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The dicotyledons, also known as dicots (or more rarely dicotyls), are one of the two groups into which all the
flowering plant Flowering plants include multiple members of the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greec ...

flowering plant
s or angiosperms were formerly divided. The name refers to one of the typical characteristics of the group, namely that the
seed A seed is an embryonic ''Embryonic'' is the twelfth studio album by experimental rock band the Flaming Lips released on October 13, 2009, on Warner Bros. Records, Warner Bros. The band's first double album, it was released to generally positi ...

seed
has two embryonic leaves or
cotyledon A cotyledon (; ; ; , gen. (), ) is a significant part of the embryo within the seed of a plant, and is defined as "the embryonic leaf in seed-bearing plants, one or more of which are the first to appear from a germination, germinating see ...
s. There are around 200,000 
species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individu ...

species
within this group. The other group of flowering plants were called
monocotyledon Monocotyledons (), commonly referred to as monocots, (Lilianae ''sensu'' Chase & Reveal) are grass and grass-like flowering plants (angiosperms), the seeds of which typically contain only one Embryo#Plant embryos, embryonic leaf, or cotyledon. Th ...
s or monocots, typically having one cotyledon. Historically, these two groups formed the two divisions of the flowering plants. Largely from the 1990s onwards,
molecular phylogenetic Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominately in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...
research confirmed what had already been suspected, namely that dicotyledons are not a group made up of all the descendants of a common ancestor (i.e. they are not a
monophyletic In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic grou ...
group). Rather, a number of lineages, such as the
magnoliids Magnoliids (or Magnoliidae or Magnolianae) are a group of flowering plant Flowering plants include multiple members of the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek#REDIRECT Greek Gre ...
and groups now collectively known as the
basal angiosperms The basal angiosperms are the flowering plant Flowering plants include multiple members of the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek#REDIRECT Greek Greek may refer to: Greece An ...
, diverged earlier than the monocots did; in other words monocots evolved from within the dicots as traditionally defined. The traditional dicots are thus a
paraphyletic In taxonomy Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term may also refer to a specific classification scheme. Originally used only ...
group. The
eudicots The eudicots, Eudicotidae or eudicotyledons are a clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyly, monophyletic – that is, composed of a common ancestor and all its lineage ...
are the largest clade within the dicotyledons. They are distinguished from all other flowering plants by the structure of their
pollen Pollen is a powdery substance consisting of pollen grains which are microsporophytes of seed plants The spermatophytes (; ), also known as phanerogams (taxon Phanerogamae) or phaenogams (taxon Phaenogamae), comprise those plant Plant ...

pollen
. Other dicotyledons and monocotyledons have
monosulcate Pollen Tube Diagram Pollen is a powdery substance consisting of pollen grains which are male microgametophytes of seed plants, which produce male gamete A gamete ( /ˈɡæmiːt/; from Ancient Greek Ancient Greek includes the forms o ...
pollen, or forms derived from it, whereas eudicots have tricolpate pollen, or derived forms, the pollen having three or more pores set in furrows called colpi.


Comparison with monocotyledons

Aside from
cotyledon A cotyledon (; ; ; , gen. (), ) is a significant part of the embryo within the seed of a plant, and is defined as "the embryonic leaf in seed-bearing plants, one or more of which are the first to appear from a germination, germinating see ...
number, other broad differences have been noted between
monocots Monocotyledons (), commonly referred to as monocots, (Lilianae Lilianae (also known as Liliiflorae) is a botanical name for a superorder (that is, a rank (botany), rank higher than that of order (biology), order) of flowering plants. Such a supe ...

monocots
and dicots, although these have proven to be differences primarily between monocots and
eudicots The eudicots, Eudicotidae or eudicotyledons are a clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyly, monophyletic – that is, composed of a common ancestor and all its lineage ...
. Many early-diverging dicot groups have monocot characteristics such as scattered
vascular bundles A vascular bundle is a part of the transport system in vascular plant Vascular plants (from Latin ''vasculum'': duct), also known as Tracheophyta (the tracheophytes , from Greek τραχεῖα ἀρτηρία ''trācheia artēria'' 'windp ...
, trimerous flowers, and non-tricolpate
pollen Pollen is a powdery substance consisting of pollen grains which are microsporophytes of seed plants The spermatophytes (; ), also known as phanerogams (taxon Phanerogamae) or phaenogams (taxon Phaenogamae), comprise those plant Plant ...

pollen
. In addition, some monocots have dicot characteristics such as reticulated leaf veins.


