The genus Hymenocardia has been placed either in Euphorbiaceae subfamily Phyllanthoideae or in its own family and then associated with the Urticales, particularly the Ulmaceae. However, the pollen exine wall of Hymenocardia lacks the microchanneled tectum, granular interstitium, and thin foot-layer of the Urticales. Hymenocardia instead has many palynological features found in the Phyllanthoideae and should be retained in the Euphorbiaceae in that subfamily. Didymocistus, which has scalelike foliar trichomes and exine sculpturing and ultrastructure similar to Hymenocardia, should be transferred from the Phyllanthoideae-Aporuseae to a position near Hymenocardia