Chordata, is the Phylum of dolphins.  All organisms in the phylum share four major similarities in characteristics.

​

1. A notochord

   • ​A flexible, rod-shaped structure that is found in the embryonic stage of all chordates, as well as in the adult stage of some chordate species​​

2. A dorsal hollow nerve cord

   • ​Derives from echinoderm that rolls into a hollow tube during development​.  In chordates, it is located dorsally, opposed to most animals that are located either ventrally or laterally.

3. Pharyngeal slits

   • Openings in the pharynx​,  that extend to the outside environment

4. Post-anal tail

   • A tail extending beyond the anus​.  Source of locomotion