A member of the phylum Chordata, characterized by having a notochord, dorsal nerve cord, pharyngeal gill slits, and a post-anal tail at some stage of development. This group includes all vertebrates as well as some invertebrate relatives like lancelets and sea squirts.
From Latin 'chorda' meaning cord or string, referring to the notochord - a flexible rod-like structure that serves as the primitive backbone. The term was established when embryologists discovered this unifying feature across diverse animal groups in the late 1800s.
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