The Japanese Bullhead Shark is a species of bullhead shark, family Heterodontidae. This species is of little interest to fisheries. Harmless to humans, the Japanese bullhead shark can be easily hand-caught by divers. The conservation status of this species has not been evaluated by the International Union for Conservation of Nature (IUCN).
A modest-sized shark reaching a maximum known length of 1.2 m (3.9 ft), the Japanese bullhead shark has a cylindrical body with the short, wide head and blunt, pig-like snout typical of the bullhead sharks. The eyes lack a nictitating membrane and are followed by tiny spiracles. Shallow supraorbital ridges are present above the eyes, and the space between them is slightly concave. The nostrils are divided into incurrent and excurrent openings by long flaps of skin that reach the mouth; the incurrent opening is encircled by a groove while another groove runs from the excurrent opening to the mouth. The small mouth is positioned nearly at the tip of the snout; the front teeth are small with a sharp central cusp flanked by a pair of lateral cusplets, while the back teeth are broad and rounded. There are deep furrows at the corners of the mouth, extending onto both jaws.
The first dorsal fin is very large and high, and is somewhat falcate (sickle-shaped); it originates over the bases of the pectoral fins. The second dorsal fin is much smaller, but similar in shape, and originates over the rear tips of the pelvic fins. Both dorsal fins bear stout spines on their leading edges. The pectoral fins are large; the pelvic fins are much smaller than the first dorsal fin. The anal fin is placed well in front of the caudal fin, which is broad with a short lower lobe and a long upper lobe bearing a strong ventral notch near the tip. The dermal denticles are large and rough, particularly on the sides of the body. The coloration is light brown, with a series of diffuse-edged, darker wide bands interspersed with narrower stripes from snout to tail, numbering 11–14 in all. There is a faint lighter band on top of the head between the eyes, and a darker blotch beneath each eye.
This bottom-dwelling shark inhabits the continental shelf at a depth of 6–37 m (20–121 ft), preferring areas covered by rocks, rocky reefs, or kelp.
The Japanese bullhead shark is a slow-moving predator that feeds on crustaceans, mollusks, small fishes, and sea urchins, often hunting for them while "walking" along the sea bottom with alternating motions of its pectoral and pelvic fins.