Flowers of Anisophylleaceae and Cunoniaceae are remarkably similar. Their current phylogenetic position based on molecular studies places them in eurosids I, but in different orders, Cucurbitales and Oxalidales, respectively (APG, 1998). We studied flowers from selected genera of both families and compared them at a morphological, anatomical and histological level, with some surprising results. This study, combined with a review of previous work on these families, has revealed many shared features including the occurrence of trimerous flowers (in addition to tetra- and pentamerous flowers), digitate petals, isomery in all floral whorls, obdiplostemony, incurved filaments in bud and similar anthers, similar pollen, similar nectaries, carpels with free styles, and similar ovules with a slit-like micropyle. A timely coincidence was the recovery of well preserved fossil flowers from the Late Cretaceous of Sweden by JS and EMF that share many features with both Anisophylleaceae and Cunoniaceae (but have been placed in Cunoniaceae based on some specific traits of the gynoecium). Combined, these results suggest either that Anisophylleaceae and Cunoniaceae are more closely related than previously assumed, or if not, that they exhibit either an unusual number of symplesiomorphic features of basal rosids, or that their floral features are the result of a striking convergent evolution. In either case, it is apparent that more extensive molecular studies are needed, and if these studies confirm the current disparate position of the families, an investigation of the significance of the suite of common structural features should be made.

Key words: Anisophylleaceae, Cucurbitales, Cunoniaceae, eudicots, floral structure, Oxalidales