Fruit structure and development in Eupomatiaceae and comparison of fruit histology with other Magnoliales and with Laurales

Based on morphological characters the monogeneric family Eupomatiaceae has been traditionally included in Magnoliales, closely related to Magnoliaceae, Himantandraceae or Annonaceae. This is well supported by molecular phylogenetic studies, and Eupomatiaceae appear strongly supported as sister to Annonaceae. Some specific characters of reproductive organs of Eupomatia have been regarded as autapomorphies of Eupomatiaceae. In earlier studies of Eupomatia fruits, the endocarp has been described as undifferentiated. Current research revealed the following notable characters of Eupomatiaceae: a difference in fruit wall structure of peripheral and inner fruiting carpels by congenital fusion of the peripheral carpels with the receptacle (epicarp) from early differentiation of mesocarp, and late growth of endocarp cells in a radial direction resulting in a parenchymatous palisade endocarp shortly before fruit maturation. This study also demonstrates that pericarp development and structure in mature fruits of Eupomatia differ conspicuously from other families of Magnoliales and are more similar to those of some Laurales. This is in addition to the cup-shaped receptacle and inferior ovary (fruit) found in several Laurales, but not other Magnoliales, which could be the result of convergence. The unexpected presence of a palisade endocarp could be a symplesiomorphy of the sister orders Magnoliales and Laurales or a synapomorphy of some Magnoliales and some Laurales.