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The technical name "osteichthyes" means "bony fishes", and denotes the
preponderance of bone in the skeleton of most species of this class. Most bony
fishes are oviparous, with fertilisation external; exceptions to this rule in southern African waters are the Clinidae, Bythitidae and a few other deep-sea
fishes, which are viviparous, with internal fertilisation. Except for a few
species of the deep-sea eel Family Synaphobranchidae (which have a single
median gill opening on the throat), bony fishes have a single gill opening on
each side of the head.
The class comprises two subclasses: the Sarcopterygii (lobefin fishes) and
the Actinopterygii (rayfin fishes).