Basal Eudicots

1. Supertaxonomy Overview

The Basal Eudicots are the early-diverging branches of the eudicot radiation that originated before the rise of the Core Eudicots. In Tree TSAR, the name provides a practical home for four living orders: Ranunculales, Proteales, Trochodendrales, and Buxales. Together they contain some of the most evolutionarily informative flowering plants on Earth, including buttercups, poppies, barberries, lotus, plane-trees, proteas, macadamias, boxwoods, Trochodendron, and Tetracentron. They preserve an extraordinary mixture of floral architectures, growth forms, ecological strategies, and genomic histories that illuminate the transition from the earliest eudicot radiation to the immensely diverse Core Eudicots (Soltis et al. 2018; Angiosperm Phylogeny Group 2026).

Unlike Core Eudicots, however, Basal Eudicots is not a clade. It is a paraphyletic evolutionary grade: a succession of branches whose common ancestor also gave rise to the Core Eudicots, which are excluded from the group by definition. “Basal Eudicots” therefore functions much like other useful evolutionary-grade terms. It describes a meaningful segment of the flowering-plant tree without implying that its constituent orders form an exclusive natural group. “Early-diverging eudicots” is the more explicitly phylogenetic alternative and is widely used in scientific literature (Soltis et al. 2018).

This distinction is particularly important because basal does not mean primitive. Living Ranunculales, Proteales, Trochodendrales, and Buxales have been evolving for more than 100 million years. Their modern species are not surviving ancestors of the Core Eudicots, nor are they evolutionary steps through which modern roses, oaks, legumes, or asters passed. Rather, their ancestral lineages diverged earlier from the common eudicot stem, and their living descendants have accumulated their own specializations, losses, radiations, and ecological adaptations.

APG V recognizes 13 living families across these four orders: seven in Ranunculales, four in Proteales, and one each in Trochodendrales and Buxales. The APG V linear classification places these orders after the beginning of the Eudicots and before the explicitly labeled Core Eudicots, which begin with Gunnerales (Angiosperm Phylogeny Group 2026). Current Angiosperm Phylogeny Website estimates place the four orders together at roughly 6,400 species in about 290 genera, although totals vary as generic and species circumscriptions change. Ranunculales alone account for about 4,510 species, and Proteales approximately 1,750 (Stevens 2001 onwards).

Despite their relatively modest diversity compared with the Core Eudicots, these lineages are disproportionately important for understanding early eudicot evolution. Their flowers range from the numerous, often separate parts of many buttercups and magnolia-like arrangements traditionally interpreted as relatively unspecialized, to the highly bilateral flowers of some Ranunculales, the tiny unisexual flowers of boxwoods, and the spectacularly specialized inflorescences of Proteaceae. Growth forms include delicate annual herbs, large perennial vines, aquatic herbs, shrubs, forest trees, and plants adapted to nutrient-poor Mediterranean-climate landscapes.

The Basal Eudicots are consequently an excellent Tree TSAR tentpole, even though the unit is intentionally paraphyletic. Tree TSAR’s supertaxonomy framework allows important explanatory grades as well as strict clades when they provide a stable and comprehensible way to navigate plant diversity. Here, the division between Basal Eudicots and Core Eudicots captures one of the most consequential transitions in flowering-plant evolution while keeping that transition legible to readers who might otherwise encounter four relatively small orders disconnected from their broader evolutionary significance.

2. Placement in Tree TSAR

Tree TSAR places Basal Eudicots directly beneath Angiosperms as one of its selected supertaxonomy tentpoles, parallel in navigational function to Core Eudicots and Monocots. Phylogenetically, Basal Eudicots and Core Eudicots together belong to the larger Eudicot clade. Tree TSAR compresses that additional node in its selected tentpole hierarchy rather than requiring every biologically valid clade to occupy another navigation level.

Seed Plants → Angiosperms → Basal Eudicots → Order

This should not be read as a claim that Basal Eudicots is a monophyletic daughter clade of Angiosperms equivalent in structure to Monocots. It is an operational Tree TSAR grade representing the successive early branches of the Eudicots. Tree TSAR explicitly permits this kind of selective scaffold rather than manufacturing additional groups simply to make every lineage occupy the same number of columns.

APG V itself does not establish “Basal Eudicots” as a formal taxonomic unit. Its linear classification instead places a heading for EUDICOTS, followed by Ranunculales, Proteales, Trochodendrales, and Buxales; only after those four orders does the separate heading CORE EUDICOTS appear, followed by Gunnerales (Angiosperm Phylogeny Group 2026). Tree TSAR’s Basal Eudicots category simply gives a useful public-facing name to this phylogenetic interval.

The first major branch is particularly stable. Ranunculales is consistently recovered as sister to all remaining living eudicots, followed by Proteales or the Proteales/Sabiaceae lineage. Large plastid datasets, nuclear datasets, and more recent genomic studies have repeatedly recovered this broad pattern (Moore et al. 2010; Sun et al. 2016; Zeng et al. 2017).

