List of cetaceans

Taxobox
name = Cetaceans
fossil_range = Early Eocene - Recent

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image_width = 250px
image_caption = "Bottlenose Dolphin breaching"
regnum = Animalia
phylum = Chordata
subphylum = Vertebrata
classis = Mammalia
ordo = Cetacea
ordo_authority = Brisson, 1762This is a list of cetaceans. The order Cetacea includes whales, dolphins, and porpoises. It has just over eighty living species, divided into the suborders Odontoceti (the toothed whales, including dolphins and porpoises) and Mysticeti (the baleen whales). In addition, numerous species of extinct cetaceans exist, but they are not listed here. This list contains only the known, extant cetacean species including several recent discoveries (the Baiji is also included though it is believed to have gone extinct in 2006).

Cetaceans are aquatic mammals characterised by having a fusiform (streamlined) body shape, paddle-shaped front limbs and vestigial hind limbs. The tail has been flattened into a fluke to aid propulsion.

uborder Mysticeti: baleen whales

The baleen whales, also called whalebone whales or great whales, form the Mysticeti, one of two suborders of the Cetacea (whales, dolphins and porpoises). Baleen whales are characterized by having baleen plates for filtering food from water, rather than having teeth, like with the Odontocetes. This distinguishes them from the other suborder of cetaceans, the toothed whales or Odontoceti. Living Mysticeti species have teeth only during the embryonal phase. Fossil Mysticeti had teeth before baleen evolved.

=Family Balaenidae: Right Whales =Balaenidae is a family of cetaceans that contains two genera. Commonly called the Right Whales as it contains mainly Right Whale species. This name can be confusing, however, since one of the species is the Bowhead Whale, which is different to the Right Whale. All the Balaenidae whales have the following features: a smooth belly and chin, with no ventral grooves; a distinctive head shape with strongly arched, narrow rostrum (anatomy) and bowed lower jaw; lower lips that enfold the sides and front of the rostrum; long, narrow, elastic baleen plates (up to 9 times longer longer than wide) with fine baleen fringes; the fusion of all the cervical vertebrae and other skeletal characteristics; a slow swimming speed.cite book| last = Martin | first = Dr. Anthony R. | title = Whales and Dolphins | publisher = Salamander Books | location = London | year = 1991 ]

Family Neobalaenidae: Pygmy Right Whale

The Pygmy Right Whale shares several characteristics with the Right Whales although what separates them from Right Whales is that they have a dorsal fin, and they have a very distinctive jaw configuration. Pygmy Right Whales also have a head no more than ¼ the size of their body, whereas the Right Whales have heads approximately ⅓ the size of their body.

Family Phocoenidae: Porpoises

The porpoises are small cetaceans of the family Phocoenidae. They are distinct from dolphins, although the word "porpoise" has been used to refer to any small dolphin, especially by sailors and fishermen. The most obvious visible difference between the two groups is that porpoises have spatulate (flattened) teeth distinct from the conical teeth of dolphins. In addition, porpoises are relatively r-selected compared with dolphins: that is, they rear more young more quickly than dolphins. All six species have small flippers, notched tail flukes, and no beak. All carry at least 11 pairs of small teeth in the upper and lower jaws.

Porpoises, divided into six species, live in all oceans, mostly near the shore. Probably best known is the Harbour Porpoise, which can be found across the Northern Hemisphere.

Family Ziphiidae: Beaked Whales

A beaked whale is any of at least 20 species of small whale in the family Ziphiidae. They are one of the least-known families of large mammals: several species have only been described in the last two decades, and it is entirely possible that more remain as yet undiscovered. Six genera have been identified.

They possess a unique feeding mechanism known as suction feeding. Instead of catching their prey with teeth, it is sucked into their oral cavity. Their tongue can move very freely, and when suddenly retracted at the same time as the gular floor is distended, the pressure immediately drops within their mouth and the prey is sucked in with the water. The family members are characterised by having a lower jaw that extends at least to the tip of the upper jaw, a shallow or non-existent notch between the tail flukes, a dorsal fin set well back on the body, three of four fused cervical vertebrae, extensive skull asymmetry and two conspicuous throat grooves forming a 'V' pattern.

Family Platanistidae: Ganges and Indus River Dolphin

The Platanistidae was originally thought to hold only one species (Ganges and Indus River Dolphin) but based on differences in skull structure, vertebrae and lipid composition scientists declared the two populations as separate species in the early 1970s. [Pilleri, G., Marcuzzi, G. and Pilleri, O., 1982. Speciation in the Platanistoidea, systematic, zoogeographical and ecological observations on recent species. Investigations on Cetacea, 14: 15-46.] In 1998 the results of these studies were questioned and the classification reverted to the pre-1970 consensus. Thus, at present, there are two subpecies recognized in the genus "Platanista", "Platanista gangetica minor" (the Indus dolphin) and "Platanista gangetica gangetica" (the Ganges River dolphin). [cite book|title=Marine mammals of the world: Systematics and distribution|date=1998|first=DW|last=Rice|publisher=Society for Marine Mammalogy|isbn=978-1891276033]

Family Pontoporiidae: La Plata River Dolphin

The La Plata River Dolphin is the only species of the Pontoporiidae family and of the Pontoporia genus.

Notes and references

;General references
*Cite journal: Rice cetacea classification
*MSW3 Cetacea
*cite web | url=http://www.iucn.org/themes/ssc/redlist2006/redlist2006.htm | title = Red List of Threatened Species | publisher = IUCN | accessdate = 2006-11-09

See also

*List of whale species
*List of dolphin species
*List of whale songs
*Evolution of cetaceans

External links

* [http://www.arkive.org/ ARKive - images and movies of Whales, Dolphins and Porpoises]
* [http://www.acsonline.org/ American Cetacean Society]
* [http://www.cms.int/reports/small_cetaceans/index.htm CMS Small Cetaceans]
* [http://www.iucn.org/ IUCN Redlist]