Sphyrna gilberti

Great Hammerhead Sphyrna mokarran

Smooth Hammerhead Sphyrna zygaena

Scalloped Hammerhead Sphyrna lewini

Great Hammerhead Sphyrna mokarran. Head hammer- or mallet-shaped and wider, its width over 3 times the preoral length. Posterior teeth not molariform crushers. Anterior margin of head nearly straight in adults, moderately convex in young. Prenarial grooves hardly developed. Teeth strongly serrated at all sizes. First dorsal fin markedly falcate; second dorsal about a third as high as first dorsal fin, with a short inner margin; posterior margins of second dorsal and pelvic fins deeply concave.

Smooth Hammerhead Sphyrna zygaena. Head hammer- or mallet-shaped and wider, its width over 3 times the preoral length. Posterior teeth not molariform crushers. Anterior margin of head moderately convex in adults, strongly so in young. Prenarial grooves well developed. Teeth smooth in young, weakly serrated in large individuals. First dorsal fin erect or slightly falcate; second dorsal-fin less than a third the height of first dorsal fin, with a long inner margin; posterior margins of second dorsal and pelvic fins slightly concave to nearly straight. Median indentation absent from anterior margin of head. Free rear tip of second dorsal fin well ahead of upper caudal-fin origin. Anal-fin base about as large as that of second dorsal fin.

Scalloped Hammerhead Sphyrna lewini. Head hammer- or mallet-shaped and wider, its width over 3 times the preoral length. Posterior teeth not molariform crushers. Anterior margin of head moderately convex in adults, strongly so in young. Prenarial grooves well developed. Teeth smooth in young, weakly serrated in large individuals. First dorsal fin erect or slightly falcate; second dorsal-fin less than a third the height of first dorsal fin, with a long inner margin; posterior margins of second dorsal and pelvic fins slightly concave to nearly straight. Median indentation present on anterior margin of head. Free rear tip of second dorsal fin nearly reaching upper caudal-fin origin. Anal-fin base noticeably larger than that of second dorsal fin. Precaudal vertebrae 92-99.