part of part of transformation of chordate pharynx primordium thyroid primordium thyroid diverticulum UBERON:0007689 diverticulum thyroideum endodermal bud derived from the endodermal epithelium of the embryonic pharyngeal floor[MP]. The thyroid diverticulum is the embryological structure from which thyroid follicular cells derive. It grows from the floor of the pharnyx[WP]. saccus thyroideus uberon