Within the framework of the APG II system of flowering plant classification, 'palaeodicots' is sometimes used (informally), as a name of convenience.

Within the flowering plants (angiosperms), APG II recognises two main groups, the monocots and the eudicots (or tricolpates). Both are "good" groups, that is they are monophyletic groups, also called clades.

Besides these two main groups there is a remainder of basal groups, formerly reckoned to belong to the dicots; these remaining groups do not form a coherent group. That is, it is a paraphyletic group. For convenience, these remaining basal groups are sometimes referred to as 'palaeodicots' (the prefix "pal(a)eo−" = old).

The eudicots and 'palaeodicots' together comprise all plants that formerly made up to the dicotyledons. The name 'palaeodicots' is convenient in that it allows the angiosperms to be divided into three groups. Since "dicots" is short for "dicotyledons" it is tempting to jump to the conclusion that "eudicots" and "palaeodicots" should be short for "eudicotyledons" and "palaeodicotyledons". However, the names are eudicots and palaeodicots.

It is conceivable that someday it may be decided to treat the palaeodicots as a taxon. It might be given the formal botanical name of Magnoliopsida (if treated at the rank of class); as the eudicots or tricolpates might be given the name Rosopsida. So far, apparently, this has not been formally done (see however the Reveal system.

Component groups

The APG II assumes that ancestors of the shrub Amborella trichopoda (the only extant species in family Amborellaceae) were the first to split off from the main angiosperm line, followed by the family Nymphaeaceae and the order 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.

• paraphyletic group "palaeodicots"

  family Amborellaceae

  family Chloranthaceae

  family Nymphaeaceae (+ family Cabombaceae)

  order Austrobaileyales

  clade magnoliids

  order Canellales

  order Laurales

  order Magnoliales

  order Piperales

Magnoliophyta | plant taxonomy | Botanical nomenclature

Einfurchenpollen-Zweikeimblättrige | דו־פסיגיים קדומים | Magnoliopsida