Description
The reported maximum lengths attained by the blackmouth catshark varies from 67 to 79 cm (26 to 31 in) for Atlantic sharks and 50 to 64 cm (20 to 25 in) for Mediterranean sharks; a length record of 90 cm (35 in) may be dubious. Females attain a larger ultimate size than males. The maximum weight on record is 1.4 kg (3.1 lb). This species has a slender, firm body with a rather long, pointed snout comprising roughly 6–9% of the total length. The anterior rim of each nostril bears a large triangular flap, which divides the nostril into incurrent and excurrent openings. The eyes are horizontally oval and equipped with rudimentary nictitating membranes (protective third eyelids). Beneath each eye is a subtle ridge, and behind is a small spiracle. The mouth forms a short, wide arch, and bears moderately long furrows around the corners. The upper and lower jaws contain around 69 and 79 tooth rows respectively. Each tooth is small, with a narrow central cusp flanked by one or two smaller cusplets on either side. There are five pairs of gill slits, with the fifth pair over the pectoral fin bases.
The two dorsal fins are roughly equal in size and placed far back on the body: the first originates behind the midpoint of the pelvic fin bases and the second behind the midpoint of the anal fin base. The pectoral fins are large, while the pelvic fins are small and low, with angular margins. The anal fin is much larger than either dorsal fin; its base measures 13–18% of the total length and greatly exceeds the distance between the pelvic and anal fins, or between the dorsal fins. The caudal peduncle is laterally compressed, with the end of the anal fin very close to the caudal fin. The caudal fin comprises around a quarter of the total length; the upper lobe is low with a ventral notch near the tip, while the lower lobe is indistinct. The skin is very thick and covered by well-calcified dermal denticles. There is a prominent row of enlarged denticles, resembling saw teeth, along the upper edge of the caudal fin. The body is grayish-brown above, with 15–18 dark, rounded saddles, blotches, and/or spots that run onto the tail; each marking is highlighted by a paler border. The underside is white, as are the tips of the dorsal and caudal fins. The inside of the mouth is black.
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