Classification


Phylogeny

The consensus
phylogenetic tree A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree (graph theory), tree showing the evolutionary relationships among va ...

phylogenetic tree
used in the
APG IV system APG is an abbreviation with several different meanings: * Aberdeen Proving Ground Aberdeen Proving Ground (APG) (sometimes erroneously called Aberdeen Proving ''Grounds'') is a U.S. Army The United States Army (USA) is the land Land is ...
shows that the group traditionally treated as the dicots is
paraphyletic In taxonomy Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term may also refer to a specific classification scheme. Originally used only ...
to the monocots:


Historical

Traditionally the dicots have been called the Dicotyledones (or Dicotyledoneae), at any rank. If treated as a class, as in the
Cronquist systemCronquist can refer to: * Arthur J. Cronquist, a North American botanist (1919–1992). * The Cronquist system, a system attributed to Arthur J. Cronquist. Many authors use their own variation of this system, which they also refer to as the ...
, they could be called the Magnoliopsida after the
type genus In biological taxonomy the type genus is the genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology, taxonomy () is the scientific study of naming, defining (Circumsc ...
''
Magnolia ''Magnolia'' is a large genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology, taxonomy () is the scientific study of naming, defining (Circumscription (taxonomy), ...

Magnolia
''. In some schemes, the eudicots were treated as a separate
class Class or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or objects * Class (philosophy), an analytical concept used differently f ...
, the
Rosopsida Rosopsida (August Batsch, Batsch, 1788) is a botanical name for a group of flowering plants recognized at the rank (botany), rank of class. The name is derived from that of the included family Rosaceae. As used in the Reveal system it is a subset of ...
(type genus ''Rosa''), or as several separate classes. The remaining dicots ( palaeodicots or basal angiosperms) may be kept in a single
paraphyletic In taxonomy Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term may also refer to a specific classification scheme. Originally used only ...

paraphyletic
class, called
Magnoliopsida Magnoliopsida is a valid botanical name for a class of flowering plant The flowering plants, also known as Angiospermae (), or Magnoliophyta (), are the most diverse group of Embryophyte, land plants, with 64 Order(biology), orders, 416 Family ...
, or further divided. Some botanists prefer to retain the dicotyledons as a valid class, arguing its practicality and that it makes evolutionary sense.


APG vs. Cronquist

The following lists show the orders in the Angiosperm Phylogeny Group
APG IV system APG is an abbreviation with several different meanings: * Aberdeen Proving Ground Aberdeen Proving Ground (APG) (sometimes erroneously called Aberdeen Proving ''Grounds'') is a U.S. Army The United States Army (USA) is the land Land is ...
traditionally called dicots, together with the older
Cronquist systemCronquist can refer to: * Arthur J. Cronquist, a North American botanist (1919–1992). * The Cronquist system, a system attributed to Arthur J. Cronquist. Many authors use their own variation of this system, which they also refer to as the ...
.


Dahlgren and Thorne systems

In the Dahlgren and the Thorne systems, the subclass name Magnoliidae was used for the dicotyledons. This is also the case in some of the systems derived from the Cronquist system. For each system, only the superorders are listed. The sequence of each system has been altered to pair corresponding taxa, although circumscription of superorders with the same name is not always the same. The Thorne system (1992) as depicted by Reveal is:


See also

* Calyciflorae


References


External links


World list of dicot species (aka Magnoliopsida) from the Catalogue of Life
253,406 species.
Tree browser for dicot orders, families and genera with species counts and estimates via the Catalogue of Life
{{Authority control Historically recognized angiosperm taxa