Holostei are
bony fish that retain
basal characteristics inherited from an early time in their evolution. There are eight species divided among two orders, the
Amiiformes represented by a single living species, the
Bowfin (
Amia calva), and the
Lepisosteiformes, represented by seven living species in two genera, the gars. Further species are to be found in the fossil record and the group is often regarded as
paraphyletic. Holosteians are closer to teleosts than are the
chondrosteans, the other group intermediate between teleosts and cartilaginous fish. The
spiracles are reduced to vestigial remnants and the bones are lightly ossified. The thick ganoid scales of the gars are more primitive than those of the bowfin.