Author: Agassiz, 1843
Field Marks:
Requiem sharks with short, broadly rounded snouts, small, wide-spaced nostrils, no spiracles, labial furrows confined to mouth corners, extremely small eyes, serrated triangular, broad-cusped upper teeth, no cusplets on lower teeth (except for first few anterolaterals in G. gangeticus) no keels on caudal peduncle, conspicuously protruding cusps on lower teeth, longitudinal precaudal pits, first dorsal midbase much closer to pectoral bases than pelvics, second dorsal fin half to 3/5 height of first, second dorsal origin slightly in front of anal origin, anal fin with preanal ridges virtually absent and with a deeply notched posterior margin.
Diagnostic Features:
Body fairly stout. Head broad and flattened but not trowel-shaped; snout broadly parabolic or rounded in dorsoventral view and short, with the preoral length varying from about equal or somewhat less than internarial space but much less than mouth width; eyes extremely small, without posterior notches; spiracles absent; no papillose gillrakers on internal gill openings; nostrils small, internarial space 3 to 6 times the nostril width; anterior nasal flaps short, broadly to narrowly triangular, but not tubular; labial furrows short, essentially confined to mouth corners, with uppers shorter than lowers and falling far behind eyes; teeth strongly differentiated in upper and lower jaws; upper anteroposteriors with more or less erect, broad, triangular cusps, no cusplets or blades, and fine serrations; lowers with or without cusplets (on first few anterior teeth) or blades but with variably oblique to erect, long cusps and with serrations generally absent; cusps of lower teeth prominently protruding when mouth is closed; 29 to 37/28 to 34 rows of teeth. Interdorsal ridge absent; no lateral keels on caudal peduncle; upper precaudal pit longitudinal and not crescentic. First dorsal origin far anterior, over last thirds of pectoral bases, midbase much closer to pectoral bases than to pelvics and free rear tip well in front of pelvic fins; second dorsal fin much smaller than first but relatively large, its height 1/2 to 3/5 of first dorsal height or less, its origin slightly anterior to anal origin; pectoral fins moderately broad and falcate or semifalcate, their lengths from origin to free rear tip about 3/5 to nearly 3/4 of pectoral anterior margins; pectoral origins varying from about under interspace between third and fourth gill slits to under fourth gill slits; anal fin slightly smaller than second dorsal, with preanal ridges very short or absent and a deeply notched posterior margin. Colour grey or brownish above, without a colour pattern. Large sharks, to at least 2 m.
Remarks:
The genus Glyphis is used here for the 'river sharks', two and possibly three or more species of poorly known, freshwater and estuarine sharks of the Indian Ocean and Western Pacific. This includes the famous, notorious, and elusive Ganges shark (G. gangeticus) of Indian waters.
The nomenclatural history of the genus Glyphis is somewhat checkered. Agassiz (1843) based his description of the genus primarily on a living species, Carcharias (Prionodon) glyphis Müller and Henle, 1839, which he mentioned in its text, but also named a new fossil species, G. hastalis. Elsewhere in the Poissons Fossils Agassiz (vol. 3, 1845, tab.mat.3e: 7) noted that Glyphis included "une espece vivante et une fossil de l'Argile de Londres, le G. hastalis". Agassiz did not designate a type for Glyphis, but this must be C. (P.) glyphis by absolute tautonymy.
Fowler (1941) and Bigelow and Schroeder (1948) assumed that Glyphis as originally described by Agassiz included only a single species, G. hastalis, which they erroneously assumed was the type species by monotypy. Bigelow and Schroeder (1948) cited 1838 as the earliest date for Glyphis, on a plate caption for G. hastalis (Agassiz, Poissons Fossils, Atlas, vol. 3, pl. 36). However, according to Woodward and Sherborn (1890) the plate in question was apparently published in 1845 and hence postdates the text description of Glyphis.
Fowler (1928, 1941) erroneously used Glyphis to replace Prionace Cantor, 1849, as a generic name for the blue shark, P. glauca (Linnaeus, 1758). Apart from the subsequent stabilization of Prionace as the generic name of the blue shark by the International Commission on Zoological Nomenclature (Opinion 723, 1965) and confusion on the type species of Glyphis, this action is unwarranted because neither the living type species of Glyphis or the fossil G. hastalis are congeneric with the blue shark.
Garrick (1982) excluded Carcharias (Prionodon) glyphis and C. (P.) gangeticus Müller and Henle, 1839 from the genus Carcharhinus, but did not place them in a given genus. He noted that these two species "....share many similarities with each other and differ less from Carcharhinus than does temmincki". Extending Garrick's conclusions requires that the genus Glyphis be expanded to include C. (P.) gangeticus as well as C. (P.) glyphis and G. hastalis. The genus Lamiopsis, as recognized here and in Compagno (1979) for C. (P.) temmincki Müller and Henle, 1839, is close to glyphis but readily distinguishable from it and from Carcharhinus.
Garrick (pers. comm.) notes that there may be at least one additional living species in this genus, similar to G. glyphis but separable by vertebral counts and possibly other characters.