A species of the genus Hydrolagus based on the absence of an anal fin. Hydrolagus

melanophasma sp. nov. is distinguished from other chimaeroids by a blunt snout with minimal sloping from the orbit to the snout tip, a large slightly curved dorsal fin spine (25.9 % BDL) extending beyond first dorsal fin apex, and a long second dorsal fin (77.3–81.1% BDL) of uniform height throughout. The pectoral fins are large, reaching beyond the pelvic fin insertion when laid flat, trifid claspers forked for 27–27.8% of the total clasper length and the preopercular and oral lateral line canals branch separately or together from the infraorbital canal. Coloration after preservation is a uniform black with no distinct mottling or markings (Ref. 82286).