Holostei Group of marine and fresh water bony fish including many fossil species, e.g. Lepidotes (Triassic—Cretaceous), and Dapedius (Jurassic). Holosteans arose at the end of the Permian from palaeoniscid ancestors and are particularly abundant in marine Jurassic deposits. The main characteristics shown by the group relate to improvements in swimming and feeding: the use of the air sac to control buoyancy; a reduction in the bony fin rays, now unjointed; the development of a shorter and more mobile jaw; the gradual reduction in scale thickness; and the development of an almost symmetrical tail. Holosteans are represented today only by the garpike (Lepisosteus), and the bowfin (Amia), both freshwater.

Actinopterygii (ray-finned fish) A subclass of the Osteichthyes (bony fish, see BONE), comprising the ray-finned fish, which include the majority of living bony fish of sea and fresh water. The fins are composed of a membranous web of skin supported by a varying number of spines and soft rays. They appeared first during the Devonian.

Actinopterygii (ray-finned fish; class Osteichthyes) A subclass of ray-finned fish, that includes the majority of living bony fish of sea and fresh water. The fins are composed of a membranous web of skin supported by a varying number of spines and soft rays. This subclass includes a diversity of fish types, ranging from the sturgeon and paddlefish to the eel and tuna. They appeared first during the Devonian Period.

Holostei (class Osteichthyes) A group of marine and freshwater bony fish including many fossil species. Recently ranked as an infraclass, the Holostei includes the families Semionotidae, Lepisosteidae, and Amiidae.