Mesoplodont whales are 16

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

toothed whale The toothed whales (also called odontocetes, systematic name Odontoceti) are a parvorder of cetaceans that includes dolphins, porpoises, and all other whales possessing teeth, such as the beaked whales and sperm whales. Seventy-three species of t ...

in the genus ''Mesoplodon'', making it the largest genus in the cetacean order. Two species were described as recently as 1991 (pygmy beaked whale) and 2002 (Perrin's beaked whale), and

marine biologist Marine biology is the scientific study of the biology of marine life, organisms in the sea. Given that in biology many scientific classification, phyla, family (biology), families and genera have some species that live in the sea and others th ...

s predict the discovery of more species in the future. A new species was described in 2021. They are the most poorly known group of large mammals. The generic name "mesoplodon" comes from the

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

''meso''- (middle) - ''hopla'' (arms) - ''odon'' (teeth), and may be translated as 'armed with a tooth in the centre of the jaw'.

Physical description

Scars from cookie-cutter shark bites on Gray's beaked whale

Mesoplodont beaked whales are small whales, (pygmy beaked whale) to (strap-toothed whale) in length, even compared with closely related whales such as the

bottlenose whale ''Hyperoodon'' (or ''Hyperoödon'') is a genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes ...

s and

giant beaked whale The four-toothed whales or giant beaked whales are beaked whales in the genus ''Berardius''. They include Arnoux's beaked whale (''Berardius arnuxii'') in cold Southern Hemispheric waters, and Baird's beaked whale (''Berardius bairdii'') in t ...

s. The spindle-shaped body has a small dorsal fin and short and narrow flippers. The head is small and tapered and has a semicircular blow hole that is sometimes asymmetric. The beak, which vary in length between species, blends with the small melon without a crease. Sexual dimorphism is poorly known, but the females tend to be the same size or larger than males at least in some species. The males typically have a bolder coloration and a unique dentition. The males of most species are covered in scars from the teeth of other males. The lower jaw often forms a huge arch in some species, sometimes extending above the rostrum in a shape comparable to a playground slide. Every species has large (sometimes tusk-like) teeth of variable size, shape, and position. Both sexes often have bites from cookie-cutter sharks. The

dorsal fin A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through conv ...

is rather small and located between two-thirds and three-quarters down the back of the animal. Information on longevity and lactation is non-existent, and information on gestation is nearly so.

Behavior

Most species are very rarely observed, and little is known about their behavior. They are typically found in groups, possibly segregated between sexes. Some species are so uncommon, they have yet to be observed alive. On the surface, they are typically very slow swimmers and do not make obvious blows. They have never been observed raising their flukes above the water. They are all very deep divers, and many feed entirely on squid.

Conservation

The mesoplodonts are completely unknown as far as population estimates are concerned. They have been hunted occasionally by the Japanese, but never directly. They are also accidentally captured in

drift net Drift netting is a fishing technique where nets, called drift nets, hang vertically in the water column without being anchored to the bottom. The nets are kept vertical in the water by floats attached to a rope along the top of the net and weig ...

s. It is not known what effect this has on the population.

Species

Andrews' beaked whale Andrews' beaked whale (''Mesoplodon bowdoini''), sometimes known as the deep-crest beaked whale or splay-toothed whale, is one of the least known members of a poorly known genus. The species has never been observed in the wild, and is known only ...

(''M. bowdoini'') Andrews, 1908 *

Blainville's beaked whale Blainville's beaked whale (''Mesoplodon densirostris''), or the dense-beaked whale, is believed to be the widest ranging mesoplodont whale. The French zoologist Henri de Blainville first described the species in 1817 from a small piece of jaw � ...

(''M. densirostris'') Blainville, 1817 *

Deraniyagala's beaked whale Deraniyagala's beaked whale (''Mesoplodon hotaula'') is a species of mesoplodont whale. Taxonomy Deraniyagala's beaked whale was once synonymous with the Ginkgo-toothed beaked whale (''Mesoplodon ginkgodens''), until several studies confirmed t ...

(''M. hotaula'')

Deraniyagala Deraniyagala is a town in the Kegalle district in the Sabaragamuwa Province of Sri Lanka. Deraniyaga city area consists major government administrative offices, textile industries and transportation hub and the district hospital which has seve ...

, 1963 *

Gervais's beaked whale Gervais's beaked whale (''Mesoplodon europaeus''), sometimes known as the Antillean beaked whale, Gulf Stream beaked whale, or European beaked whale (from which its scientific name is derived) is the most frequently stranding type of mesoplodont ...

(''M. europaeus'') Gervais, 1855 * Ginkgo-toothed beaked whale (''M. ginkgodens'') Nishiwaki and Kamiya, 1958 *

Gray's beaked whale Gray's beaked whale (''Mesoplodon grayi''), sometimes known as Haast's beaked whale, the scamperdown whale, or the southern beaked whale, is one of the better-known members of the genus ''Mesoplodon''. This species is fairly gregarious and strand ...

(''M. grayi'') von Haast, 1876 *

Hector's beaked whale Hector's beaked whale (''Mesoplodon hectori''), is a small mesoplodont living in the Southern Hemisphere. This whale is named after Sir James Hector, a founder of the colonial museum in Wellington, New Zealand. The species has rarely been seen i ...

(''M. hectori'') Gray, 1871 *

Hubbs' beaked whale Hubbs' beaked whale (''Mesoplodon carlhubbsi'') was initially thought to be an Andrews' beaked whale when discovered by ichthyologist Carl Hubbs; however, it was named in his honor when it was discovered to be a new species. This species has the ...

