The black dogfish adult is usually between 60 and 75 cm long and can reach up to 1.1 m, making it the largest member of the family Etmopterides. A male of 60 cm weighs nearly a kilogram, the largest reach 80 cm 2.3 kg. The female is larger than that of the male and the largest weigh up to 4 kg for a length of 90 cm. This fish has a body rather stocky and laterally compressed, with a moderately long snout, thick and flattened forming a wide arc in front. The eyes, large and oval, are green, reflective, and have no nictitating membrane (third eyelid) and are followed by stigma much smaller (openings accessories for breathing). The nostrils are placed forward and preceded by small flaps of skin. The mouth is wide and evenly curved, with thin lips and short, but deep furrows in the corners. It has about 34 rows of teeth on both sides of both jaws. Each tooth has three (sometimes five) cusp slender, with the longest central.
The two dorsal fins are preceded by two large white spines grooved, with the second much longer than the first. The first dorsal fin has a rounded top and a rear margin almost straight, running from behind the pectoral fins. The second dorsal fin is more angular and has about twice the size of the first, with its origin in the middle of the base of the pelvic fin. The pectoral fins are small and rounded. Pelvic fins about as large as the second dorsal fin, with rounded ends and almost straight back. The caudal peduncle is short and leads to a large tail fin includes at least one quarter of the total length and the upper lobe has a convex upper margin, leading to a square tip, while the lower lobe is indistinct. The skin is densely covered with tiny denticles skin, each base has a star-shaped irregular and curved spine. This species is dark brown on the dorsal and almost black on the ventral, and dorsal fin spines are white. Juveniles have white edges on the dorsal fin, pectoral fins and pelvic fins. Her skin is dotted with small dots bioluminescent without forming a regular pattern