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Heterodontus mexicanus:   (click for more)

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Synonyms
Other Combinations:  None
FAO Names
En - Mexican hornshark, Fr - Requin dormeur buffle, Sp - Dormilón búfalo.
3Alpha Code: HEM     Taxonomic Code: 1040100104
Scientific Name with Original Description
Heterodontus mexicanus  Taylor and Castro-Aguirre, 1972, An. Esc. Nac. Cienc. Biol. México, 19: 125, figs 1-5, 8-9. Holotype: Scripps Institution of Oceanography, SIO-70-90, 610mmadult female, Cerro Colorado, Sonora, Gulf of California, Mexico.
Diagnostic Features
fieldmarks: Dorsal fins with spines, anal fin present, colour pattern of large dark spots of one-half eye diameter or more on light background, a light bar present on space between supraorbital ridges, first dorsal-fin origin over pectoral-fin bases.

Supraorbital ridges low, gradually ending posteriorly; interorbital space shallowly concave, depth between ridges less than one-fourth eye length.  Anterior holding teeth with a cusp and a pair of cusplets in adults, posterior molariform teeth strongly carinate and not greatly expanded and rounded.  Pre-first dorsal-fin length 24 to 29% and anal-caudal space 6 to 9%of total length. Lateral trunk denticles large and rough, area behind first dorsal fin with about 70 to 130 denticles per cm² in adults.  Propterygium fused to mesopterygium.  First dorsal-fin spine directed obliquely posterodorsally in juveniles and adults; first dorsal-fin origin slightly anterior to pectoral-fin insertions, behind pectoral-fin midbases, and well posterior to fifth gill openings; first dorsal-fin insertion well anterior to pelvic-fin origins and well behind pectoral-fin insertions; first dorsal-fin free rear tip about opposite to or slightly ahead of pelvic-fin origins; first dorsal fin low and weakly falcate in adults, height 8 to 18% of total length, first dorsal fin about as large as pelvic fins; second dorsal-fin origin over or slightly in front of pelvic-fin rear tips, weakly falcate and nearly as large as first dorsal fin. Anal fin subangular and rounded to weakly falcate, with apex reaching lower caudal-fin origin or falling somewhat behind it when laid back; anal-caudal space between 1 and 2 times anal-fin base.  Total vertebral count unknown, precaudal count 60 to 70, monospondylous precaudal count 30 to 34, diplospondylous precaudal count 30 to 38, pre-first dorsal-fin spine count 14 to 16, and count from diplospondylous transition to second dorsal-fin spine 9 to 14.  Egg cases with thick, T-shaped paired spiral flanges, transverse to case axis, and a pair of long, slender tendrils on case apex; flanges with five turns.  A small species, mature between 50 and 70 cm.  Background colour of dorsal surface light grey-brown with large black spots on body and fins, these one-half eye diameter or more in size; body without a dark harness pattern; head with a light-coloured bar on interorbital surface of head and 1 or 2 dusky indistinct blotches under eye; fins without abrupt dark tips and white dorsal-fin apices; hatchlings without whorls on fins and body. 
Geographical Distribution

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Eastern Pacific: Mexico (southern Baja California, the Gulf of California, and southern Pacific coast) south to Guatemala, Panama (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 including reefs and seamounts, on coral reefs, and on sandy areas.From close inshore down to 20 to 50 m depth.

Common in the upper Gulf of California.
Oviparous. The long tendrils and rigid, T-shaped spiral flanges on the egg cases of this shark suggest that wedging of the eggs in crevices through the action of flexible flanges has been replaced by anchoring of the cases to the substrate by the tendrils, unlike other bullhead sharks with flexible-flanged eggs. The heavy T-flanges may serve instead to protect the egg from impacts and egg-predators.  Feeds on crabs and demersal fishes including midshipman (Porichthys, Batrachoididae).
Size
Maximum size about 70 cm. Egg cases about 8 to 9 cm long, young hatch at about 14 cm; males maturing between 40 and 50 cm and reaching at least 55 cm.
Interest to Fisheries
Interest to fisheries minimal. Small numbers are or were taken as a bycatch of the shrimp fishery in Mexico and processed into fishmeal along with other sharks. It is also caught in gill nets set for small sharks. Observed by divers in the Gulf of California, but not a special focus for ecotouristic diving.
Local Names
Widespread : Buffalo hornshark ,  Mexican horn shark .
Remarks
This shark had been collected in the Gulf of California many years ago by ichthyologists at the Scripps Institution of Oceanography and referred to under the unpublished manuscript names "H. seftoni" and "H. oligostictus". It was eventually published as H. mexicanus.
Source of Information
Sharks of the world An annotated and illustrated catalogue of shark species known to date. Volume 2 Bullhead, mackerel and carpet sharks (Heterodontiformes, Lamniformes and Orectolobiformes). Leonard J.V. Compagno 2001.  FAO Species Catalogue for Fishery Purposes. No. 1, Vol. 2. Rome, FAO. 2001. p.269.
Bibliography
Applegate  et al.,  1979. 
Chirichigno, 1980
Compagno, 1984
Compagno, Krupp & Schneider, 1995
Franke & Acero, 1991
Michael, 1993
Taylor, 1972
Taylor & Castro-Aguirre, 1972
 
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