The Prickly Shark is one of the two species of sharks in the family Echinorhinidae. The prickly shark is not known to be dangerous to humans and has minimal economic value. It is caught incidentally by commercial deepwater fisheries, which are expanding and may potentially threaten its population. Thus, the International Union for Conservation of Nature (IUCN) has assessed this species as Near Threatened.
The prickly shark has a flabby and cylindrical body, with the adults markedly bulkier than juveniles, and a short, moderately flattened head. The nostrils are placed far apart and preceded by small flaps of skin. The spiracles are tiny and positioned well behind the eyes, which lack nictitating membranes. The mouth forms a broad arch, with very short furrows at the corners. There are 21–25 and 20–27 tooth rows in the upper and lower jaws respectively. The knife-like teeth each have a strongly angled main cusp flanked by up to three smaller cusplets on either side; the lateral cusplets are absent in young sharks. There are five pairs of gill slits, with the fifth pair the longest.
The lateral line runs along each side of body in a conspicuous furrow. The pectoral fins are short, while the pelvic fins are relatively large with long bases. The first dorsal fin is small and originates at or behind the level of the pelvic fin origins; the second dorsal fin is similar to the first and positioned close behind. The anal fin is absent, and the stout caudal peduncle lacks depressions at the caudal fin origins. The caudal fin has a longer upper lobe without a notch in the trailing margin, and an indistinct lower lobe. The skin has a dense, uniform covering of non-overlapping dermal denticles measuring up to 0.4 cm (0.16 in) across, which are never fused together as in the bramble shark. Each denticle is thorn-like, with strong ridges running down the central spine and radiating out over the star-shaped base. The denticles beneath the snout are very fine in adults. The prickly shark is plain brown or gray, often with a purplish tint, and has black trailing margins on the fins. The underside is paler, most obviously on the snout and around the mouth. It may reach a length of 4.0 m (13.1 ft). The maximum recorded weight is 266 kg (590 lb) for a 3.1 m (10 ft) long female.
Favoring cooler temperatures of 5.5–11 °C (42–52 °F), the prickly shark is mostly found below depths of 100–200 m (330–660 ft), particularly in the tropics. It has been recorded from at least 650 m (2,130 ft) down and may occur much deeper, possibly to 1,500 m (4,900 ft). On the other hand, at higher latitudes it frequently enters shallow inshore waters; for example, in Monterey Canyon it can be consistently found at depths of 15–35 m (49–115 ft), and off Moss Landing one individual was captured in water only 4 m (13 ft) deep. This shark inhabits continental and insular shelves and slopes, where it swims close to the bottom. It can also be found inside submarine canyons, close to the walls. It prefers areas with a muddy or sandy substrate. It is tolerant of low dissolved oxygen levels, allowing it to inhabit oceanic basins inaccessible to other sharks.
The size and structure of the prickly shark's mouth and pharynx suggests that it uses suction to capture prey. This species feeds on a variety of benthic and pelagic bony fishes, including hake, flounders, rockfishes, lingcod, topsmelt, mackerel, and herring, and on cartilaginous fishes, including elephantfishes (Callorhinchus), spiny dogfish (Squalus acanthias), young bluntnose sixgill sharks(Hexanchus griseus), and ghost catshark (Apristurus) egg cases. Octopuses and Squid, including the Humboldt squid (Dosidicus gigas) are also consumed.