All the chordates are not vertebrates. Why ?

Explanation

### Step-by-Step Solution:

1. **Understanding the Classification**:
- The animal kingdom is classified into various groups based on shared characteristics. One of these major classifications is the phylum, and within phyla, there are subphyla.
- Chordates belong to the phylum Chordata, which is characterized by certain features such as a notochord, dorsal nerve cord, and pharyngeal slits.

2. **Defining Chordates and Vertebrates**:
- Chordates are divided into different subphyla, one of which is Vertebrata (vertebrates).
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