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Finetooth shark
The finetooth shark (''Carcharhinus isodon'') is a species of requiem shark, in the family Carcharhinidae, found in the western Atlantic Ocean, from North Carolina to Brazil. It forms large schools in shallow, coastal waters, and migrates seasonally following warm water. A relatively small, slender-bodied shark, the finetooth shark can be identified by its needle-like teeth, dark blue-gray dorsal coloration, and long gill slits. It attains a maximum length of 1.9 m (6.2 ft). The diet of this species consists primarily of small bony fishes, in particular menhaden. Like other members of its family, it is viviparous with females giving birth to 2–6 pups in estuarine nursery areas every other year.
Valued for its meat, the finetooth shark forms an important component of the commercial gillnet shark fishery operating off the southeastern United States. Population assessments suggest that this fishery does not currently pose a threat to U.S. populations of the species. The International Union for Conservation of Nature (IUCN) has therefore listed the finetooth shark under Least Concern, though there is no fishery data available for this species off South America. This shark is not known to pose a danger to humans, though it snaps vigorously when captured and should be handled with caution.
==Taxonomy and phylogeny==
The finetooth shark was originally described as ''Carcharias (Aprionodon) isodon'' by French zoologist Achille Valenciennes, in Müller and Henle's 1839 ''Systematische Beschreibung der Plagiostomen''. The type specimen is a juvenile male, possibly caught off the U.S. state of New York. This species was later moved to the genus ''Carcharhinus''. The specific epithet ''isodon'' means "equal teeth" in Greek, and refers to the similar number of teeth in the upper and lower jaws.〔Bester, C. (Biological Profiles: Finetooth Shark ). ''Florida Museum of Natural History Ichthyology Department''. Retrieved on May 5, 2009.〕 This species may also be referred to as the eventooth shark, smoothtooth shark, or night shark (usually used for ''C. signatus'').
As is the case for most ''Carcharhinus'' species, attempts to analyze the finetooth shark's phylogenetic relationships have yielded variable results. In 1988, Leonard Compagno grouped this species with the spinner shark (''C. brevipinna''), blacktip shark (''C. limbatus''), graceful shark (''C. amblyrhynchoides''), and the smooth tooth blacktip shark (''C. leiodon''), on the basis of morphological characters. Gavin Naylor's 1992 allozyme analysis found that the finetooth shark is the second-most basal member of the genus next to the blacknose shark (''C. acronotus''). Mine Dosay-Akbulut's 2008 study, based on ribosomal DNA, suggested that the closest relative of the finetooth shark is the smalltail shark (''C. porosus''), and that the two species form a clade apart from other ''Carcharhinus'' species.
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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