinidae, oceanic Dolphins
  - Genus Delphinus
    - Long-Beaked Common Dolphin, Delphinus capensis
    - Short-Beaked Common Dolphin, Delphinus delphis
  - Genus Tursiops
    - Bottlenose Dolphin, Tursiops truncatus
  - Genus Lissodelphis
    - Northern Rightwhale Dolphin, Lissodelphis borealis
    - Southern Rightwhale Dolphin, Lissiodelphis peronii
  - Genus Sotalia
    - Tucuxi, Sotalia fluviatilis
  - Genus Sousa
    - Indo-Pacific Hump-backed Dolphin Sousa chinensis
      - Chinese White Dolphin is the Chinese variant
    - Atlantic Humpbacked Dolphin, Sousa teuszii
  - Genus Stenella
    - Atlantic Spotted Dolphin, Stenella frontalis
    - Clymene Dolphin, Stenella clymene
    - Pantropical Spotted Dolphin, Stenella attenuata
    - Spinner Dolphin, Stenella longirostris
    - Striped Dolphin, Stenella coeruleoalba
  - Genus Steno
    - Rough-Toothed Dolphin, Steno bredanensis
  - Genus Cephalorynchus
    - Chilean Dolphin, Cephalorhynchus eutropia
    - Commerson's Dolphin, Cephalorhynchus commersonii
    - Heaviside's Dolphin, Cephalorhynchus heavisidii
    - Hector's Dolphin, Cephalorhynchus hectori
  - Genus Grampus
    - Risso's Dolphin, Grampus griseus
  - Genus Lagenodelphis
    - Fraser's Dolphin, Lagenodelphis hosei
  - Genus Lagenorhyncus
    - Atlantic White-Sided Dolphin, Lagenorhynchus acutus
    - Dusky Dolphin, Lagenorhynchus obscurus
    - Hourglass Dolphin, Lagenorhynchus cruciger
    - Pacific White-Sided Dolphin, Lagenorhynchus obliquidens
    - Peale's Dolphin, Lagenorhynchus australis
    - White-Beaked Dolphin, Lagenorhynchus albirostris
  - Genus Orcaella
    - Irrawaddy Dolphin, Orcaella brevirostris
  - Genus Peponocephalia
    - Melon-headed Whale, Peponocephalia electra
  - Genus Orcinus
    - Killer Whale, Orcinus orca
  - Genus Feresa
    - Pygmy Killer Whale, Feresa attenuata
  - Genus Pseudorca
    - False Killer Whale, Pseudorca crassidens
  - Genus Globicephala
    - Long-finned Pilot Whale, Globicephala melas
    - Short-finned Pilot Whale, Globicephala macrorhynchus
- Family Platanistoidae, River Dolphins
  - Genus Inia
    - Boto (Amazon River Dolphin,)Inia geoffrensis
  - Genus Lipotes
    - Chinese River Dolphin (Baiji) Lipotes vexillife
  - Genus Platanista
    - Ganges River Dolphin Platanista gangetica
    - Indus River Dolphin Platanista minor
  - Genus Pontoporia
    - La Plata Dolphin (Franciscana) Pontoporia blainvillei

Six animals in the family Delphinidae are commonly called "whales" but are strictly speaking dolphins. They are sometimes called "blackfish":

Melon-headed Whale, Peponocephalia electra
Killer Whale, Orcinus orca
Pygmy Killer Whale, Feresa attenuata
False Killer Whale, Psudoorca crassidens
Long-finned Pilot Whale, Globicephala melas
Short-finned Pilot Whale, Globicephala macrorhynchus

2 Evolution of dolphins

Dolphins, along with whales and porpoises, are descendants of land-living mammals, most likely of the Artiodactyl order. They entered the water roughly 50 million years ago. See evolution of cetaceans for the details.

3 Dolphin anatomy

Dolphins have a fusiform body, adapted for fast swimming. The head contains the melon, a round organ used for echolocation. In many species, the jaws are elongated, forming a distinct beak; for some species like the Bottlenose, there is a curved mouth that looks like a fixed smile. Teeth can be very numerous in several species. The dolphin brain is large and has a highly structured cortex, which often is referred to in discussions about their high intelligence.

The basic coloration pattern are shades of gray with a light underside and a distinct dark cape on the back. It is often combined with lines and patches of different hue and contrast. See individual species articles for details.

4 Dolphin behaviour

Dolphins are widely believed to be amongst the most intelligent of all animals, although the difficulties and expense of doing experimental work with a large marine animal, with a very different sensory apparatus from our own, mean that many of the tests required to confirm this belief have not yet been done, or have been carried out with inadequate sample sizes and methodology. See the Dolphin intelligence article for more details.

Dolphins often leap above the water surface, sometimes performing acrobatic figures (e.g. the spinner dolphin). This and other behaviour is interpreted as playing. They are capable of diving up to 260 m deep and 15 min long, but rarely stay underwater longer than few minutes. Frequently dolphins will accompany boats, riding the bow waves.

They are also famous for their willingness to occasionally approach humans and playfully interact with them in the water. In return, in some cultures like in Ancient Greece they were treated with welcome; a ship spotting dolphins riding in their wake was considered a good omen for a smooth voyage. There has been a report of dolphins protecting swimmers against a shark by swimming circles around the swimmers.

Dolphins are social animals, living in so called schools of up to a dozen animals. In places with high abundance of food, schools can join temporarily forming aggregations of over 1000 dolphins. The individuals communicate using a variety of clicks, whistles and other vocalizations. They also use ultrasonic sounds for echolocation.

Membership in schools is not rigid, interchange is common. However, the animals can establish strong bonds between each other. This leads to them staying with injured or ill fellows for support.

Because of their high capacity for learning, humans have employed dolphins for any number of purposes. Dolphins trained to perform in front of an audience have become a favorite attracton at places such as SeaWorld. Dolphin/Human interaction is also employed in a curative sense at places where dolphins work with autistic or otherwise disabled children. The military too has employed dolphins for various purposes from finding mines to rescuing lost or trapped persons. Such military dolphins, however drew scrutiny during the Vietnam War when rumors circulated that dolphins were being trained to kill Vietnamese Skin Divers.

Dolphins do not have acute eyesight, but have good hearing and a keen sense of smell.

Compare also: whale behaviour

5 Feeding

Dolphins are predators, chasing their prey at high speed. The dentition is adapted to the animals they hunt: Species with long beaks and many teeth forage on fish, whereas short beaks and lesser tooth count are linked to catching squid. Some dolphins may take crustaceans. Usually, the prey is swallowed whole. The bigger species, especially the orca, are capable of eating marine mammals, even large whales. There are no known reports of cannibalism amongst dolphins. (See external link: Common Dolphin Prey Species in the Eastern Ionian Sea)

6 Dolphin lore

The popular television show Flipper , created by Ivan Tors , portrayed a dolphin in a friendly relationship with two boys, Sandy and Bud; a kind of sea-going Lassie, Flipper understood English unusually well and was a marked hero: "Go tell Dad we're in trouble, Flipper! Hurry!" The show's theme song contains the lyric no one you see / is smarter than he.

In The Hitchhiker's Guide to the Galaxy, dolphins are actually very intelligent creatures who tried in vain to warn humans of the impending destruction of Earth. However, their behaviour was misinterpreted as playful acrobatics. Their story is told in So Long, and Thanks for All the Fish.

Ecco The Dolphin stars in a series of games for the Sega Genesis and Sega Dreamcast.

See also: dolphin (mythology)

7 Related articles

John Lilly – Dolphin intelligence researcher
Dolphin brain – Article on dolphin intelligence

8 External links

Cetaceans

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