Anaxagorea is the phylogenetically basal-most genus in the large, tropical magnoliid family Annonaceae (custard apple). Endress and Armstrong  study floral development for the first time in the genus and show complex whorled floral phyllotaxis, with double organ positions in the outer androecium whorl resulting in a switch from trimery to hexamery and completely plicate carpels. The floral [...]