(class Chondrichthyes, subclass Holocephali)
An order of marine fish that have a cartilaginous skeleton, a gill cover over the four gill openings, a naked skin, and no spiracle opening. The males have a pair of pelvic claspers and a peculiar clasping structure on the head. The order includes a number of fossil families as well as the living ghostfish. They are not considered to be closely related to either the sharks or the bony fish.
Subjects: Zoology and Animal Sciences.