The deepest relationships immediately adjacent to the Core Eudicots require more nuance. Trochodendrales and Buxales occupy the portion of the tree closest to Core Eudicots, but genomic analyses have differed over whether they form a sister pair or whether Buxales alone is the immediate sister lineage of Core Eudicots with Trochodendrales diverging just before it. In genome-scale analyses of Buxus and Tetracentron, coalescent analyses supported a Trochodendrales + Buxales clade sister to Core Eudicots, whereas concatenated analyses placed Buxales alone next to Core Eudicots (Chanderbali et al. 2022). This is precisely the kind of deep, short-branch conflict for which Tree TSAR should preserve stable higher-level units without overstating an exact branching order.

APG V’s broader methodology reinforces this approach. Where extensive nuclear-gene discordance remains, relationships may be treated as uncertain rather than forced into an apparently definitive topology (Angiosperm Phylogeny Group 2026). Tree TSAR can therefore confidently recognize Ranunculales, Proteales, Trochodendrales, and Buxales as the Basal Eudicot grade while allowing the final arrangement of the two crownward orders to remain responsive to future evidence.

One important exclusion should also be explicit. Ceratophyllales is not a Basal Eudicot in the APG V framework. APG V removes Ceratophyllaceae from the Eudicots altogether for classificatory purposes and places it immediately beforehand under the informal heading Ceratophyllids, because conflicting genomic analyses have not yet established its position confidently (Angiosperm Phylogeny Group 2026). This distinction will become especially important when Tree TSAR updates the Angiosperms narrative.

3. Evolutionary History and Fossil Context

The history of the Basal Eudicots begins with the origin of the Eudicots themselves. Their defining evolutionary marker is the appearance of triaperturate pollen, ancestrally expressed as pollen with three elongated apertures, or colpi. This pollen architecture is sufficiently distinctive that it provides one of the strongest links between molecular phylogeny and the Cretaceous fossil record (Soltis et al. 2018).

A major 2025 reassessment of Early Cretaceous pollen from Portugal established well-dated tricolpate grains at approximately 122.97 ± 0.34 million years ago, in the late Barremian. This provides an exceptionally well-constrained minimum age for the Eudicot lineage and confirms that the initial eudicot radiation was underway by roughly 123 million years ago (Gravendyck et al. 2025). Molecular-clock estimates have sometimes placed the eudicot crown substantially earlier, but these estimates remain sensitive to methodology and calibration; the fossil pollen provides the firmer direct minimum.

The early eudicot fossil record is especially relevant to the Basal Eudicots because the first identifiable eudicot flowers and vegetative remains disproportionately resemble these early-diverging lineages. Fossil structures with relationships to Ranunculales, Proteales, and Buxales occur in Early Cretaceous deposits, whereas unmistakable representatives of the great Core Eudicot radiations become conspicuous somewhat later (Friis et al. 2010; Soltis et al. 2018).

Ranunculalean fossils include several intriguing Early Cretaceous forms. Leefructus mirus from the Yixian Formation of China has been interpreted as a close relative of living Ranunculales, and other fossils from Europe, North America, and the Brazilian Crato Formation exhibit combinations of vegetative and reproductive characters consistent with early ranunculalean affinities. The record remains patchy enough that the exact placement of individual fossils is sometimes debated, but it demonstrates that ranunculalean-type eudicots were already diversifying early in eudicot history (Soltis et al. 2018).

Proteales have an exceptionally informative Cretaceous record. Fossils related to Platanaceae appear early and widely, while lotus relatives document the antiquity of the highly specialized aquatic Nelumbonaceae body plan. The 2023 description of Notocyamus hydrophobus from the Crato Formation of northeastern Brazil provided the oldest particularly complete evidence for the Nelumbonaceae lineage. Its mosaic of features bridges part of the otherwise remarkable morphological gap between aquatic lotus relatives and woody protealeans such as Platanaceae and Proteaceae (Gobo et al. 2023). This fossil is especially valuable because the living members of Proteales look so different that their close relationship was scarcely imaginable before molecular phylogenetics.

Buxalean flowers are also known from Aptian-Albian and younger Cretaceous deposits. Charcoalified flowers from Portugal and eastern North America document a surprisingly diverse early history of the lineage. Fossil platanoid flowers and leaves similarly demonstrate that several distinctive Basal Eudicot body plans were established early in the Cretaceous (Friis et al. 2010).

These fossils also complicate the traditional assumption that the first eudicots were primarily woody plants. Some of the best Early Cretaceous eudicot megafossils appear to represent small, rapidly growing herbs occupying bright, wet, disturbance-prone habitats. Jud (2015) proposed that an early herbaceous phase could help explain both the sparse megafossil record and the rapid diversification of the first eudicots. Modern Basal Eudicots retain both sides of this ecological spectrum, from herbaceous Ranunculaceae and Papaveraceae to ancient woody lineages such as Platanaceae, Proteaceae, Buxaceae, and Trochodendraceae.

