Mesoplodont whales are 16

species In biology, a species is the basic unit of Taxonomy (biology), 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 ...

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 ...

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

order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of d ...

. 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 phyla, families and genera have some species that live in the sea and others that live on land, marine biology classifies sp ...

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 whales 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 shark The cookiecutter shark (''Isistius brasiliensis''), also called the cigar shark, is a species of small squaliform shark in the family Dalatiidae. This shark occurs in warm, oceanic waters worldwide, particularly near islands, and has been reco ...

s. 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 c ...

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 (''M. bowdoini'') Andrews, 1908 * Blainville's beaked whale (''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 th ...

(''M. hotaula'')

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, 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 The ginkgo-toothed beaked whale (''Mesoplodon ginkgodens'') is a poorly known species of whale even for a beaked whale, and was named for the unusual shape of its dual teeth. It is a fairly typical-looking species, but is notable for the males no ...

(''M. ginkgodens'') Nishiwaki and Kamiya, 1958 * Gray's beaked whale (''M. grayi'') von Haast, 1876 * Hector's beaked whale (''M. hectori'') Gray, 1871 * Hubbs' beaked whale (''M. carlhubbsi'') Moore, 1963 * Perrin's beaked whale (''M. perrini'') Dalebout, Mead, Baker, Baker & van Helden, 2002 * Pygmy beaked whale (''M. peruvianus'') Reyes, Mead, and Van Waerebeek, 1991 * Sowerby's beaked whale (''M. bidens'') Sowerby, 1804 * Spade-toothed whale (''M. traversii'') Gray, 1874 * Stejneger's beaked whale (''M. stejnegeri'') True, 1885 * Strap-toothed whale (''M. layardii'') Gray, 1865 * True's beaked whale (''M. mirus'') True, 1913 * Ramari's beaked whale (''M. eueu'') Carroll ''et al'', 2021 Longman's beaked whale (''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, Sowerby's beaked whale, ''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, ''M. bowdoini'' File:Hubbs' beaked whale skull.jpg, Skull of a Hubbs' beaked whale (''M. carlhubbsi'') File:Beaked Whale.jpg, Blainville's beaked whale (''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 North Atlantic. It takes up 97% of the Lucayan Archipelago's land area and is home to 88% of the archi ...

File:Gervais' Beaked Whale.jpg,

(''M. europaeus'') in the

Gulf Stream The Gulf Stream, together with its northern extension the North Atlantic Drift, 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 Uni ...

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 a ...

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, True's beaked whale (''M. mirus'') off the

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File:Mesoplodon traversii.svg, The Spade-toothed whale (''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