Here's why:
* Chordates are animals that possess a notochord (a flexible rod that supports the body) at some point in their development. Other characteristics include a dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail.
* Golden Retrievers, being mammals, fit into this category as they have all of these characteristics at some point in their development.
Let me know if you'd like to know more about the classification of animals!