any shark of the genus Heterodontus, which contains about 10 species and constitutes the family Heterodontidae (order Heterodontiformes). This exclusively marine group is found only in the tropical reaches of the Pacific and Indian oceans and in the eastern Pacific from California to the Galápagos Islands. Bullhead sharks are harmless to humans and eat mollusks, crabs, and sea urchins; their teeth are designed primarily for crushing and grinding. The Port Jackson shark (H. philippi or portusjacksoni), found in Australian Pacific waters, reaches a length of 1.5 m (5 feet).