The cetacean family Monodontidae comprises two living

whale Whales are a widely distributed and diverse group of fully aquatic placental marine mammals. As an informal and colloquial grouping, they correspond to large members of the infraorder Cetacea, i.e. all cetaceans apart from dolphins and ...

species, the narwhal and the

beluga whale The beluga whale () (''Delphinapterus leucas'') is an Arctic and sub-Arctic cetacean. It is one of two members of the family Monodontidae, along with the narwhal, and the only member of the genus ''Delphinapterus''. It is also known as the whi ...

and at least four extinct species, known from the fossil record. Beluga and Narwhal are native to coastal regions and pack ice around the

Arctic Ocean The Arctic Ocean is the smallest and shallowest of the world's five major oceans. It spans an area of approximately and is known as the coldest of all the oceans. The International Hydrographic Organization (IHO) recognizes it as an ocean, ...

. Both species are relatively small whales, between three and five metres in length, with a forehead

melon A melon is any of various plants of the family Cucurbitaceae with sweet, edible, and fleshy fruit. The word "melon" can refer to either the plant or specifically to the fruit. Botanically, a melon is a kind of berry, specifically a " pepo". The ...

, and a short or absent snout. They do not have a true dorsal fin, but do have a narrow ridge running along the back, which is much more pronounced in the narwhal. They are highly vocal animals, communicating with a wide range of sounds. Like other whales, they also use echolocation to navigate. Belugas can be found in the far north of the

Atlantic The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the "Old World" of Africa, Europe an ...

and Pacific Oceans; the distribution of narwhals is restricted to the Arctic and Atlantic Oceans. Monodontids have a wide-ranging

carnivorous A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant whose food and energy requirements derive from animal tissues (mainly muscle, fat and other ...

diet, feeding on fish, molluscs, and small crustaceans. They have reduced teeth, with the beluga having numerous simple teeth, and the narwhal having only two teeth, one of which forms the tusks in males.

Gestation Gestation is the period of development during the carrying of an embryo, and later fetus, inside viviparous animals (the embryo develops within the parent). It is typical for mammals, but also occurs for some non-mammals. Mammals during preg ...

lasts 14–15 months in both species, and almost always results in a single calf. The young are not weaned for a full two years, and do not reach sexual maturity until they are five to eight years of age. Family groups travel as part of herds, or 'pods', which may contain several hundred individuals.

Taxonomy

The monodontids, oceanic dolphins (Delphinidae) and

porpoise Porpoises are a group of fully aquatic marine mammals, all of which are classified under the family Phocoenidae, parvorder Odontoceti (toothed whales). Although similar in appearance to dolphins, they are more closely related to narwhals ...

s (Phocoenidae) together comprise the Delphinoidea superfamily. Genetic evidence suggests the porpoises are more closely related to the white whales, and these two families constitute a separate clade which diverged from the Delphinidae within the past 11 million years. *Suborder Odontoceti **Superfamily Delphinoidea ***Family Monodontidae ****Genus †'' Haborodelphis'' *****''Haborodelphis japonicus'' ****Genus † '' Denebola'' *****''Denebola brachycephala'' ***Subfamily Delphinapterinae ****Genus '' Delphinapterus'' *****''Delphinapterus leucas'', beluga ****Genus †'' Casatia'' *****''Casatia thermophila'' ***Subfamily Monodontinae ****Genus † '' Bohaskaia *****''Bohaskaia monodontoides'' ****Genus '' Monodon'' *****''Monodon monoceros'', narwhal

References

External links

* * {{Taxonbar, from=Q219419 Mammal families Extant Miocene first appearances Taxa named by John Edward Gray