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The eudicots or eudicotyledons are that have two seed leaves (cotyledons) upon germination. The term derives from dicotyledon (etymologically, eu = true; di = two; cotyledon = seed leaf). Historically, authors have used the terms tricolpates or non-magnoliid dicots. The current botanical terms were introduced in 1991, by evolutionary botanist James A. Doyle and Paleobotany Carol L. Hotton, to emphasize the later evolutionary divergence of tricolpate dicotyledon from earlier, less specialized, dicots.
Scores of familiar plants are eudicots, including many commonly cultivated and edible plants, numerous , tropicals and ornamentals. Among the most well-known eudicot genera are those of the sunflower ( Helianthus), dandelion ( Taraxacum), forget-me-not ( Myosotis), cabbage ( Brassica), apple ( Malus), buttercup ( Ranunculus), maple ( Maple) and macadamia ( Macadamia). Most leafy, mid-latitude trees are also classified as eudicots, with notable exceptions being the and American tulip tree ( Liriodendron)—which belong to the magnoliids—and Ginkgo biloba, which is not an angiosperm.
Later molecular evidence confirmed the genetic basis for the evolutionary relationships among flowering plants with tricolpate pollen grains and dicotyledonous traits. The term means "true dicotyledons", as it contains the majority of plants that have been considered dicots and have Phenotypic trait of the dicots. One of the genetic traits which defines the eudicots is the Gene duplication of in their most recent common ancestor. The term "eudicots" has subsequently been widely adopted in botany to refer to one of the two largest clades of (constituting over 70% of the angiosperm species), monocots being the other. The remaining angiosperms include magnoliids and what are sometimes referred to as basal angiosperms or paleodicots, but these terms have not been widely or consistently adopted, as they do not refer to a monophyletic group.
According to molecular clock calculations, the lineage that led to eudicots split from other plants about 134 million years ago or 155–160 million years ago. Fossil records suggested that basal eudicots were already diverse around 121 million years ago .
The name "eudicots" (plural) is used in the APG systems (from APG system, of 1998, to APG IV system, of 2016) for classification of angiosperms. It is applied to a clade, a monophyletic group, which includes most of the (former) dicots.
"Tricolpate" is a synonym for the "Eudicot" monophyletic group, the "true dicotyledons" (which are distinguished from all other flowering plants by their tricolpate pollen structure). The number of pollen grain furrows or pores helps classify the , with eudicots having three colpus ( tricolpate), and other groups having one sulcus.
Pollen apertures are any modification of the wall of the pollen grain. These modifications include thinning, ridges and pores, they serve as an exit for the pollen contents and allow shrinking and swelling of the grain caused by changes in moisture content. The elongated apertures/ furrows in the pollen grain are called colpi (singular colpus), which, along with pores, are a chief criterion for identifying the pollen classes.
The Pentapetalae can be then divided into three clades:
This division of the eudicots is shown in the following cladogram:Based on:
The following is a more detailed breakdown according to APG IV, showing within each clade and orders:
Subdivisions
The eudicots can be divided into two groups: the basal eudicots and the core eudicots. Basal eudicot is an informal name for a paraphyletic group. The core eudicots are a monophyletic group. A 2010 study suggested the core eudicots can be divided into two clades, Gunnerales and a clade called Pentapetalae, comprising all the remaining core eudicots.
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