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The notochord provides skeletal support, gives the phylum its name, and develops into the vertebral column in vertebrates.The dorsal hollow nerve cord develops into the central nervous system: the brain and spine.Pharyngeal slits are openings in the pharynx that develop into gill arches in bony fish and into the jaw and inner ear in terrestrial animals.The post-anal tail is a skeletal extension of the posterior end of the body, being absent in humans and apes, although present during embryonic development.
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Four distinctive derived characteristics of chordates distinguish them from their ancestors:

A. Notochord, or a rod of vacuolated cells, encased by a firm sheath that lies ventral to the neural tube in vertebrate embryos and some adults.B. Hollow nerve cord that lies dorsal to the notochordC. Pharyngeal pouchesD. Endostyle - elongated groove in the pharynx floor of protochordates that may develop as the thyroid gland in chordates