Here's why:
* Chordates are a diverse group of animals that share certain key characteristics at some point in their development:
* Notochord: A flexible rod that provides support.
* Dorsal hollow nerve cord: A tube of nerve tissue running along the back.
* Pharyngeal slits: Openings in the throat that are used for filter feeding in some species.
* Post-anal tail: A tail that extends beyond the anus.
Clownfish, being fish, have all these characteristics at some point in their development.