Fr:	Requin-marteau halicorne
Sp:	Cornuda comun
It:	Pesce stampella
Ma:	N/A

Diagnosis

A large (to over 300 cm), gracefully-proportioned hammerhead shark with a broadly convex head measuring 24 to 30% of TL; its anterior margin arched with a conspicuous central indentation, a  further  prominent notch more laterally on each side. Tooth count 15-16 (excluding small symphyseals) in each side of the jaws; teeth smooth-edged or very weakly serrated. First dorsal fin tall, measuring 11.9 to 14.5% of TL, with a rounded apex and falcate in shape; its origin opposite or slightly posterior to the pectoral insertions and with its free rear tip not extending rearwards to above the pelvic fin origins. Posterior margins of pelvic fins essentially straight. Second dorsal fin small and low, smaller than the anal fin with its posterior margin roughly twice the fin height; free rear tip long and extending almost to the precaudal pit. Pectoral fins moderate in size, their anterior edges equating to 12.6 - 15.2% of TL. Dorsal colour mid brown-grey or bronzy-grey, fading gradually to white ventrally. Apices of pectoral fins noticeably dusky or black, particularly on their ventral surfaces; also apices of ventral caudal lobe and second dorsal fin dusky in juveniles.

Size

Maximum ca. 400 cm; mostly to 350cm; size at birth 42 to 55 cm.

Status & Distribution

Rather rare or occasional; restricted on current data to western basin, principally near the Atlantic interface off Morrocco and southern Spain; Alboran Sea and Algeria; sporadic further eastwards to the Sicilian Channel although not reported from Malta. Probably more cosmopilitan as occasional nomads, at least within the confines of the western Mediterranean, but liable to misidentification with other sympatric congeners.

Biology A coastal and semi-oceanic shark of warm temperate and tropical seas, the scalloped hammerhead is a highly mobile, migratory pelagic species occuring from the surfline to well offshore, from tidal shallows and bays to depths of at least 275 m. Juveniles are often found very close inshore. In many parts of the world where these sharks are abundant (e.g., Red Sea; Sea of Cortez) these hammerheads readily form large, mysterious schools which are frequently orientated to submarine features such as seamounts. There is no evidence of this behaviour in Mediterranean waters and capture data, although presently sketchy, suggests a more sporadic and diffuse population whose origins are Atlantic and Mediterranean incursions essentially nomadic in nature. These sharks display a high degree of complex intraspecific behaviours including a great variance in swimming modes which may even involve complete "corkscrew" rotations on their horizontal axis. These sharks may occur in deeper water nocturnally for feeding, as demonstrated by telemetry experiments off California. Piscivorous, feeding upon a wide range of bony fishes including clupeids, jacks, small scombrids, damselfish, conger eels, barracuda, gobies and flatfishes; also elasmobranchs including smaller sharks, angelsharks and rays; benthic and pelagic invertebrates, especially cephalopods but also crustaceans and gastropods.  A viviparous shark, with litters between 15 to 30; females mature at about 212 cm TL and males at ca. 140 to 165 cm.