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Author: Compagno and Garrick, 1983

Diagnostic Features:
Body rather slender. Head very narrow, conical and only slightly depressed, not trowelshaped; snout narrowly pointed in dorsoventral view, very long, with preoral length greater than internarial space and mouth width; eyes fairly large, without notches; spiracles absent; no papillose gillrakers on internal gill openings; nostrils very large, close-spaced and nearly transverse, internarial space about 1.1 to 1.3 times the nostril width; anterior nasal flaps vestigial, not tubular; labial furrows very short, uppers shorter than lowers and falling far behind eyes; teeth differentiated in upper and lower jaws; upper anteroposteriors with fairly broad semierect to oblique cusps, distal blades and serrations but no cusplets; lowers with slender, narrow, semierect cusps, blades and serrations but no cusplets; lower teeth not prominently protruding when mouth is closed; 27 to 30/24 to 28 (usually 28/25 to 27) rows of teeth. Interdorsal ridge absent; no dermal keels present on caudal peduncle; upper precaudal pit transverse and crescentic. First dorsal origin over pectoral inner margins, its midbase somewhat closer to pectoral bases than pelvic, and its free rear tip slightly anterior to pelvic origins; second dorsal fin much smaller than first, its height less than 1/3 of first dorsal height; its origin over or slightly anterior to anal insertion; pectoral fins moderately broad and triangular, slightly falcate, pectoral length from origin to free rear tip about 3/4 of pectoral anterior margin; pectoral origins under third gill slit or interspace between third and fourth gill slits; anal slightly larger than second dorsal, with short preanal ridges and a deeply notched posterior margin. Colour light grey or brownish grey above, without a colour pattern. Moderately large sharks, adults not exceeding 1.6 m.

Remarks:
This 'satellite genus' of Carcharhinus differs from it and all other carcharhinids in its enlarged, close-set nostrils, narrow conical snout and various cranial characters (see Compagno and Garrick, 1983). Its only species, Nasolamia velox, is close to Carcharhinus acronotus in dentition and other features and may be a sister species to it by common ancestry. However, acronotus lacks the derived peculiarities of velox and is retained in Carcharhinus.

The aggregation of odd rostral and cranial characters of N. velox is reminiscent of incipient stages of the teratogenic continuum of cyclopia in vertebrates. It is tempting to speculate that Nasolamia is derived from an acronotus-like ancestry in Carcharhinus by stabilization of a complex of incipient, cyclopic abnormalities that gave N. velox a selective advantage over normal acronotus-like Carcharhinus.

Genus Nasolamia