Genomics adds another dimension to this history. Whole-genome duplications occurred repeatedly during early eudicot evolution, but recent comparative genomes of Buxus and Tetracentron indicate that their duplications were independent of the gamma palaeohexaploidy characteristic of the Core Eudicot lineage. Reconstruction of ancestral genomes suggests that the major gamma event occurred on the Core Eudicot stem rather than being inherited from a common Basal Eudicot ancestor (Chanderbali et al. 2022). Basal Eudicots consequently provide an essential comparative window onto what the eudicot genome looked like immediately before one of the most consequential genome reorganizations in flowering-plant history.

Tree TSAR treats these fossil lineages as evolutionary context rather than extending the active family hierarchy to every extinct form. Their value is greater than simple age calibration: they reveal that the apparently disparate living orders now gathered as Basal Eudicots are remnants of an early Cretaceous radiation that was once more morphologically and ecologically diverse.

4. Classification and Circumscription

The concept of Basal Eudicots emerged from the same molecular revolution that dismantled the traditional “dicotyledon” classification. The old dicot category combined nearly all flowering plants with two cotyledons, but it included several lineages that diverged before the common ancestor of modern Eudicots. Recognition of the Eudicots, originally also described as the tricolpates, brought pollen morphology and molecular evidence into remarkable agreement: a large clade of flowering plants could be recognized by descent from an ancestor with triaperturate pollen (Soltis et al. 2018).

Once the Eudicots were recognized, molecular studies consistently revealed that their living members fell into two very unequal evolutionary components. The overwhelming majority belonged to a single large clade, now called Core Eudicots or Gunneridae, while a small number of lineages diverged successively before that radiation. Those early branches became known informally as basal or early-diverging eudicots.

Modern APG classifications have progressively stabilized their ordinal circumscriptions. Under APG V, Tree TSAR’s Basal Eudicot grade consists of four orders and 13 families. Ranunculales contains Eupteleaceae, Papaveraceae, Circaeasteraceae, Lardizabalaceae, Menispermaceae, Berberidaceae, and Ranunculaceae. Proteales contains Sabiaceae, Nelumbonaceae, Platanaceae, and Proteaceae. Trochodendrales contains Trochodendraceae, and Buxales contains Buxaceae (Angiosperm Phylogeny Group 2026).

These circumscriptions conceal several important historical changes. Sabiaceae, for example, was once frequently treated as an independent lineage called Sabiales because its relationship to the remaining Proteales was difficult to resolve. Large plastid and nuclear analyses now support its inclusion within Proteales, and APG V treats it there (Sun et al. 2016; Angiosperm Phylogeny Group 2026). Earlier phylogenies therefore sometimes describe five basal-eudicot lineages where Tree TSAR and current APG classification recognize four orders.

Trochodendraceae likewise once competed with a separate Tetracentraceae. APG ultimately united Trochodendron and Tetracentron in a single Trochodendraceae because their similarities and molecular relationship make two monogeneric families unnecessarily redundant. Modern Trochodendrales therefore contains one family and only two living genera and species (Stevens 2001 onwards).

Buxaceae has also become broader than some older classifications. Genera previously isolated in Didymelaceae and Haptanthaceae are accommodated within the modern family, leaving Buxales as a one-family order. The extraordinary Central American genus Haptanthus, Malagasy Didymeles, familiar boxwoods (Buxus), Pachysandra, Sarcococca, and several other genera are thus all members of Buxaceae in the broad APG treatment (Stevens 2001 onwards).

The most important remaining uncertainty is no longer whether these orders belong among the Eudicots, but exactly how some of the deepest branches connect. Ranunculales is robustly the earliest-diverging living eudicot order. Proteales follows. The relationship between Trochodendrales, Buxales, and Core Eudicots is more sensitive to genes and analytical method. Plastid analyses often recovered a sequential grade, while modern nuclear datasets sometimes support Trochodendrales + Buxales as a clade. Genome-scale analyses have demonstrated both alternatives depending on whether coalescent or concatenated methods are used (Moore et al. 2010; Chanderbali et al. 2022).

That uncertainty does not weaken the usefulness of Basal Eudicots in Tree TSAR. Quite the opposite: the grade remains stable even if the order of its final two branches changes. Tree TSAR therefore uses Basal Eudicots as an explanatory classification unit, while retaining the four constituent APG V orders as the actual monophyletic taxa. It should never be assigned a formal botanical rank or presented as though it had a single synapomorphy separating it from Core Eudicots.

5. Morphology, Biology, and Identification

The Basal Eudicots cannot be diagnosed as a group by one exclusive morphological feature because they do not form a clade. Their shared characteristics are primarily those inherited from the broader Eudicot ancestor, combined with a fascinating variety of traits retained, transformed, or independently specialized along each early branch.

