Author: Compagno, 1973
Diagnostic Features:
Trunk greatly depressed and raylike; head greatly depressed and laterally expanded, with a distinct neck between itself and the trunk; 5 pairs of gill slits present on ventrolateral surface of head, with the posteriormost in front of pectoral fin origins; spiracles present and very large, just behind the eyes; nostrils with barbels, poorly developed nasoral grooves and weak circumnarial grooves, very close to mouth, anterior nasal flaps elongated and bordering mouth; eyes on dorsal surface of head, without nictitating lower eyelids; snout very short and truncated, not sawlike and without rostral barbels; mouth large, arched and moderately long, extending behind eyes; labial furrows very large, present on both jaws; teeth moderately differentiated along 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 opposite or behind free rear tips of pelvic fins; pectoral fins very large, expanded and raylike, with unique triangular anterior lobes that extend forward from the pectoral bases and cover the gill slits laterally; pelvic fins large, with vent separate from the pelvic inner margins; anal fin absent; caudal fin with a moderately long dorsal lobe but with the ventral lobe longer than it; vertebral axis depressed into the ventral caudal lobe; intestinal valve of spiral type.