Palaeodicots
From Freepedia
In the APG system of flowering plant classification, Palaeodicots is a name of convenience. Within the flowering plants (Angiosperms), APG recognises two main groups, the monocots and the "eudicots" (or "tricolpates"). Both are "good" groups, i.e. monophyletic. There is a remainder of basal groups, formerly reckoned to be dicots; these do not form a coherent group (i.e. not monophyletic but paraphyletic). For convenience, these remaining basal groups are sometimes referred to as "palaeodicots" (the prefix "palaeo−" = old) to match the eudicots and monocots. Since "dicots' is short for "dicotyledons" it is tempting to jump to the conclusion that "palaeodicots" should be short for "palaeodicotyledons". However, the name is "palaeodicots".
Under the ICBN, the palaeodicots would be called the Magnoliopsida if treated as a separate class, parallel to using Rosopsida for the eudicots or tricolpates. However the name Magnoliopsida also applies to all the dicotyledons when they are treated as a single class, and in a system that recognises monophyletic groups, would apply to part of the palaeodicots only.
Component groups
Based on recent DNA analyses, it appears that ancestors of the shrub Amborella trichopoda (the only extant 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 sibling taxa Chloranthales, the Magnoliid complex, and Monocots. The Magnoliid complex is monophyletic, and includes orders Canellales, Piperales, Laurales, and Magnoliales.