The most important shared evolutionary feature is triaperturate pollen. The ancestral eudicot pollen grain possessed three principal apertures, commonly expressed as three elongated colpi. Numerous descendants have subsequently modified this pattern into tricolporate, multiporate, spiraperturate, or other configurations, but the three-aperture developmental ground plan remains one of the strongest morphological signatures of eudicot ancestry. Basal Eudicot pollen itself is far from uniform: a broad survey found extensive variation in pollen size, shape, aperture number, aperture form, and surface sculpture across the grade (Zhang et al. 2017).

Floral morphology is equally diverse. Many Ranunculales retain flowers with numerous, separate organs, variable merosity, spiral or mixed floral phyllotaxis, and multiple free carpels. A buttercup or anemone can therefore look superficially reminiscent of some earlier-diverging angiosperms. Yet Ranunculales also contain highly derived flowers, including the strongly bilateral blossoms of larkspurs, monkshoods, and bleeding hearts. “Early-diverging” must not be mistaken for morphologically unspecialized.

Ranunculales are also notable for their chemical diversity. Benzylisoquinoline and related alkaloids occur prominently in several families. Papaveraceae frequently possess latex and include plants with powerful pharmacologically active compounds, while Berberidaceae and Ranunculaceae contain many species with distinctive alkaloid chemistry. The same chemical diversity that has made these plants important medicinally also makes numerous species toxic (Stevens 2001 onwards).

Proteales provide perhaps the clearest warning against trying to infer deep relationships from superficial resemblance. The aquatic sacred lotus, a London plane-tree, a macadamia tree, and a tropical Sabia scarcely look like close relatives. Nelumbonaceae, Platanaceae, Proteaceae, and Sabiaceae were united convincingly only after molecular phylogenetics revealed their common ancestry. Current morphological work and fossils increasingly identify combinations of developmental, anatomical, ovular, floral, and fruit characters consistent with that relationship, but the order remains one of the most striking examples of morphological divergence within a relatively old angiosperm clade (Stevens 2001 onwards).

The case of Nelumbo is especially instructive. Lotus plants superficially resemble water lilies because both have large floating or emergent leaves and spectacular aquatic flowers. Yet Nelumbo is not closely related to Nymphaeaceae. Its aquatic habit evolved within Proteales, surrounded phylogenetically by predominantly terrestrial woody lineages. The resemblance is a classic example of convergent evolution.

Trochodendrales consist of the East Asian genera Trochodendron and Tetracentron. Their wood anatomy played an outsized role in historical ideas about “primitive” flowering plants, particularly because these genera were long discussed in connection with the absence or unusual structure of vessel elements. Modern anatomical and genomic evidence has shown that the evolution of water-conducting cells in the lineage is considerably more complex than a simple retention of an ancestral vesselless condition. Genomic study of Tetracentron has provided new insight into both vessel evolution and the independent genomic history of the lineage (Chanderbali et al. 2022).

Buxales are mostly woody and frequently bear small, inconspicuous, often unisexual flowers. The familiar evergreen boxwoods exemplify one part of the family, but Buxaceae also contains the herbaceous groundcover Pachysandra, fragrant Sarcococca, Malagasy Didymeles, and morphologically extraordinary Haptanthus. This variation again shows why the Basal Eudicots cannot be summarized as a collection of generalized or ancestral-looking flowering plants.

Identification therefore normally proceeds through the constituent orders and families rather than through a “Basal Eudicot” key. Triaperturate pollen can identify the larger Eudicot affinity, while floral organization, leaf arrangement, fruit type, secondary chemistry, anatomy, habit, and increasingly molecular evidence separate the four early-diverging lineages.

6. Distribution and Ecology

Basal Eudicots collectively occur across much of the world, but their individual lineages have strikingly different geographic histories. The grade includes globally distributed temperate herbs, pantropical woody vines, southern-hemisphere shrublands, aquatic plants, northern temperate trees, and exceptionally localized evolutionary relicts.

Ranunculales are the most geographically widespread and species-rich component. Ranunculaceae are especially diverse in temperate and cool regions of the Northern Hemisphere, extending into alpine and arctic habitats as well as mountains of the Southern Hemisphere. Papaveraceae likewise have important temperate centers of diversity. Menispermaceae, by contrast, consist largely of tropical and subtropical woody climbers, while Berberidaceae combine temperate shrubs and perennial herbs. The order consequently spans forests, meadows, wetlands, alpine habitats, deserts, tropical forests, and disturbed environments (Stevens 2001 onwards).

