Chordates (phylum Chordata) are a group of animals that includes the vertebrates, together with several closely related invertebrates. They are united by having, at some time in their life cycle, a notochord, a hollow dorsal nerve cord, pharyngeal slits, an endostyle, and a post-anal tail. Some scientists argue that the true qualifier should be pharyngeal pouches rather than slits. The phylum Chordata is broken down into three subphyla: Urochordata, Cephalochordata, and Vertebrata. Some conside… (More on Chordate)