Palaeodicotyledon

The palaeodicotyledons ("ancient dicots") comprise the basal dicots, i.e. those flowering plants that do not belong to either the monocots or the eudicots. In some newer classifications, the eudicots are treated as a separate class Rosopsida, in which case the palaeodicots are grouped as a paraphyletic class Magnoliopsida or further divided into several classes.

Based on recent DNA analyses, it appears that ancestors of the shrub Amborella trichopoda, the only species in order Amborellales, were the first to split off from the main Angiosperm line, followed by the Nymphaeales and Austrobaileyales. The next main split occurred when the ancestor of the Ceratophyllales and Eudicots diverged from the ancestor of the sister taxa Chloranthales, Magnoliids, and Monocots. The Magnoliid group is monophyletic, and includes orders Canellales, Piperales, Laurales, and Magnoliales.