Ray-finned fish, or Actinopterygii, are a diverse group of fish characterized by their bony skeletons and fins supported by thin, flexible rays. They are the most numerous and varied class of vertebrates, with over 30,000 species found in oceans, rivers, and lakes worldwide. Their adaptations allow them to thrive in various environments, from deep sea to freshwater habitats. These fish have a streamlined body shape that aids in swimming and often possess scales that provide protection. Ray-finned fish include familiar species such as salmon, trout, and tuna. They play essential roles in aquatic ecosystems and are significant for human food sources and recreational fishing.