Proteales have a particularly vivid biogeographic signature. Proteaceae are strongly associated with southern-hemisphere floras and reach extraordinary diversity in Australia and southern Africa, where many species occupy nutrient-poor, fire-prone Mediterranean-climate ecosystems. Their specialized cluster roots can dramatically increase nutrient acquisition in phosphorus-poor soils. Other Proteales tell very different stories: Platanus consists of northern-hemisphere trees associated especially with rivers and floodplains, while the two living Nelumbo species are aquatic plants with a striking East Asian/Australasian versus North American disjunction. Proteales therefore illustrate how profoundly ecology and geography can diverge within an ancient lineage (Stevens 2001 onwards).

Trochodendrales are today restricted to eastern Asia. Trochodendron and Tetracentron are remnants of lineages with deeper fossil histories and are often described as relictual components of East Asian forests. Their modern geographic restriction contrasts with evidence that related plants were more widespread in the past.

Buxales span tropical and temperate regions but likewise contain strong biogeographic contrasts. Buxus has a broad, disjunct distribution with centers of diversity in several warm-temperate and tropical regions. Pachysandra occurs in eastern Asia and eastern North America, Didymeles is Malagasy, and the exceptional Haptanthus is known from Central America. Such patterns make Buxaceae useful for investigating both ancient continental history and long-distance dispersal.

Ecologically, these plants participate in an equally broad spectrum of interactions. Flowers may be wind-pollinated or animal-pollinated; animals ranging from insects to birds and mammals interact with Proteaceae flowers; fleshy fruits of Menispermaceae and Berberidaceae are dispersed by vertebrates; hooked or specialized structures aid dispersal in other groups; and aquatic Nelumbonaceae disperse in freshwater environments.

The living Basal Eudicots therefore do not represent a single ecological strategy left over from early angiosperm history. They document what happened when several ancient eudicot branches independently entered different ecological arenas over more than 100 million years.

7. Human Uses and Cultural Importance

Although far less species-rich than the Core Eudicots, Basal Eudicots contain an unusually recognizable collection of economically, horticulturally, medicinally, and culturally important plants.

Ranunculales are especially prominent in horticulture. Clematis, columbines (Aquilegia), anemones, buttercups (Ranunculus), delphiniums, monkshoods (Aconitum), hellebores, baneberries, bleeding hearts, poppies, barberries, and mayapples all belong to the order. Many have been cultivated for centuries. The same lineage also supplies numerous medicinal compounds, although the pharmacological activity of many species is accompanied by substantial toxicity.

Papaver somniferum, the opium poppy, is one of the most historically consequential medicinal plants, yielding both edible poppy seeds and a suite of benzylisoquinoline alkaloids that have profoundly influenced medicine and human history. Other Ranunculales have long traditions in herbal medicine, including goldenseal and several barberries, though medicinal use should not be confused with evidence of safety or efficacy for every traditional preparation.

Proteales contribute several economically and culturally iconic plants. Macadamia species in Proteaceae produce one of the world’s important commercial tree nuts. Proteas, banksias, grevilleas, leucadendrons, and related genera are major ornamental and cut-flower crops, particularly in Mediterranean and subtropical horticulture. Many Proteaceae are also central components of Australian and South African native-plant gardening.

Platanus species and hybrids are among the most familiar urban shade trees of the Northern Hemisphere. London plane-tree and related plane-trees have been planted extensively along streets and in parks because of their large stature and tolerance of demanding urban environments.

Few plants carry more cultural symbolism than the sacred lotus, Nelumbo nucifera. Its flowers have major religious and artistic significance across Asia, particularly in Hindu and Buddhist traditions. Its rhizomes, seeds, and other parts are also widely eaten. The American lotus, N. lutea, has its own long history of human use in North America. The close relationship of lotus to plane-trees and proteas remains one of the most memorable examples of how molecular classification can overturn assumptions based on growth form.

Buxales are particularly important horticulturally. Buxus species have been cultivated for centuries as evergreen hedges, topiary, edging plants, and formal garden elements; boxwood also supplied a dense, fine-grained timber historically prized for carving, engraving, musical instruments, and other precision uses. Pachysandra is a familiar shade groundcover, while Sarcococca is valued for evergreen foliage and intensely fragrant winter flowers.

Trochodendraceae are economically minor by comparison, but Trochodendron and Tetracentron are important specialty ornamentals and botanical-garden plants. Their value in collections is amplified by their exceptional phylogenetic distinctiveness and their importance for teaching flowering-plant evolution.

8. Conservation Significance

The Basal Eudicots pose an unusual conservation problem: their approximately 6,400 living species represent far fewer species than the Core Eudicots, yet they encompass a disproportionate amount of deep eudicot evolutionary history. Losing a highly isolated lineage within Trochodendraceae or Buxaceae can therefore erase evolutionary information that is poorly represented elsewhere.

Habitat loss affects lineages throughout the grade. Tropical Menispermaceae and Sabiaceae depend upon increasingly fragmented forest habitats, while localized temperate and montane Ranunculales may be vulnerable to development, altered hydrology, invasive species, recreation, or climatic displacement. Many narrowly distributed Proteaceae occur in biodiversity hotspots subject to land conversion, altered fire regimes, and invasive pathogens.

