Actinopterygii

Ray-finned fish Temporal range: Late Silurian–Present, 425–0 Ma[1] PreꞒ Ꞓ O S D C P T J K Pg N
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Superclass:	Osteichthyes
Class:	Actinopterygii Klein, 1885
Subclasses
Cladistia (bichirs) Actinopteri Chondrostei (sturgeon and paddlefish) Neopterygii Holostei (bowfin and gars) Teleosteomorpha Teleostei (teleosts)

Actinopterygii (/ˌæktɪnɒptəˈrɪdʒiaɪ/; from actino- 'having rays', and Ancient Greek πτέρυξ (ptérux) 'wing, fins'), members of which are known as ray-finned fish or actinopterygians, is a class of bony fish^[2] that comprise over 50% of living vertebrate species.^[3] They are so called because of their lightly built fins made of webbings of skin supported by radially extended thin bony spines called lepidotrichia, as opposed to the bulkier, fleshy lobed fins of the sister class Sarcopterygii (lobe-finned fish). Resembling folding fans, the actinopterygian fins can easily change shape and wetted area, providing superior thrust-to-weight ratios per movement compared to sarcopterygian and chondrichthyian fins. The fin rays attach directly to the proximal or basal skeletal elements, the radials, which represent the articulation between these fins and the internal skeleton (e.g., pelvic and pectoral girdles).

The vast majority of actinopterygians are teleosts. By species count, they dominate the subphylum Vertebrata, and constitute nearly 99% of the over 30,000 extant species of fish.^[4] They are the most abundant nektonic aquatic animals and are ubiquitous throughout freshwater and marine environments from the deep sea to subterranean waters to the highest mountain streams. Extant species can range in size from Paedocypris, at 8 mm (0.3 in); to the massive ocean sunfish, at 2,300 kg (5,070 lb); and to the giant oarfish, at 11 m (36 ft). The largest ever known ray-finned fish, the extinct Leedsichthys from the Jurassic, has been estimated to have grown to 16.5 m (54 ft).