Author: Compagno, 1973
Field Marks:
Cylindrical or compressed body, not raylike, 5 gill slits, 2 dorsal fins, no anal fin, snout normal, not sawlike.
Diagnostic Features:
Trunk cylindrical, slightly depressed or somewhat compressed, not flattened and raylike. Head conical to depressed, not expanded laterally; five pairs of gill slits present on sides of head, with the posteriormost in front of pectoral fin origins; spiracles present and small to very large, well behind or close behind eyes and often above level of eyes; nostrils without nasoral grooves or circumnarial grooves, separate from mouth, anterior nasal flaps usually short and not reaching mouth, expanded into barbels in one genus (Cirrhigaleus) but without separate barbels on their outer edges; eyes on sides of head, without nictitating lower eyelids; snout short to long, flattened or conical, not greatly elongated into a flattened blade with lateral teeth and rostral barbels; mouth moderately large to short, arched and elongated to nearly transverse, below eyes; labial furrows well-developed, short to very long, on both jaws; teeth only moderately 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 dorsal fins, with or without fin spines (Squaliolus with a spine on the first dorsal only), the first with origin varying from over the pectoral bases or gill slits to over the anterior halves of the pelvic bases; pectoral fins small to moderately large, not expanded and raylike, without triangular anterior lobes that cover the gill slits; pelvic fins small to moderately large, with vent continuous with their inner margins; anal fin absent; caudal fin with a long to moderate-sized dorsal lobe and the ventral lobe long to absent but always shorter than the dorsal lobe when present; vertebral axis elevated into the dorsal caudal lobe. Intestinal valve of spiral type.