Author: Compagno, 1973
Diagnostic Features:
Trunk somewhat depressed but not greatly flattened and raylike. Head somewhat depressed but not expanded laterally; 5 or 6 pairs of gill slits present on sides of head, with the posteriormost in front of pectoral fin origins; spiracles present and very large, just behind and above level of eyes; nostrils without barbels, nasoral grooves or circumnarial grooves, separate from mouth, anterior nasal flaps short and not reaching mouth; eyes on dorsal surface of head, without nictitating lower eyelids; snout very long and greatly depressed, forming a sawlike blade with lateral denticles and a pair of long rostral barbels on its ventral surface well in front of the nostrils; mouth small, arched but short, behind eyes; labial furrows greatly reduced, at mouth corners only; teeth weakly differentiated along the jaws, without enlarged anterior or posterior teeth and without a gap or small intermediate teeth between anterior and lateral teeth in the upper jaw. Two spineless dorsal fins present, the first with its origin over the interspace between the pectoral and pelvic bases; pectoral fins moderately large, not expanded and raylike, without triangular anterior lobes that cover the gill slits; pelvic fins small, with vent continuous with their inner margins; anal fin absent; caudal fin with a moderately long dorsal lobe but with ventral lobe absent; vertebral axis elevated into the dorsal caudal lobe. Intestinal valve of spiral type.