Same animal, two English names
If a guide says sea star and a beach sign says starfish, they are pointing at the same creatures. The rename push is about accuracy, not a newly discovered species split.
Related echinoderms include brittle stars and basket stars (different classes/orders); those are not interchangeable with true sea stars even when people use loose starfish talk.
Why “sea star” won in science writing
| Trait | Sea stars | Bony fish |
|---|---|---|
| Group | Echinoderms | Vertebrate fishes |
| Skeleton | Calcareous plates under skin | Internal bone/cartilage spine |
| Breathing / circulation motifs | Water-vascular system, tube feet | Gills and bloodstream |
Educators adopted sea star to stop the false fish association, especially for kids. Museums and NOAA education pages commonly use sea star while acknowledging starfish in parentheses.
Field note
Five arms is common but not a rule; some species have many more. Do not pry them off rocks; tube feet and arm tips tear easily.
If you care about wording in a school report, use sea star and mention starfish as the older common name.