Ray-finned fish
Ray-finned fish
Ray-finned fish (Actinopterygii /ˌæktɪnɒptəˈrɪdʒi.aɪ/), also known as spiny-rayed fish, are a major group within the phylum Chordata that includes the vast majority of fish species.
Etymology
The term Actinopterygii is derived from the Greek words aktinos, meaning ray, and pteryx, meaning fin. This refers to the characteristic bony or spiny rays that support their fins.
Characteristics
Ray-finned fish are characterized by their fins, which are webs of skin supported by bony or horny spines ("rays"), as opposed to the fleshy, lobed fins that characterize the sarcopterygii (lobe-finned fish). These fish make up half of all living vertebrates.
Classification
Ray-finned fish belong to the class Actinopterygii, which is further divided into three subclasses: Chondrostei, Holostei, and Teleostei. The Teleostei subclass contains the majority of ray-finned fish species.
Evolution
The first ray-finned fish appeared in the Silurian period, around 420 million years ago. They have since diversified into a wide variety of forms, including eels, tuna, and seahorses.
Related Terms
This WikiMD.org article is a stub. You can help make it a full article.