Author: Rafinesque, 1810
Diagnostic Features:
Head variably spade, mallet or axe-shaped in dorsoventral view and moderately broad, width across head about 17 to 33% of total length; lateral blades of head broad, not winglike; nostrils short, their widths 7 to 14 in internarial width and less than half mouth width; no bumps along anterior margin of head. Upper precaudal pit transverse and crescentic.
Remarks:
Arrangement of the species follows Gilbert (1967, 1967a) and Compagno (1979), who recognize two subgenera: Platysgualus, for S. corona, S. media, S. tiburo, and S. tudes and Sphyrna, for S. couardi, S. lewini, S. mokarran, and S. zygaena. Gilbert (1967, 1967a) included Eusphyra as a subgenus of Sphyrna but Compagno 5979) ranked it as a genus.
According to Johnson (1978), there may be another species of large (to at least 3 m) hammerhead in French Polynesian waters, presumably belonging to the genus Sphyrna, subgenus Sphyrna, but which has a fairly narrow, relatively long mallet-shaped head rather like S. media. This has been seen several times by divers but specimens have not been collected yet.