part of part of develops from develops from future foramen cecum EHDAA2:0000550 EHDAA:2977 UBERON:0001761 foramen cecum EHDAA:2150 future foramen caecum foramen caecum EMAPA:17069 future foramen cecum of tongue A thickened and indented region in the midline in the floor of the rostral part of the pharyngeal region of the foregut, located between the second and third branchial arches that is the first indication of the thyroid primordium. [Kaufman_MH_and_Bard_JBL, The_anatomical_basis_of_mouse_development_(1999)_San_Diego:_Academic_Press, p.132]. VHOG:0000826 thyroid primordium 3rd arch endoderm pit