Fr:	Grand requin-marteau
Sp:	Cornuda gigante
It:	Pesce martello maggiore
Ma:	N/A

Diagnosis

A large or very large (to over 500 cm)  distinctive hammerhead shark with an angular head measuring 23 to 27% of TL; its anterior margin conspicuously straight and with a shallow median indentation. Tooth count 17 on each side of upper jaw; 16 or 17 in lower (discounting small symphyseals); teeth strongly serrated. First dorsal fin noticeably tall, with an acute, pointed apex and strongly falcate in shape; its origin opposite or just posterior to the pectoral axil and free rear tip not extending rearwards to above the pelvic fin origins. Posterior margins of pelvic fins concave and strongly falcate. Second dorsal fin fairly tall compared to congeners, its height 4.7-6.5% of TL with its posterior margin concave and the inner margin rather short, equating to about the fin height; free rear tip not extending to the precaudal pit. Anal fin marginally larger, strongly concave and originating anterior to the second dorsal origin. Pectoral fins moderately falcate in shape, their anterior margins measuring 13.4 to 18.4% of TL. Dorsal colour dark brown-grey or bronzy-grey, fading to white ventrally. Ventral apices of pectoral fins plain, not dusky; apex of second dorsal fin somewhat dusky in juveniles.

Size

Maximum perhaps in excess of 550cm and possibly over 600cm; most adults to 350-450cm TL; size at birth ca. 65 cm. First Mediterranean example measured ca. 300 cm and weighed ca. 120kg (Boero & Carli, 1977).

Status and Distribution

Mediterranean Sea: Very rare; occasional reliable reports originating from the North African coast between Gibraltar and Tunisia; also Ionian Sea and Sicilian Channel  but misidentification with large S. zygaena  very possible in these fisheries; first regionally-recorded capture was comparatively recent, from the Gulf of Genova at Camogli (Liguria, Italy) in September 1969. Probably more cosmopolitan in the Mediterranean as nomads and liable to be caught anywhere in the region, particularly off more southern coasts.

Biology

A large, voracious species - and one of the largest predatory sharks - occuring both as a coastal and semi-oceanic pelagic inhabitant of continetal and insular shelves; ranging from the surfline to well offshore at depths from the surface down to 80m or greater. Great hammerheads are highly nomadic, with poleward summertime migrations in parts of their global range. The origin of these sharks within Mediterranean waters may be from either the Atlantic ocean off NW Africa (where they are caught sporadically off the coast from Senegal northwards) or even conceivably (albeit much less probable) from the Red Sea as Suez Canal migrants, rather like Carcharhinus melanopterus. They are predators upon a wide variety of (primarily demersal) bony fish and elasmobranchs, particularly groupers and dasyatid stingrays (a favoured prey-item, consumed complete with tail-spines), but also jacks, clupeids and flatfish;  other elasmobranch prey included smoothhounds (Mustelus spp.), skates, guitarfish and Rhinoptera spp; invertebrates taken by these sharks include crabs and cephalopods (squid). Reproduction is viviparous, with a yolk-sac placenta; litter-sizes range between 6 - 42 young. Gestation period is 11 months. Females mature at ca. 210-250cm and males at ca. 225-269cm.