Chordates are derterostome animals that possess a notochord, hollow nerve cord, pharyngeal slits, an endostyle, and a tail (only found during their time as a tadpole). This phylum contains various vertebrate animals including mammals, fish, amphibians, reptiles, and birds. Chordates are known for their bilateral body plan. They are monophyletic, which is the sharing of one ancestor that is a chordate. In total there are about 75,000 living species of chordates.