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blackmouth catshark
The blackmouth catshark (''Galeus melastomus'') is a species of catshark, and part of the family Scyliorhinidae, common in the northeastern Atlantic Ocean from Iceland to Senegal, including the Mediterranean Sea. It is typically found over the continental slope at depths of , on or near muddy bottoms. The youngest sharks generally inhabit shallower water than the older juveniles and adults. This slim-bodied species is characterized by the black interior of its mouth, a marbled pattern of pale-edged brownish saddles or blotches along its back and tail, and a prominent saw-toothed crest of enlarged dermal denticles along the upper edge of its caudal fin. It reaches lengths of , with sharks in the Atlantic growing larger than those in the Mediterranean.
Slow-swimming but active, the blackmouth catshark is a generalist that preys on a wide variety of crustaceans, cephalopods, and fishes. Its visual and electroreceptive systems are adept at tracking moving, bioluminescent prey. This species is oviparous, with females producing batches of up to 13 egg cases throughout the year. Because of its abundance, the blackmouth catshark forms a substantial part of the bycatch of deepwater commercial fisheries across much of its range. It has low economic value and is usually discarded, though the largest sharks may be marketed for meat and leather. The International Union for Conservation of Nature (IUCN) has listed this species under Least Concern, as there is no indication that its numbers have declined despite fishing pressure.
== Taxonomy and phylogeny ==
Constantine Samuel Rafinesque briefly described the blackmouth catshark in his 1810 ''Caratteri di alcuni nuovi generi e nuove specie di animali e piante della Sicilia: con varie osservazioni sopra i medesimi'', wherein he referenced the distinctive black interior of its mouth (from which the specific epithet ''melastomus'' is derived). No type specimen was designated.〔 This species may also be called the black-mouthed dogfish.〔 A 2005 phylogenetic analysis that included five ''Galeus'' species, based on mitochondrial and nuclear DNA, found that ''G. melastomus'' forms a clade with ''G. murinus'', apart from the clade of ''G. eastmani'', ''G. gracilis'', and ''G. sauteri''.〔 The oldest documented blackmouth catshark fossils come from the northern Apennines and date to the Lower Pliocene (5.3–3.6 Ma).〔
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