Author: Smith, 1957
Diagnostic Features:
Snout moderately long and parabolic in dorsoventral view, preoral length about equal to mouth width; eyes horizontally oval and lateral, subocular ridges obsolete; anterior nasal flaps vestigial, formed as small, low, angular points, well separated from each other and mouth; no nasoral grooves; internarial width over 2.5 times nostril width; mouth angular and long; labial furrows moderately long, uppers ending well behind level of upper symphysis; teeth bladelike compressed, and cuspidate, similar in upper and lower jaws, anteroposteriors with oblique cusps and cusplets; medial teeth well differentiated from anteroposteriors. First dorsal fin moderately large, its base half length of dorsal caudal margin or less; its origin over or slightly behind pectoral free rear tips, its midbase somewhat closer to pectoral bases than pelvics; second dorsal considerably smaller than first, about 1/2 to 3/5 as high as first; anal fin considerably smaller than second dorsal; ventral caudal lobe strong in young and adults; terminal lobe of caudal fin moderately long and about 2.6 to 3 times in dorsal caudal margin.
Remarks:
The subgenus Hypogaleus was raised in rank to genus by Compagno (1970) and subsequently recognized by Bass, D'Aubrey and Kistnasamy (1975b). The genus has a disjunct geographic distribution, in the western Indian Ocean off southeastern Africa and western North Pacific off Japan and Taiwan Island (Province of China), but this may be indicative of inadequate collecting in deeper continental waters between these extremes as well as the relative rarity of Hypogaleus individuals. Hypogaleus from the two areas have placed in separate species, H. hyugaensis (Miyosi, 1939) from Japan and H. zanzibariensis (Smith, 1957) from Tanzania, but there are no obvious differences between them and they have been tentatively synonymized (see Compagno, 1970, 1979, Bass, D'Aubrey and Kistnasamy (1975b).