Mesoplodont whale

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Mesoplodont whale
Faroe stamp 197 Mesoplodon bidens.jpg
Sowerby's beaked whale (on Faroese stamp)
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Artiodactyla
Infraorder: Cetacea
Family: Ziphiidae
Subfamily: Hyperoodontinae
Genus: Mesoplodon
Gervais, 1850
Species

15, See text.

Mesoplodont whales are 16 species of toothed whale in the genus Mesoplodon, making it the largest genus in the cetacean order. [1] Two species were described as recently as 1991 (pygmy beaked whale) and 2002 (Perrin's beaked whale), and marine biologists predict the discovery of more species in the future. [2] A new species was described in 2021. [3] They are the most poorly known group of large mammals. [1] The generic name "mesoplodon" comes from the Greek meso- (middle) - hopla (arms) - odon (teeth), and may be translated as 'armed with a tooth in the centre of the jaw'. [2]

Contents

Physical description

Round scars from cookiecutter shark bites can be seen on the flank of this stranded Gray's beaked whale. Scars from cookie-cutter shark bites on Gray's beaked whale.jpg
Round scars from cookiecutter shark bites can be seen on the flank of this stranded Gray's beaked whale.

Mesoplodont beaked whales are small whales, 3.9 m (13 ft) (pygmy beaked whale) to 6.2 m (20 ft) (strap-toothed whale) in length, [2] 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. [2]

Sexual dimorphism is poorly known, but the females tend to be the same size or larger than males at least in some species. [2] 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 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. [1] They are typically found in groups, possibly segregated between sexes. Some species are so uncommon, they have yet to be observed alive. [1] 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 nets. It is not known what effect this has on the population.

Species

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. [2]

Three extinct species of Mesoplodon are known, M. posti, [5] M. slangkopi. [6] and M. tumidirostris. [7]

Related Research Articles

Beaked whales are a family of cetaceans noted as being one of the least known groups of mammals because of their deep-sea habitat and apparent low abundance. Only three or four of the 24 species are reasonably well-known. Baird's beaked whales and Cuvier's beaked whales were subject to commercial exploitation, off the coast of Japan, while the northern bottlenose whale was extensively hunted in the northern part of the North Atlantic late in the 19th and early 20th centuries.

Blainvilles beaked whale Species of mammal

Blainville's beaked whale, 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 — the heaviest bone he had ever come across — which resulted in the name densirostris. Off the northeastern Bahamas, the animals are particularly well documented, and a photo identification project started sometime after 2002.

Gervaiss beaked whale Species of whale

Gervais's beaked whale, sometimes known as the Antillean beaked whale, Gulf Stream beaked whale, or European beaked whale is the most frequently stranding type of mesoplodont whale off the coast of North America. It has also stranded off South America and Africa.

Ginkgo-toothed beaked whale Species of mammal

The ginkgo-toothed beaked whale 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 not having any scarring.

Hectors beaked whale Species of mammal

Hector's beaked whale, 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 in the wild.

Strap-toothed whale Species of whale

The strap-toothed beaked whale, also known as Layard's beaked whale, is one of the largest members of the mesoplodont family, growing to 6.2 metres (20 ft) in length and reaching up to 1,300 kilograms (2,900 lb). The common and scientific name was given in honor of Edgar Leopold Layard, the curator of the South African Museum, who prepared drawings of a skull and sent them to the British taxonomist John Edward Gray, who described the species in 1865.

Trues beaked whale Species of mammal

True's beaked whale 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.

Tropical bottlenose whale Species of mammal

The tropical bottlenose whale, 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. As of 2010, the species is now known from nearly a dozen strandings and over 65 sightings.

Perrins beaked whale Species of mammal

Perrin's beaked whale 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 marine mammals with over 20 species currently recognized. Although diverse, little is understood about these timid, deep divers that can dive for up to two hours. The whales are partially named after their beak shaped jaw, which extends from their small head. The genus name Mesoplodon comes from the Greek meanings of meso- (middle), - hopla (arms), - odon (teeth), and may be translated as 'armed with a tooth in the center of the jaw'.

Spade-toothed whale Species of beaked whale

The spade-toothed whale 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 Hector, and described the next year by John Edward Gray, who named it in honor of Henry Hammersley Travers, the collector. This was eventually lumped with the strap-toothed whale, starting as early as an 1878 article by Hector, who never considered the specimen to be specifically distinct. A calvaria found in the 1950s at White Island, also New Zealand, initially remained undescribed, but was later believed to be from a ginkgo-toothed beaked whale.

Deraniyagala's beaked whale is a species of mesoplodont whale.

References

Notes

  1. 1 2 3 4 Pitman 2008 , p. 721
  2. 1 2 3 4 5 6 Pitman 2008 , Characters and Taxonomic Relationships, pp. 721–724
  3. 1 2 Carroll et al 2021.
  4. Dalebout et al. 2014
  5. Olivier Lambert and Stephen Louwye (2016). "A new early Pliocene species of Mesoplodon: a calibration mark for the radiation of this species-rich beaked whale genus". Journal of Vertebrate Paleontology 36 (2): e1055754. doi : 10.1080/02724634.2015.1055754.
  6. G. Bianucci, O. Lambert, and K. Post. 2007. A high diversity in fossil beaked whales (Mammalia, Odontoceti, Ziphiidae) recovered by trawling from the sea floor off South Africa. Geodiversitas 29(4):561-618
  7. 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.

Sources

  • Dalebout, M. L.; Baker, C. S.; Steel, D.; Thompson, K.; Robertson, K. M.; Chivers, S. J.; Perrin, W. F.; Goonatilake, M.; Anderson, R. C.; Mead, J. G.; Potter, C. W.; Thompson, L.; Jupiter, D.; Yamada, T. K. (2014). "Mesoplodon hotaula: Resurrection of Mesoplodon hotaula Deraniyagala, 1963: A New Species of Beaked Whale in the tropical Indo-Pacific". Marine Mammal Science. 30 (3): 1081–1108. doi:10.1111/mms.12113. hdl: 1957/51503 .
  • Pitman, R. (2008). "Mesoplodont Whales (Mesoplodon spp.)". In Perrin, W. F.; Würsig, B.; Thewissen, J. G. M. (eds.). Encyclopedia of Marine Mammals (2nd ed.). Academic Press. pp. 721–726. ISBN   978-0-12-373553-9.
  • Carroll, Emma L.; McGowen, Michael R.; McCarthy, Morgan L.; Marx, Felix G.; Aguilar, Natacha; Dalebout, Merel L.; Dreyer, Sascha; Gaggiotti, Oscar E.; Hansen, Sabine S.; van Helden, Anton; Onoufriou, Aubrie B.; Baird, Robin W.; Baker, C. Scott; Berrow, Simon; Cholewiak, Danielle; Claridge, Diane; Constantine, Rochelle; Davison, Nicholas J.; Eira, Catarina; Fordyce, R. Ewan; Gatesy, John; Hofmeyr, G. J. Greg; Martín, Vidal; Mead, James G.; Mignucci-Giannoni, Antonio A.; Morin, Phillip A.; Reyes, Cristel; Rogan, Emer; Rosso, Massimiliano; Silva, Mónica A.; Springer, Mark S.; Steel, Debbie; Olsen, Morten Tange (27 October 2021). "Speciation in the deep: genomics and morphology reveal a new species of beaked whale Mesoplodon eueu". Proceedings of the Royal Society B: Biological Sciences. 288 (1961): 20211213. doi:10.1098/rspb.2021.1213 . Retrieved 27 October 2021.</ref>