Proteaceae illustrate the importance of matching conservation to ecology. Many species evolved in nutrient-poor, fire-influenced environments where inappropriate fire frequency can be as damaging as complete fire suppression. In parts of Australia, the introduced water mold Phytophthora cinnamomi has caused severe decline in susceptible native vegetation, including numerous Proteaceae. Habitat protection without management of disease, fire, and hydrology may therefore be insufficient.

Buxaceae face different threats. Boxwoods have acquired major horticultural and ecological concern from boxwood blight and the invasive box tree moth, while some wild Buxus populations are additionally affected by habitat degradation and harvesting. Other genera in the family have extremely restricted distributions, making protection of individual habitats particularly important.

The tiny living diversity of Trochodendrales makes its conservation significance immediately apparent. Only Trochodendron and Tetracentron survive from this deep branch of eudicot history. Even where individual species are not globally on the brink of extinction, maintaining geographically and genetically diverse wild populations protects a lineage that has no species-rich sister radiation in which comparable evolutionary information can be duplicated.

Botanical gardens, arboreta, seed banks, tissue collections, and living germplasm repositories are consequently particularly valuable for Basal Eudicot conservation. Living collections can simultaneously support ex situ conservation, horticultural research, genomic study, public education, and direct comparison of some of the earliest surviving branches of the Eudicot tree.

9. Major Included Groups

Ranunculales

Ranunculales is the largest and earliest-diverging living branch of the Eudicots. Current Angiosperm Phylogeny Website estimates place it at roughly 199 genera and 4,510 species, distributed among seven APG V families (Stevens 2001 onwards; Angiosperm Phylogeny Group 2026). Those families are Eupteleaceae, Papaveraceae, Circaeasteraceae, Lardizabalaceae, Menispermaceae, Berberidaceae, and Ranunculaceae.

The order ranges from the two species of Euptelea to enormous and familiar radiations in Ranunculaceae, Papaveraceae, Berberidaceae, and Menispermaceae. Herbs predominate in several families, but woody shrubs and vines are also important. Familiar plants include buttercups, clematis, columbines, hellebores, monkshoods, delphiniums, poppies, bleeding hearts, barberries, moonseeds, mayapples, and Akebia.

Ranunculales are particularly informative about early floral evolution because they combine flowers with numerous and often free floral organs with repeated origins of highly specialized structures and bilateral symmetry. The order also appears very early in the eudicot fossil record and is robustly recovered as sister to all other living Eudicots (Moore et al. 2010; Sun et al. 2016).

Proteales

Proteales contains four APG V families: Sabiaceae, Nelumbonaceae, Platanaceae, and Proteaceae. Current estimates place the order at approximately 85 genera and 1,750 species (Stevens 2001 onwards; Angiosperm Phylogeny Group 2026).

Few orders better demonstrate the power of phylogenetics. The woody, often sclerophyllous Proteaceae; northern-temperate plane-trees; aquatic lotuses; and largely woody Sabiaceae were never an intuitively obvious natural assemblage. Their relationship emerged from molecular evidence and has subsequently gained support from detailed morphological and fossil studies.

Proteaceae dominate the living species diversity of the order and include proteas, banksias, grevilleas, macadamias, and many other ecologically important southern-hemisphere plants. Platanaceae contain Platanus, Nelumbonaceae contain Nelumbo, and Sabiaceae comprise smaller woody lineages concentrated largely in tropical and subtropical regions.

The Early Cretaceous record of Proteales is unusually rich. Fossils related to Platanaceae and Nelumbonaceae demonstrate that much of the order’s extraordinary morphological disparity had already emerged very early, while transitional fossils such as Notocyamus help reveal how those apparently disconnected body plans arose (Gobo et al. 2023).

Trochodendrales

Trochodendrales is now one of the smallest flowering-plant orders: one family, two genera, and two living species according to the Angiosperm Phylogeny Website (Stevens 2001 onwards). APG V recognizes only Trochodendraceae (Angiosperm Phylogeny Group 2026).

The living species are Trochodendron aralioides and Tetracentron sinense. Both are woody East Asian plants, but their historical and evolutionary importance is vastly greater than their species count suggests. Their anatomy, floral structure, fossils, and genomes have figured prominently in attempts to understand the transition from early Eudicots to Core Eudicots.

Older classifications sometimes recognized Tetracentraceae separately, but APG combines the two genera in Trochodendraceae. Genome-scale studies also demonstrate independent whole-genome duplication within this lineage and make Trochodendrales a particularly valuable comparator for reconstructing the genomic state immediately preceding the Core Eudicot radiation (Chanderbali et al. 2022).

