A ray-finned fish is a member of the scientific group Actinopterygii, named for the slender rays that support its fins. Tuna, bass, trout, and salmon are familiar examples; the group includes species that live in both freshwater and the ocean.
What does “ray-finned” mean?
The name describes fin structure: the fins of ray-finned fishes are supported by rays. Actinopterygii is the scientific group commonly called ray-finned fishes. Taxonomic databases do not all label the group with the same rank, so the group name is more useful here than a particular rank label. ITIS and the NCBI Taxonomy Browser both list Actinopterygii.
How are ray-finned fishes different from lobe-finned fishes?
The useful introductory distinction is the structure of the fins. In ray-finned fishes, rays support the fins; in lobe-finned fishes, the fins are fleshy and lobed. This is a comparison of two fish groups, not a distinction between fish that live in different kinds of water. Animal Diversity Web and OpenStax Biology 2e describe this fin contrast.
What are examples of ray-finned fish?
Tuna, bass, trout, and salmon are familiar members of Actinopterygii. They are examples from a much broader group, not a complete list. The group includes fishes from freshwater habitats as well as marine environments. The American Museum of Natural History gives examples and describes the group’s range across aquatic environments.
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How many ray-finned fish species are there?
Published reference pages give different totals, so there is no single figure established by these sources as an undisputed current count. Animal Diversity Web reports approximately 24,000 recognized species in its account, while the American Museum of Natural History page displays 34,000 known species. The pages do not supply publication years in the available metadata, and their counts may reflect different taxonomic coverage or page vintages; treat both as source-specific figures rather than a precise, current total.
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