Author: Boulenger, 1902
Diagnostic Features:
Snout short and broadly rounded in dorsoventral view, preoral length 0.7 to 0.9 times mouth width; eyes horizontally elongated and dorsolateral, subocular ridges strong; anterior nasal flaps triangular, greatly expanded posteriorly and medially, nearly meeting each other medially and overlapping mouth posteriorly; broad, shallow nasoral grooves present between excurrent apertures of nostrils and mouth; internarial width about half of nostril width; mouth broadly arched and short; labial furrows long, uppers reaching level of upper symphysis; teeth deep, blunt-crowned, molariform, and without cusps and cusplets; medial teeth not differentiated from anteroposteriors. First dorsal fin moderately large, base about 3/5 of dorsal caudal margin; its origin over pectoral inner margins or free rear tips, its midbase about equidistant between pectoral and pelvic bases or slightly closer to pelvic bases; second dorsal about as large as first, height over 3/4 as high as first; anal fin considerably smaller than second dorsal; ventral caudal lobe hardly developed in young but very short in adults; terminal lobe of caudal fin moderately long and about 2.8 to 3.2 times in dorsal caudal margin.
Remarks:
This genus is occasionally placed in its own family, with or without Mustelus, because of its molariform teeth, but it otherwise is close to other triakids while differing from all of them in having expanded anterior nasal flaps and nasoral grooves. For further discussion of its systematic position see Compagno (1979).