
Floral bilateral symmetry (zygomorphy) has evolved at least 70 times during the history of angiosperms, whilst radial symmetry (actinomorphy) is the ancestral and most common state for angiosperms as a whole. Sauquet et al. reconstruct the phylogeny and floral evolution of Papaveraceae (Ranunculales) and find that in this family zygomorphy evolved from a rare, intermediate symmetry form, disymmetry, which is defined by two perpendicular planes of bilateral symmetry. This important transition occurred in subfamily Fumarioideae (fumitories) and is correlated with the loss of a nectar spur.