In most dinoflagellates, the cingulum divides the cell into an upper (epi...) and a lower (hypo...) part. The sulcus defines the ventral cell side.

In some taxa no depressed cingulum exists (podolampids). Species with cingulum and sulcus have a dinokont flagellation (i.e., the transverse and longitudinal flagellum run in the transverse and longitudinal furrow/groove) in prorocentroids the flagellation is desmokont (i.e., the typical dino-flagellation is not associated with grooves).