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HEMICHORDATA was earlier placed under Chordata but is now classified as a separate phylum under non-chordata because:
AThey have a true notochord
BThey possess only a STOMOCHORD in the collar region — a rudimentary structure SIMILAR TO but not the same as a notochord
CThey are non-coelomate
DThey lack pharyngeal gills
Answer & Solution
Correct answer: B. They possess only a STOMOCHORD in the collar region — a rudimentary structure SIMILAR TO but not the same as a notochord
Hemichordates have a STOMOCHORD (a short structure in the collar/proboscis region) — superficially similar to a notochord but rudimentary. Examples: Balanoglossus, Saccoglossus. Reclassified out of Chordata into a separate non-chordate phylum.
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