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Author: Taylor and Castro-Aguirre, 1972

Field Marks:
Dorsal fins with spines, anal fin present, colour pattern of large dark spots 1/2 eye diameter or more on light background, a light bar present on interorbital space between supraorbital ridges, first dorsal origin over pectoral bases.

Diagnostic Features:
Supraorbital ridges low, not abruptly ending behind eyes; molariform teeth in rear of mouth not greatly expanded and rounded, with strong medial ridges. First dorsal origin over pectoral bases; apex of anal fin reaches lower caudal origin when laid back; anal base length between 1 and 2 times in space between anal insertion and lower caudal origin. Colour light grey-brown with scattered large black spots on fins and body, these usually half eye diameter or more, and a light transverse band between supraorbital ridges on interorbital space. Egg cases with thick, T-shaped paired spiral flanges, transverse to case axis and with 5 turns visible on sides, case apex with very long tendrils.

Geographical Distribution:
Eastern Pacific: From southern Baja California, the Gulf of California, and Pacific Mexico southward to Guatemala, the Gulf of Panama, Colombia, probably Ecuador, and Peru.

Habitat and Biology:
A warm-temperate and tropical bullhead shark of littoral continental waters, found on rocky bottom and on sandy areas from close inshore down to at least 20 m depth. Oviparous. The long tendrils and rigid, Tshaped spiral flanges on the egg-cases of this shark suggest that wedging of the eggs in crevices through the action of flexibleflanges has been replaced by anchoring of the cases to the substrate by the tendrils, unlike other bullhead sharks with flexible-flanged eggs. The heavyT-flanges may serve instead to protect the egg from impacts and egg-predators.

Maximum size 70 cm, matures at a size above 55 cm; young hatch at 14 cm.

Interest to Fisheries:
Minimal; small numbers are taken as a byeatch of the shrimp fishery in Mexico and processed into fishmeal along with other sharks.

Type material:
Holotype: Scripps Institution of Oceanography, SIO 70 to 90, 610 mm adult female. Type Locality: Ceiro Colorado, Sonora, Mexico, Gulf of California.

Mexican hornshark (Heterodontus mexicanus)