* Birds: Phylum Chordata, Subphylum Vertebrata, Class Aves
* Bony Fish: Phylum Chordata, Subphylum Vertebrata, Class Actinopterygii
The feature that places them in the same phylum (Chordata) is the presence of a notochord at some point in their development.
Here's a breakdown of why:
* Notochord: A flexible rod that provides support and helps with movement. It's present in all chordates at some stage of their life cycle.
* Vertebrates: A subphylum of Chordata, characterized by the development of a vertebral column (backbone) that replaces the notochord. Both birds and bony fish are vertebrates.
Therefore, while they share some common ancestry and are both vertebrates, they are not in the same phylum because they have different evolutionary paths and distinct physical characteristics beyond the presence of a notochord.