Subclass HOLOCEPHALI
Introduction
The subclass Holocephali, a group of cartilaginous fishes, contains only one living order, the Chimaeriformes, and at least eight fossil orders. Holocephalans are usually deepwater bottom-dwelling fishes. They have the four gills covered by a soft gill cover and have grinding tooth plates. The group is thought to be the primitive sister group to the elasmobranchs, sharing the character state of having a cartilaginous skeleton. Nelson (1994) reviewed the literature on the group.
General References
Nelson, J.S. 1994. Fishes of the World. New York : John Wiley & Sons 600 pp.