substage of immediately preceded by late extended germ band stage developmental stage embryonic stage extended germ band stage embryonic stage 12 dorsal closure stage FBdv:00005331 FlyBase_development_CV Temporal ordering number - 330. Stage following germ band retraction, during which dorsal closure happens (Hartenstein, 1993). Dorsal closure occurs by extension of the dorsal epidermal primordium on either side, leading to fusion at the dorsal midline (Campos-Ortega and Hartenstein, 1997). This corresponds to embryonic stages 13-15 (Hartenstein, 1993; Campos-Ortega and Hartenstein, 1997).