The posterior half of the abdomen is folded back on the anterior half, due to a failure of germband retraction, resulting in an eponymous phenotype. At full germband extension A8 is often opposite T2/3. Head involution fails and major head parts are missing. Some components of the head skeleton are absent or rudimentary, including the dorsal arms, dorsal bridge and vertical plate. Filzkorper spacing is comparable to wild type. A cuticle hole at the dorsal anterior is sometimes present. Anti-β-tubulin staining reveals a premature loss of amnioserosa cells after stage 11. The amnioserosa undergoes programmed cell death. Development of the midgut is affected.