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Mesoplodont whales are fifteen species of toothed whale 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 biologists predict the discovery of more species in the future.〔 They are the most poorly known group of large mammals.〔 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'. ==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 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. Gray's beaked whale, the exception, has numerous small and possibly functional teeth in the lower jaw. 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. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Mesoplodont whale」の詳細全文を読む スポンサード リンク
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