Buxales

Buxales likewise contains a single APG V family, Buxaceae. The Angiosperm Phylogeny Website estimates approximately seven genera and 120 species (Stevens 2001 onwards; Angiosperm Phylogeny Group 2026).

The best-known genus is Buxus, the boxwoods, but modern Buxaceae also contain Pachysandra, Sarcococca, Styloceras, Didymeles, Haptanthus, and other genera (Stevens 2001 onwards). The family therefore encompasses far more morphological and geographic diversity than familiar horticultural boxwoods alone suggest.

Buxales occupy a particularly significant phylogenetic position close to the Core Eudicots. Some genomic analyses make Buxales the immediate sister lineage of Core Eudicots, while others unite Buxales with Trochodendrales. That uncertainty concerns the precise branch order, not the integrity of Buxales itself (Chanderbali et al. 2022).

The family’s scattered geography and combination of widespread and exceptionally isolated genera give it substantial biogeographic and conservation interest. Its genome also provides an important comparison for determining which genomic changes arose before versus after the origin of the Core Eudicots.

10. Similar, Overlapping, or Historically Confused Groups

Basal Eudicots and Core Eudicots are not equivalent kinds of group. Core Eudicots is monophyletic: it includes a common ancestor and all of its living descendants. Basal Eudicots is paraphyletic because the common ancestor of Ranunculales, Proteales, Trochodendrales, and Buxales is also ancestral to the Core Eudicots, which are deliberately excluded.

Early-diverging eudicots is therefore often the preferable technical phrase and is essentially equivalent to the Tree TSAR Basal Eudicots concept. “Basal Eudicots” remains useful because it is concise, familiar, easy to contrast with Core Eudicots, and immediately comprehensible once its grade status is explained.

The word basal should never be interpreted as “primitive,” “inferior,” or “unchanged.” A modern poppy, lotus, macadamia, boxwood, or Tetracentron is just as contemporary as a sunflower or oak. The difference lies only in when its ancestral branch diverged from other lineages.

Basal angiosperms is a different term entirely. It is generally used for lineages near the base of the entire flowering-plant tree, especially Amborella, Nymphaeales, and Austrobaileyales, and sometimes more loosely for other early angiosperm branches. Basal Eudicots are nested much farther inside the Angiosperms.

Tricolpates or Tricolpatae are historical and descriptive names associated with the Eudicots as a whole, not specifically with the Basal Eudicots. Tricolpate and tricolpate-derived pollen characterizes the ancestry shared by Basal and Core Eudicots alike (Soltis et al. 2018).

Dicots are broader still and do not constitute a natural clade. The traditional dicotyledons also included magnoliids and several other flowering-plant lineages that are not Eudicots. The discovery of the Eudicot clade was one of the principal reasons the old monocot-versus-dicot classification was abandoned as a formal representation of angiosperm phylogeny.

Ranunculids is sometimes encountered for Ranunculales or a closely related concept. It should not be used as a synonym for all Basal Eudicots. Ranunculales represents only the first and largest branch of the grade.

Sabiales appears in older or alternative classifications for Sabiaceae. Modern APG classification incorporates Sabiaceae within Proteales instead. Earlier literature may consequently describe five major early-diverging eudicot lineages where APG V and Tree TSAR recognize four orders (Sun et al. 2016; Angiosperm Phylogeny Group 2026).

Nelumbo is frequently mistaken for a water lily because of its aquatic growth form, peltate leaves, and large showy flowers. Water lilies belong to the deeply diverging order Nymphaeales, whereas lotus belongs to Nelumbonaceae within Proteales. Their resemblance represents ecological convergence across an enormous evolutionary distance.

Finally, Ceratophyllales must remain outside the Basal Eudicots in the APG V-informed Tree TSAR framework. Although many analyses have placed Ceratophyllaceae near or as sister to Eudicots, conflicting nuclear results prevent confident inclusion. APG V therefore recognizes the informal Ceratophyllids immediately before the Eudicots rather than placing Ceratophyllales inside them (Angiosperm Phylogeny Group 2026).

11. Additional Information

The APG V classification is the primary contemporary reference for the order and family circumscriptions used by Tree TSAR. Its importance extends beyond the few names that changed from APG IV: it marks a deliberate shift toward incorporating large nuclear phylogenomic datasets alongside plastid evidence and explicitly recognizes that ancient hybridization and incomplete lineage sorting can produce genuine gene-tree conflict (Angiosperm Phylogeny Group 2026).

The Angiosperm Phylogeny Website provides extensive treatments of the four constituent orders, including morphology, chemistry, fossil history, phylogeny, family relationships, and literature. Its order pages are especially useful for readers moving from the broad Basal Eudicots concept into Ranunculales, Proteales, Trochodendrales, or Buxales (Stevens 2001 onwards).

Plants of the World Online is useful for current accepted names, synonyms, distributions, descriptions, and taxon-level information within the constituent families. World Flora Online provides complementary global taxonomic information.

