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Why hemichordata was earlier considered as sub phylum under chordata but y now it is a separate phylum?

Why hemichordata was earlier  considered as sub phylum under chordata but y now it is a separate phylum?
 

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2 Answers

Arun
25750 Points
5 years ago
Hemichordata was earlier considered as a sub-phylum under phylum Chordata. But now it is placed as a separate phylum under non-chordata. This phylum consists of a small group of worm-like marine animals with organ-system level of organisation.
Apurva Sharma
220 Points
5 years ago
Hemichordates was earlier considered as a sub phylum under chordates due to presence of flexible hollow tube called stomocord.
 
Later many structural and physical differences were found between notochord and stomochord. And stomochord was said to be a different structure wrt. Notochord.
Thus hemichordata/stomochordata was created as a separate phylum.
 
E.g- stomochord is endodermal in origin and a non-supportive structure. Whereas notochord is mesodermal in origin and is a supportive structure.
 
Hope it helps. Then do give a thumbsup! 

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