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Author: (Girard,1854)

Field Marks:
Dorsal fins with spines, anal fins present, colour patterns of small dark spots less than 1/3 eye diameter on light background, no light bar on interorbital space between supraorbital ridges, first dorsal origin over pectoral bases.

Diagnostic Features:
Supraorbital ridges moderately high, abruptly ending posteriorly; molariform teeth in rear of mouth not greatly expanded and rounded, with a strong medial ridge. First dorsal origin over pectoral bases; apex of anal fin falling opposite or slightly behind lower caudal origin when laid back; anal base length equal or less than distance between anal insertion and lower caudal origin. Colour dark to light grey or brown with scattered small spots on fins and body, less than 1/3 length of eye; no light bar on interorbital space. Egg cases with paired simple flat spiral flanges, diagonalto case axis and with 5 turns visible on sides,case apex without
tendrils.

Geographical Distribution:
Warm-temperate and subtropical waters of the eastern Pacific: Central California to Gulf of California, and probably Ecuador

Habitat and Biology:
A common benthic and epibenthic shark, found on the eastern Pacific continental shelf most abundantly at depths of 2 to 11 m but ranging from the intertidal down to at least 150 m. Found on rocky bottom, kelp beds, sandy draws between rocks, and on sand flats. On rocks it often occurs in deep crevices and small caves, and ventures far into large underwater caverns.
The horn shark is sluggish, nocturnal, and mostly solitary. It is seldom seen moving during the daytime but commonly has its head in a crevice. Shortly after dusk this shark becomes, active and apparently feeds mostly at night, but ceases activity after dawn. Experimentation with captive horn sharks indicates that their diel activity pattern is controlled by light intensity.
The broad, muscular paired fins of the horn shark are used as limbs for clambering on the bottom, and are highly mobile and flexible. Swimming is slow and sporadic.

Courtship and copulation has been observed in captivity. The male horn shark chases the female until the latter is ready, then both drop to the bottom. The male grabs the female's pectoral fin with his teeth and inserts a single clasperin her cloaca; copulation lasts 30 to 40 minutes. One to two weeks later eggs are laid by captive females, one of which laid 2 eggs per day at 11 to 14 day intervals for 4 months. In nature these sharks mate in December or January and females drop eggs in February to April. Females normally deposit eggs under rocks or in crevices between them, but in captivity they drop eggs on the bottom where the contents of egg cases may be subsequently sucked out and eaten by these sharks. Eggs can be readily hatched in aquaria and take 7 to 9 months to hatch; the young begin to feed a month after hatching.

The horn shark feeds on benthic invertebrates, especially sea urchins (echinoids), crabs and possibly abalone, but less commonly on small fishes. Horn sharks are harmless and are often harassed and grabbed by divers, but when provoked may swim after their assailants and bite them.

Size:
Maximum total length 122 cm but most adults below 97 cm; males mature at 58 to 71 cm, females above 58 cm. Size at hatching 15 or 16 cm.

Interest to Fisheries:
Minimal, probably utilized for fishmeal as a byeatch of the shrimp fishery and other bottom-trawling operations in Pacific Mexican waters. It is often captured by divers for sport and for its large fin spines, which are made into jewelry; decreases in numbers of horn sharks have been noted in areas with intense diver activity in southern California.

Type material:
Holotype: US National Museum of Natural History, apparently lost? Type Locality: Monterey Bay, California.

Horn shark (Heterodontus francisci)