Answer:
descendants. Chordates share a common, generalized body plan and can be diagnosed by four features shared by members of all the major groups: a notochord, pharyngeal slits, a hollow dorsal nerve tube, and a postanal tail (an extension of the body posterior to the anus). The notochord is a stiff, flexible rod running dorsal to the coelom along the length of the body beneath the central nervous system. In many vertebrates, the notochord is almost completely replaced by blocks of bone forming vertebrae. Pharyngeal slits are lateral openings from the pharynx (an organ situated behind the mouth that constitutes part of the digestive tract). These features are found in all chordates at some point during their lifetime, but they are not retained as fully functional units throughout life in all chordates.
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