noun Zoology.
any of the nonvertebrate chordates, as the tunicates, cephalochordates, and hemichordates.

1890–95; < Neo-Latin Protochordata name of the group; see proto-, chordate Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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World English Dictionary
protochordate (ˌprəʊtəʊˈkɔːdeɪt)
1.  any chordate animal of the subphyla Hemichordata (acorn worms), Urochordata (tunicates), and Cephalochordata (lancelets)
2.  of or relating to protochordates

Collins English Dictionary - Complete & Unabridged 10th Edition
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Encyclopedia Britannica


any member of either of two invertebrate subphyla of the phylum Chordata: the Tunicata (sea squirts, salps, etc.) and the Cephalochordata (amphioxus). Like the remaining subphylum of the chordates, the Vertebrata, the protochordates have a hollow dorsal nerve cord, gill slits, and a stiff supporting rod, the notochord, the forerunner of the backbone. The protochordates differ chiefly from the vertebrates in not having a backbone. Recent protochordates are thought to have evolved from the same ancestral stock as that which gave rise to the vertebrates.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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