Heterodontiformes appear in the fossil record in the Early Jurassic, before any of other (Galeomorphii) a group which includes all modern sharks except the dogfish and it relatives. They have never been common, and probably their origin lies even further back. These Bullhead sharks are a small order of very primitive modern sharks. They are relatively small 20 to 50 inches, bottom feeders in both tropical and subtropical waters that are Shallow to moderately deep continental and insular waters at depths from intertidal to at least 900 ft. These Bullhead sharks are a single family with just eight species and are the only living sharks that feature fin spines on their two dorsal fins and an anal fin.

The Bullhead sharks have large, thick heads with a broad crest over both eyes. They have snub snouts and short mouths with grooves connecting to the nostrils and teeth both for holding (in the front) and crushing (in the rear). The nasal capsules are "trumpet shaped" and well separated from orbits. The eyes lack a nictitating membrane, a spiral is present but small. The dorsal ends of branchial arches 4 and 5 are attached but not fused into a "pickax" as in the lamniform sharks.

Their diet includes sea-urchins, starfishes, crabs, shrimps, barnacles, marine worms, sea-snails, , and other hard prey they crush with their rear teeth and they also catch small fishes.

The egg cases of bullhead sharks are auger-shaped and surrounded by two broad spiral flanges and considered the most bizarre in all of nature. The shape enables the mother to wedge her eggs into crevices keeping most predators from removing them. The eggs hatch after 5 to 12 months.depending on species and water temperature.

Order Heterodontiformes - Bullhead Sharks

Family Heterodontidae - Bullhead sharks

Eight Species
species in the Family Heterodontidae
Heterodontus francisciHorn shark
Heterodontus galeatusCrested bullhead shark
Heterodontus japonicusJapanese bullhead shark
Heterodontus mexicanusMexican hornshark
Heterodontus portusjacksonjPort Jackson shark
Heterodontus quoyiGalapagos bullhead shark
Heterodontus ramalheiraWhitespotted bullhead shark
Heterodontus zebraZebra bullhead shark