For occurrence records and geographic exploration, GBIF provides extensive biodiversity data for living taxa. Fossil occurrences and extinct representatives can be explored through the Paleobiology Database, although fossil assignments should always be evaluated in light of the primary paleobotanical literature.

These resources generally do not treat “Basal Eudicots” as a formal taxon because it is not one. Tree TSAR’s treatment is intentionally explanatory: the grade gives readers a comprehensible evolutionary bridge between the origin of the Eudicots and the rise of the Core Eudicots without misrepresenting the four constituent orders as a clade.

12. References and Further Reading

Angiosperm Phylogeny Group (2016) An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG IV. Botanical Journal of the Linnean Society 181(1): 1–20. https://doi.org/10.1111/boj.12385 (opens in a new tab)

Angiosperm Phylogeny Group, Byng JW, Chase MW, Christenhusz MJM, Fay MF, Li D-Z, Ma H, Mabberley DJ, Soltis DE, Soltis PS, et al. (2026) Large-scale nuclear and plastid phylogenomic analyses inform an updated Angiosperm Phylogeny Group classification: APG V. Journal of Systematics and Evolution. Online 18 June 2026. https://www.jse.ac.cn/EN/abstract/abstract103821.shtml (opens in a new tab)

Chanderbali AS, Jin L, Xu Q, Zhang Y, Zhang J, Jian S, Carroll E, Sankoff D, Albert VA, Howarth DG, et al. (2022) Buxus and Tetracentron genomes help resolve eudicot genome history. Nature Communications 13: 643. https://doi.org/10.1038/s41467-022-28312-w (opens in a new tab)

Friis EM, Pedersen KR, Crane PR (2010) Diversity in obscurity: Fossil flowers and the early history of angiosperms. Philosophical Transactions of the Royal Society B 365: 369–382. https://doi.org/10.1098/rstb.2009.0227 (opens in a new tab)

Gobo WV, Kunzmann L, Iannuzzi R, dos Santos TB, da Conceição DM, do Nascimento DR Jr, da Silva Filho WF, Bachelier JB, Coiffard C (2023) A new remarkable Early Cretaceous nelumbonaceous fossil bridges the gap between herbaceous aquatic and woody protealeans. Scientific Reports 13: 8978. https://doi.org/10.1038/s41598-023-33356-z (opens in a new tab)

Gravendyck J, Krencker F-N, Riding JB, et al. (2025) Barremian tricolpate pollen from Portugal: New evidence for the age of eudicot-related angiosperms. Proceedings of the National Academy of Sciences of the United States of America 122(21): e2421470122. https://doi.org/10.1073/pnas.2421470122 (opens in a new tab)

Jud NA (2015) Fossil evidence for a herbaceous diversification of early eudicot angiosperms during the Early Cretaceous. Proceedings of the Royal Society B 282: 20151045. https://doi.org/10.1098/rspb.2015.1045 (opens in a new tab)

Moore MJ, Soltis PS, Bell CD, Burleigh JG, Soltis DE (2010) Phylogenetic analysis of 83 plastid genes further resolves the early diversification of eudicots. Proceedings of the National Academy of Sciences of the United States of America 107(10): 4623–4628. https://doi.org/10.1073/pnas.0907801107 (opens in a new tab)

Soltis DE, Soltis PS, Endress PK, Chase MW, Manchester SR, Judd WS, Majure LC, Mavrodiev EV (2018) Phylogeny and Evolution of the Angiosperms: Revised and Updated Edition. University of Chicago Press, Chicago. https://doi.org/10.7208/chicago/9780226441757.001.0001 (opens in a new tab)

Stevens PF (2001 onwards) Angiosperm Phylogeny Website. Missouri Botanical Garden. http://www.mobot.org/MOBOT/research/APweb/ (opens in a new tab)

Sun Y, Moore MJ, Zhang S, Soltis PS, Soltis DE, Zhao T, Meng A, Li X, Li J, Wang H (2016) Phylogenomic and structural analyses of 18 complete plastomes across nearly all families of early-diverging eudicots, including an angiosperm-wide analysis of IR gene content evolution. Molecular Phylogenetics and Evolution 96: 93–101. https://doi.org/10.1016/j.ympev.2015.12.006 (opens in a new tab)

Zeng L, Zhang N, Zhang Q, Endress PK, Huang J, Ma H (2017) Resolution of deep eudicot phylogeny and their temporal diversification using nuclear genes from transcriptomic and genomic datasets. New Phytologist 214(3): 1338–1354. https://doi.org/10.1111/nph.14503 (opens in a new tab)

Zhang M-Y, Lu L, Wortley AH, Wang H, Li D-Z, Blackmore S (2017) Evolution of angiosperm pollen: 4. Basal Eudicots. Annals of the Missouri Botanical Garden 102: 141–182. https://doi.org/10.3417/2015035 (opens in a new tab)