However, the genus has an anatomical feature, laterocytic stomata (having 3 or more parallel specialised subsidiary cells), which it shares with the Platanaceae (next closest relatives to the Proteaceae) and no other Proteaceae, which indicate it diverged from all other members of the family first.
It is divided into two sub-genera: the sub-genus Castaneophyllum J.-F. Leroy, 1982, with elliptical, penninerved leaves with small scarious, stipules, that only includes Platanus kerrii Gagnep., 1939, an isolated relict species that represents the genus’ evolutionary basal branch and which is a sister genus and is the sister group of the other species, including the sub-genus Platanus.