Author: Müller and Henle, 1838
Field Marks:
Usually stout-bodied houndsharks with short snouts, dorsolateral eyes and strong subocular ridges, broadly arched mouths, teeth formed into a semipavement or not, with cusps and cusplets variably developed but present on at least more medial teeth, medial teeth not differentiated from anterolaterals, second dorsal fin nearly as large as first, and ventral caudal lobe short but strong in adults.
Diagnostic Features:
Snout short and broadly rounded in dorsoventral view, preoral length less than 1.1 times mouth width; eyes horizontally elongated and dorsolateral, subocular ridges strong; anterior nasal flaps elongated and lobate, well separated from each other and mouth; no nasoral grooves; internarial width about 1.5 to 2 times the nostril width; mouth broadly arched and moderately short; labial furrows long, uppers nearly or quite reaching level of upper symphysis; teeth semibladelike, somewhat compressed, and similar in both jaws, usually with erect or oblique cusps (sometimes absent from posterior teeth) and variably developed cusplets; medial teeth not differentiated from anteroposteriors. First dorsal fin moderately large, base less than 3/4 of dorsal caudal margin; its origin over pectoral inner margins, its midbase about equidistant between pectoral and pelvic bases or slightly closer to pelvic bases; second dorsal nearly as large as first, height about 3/4 as high as first; anal fin considerably smaller than second dorsal; ventral caudal lobe hardly developed in young but short and strong in adults; terminal lobe of caudal fin moderately long and about 2.5 to 3 times in dorsal caudal margin.
Remarks:
The present arrangement of Triakis follows the revisions of Compagno (1970, 1973a, b, c, 1979). The species form two well-defined subgenera, Triakis Müller and Henle, 1838 for T. scyllium and T. semifasciata, and Cazon de Buen, 1959 for T. acutipinna, T. maculata and T. Megalopterus.