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Smalltooth sand tiger
The smalltooth sand tiger or bumpytail ragged-tooth (''Odontaspis ferox'') is a species of mackerel shark in the family Odontaspididae, with a patchy but worldwide distribution in tropical and warm temperate waters. They usually inhabit deepwater rocky habitats, though they are occasionally encountered in shallow water, and have been known to return to the same location year after year. This rare species is often mistaken for the much more common grey nurse shark (''Carcharias taurus''), from which it can be distinguished by its first dorsal fin, which is larger than the second and placed further forward. It grows to at least 4.1 m (13.5 ft) in length.
Very little is known of the biology and behavior of the smalltooth sand tiger. It is an active predator of benthic bony fishes, invertebrates, and cartilaginous fishes. This species is thought to be ovoviviparous with oophagous embryos like other mackerel sharks. In contrast to its formidable size and appearance, this shark is harmless, having never been known to behave aggressively towards humans. There is concern that its numbers are declining due to human activities in the Mediterranean and elsewhere, though existing data is inadequate for a full assessment of its conservation status.
==Taxonomy and phylogeny==
The smalltooth sand tiger was originally described as ''Squalus ferox'' by Italian-French naturalist Antoine Risso in 1810, based on a specimen from Nice, France. In 1950, Gilbert Percy Whitley described ''O. herbsti'' from Australian specimens, separating them from ''O. ferox'' on the basis of dentition and the absence of spots. Leonard Compagno synonymized the two species in 1984, as subsequently discovered Pacific specimens had blurred Whitley's distinguishing characters.〔 The specific epithet ''ferox'' is Latin for "fierce". Other common names for this shark include blue nurse shark, fierce shark, Herbst's nurse shark, and sand tiger shark.〔
A phylogenetic study based on mitochondrial DNA, performed by Naylor ''et al.'' in 1997, suggests that the smalltooth sand tiger and its relative, the bigeye sand tiger (''O. noronhai''), are more closely related to the thresher sharks than to the grey nurse shark, to which it bears a strong resemblance. If true, this would indicate that the similarities between this species and the grey nurse shark arose as the result of convergent evolution. Fossil teeth belonging to the smalltooth sand tiger have been found from Lower Pliocene (5.3–3.6 Ma) deposits in Italy and Venezuela.
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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