The Borasseae form a highly supported monophyletic clade in the Arecaceae–Coryphoideae, and the large fruits of borassoid palms contain massive pyrenes, which develop from the middle zone of the mesocarp. Romanov et al. study pericarp anatomy during development in all eight Borasseae genera and find that the multilayered pyrene develops in the middle zone of the mesocarp, and that the growing seed dramatically compresses the inner parenchymatous zone of the mesocarp. The pericarp anatomical structure and mode of its development differ significantly from fruits of other Coryphoideae.
