Basal angiosperms

The basal angiosperms are the flowering plants which diverged from the lineage leading to most flowering plants. In particular, the most basal angiosperms were called the ANITA grade which is made up of Amborella (a single species of shrub from New Caledonia), Nymphaeales (water lilies, together with some other aquatic plants) and Austrobaileyales (woody aromatic plants including star anise). ANITA stands for Amborella, Nymphaeales and Illiciales, Trimeniaceae-Austrobaileya. Some authors have shortened this to ANA-grade for the three orders, Amborellales, Nymphaeales, and Austrobaileyales, as the order Illiciales was reduced to the family Illiciaceae and placed, along with the family Trimeniaceae, within the Austrobaileyales.

The basal angiosperms are only a few hundred species, compared with hundreds of thousands of species of eudicots, monocots or magnoliids. They diverged from the ancestral angiosperm lineage before the five groups comprising the mesangiosperms diverged from each other.

The exact relationships between Amborella, Nymphaeales and Austrobaileyales are not yet clear. Although most studies show that Amborella and Nymphaeales are more basal than Austrobaileyales, and all three are more basal than the mesangiosperms, there is significant molecular evidence in favor of two different trees, one in which Amborella is sister to the rest of the angiosperms, and one in which a clade of Amborella and Nymphaeales is in this position. A 2014 paper says that it presents "the most convincing evidence to date that Amborella plus Nymphaeales together represent the earliest diverging lineage of extant angiosperms".

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