Chordata contains two clades of invertebrates: Urochordata (tunicates) and Cephalochordata (lancelets), together with the vertebrates in the Vertebrata/Craniata. The five characteristic features of chordates present during some time of their life cycles are a notochord, a dorsal hollow tubular nerve cord, pharyngeal slits, endostyle/thyroid gland, and a post-anal tail.

The name Craniata (organisms with a cranium) is considered to be synonymous with Vertebrata Most tunicates live on the ocean floor and are suspension feeders.

notochord — flexible, rod-shaped support structure that is found in the embryonic stage of all chordates and in the adult stage of some chordates. hagfish — eel-like jawless fish that live on the ocean floor and are scavengers. tunicate — sessile chordate that is a member of Urochordata. Cephalochordata — chordate clade whose members possess a notochord, dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail in the adult stage.