“All vertebrates are chordates but all chordates are not vertebrates” justify the statement.
All vertebrates (animals having a backbone) and a few invertebrates belong to the Phylum Chordata, which is part of the Kingdom Animalia (organisms without a backbone).
Vertebrates: Vertebrates are animals with a vertebral column and/or a notochord at some point throughout their existence.
Phylum Chordata – Phylum Chordata is a subclass of the Kingdom Animalia that includes both backboned animals and non-backboned creatures.
The notochord is only found in the larval tail area of some chordates. The notochord can be found in a variety of chordates throughout the body. The notochord is replaced by the vertebral column in some chordates. As a result, not all chordates are classified in the same way.