Overview
The subclass Holocephali is defined by having one gill opening each side of the head, fused tooth plates, and the first dorsal fin with an elongate spine. It is represented by three families of the order Chimaeriformes: plownose chimaeras (Callorhinchidae, 1 sp.), shortnose chimaeras (Chimaeridae, 9 spp. - 6 endemic), and longnose chimaeras (Rhinochimaeridae, 3 spp.). Several species lack scientific names even though they are reasonably well known, reflecting their taxonomic complexity. Several species (including undescribed ones) are caught commercially; some as bycatch of deep water trawls and one, the elephantfish Callorhinchus milii, is targeted in coastal waters.