The four distinguishing chordate traits are a notochord, a hollow dorsal nerve cord running parallel to the notochord, gill slits, and a post-anal tail.
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These four traits are not necessarily found in the adult organism, but they are definitely seen in the embryos of chordates. The notochord is a stiff yet flexible structure that runs the entire length of the animal's body. The nerve cord can be found on the dorsal surface of the animal. Gill slits are narrow openings found in the area of the throat or pharynx. The tail is muscular and reaches beyond the anus.