part of parasegmental furrow fly_anatomy.ontology FBbt:00000100 Furrow of the embryo that separates each segment into anterior and posterior compartments (Larsen et al., 2008). It forms in the ventrolateral region of its segment in early stage 11 and disappears late in stage 11 (Larsen et al., 2008). PS groove parasegment groove stage 11 embryo epithelial furrow