A molecular dating study using Metzgar et al.'s data and a comprehensive set of rhizome and leaf fossils estimated that (sub)generic differentiation within Osmundaceae started by the Triassic and was finished by the Early Cretaceous with the formation of "Osmunda" and "Plenasium". Accordingly, the PPG I classification of 2016 continues to place Osmundales in Polypodiidae, but splits "Osmunda" further by elevating its subgenera to genera ("Claytosmunda", "Plenasium"). The following cladogram reproduces the PPG I concept for the extant members of the family: