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Longfin mako shark
The longfin mako shark (''Isurus paucus'') is a species of mackerel shark in the family Lamnidae, with a probable worldwide distribution in temperate and tropical waters. An uncommon species, it is typically lumped together under the name "mako" with its better-known relative, the shortfin mako shark (''I. oxyrinchus''). The longfin mako is a pelagic species found in moderately deep water, having been reported to a depth of . Growing to a maximum length of , the slimmer build and long, broad pectoral fins of this shark suggest that it is a slower and less active swimmer than the shortfin mako.
Longfin mako sharks are predators that feed on small schooling bony fishes and cephalopods. It is uncertain whether this shark is capable of elevating its body temperature above that of the surrounding water like the other members of its family, though it possesses the requisite physiological adaptations. Reproduction in this species is aplacental viviparous, meaning that the embryos hatch from eggs inside the uterus. In the latter stages of development, the unborn young are fed non-viable eggs by the mother (oophagy). The litter size is typically two but may be as many as eight. The longfin mako is of limited commercial value as its meat and fins are of lower quality than those of other pelagic sharks; it is caught unintentionally in low numbers across its range. The International Union for Conservation of Nature (IUCN) has assessed this species as Vulnerable due to its rarity, low reproductive rate, and continuing bycatch mortality.
==Taxonomy and phylogeny==
The original description of the longfin mako was published in 1966 by Cuban marine scientist Darío Guitart-Manday, in the scientific journal ''Poeyana'', based on three adult specimens from the Caribbean Sea. An earlier synonym of this species may be ''Lamiostoma belyaevi'', described by Glückman in 1964. However, the type specimen designated by Glückman consists of a set of fossil teeth that could not be confirmed as belonging to the longfin mako, and thus the name ''paucus'' took precedence over ''belyaevi'' despite being published later. The specific epithet ''paucus'' is Latin for "few", referring to the rarity of this species relative to the shortfin mako.
The sister species relationship between the longfin and shortfin makos has been confirmed by several phylogenetic studies based on mitochondrial DNA. In turn, the closest relative of the two mako sharks is the great white shark (''Carcharodon carcharias''). Fossil teeth belonging to the longfin mako have been recovered from the Muddy Creek Marl of the Grange Burn formation, south of Hamilton, Australia, and from Mizumani Group in Gifu Prefecture, Japan. Both deposits date to the Middle Miocene epoch (15–11 Ma).
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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