longitudinal flagellum longitudinal cilium GO:0097609 cellular_component 2014-06-09T11:21:10Z Note that we deem cilium and microtubule-based flagellum to be equivalent. In this case community usage refers to 'flagellum' rather than 'cilium', hence the primary term name, but the cilium parentage is deliberate. A motile cilium found in dinoflagellates. It trails the cell and acts as a steering rudder. It is often partially contained in a furrow called the sulcus, and emerges from a flagellar pore located in the sulcus. pr 9+2 motile cilium