Question
Why was phylum Elemichordata earlier considered as a sub phylum of Chordata?

Answer

  1. Hemiehordata was earlier considered as sub phylum of Chordata because the buccal diverticulum was considered a notochord. It is now placed as a separate phylum under Non-Chordata.
  2. It possesses certain characteristics of both Chordates and Non-chordates.
  3. Absence of notochord worm-like body, heart located on the dorsal side are the Non-chordate like characteristics seen in Hemiehordata.
  4. Presence of nerve chord, pharyngeal gill slits are some of the Chordate-like characters seen in Hemiehordata. Hence, Hemiehordata is considered as a connecting link between Non-chordata and Chordata.

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