Mesoplodont whales are 16

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

toothed whale The toothed whales (also called odontocetes, systematic name Odontoceti) are a parvorder of cetaceans that includes dolphins, porpoises, and all other whales with teeth, such as beaked whales and the sperm whales. 73 species of toothed wha ...

in the genus ''Mesoplodon'', making it the largest genus in the cetacean

order Order, ORDER or Orders may refer to: * A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica * Categorization, the process in which ideas and objects are recognized, differentiated, and understood ...

. 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 that inhabit the sea. Given that in biology many phyla, families and genera have some species that live in the sea and others that live on land, marine biology clas ...

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: 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 of all kno ...

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

Physical description

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 of beaked whale, containing just two species: the Northern and Southern bottlenose whales. While not in the genus ''Hyperoodon'', Longman's beaked whales are alternatively called tropical bottle ...

s and giant beaked whales. 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 on the back of most marine and freshwater vertebrates. Dorsal fins have evolved independently several times through convergent evolution adapting to marine environments, so the fins are not all homologous. They are found ...

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 wei ...

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 closely related to the ginkgo-toothed beaked whale. Taxonomy Deraniyagala's beaked whale was initially known from seven stranded individuals. The first sight ...

(''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 seven ...

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

Perrin's beaked whale Perrin's beaked whale (''Mesoplodon perrini'') is a species of ziphiid beaked whale belonging to the toothed whale suborder. The genus name '' Mesoplodon'' comes from the Greek meanings of ''meso''- (middle), - ''hopla'' (arms), - ''odon'' (te ...

(''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 sigh ...

(''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, fir ...

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

Spade-toothed whale The spade-toothed whale (''Mesoplodon traversii'') is the rarest species of beaked whale. Only six confirmed specimens have ever been found, over the timespan from 1872 to 2024. All six were found in the South Pacificfive in New Zealand and one ...

(''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 co ...

(''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 ''Mesoplodon'' genus, growing to in length and reaching up to . The common and scientific name was given in honor ...

(''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 (n ...

(''M. mirus'') True, 1913 * Ramari's beaked whale (''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 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 position ...

'', a taxonomic assignment which has been followed by all researchers. Four extinct species of ''Mesoplodon'' are known: ''M. longirostris'' ''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

, ''M. bowdoini'' File:Hubbs' beaked whale skull.jpg, Skull of a Hubbs' beaked whale (''M. carlhubbsi'') File:Beaked Whale.jpg,

(''M. densirostris'') in the

Bahamas The Bahamas, officially the Commonwealth of The Bahamas, is an archipelagic and island country within the Lucayan Archipelago of the Atlantic Ocean. It contains 97 per cent of the archipelago's land area and 88 per cent of its population. ...

File:Gervais' Beaked Whale.jpg,

(''M. europaeus'') in the

Gulf Stream The Gulf Stream is a warm and swift Atlantic ocean current that originates in the Gulf of Mexico and flows through the Straits of Florida and up the eastern coastline of the United States, then veers east near 36°N latitude (North Carolin ...

off

North Carolina North Carolina ( ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It is bordered by Virginia to the north, the Atlantic Ocean to the east, South Carolina to the south, Georgia (U.S. stat ...

File:Researchers conduct autopsy on stranded beaked whale.jpg, Autopsy of a stranded Gray's beaked whale (''M. grayi'') File:First underwater video of True's beaked whales underwater.ogv,

(''M. mirus'') off the

Azores The Azores ( , , ; , ), officially the Autonomous Region of the Azores (), is one of the two autonomous regions of Portugal (along with Madeira). It is an archipelago composed of nine volcanic islands in the Macaronesia region of the North Atl ...

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 {{Authority control Ziphiids Taxa named by Paul Gervais Articles containing video clips