Here's why:

* Chordates are a diverse group of animals that share several key characteristics at some point in their development:

* Notochord: A flexible rod that supports the body.

* Dorsal hollow nerve cord: A tube of nerve tissue along the back.

* Pharyngeal slits: Openings in the throat that are used for filter feeding in some chordates.

* Post-anal tail: A tail that extends beyond the anus.

* Bats clearly fit into the Chordate phylum as they possess all of these characteristics at some stage in their development.