Monodontidae Temporal range: | |
---|---|
Beluga whale | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Mammalia |
Order: | Artiodactyla |
Infraorder: | Cetacea |
Superfamily: | Delphinoidea |
Family: | Monodontidae J. E. Gray, 1821 |
Type genus | |
Monodon C. Linnaeus, 1758 | |
Extant genera | |
The cetacean family Monodontidae comprises two living whale species, the narwhal and the beluga whale 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. Both species are relatively small whales, between three and five metres in length, with a forehead melon, and a short or absent snout. Premaxillary teeth are absent. [1] 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. [2] Belugas can be found in the far north of the Atlantic and Pacific Oceans; the distribution of narwhals is restricted to the Arctic and Atlantic Oceans.
Monodontids have a wide-ranging carnivorous 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 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. [2]
The monodontids, oceanic dolphins (Delphinidae) and porpoises (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. [3] [4]
Porpoises are small dolphin-like cetaceans classified under the family Phocoenidae. Although similar in appearance to dolphins, they are more closely related to narwhals and belugas than to the true dolphins. There are eight extant species of porpoise, all among the smallest of the toothed whales. Porpoises are distinguished from dolphins by their flattened, spade-shaped teeth distinct from the conical teeth of dolphins, and lack of a pronounced beak, although some dolphins also lack a pronounced beak. Porpoises, and other cetaceans, belong to the clade Cetartiodactyla with even-toed ungulates.
The narwhal, is a species of toothed whale, and the only member of the genus Monodon. Its closest living relative is the beluga whale, and a single case of interbreeding between the two species has been recorded. It is sexually dimorphic, as adult males are larger than females and have a single tusk that can be up to 3 m (9.8 ft) long. The narwhal has a mottled pigmentation, with blackish-brown markings over a white background. It has a short dorsal ridge in place of a dorsal fin, which is thought to facilitate movement under the ice, or reduce surface area and heat loss. An adult narwhal is typically 3.0 to 5.5 m in length and 800 to 1,600 kg in weight. Carl Linnaeus scientifically described the species in his 1758 work Systema Naturae.
The beluga whale 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 white whale, as it is the only cetacean to regularly occur with this colour; the sea canary, due to its high-pitched calls; and the melonhead, though that more commonly refers to the melon-headed whale, which is an oceanic dolphin.
Kentriodon is an extinct genus of toothed whale related to modern-day dolphins. Fossils have been found in North America, Europe and Japan. Several species have been described.
The Cetruminantia are a clade made up of the Cetancodontamorpha and their closest living relatives, the Ruminantia.
Australodelphis mirus is an extinct Pliocene dolphin. A. mirus is known from fossils found in the Sørsdal Formation, Mule Peninsula, Vestfold Hills, East Antarctica. The genus has been described as an example of convergent evolution with beaked whales.
Kentriodontidae is an extinct family of odontocete whales related to modern dolphins. The Kentriodontidae lived from the Oligocene to the Pliocene before going extinct.
Delphinoidea is the largest group of toothed whales with 66 genera in 6 families. The largest living member of the superfamily is the killer whale, which can reach 6 tons, while the smallest is the vaquita.
Artiofabula is a clade made up of the Suina and the Cetruminantia. The clade was found in molecular phylogenetic analyses and contradicted traditional relationships based on morphological analyses.
Bohaskaia is an extinct genus of beluga-like odontocete cetacean known from the Early Pliocene of Virginia and North Carolina, United States. It was first named by Jorge Vélez-Juarbe and Nicholas D. Pyenson in 2012 and the type species is Bohaskaia monodontoides.
Lophocetus is an extinct genus of dolphin belonging to the clade Delphinida that is known from late Miocene (Tortonian) marine deposits in California and Maryland. Although usually placed in Kentriodontidae, recent studies have found it only distantly related to Kentriodon.
Eodelphinus is an extinct genus of oceanic dolphins belonging to the family Delphinidae.
Casatia is a genus of extinct cetacean from the Early Pliocene, approximately between 5.1 and 4.5 million years ago. The genus contains a single species, C. thermophila. It was described from a partial skull. Its closest relatives are the narwhal and beluga, yet the remains were found farther south than its relatives, supporting the theory that monodontids evolved from warm water genera before becoming adapted to cold water.
A narluga is a hybrid born from mating a female narwhal and a male beluga whale. Narwhals and beluga whales are both cetaceans found in the High Arctic and are the only two living members of the family Monodontidae.