Triakidae
by S. Branstetter
Head of normal shape, not laterally expanded into cephalofoil. Snout not greatly elongate, gently rounded at tip, 3 rostral cartilages, united terminally; nostrils without barbels, anterior flaps vestigial to long, medial flaps well developed, posterior flaps present or absent. Mouth parabolic to triangular in shape; labial furrows relatively long; teeth low, blades present or absent, rows weakly differentiated, forming crushing plates, with as many as three cusps. Eyes elongate and oval, nictitating membrane external, transitional or internal, sub-ocular ridge strongly to weakly developed. Spiracle present. Gill-slits 5, all short and of similar length, fourth and fifth over or posterior to pectoral fin origin. First dorsal fin midpoint varying from closer to pectoral base to closer to pelvic base, insertion of fin sometimes over or posterior to pelvic origin; second dorsal fin large, only slightly smaller and similar in shape to first dorsal fin; pectoral fins short, broad, triangular; anal fin origin posterior to second dorsal fin origin; no pre-caudal pits; caudal fin with a large well-developed sub-terminal notch on upper lobe, lower lobe poorly differentiated or moderately developed. Intestinal valve corkscrew type. Colour grey or brown above, white below, some with white spots dorsally.
Demersal species of shelf waters. Sluggish swimmers. Feeds on crustaceans, molluscs, fishes. Ovoviviparous or viviparous, number of young few. Some commercial value for flesh.
Genera 10; in Clofnam area 3 (including Leptocharias).
Recent revisions: Bigelow and Schroeder (1948), Heemstra (1969, 1973— Mustelus), Compagno (1978, 1979—separates from Carcharhinidae).