(''M. carlhubbsi'') Moore, 1963 *

Perrin's beaked whale Perrin's beaked whale (''Mesoplodon perrini'') is part of the toothed whale suborder and is one of over 90 known cetaceans in existence today. Beaked whales are part of the family Ziphiidae, which are the second most diverse group out of all mari ...

(''M. perrini'') Dalebout, Mead, Baker, Baker & van Helden, 2002 *

Pygmy beaked whale The pygmy beaked whale (''Mesoplodon peruvianus''), also known as the bandolero beaked whale, Peruvian beaked whale and lesser beaked whale, is the smallest of the mesoplodonts and one of the newest discoveries. There were at least two dozen sight ...

(''M. peruvianus'') Reyes, Mead, and Van Waerebeek, 1991 *

Sowerby's beaked whale Sowerby's beaked whale (''Mesoplodon bidens''), also known as the North Atlantic or North Sea beaked whale, is a species of toothed whale. It was the first mesoplodont whale to be described. James Sowerby, an English naturalist and artist, firs ...

(''M. bidens'') Sowerby, 1804 *

Spade-toothed whale The spade-toothed whale (''Mesoplodon traversii'') is a very little-known species, the rarest species of beaked whale. It was first named from a partial jaw found on Pitt Island, New Zealand, in 1872; reported and illustrated in 1873 by James He ...

(''M. traversii'') Gray, 1874 *

Stejneger's beaked whale Stejneger's beaked whale (''Mesoplodon stejnegeri''), also known as the Bering Sea beaked whale or the saber-toothed whale, is a relatively unknown member of the genus ''Mesoplodon'' inhabiting the North Pacific Ocean. Leonhard Hess Stejneger col ...

(''M. stejnegeri'') True, 1885 *

Strap-toothed whale The strap-toothed beaked whale (''Mesoplodon layardii''), also known as Layard's beaked whale, is one of the largest members of the mesoplodont genus, growing to in length and reaching up to . The common and scientific name was given in honor o ...

(''M. layardii'') Gray, 1865 *

True's beaked whale True's beaked whale (''Mesoplodon mirus'') is a medium-sized whale in the genus ''Mesoplodon''. It is native to the northern Atlantic Ocean. The common name is in reference to Frederick W. True, a curator at the United States National Museum (no ...

(''M. mirus'') True, 1913 *

Ramari's beaked whale Ramari's beaked whale (''Mesoplodon eueu'') is a medium size whale in the genus ''Mesoplodon''. It is found in cool waters of the Southern Hemisphere. The species name, ''eueu'', comes from the Khwedam word meaning 'big fish', as most of the stra ...

(''M. eueu'') Carroll ''et al'', 2021

Longman's beaked whale The tropical bottlenose whale (''Indopacetus pacificus''), also known as the Indo-Pacific beaked whale or Longman's beaked whale, was considered to be the world's rarest cetacean until recently, but the spade-toothed whale now holds that positio ...

(''Indopacetus pacificus'', also known as the Indo-Pacific beaked whale or the tropical bottlenose whale) was originally assigned to ''Mesoplodon'', but Joseph Curtis Moore placed it in its own genus, '' Indopacetus'', a taxonomic assignment which has been followed by all researchers. Three extinct species of ''Mesoplodon'' are known, ''M. posti'', ''M. slangkopi''. and ''M. tumidirostris''.Miyazaki, N.; Hasegawa, Y. 1992: A new species of fossil beaked whale, Mesoplodon tumidirostris sp. nov. (Cetacea, Ziphiidae) from the Central North Pacific. Bulletin of the National Science Museum (A), 18: 167–174. File:Mesoplodon bidens British mammals (Pl. 46) (21866206616).jpg,

, ''Mesoplodon bidens''; a male, with conspicuous teeth in the lower jaw File:Andrews' Beaked Whale (neonate, beachwashed) (cropped).JPG, A stranded newborn

Andrews' Beaked Whale Andrews' beaked whale (''Mesoplodon bowdoini''), sometimes known as the deep-crest beaked whale or splay-toothed whale, is one of the least known members of a poorly known genus. The species has never been observed in the wild, and is known only ...

, ''M. bowdoini'' File:Hubbs' beaked whale skull.jpg, Skull of a

(''M. carlhubbsi'') File:Beaked Whale.jpg,

(''M. densirostris'') in the

Bahamas The Bahamas (), officially the Commonwealth of The Bahamas, is an island country within the Lucayan Archipelago of the West Indies in the Atlantic Ocean, North Atlantic. It takes up 97% of the Lucayan Archipelago's land area and is home to ...

File:Gervais' Beaked Whale.jpg,

(''M. europaeus'') in the

Gulf Stream The Gulf Stream, together with its northern extension the North Atlantic Current, North Atlantic Drift, is a warm and swift Atlantic Ocean, Atlantic ocean current that originates in the Gulf of Mexico and flows through the Straits of Florida a ...

off

North Carolina North Carolina () is a state in the Southeastern region of the United States. The state is the 28th largest and 9th-most populous of the United States. It is bordered by Virginia to the north, the Atlantic Ocean to the east, Georgia and So ...

File:Researchers conduct autopsy on stranded beaked whale.jpg, Autopsy of a stranded

(''M. grayi'') File:First underwater video of True's beaked whales underwater.ogv,

(''M. mirus'') off the

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File:Mesoplodon traversii.svg, The

(''M. traversii'') was only morphologically described in 2012

References

Notes

Sources

* * *

External links

* Carly Cassella
Scientists Think They've Discovered a New Species of Beaked Whale
On: science^alert 12 December 2020 {{Taxonbar, from=Q243810 Ziphiids Taxa named by Paul Gervais Articles containing video clips