Phylum Chordata, our phylum, is made of animals that show five distinguishing features in either the adult or larvae stage. These features are a hollow nerve cord in the dorsal side of the body; a notochord, which is a flexible rod between the nerve cord and the digestive tract; gill structures in the pharynx; the digestive tube located just behind the mouth; and a post-anal tail. This phylum, although not the largest, is the most diverse phylum in the animal kingdom. Chordates have bilateral symmetry in some stage of the life cycle and have a coelom made from an outgrowth of the digestive tube. Therefore, all chordates are deuterosomes, and their organs are suspended in the mesentary tissue between the endoderm tissue of the digestive tract (alimentary canal) and the ectoderm tissue on the surface. Chordates also, for the most part, show body segmentation and other characteristics present in the more evolved phyla in the kingdom Animalia, such as true tissue.
There are three subphyla in the phylum Chordata. Subphylum Urochordata consists of the tunicates, that show the characteristics of being a chordate in the larval stage but not as an adult. Subphylum Cephalachordata consists of all lancelets, very primitive animals that do show the chordate characteristics in maturity. The final subphylum, subphylum Vertebrata, is by far the largest and consists of seven classes, including our own.