Author: Blainville, 1816
Field Marks:
Requiem sharks with small, wide-spaced nostrils, no spiracles, labial furrows confined to mouth corners, usually serrated upper teeth, no cusplets on lower teeth, no keels on caudal peduncle, transverse crescentic precaudal pits, first dorsal midbase closer to pectoral bases than to pelvics or at most about equidistant between them, second dorsal fin less than half the height of first, second dorsal origin usually about opposite anal origin, anal fin with preanal ridges short to absent and with a deeply notched posterior margin.
Diagnostic Features:
Body fairly slender to very stout. Head narrow to broad, flattened but not trowelshaped; snout varying from narrowly parabolic or subangular to bluntly rounded or nearly truncate in dorsoventral view, very short to long, with preoral length varying from about equal to much greater than internarial sspace and from much less to considerably greater than mouth width; eyes small to large, without posterior notches; spiracles absent; no papillose gillrakers on internal gill openings; nostrils small, internarial space 3 to 6 times nostril width; anterior nasal flaps short, varying from vestigial to narrowly or broadly triangular, but not tubular; labial furrows short, essentially confined to mouth corners, with uppers about as long as lowers or shorter, ends of uppers falling far behind eyes; teeth highly variable, anteroposteriors similar or strongly differentiated in upper and lower jaws; uppers usually with more or less erect, broad to narrow cusps, variably developed cusplets or blades, and serrations usually present; lowers without cusplets but with variably oblique to erect cusps and with serrations and blades present or absent; cusps of lower teeth no prominently protruding when mouth is closed; 24 to 37/23 to 35 rows of teeth, with most species not exceeding 33/33. Interdorsal ridge variably absent, present and prominent, or sometimes vestigial; no dermal keels on caudal peduncle; upper precaudal pit transverse and crescentic. First dorsal origin varying from over or slightly anterior to pectoral insertions to slightly behind their rear tips, midbase usually closer to pectoral bases than pelvics but sometimes equidistant between them, and free rear tip usually well in front of pelvic fins but occasionally opposite their origins; second dorsal fin much smaller than first, height 2/5 of first dorsal height or less; its origin usually about opposite anal origin but slightly anterior to it in some species and well behind it in others (but usually in front of anal insertion); pectoral fins varying from moderately broad and semifalcate, to narrow and falcate or broad-tipped, their lengths from origin to free rear tip about 1/3 to 2/3 of pectoral anterior margins; pectoral origins varying from about under 3rd to 5th gill slits; anal fin varying from considerably larger than second dorsal to about as large, with preanal ridges very short or absent and a deeply notched posterior margin. Colour variably grey, bronze, brownish above, without a colour pattern other than variable light or dark fin markings and lateral light stripes. Small to very large sharks, adults from below 1 to about 4 m.
Remarks:
Following its revision by Garrick (1982), this is currently the largest genus of sharks, with some 29 species; although the writer predicts that it will be surpassed in number of species by the scyliorhinid genus Apristurus, and possibly by Mustelus. The arrangement of Carcharhinus adopted here follows Compagno (1979) and Garrick (1982) in most details. The genera Hypoprion and Aprionodon were recognized by most previous writers, but they are synonymized with Carcharhinus following the revisionary work on carcharhinid genera by Compagno (1979), and four species formerly included in these genera (A. isodon, H. macloti, H. hemiodon and H. signatus) are placed in Carcharhinus. In addition, there is apparently a new western Pacific species of porosus and borneensis-like shark (placed by Garrick, 1982, in the Western Hemisphere C. porosus but clearly not conspecific with that species), and a new C. amblyrhynchoides-like shark from the western Indian Ocean (J.A.F. Garrick, pers. comm.).
The 'river sharks', C. glyphis and C. gangeticus, were placed by Compagno (1979) in Carcharhinus, but following Garrick's (1982) revision of Carcharhinus and examination of more material of these sharks, these species are referred to the genus Glyphis.
The following key to species is derived from that of Garrick (1982), with considerable modifications.