Chordata and Hemichordata

Abstract Chordata is the phylum that vertebrates, including ourselves, belong to. Chordates have a series of unifying characters, including a semi-rigid support structure or notochord, a dorsal hollow neural tube, pharyngeal slits, and a post-anal tail. There are three sub-phyla within chordates. One is the vertebrates, which will be discussed separately. The other two are Cephalochordata—small, fish-like animals with a translucent body and a small head—and Tunicata—planktonic or sessile suspension feeders that lose many typical chordate characters in the adult stage. Hemichordata is a separate phylum, once thought to be closely related to chordates, but now believed to be closer to echinoderms. Hemichordates share some characters with chordates, but not all. They are worm-like animals, either benthic or planktonic.