Editing Clade (section)

== History of nomenclature and taxonomy ==
[[File:Haeckel arbol bn.png|thumb|right|upright|Early phylogenetic tree by [[Ernst Haeckel|Haeckel]], 1866. Groups once thought to be more advanced, such as birds ("Aves"), are placed at the top.]]

The idea of a clade did not exist in pre-[[Charles Darwin|Darwinian]] [[Linnaean taxonomy]], which was based by necessity only on internal or external [[morphology (biology)|morphological]] similarities between organisms. Many of the better known animal groups in Linnaeus's original ''[[Systema Naturae]]'' (mostly [[vertebrate]] groups) do represent clades. The phenomenon of [[convergent evolution]] is responsible for many cases of misleading similarities in the [[Morphology (biology)|morphology]] of groups that evolved from different lineages.

With the increasing realization in the first half of the 19th century that species had changed and split through the ages, classification increasingly came to be seen as branches on the evolutionary [[tree of life (biology)|tree of life]]. The publication of Darwin's [[Evolution|theory of evolution]] in 1859 gave this view increasing weight. In 1876 [[Thomas Henry Huxley]], an early advocate of evolutionary theory, proposed a revised taxonomy based on a concept strongly resembling clades,<ref name="Huxley-1876">Huxley, T.H. (1876): Lectures on Evolution. ''New York Tribune''. Extra. no 36. In Collected Essays IV: pp 46–138 [http://aleph0.clarku.edu/huxley/CE4/LecEvol.html original text w/ figures]</ref> although the term ''clade'' itself would not be coined until 1957 by his grandson, [[Julian Huxley]].

German biologist [[Emil Hans Willi Hennig]] (1913–1976) is considered to be the founder of [[cladistics]].<ref>{{Cite journal|author=Brower, Andrew V. Z.|year=2013|title=Willi Hennig at 100|journal=Cladistics|volume=30|issue=2|pages=224–225|doi=10.1111/cla.12057|doi-access=free}}</ref>
He proposed a classification system that represented repeated branchings of the family tree, as opposed to the previous systems, which put organisms on a "ladder", with supposedly more "advanced" organisms at the top.<ref name="Palmer-2009" /><ref name="Evolution 101">"Evolution 101". [http://evolution.berkeley.edu/evolibrary/article/evo_10 page 10]. Understanding Evolution website. University of California, Berkeley. Retrieved 26 February 2016.</ref>

Taxonomists have increasingly worked to make the taxonomic system reflect evolution.<ref name="Evolution 101"/> When it comes to [[Nomenclature#Biology|naming]], this principle is not always compatible with the traditional [[Linnaean taxonomy|rank-based nomenclature]] (in which only taxa associated with a [[Taxonomic rank|rank]] can be named) because not enough ranks exist to name a long series of nested clades. For these and other reasons, [[phylogenetic nomenclature]] has been developed; it is still controversial.

As an example, see the full current{{when|date=May 2024}} classification of ''[[Anas platyrhynchos]]'' (the mallard duck) with 40 clades from ''[[Eukaryota]]'' down by following [[species:Anas  platyrhynchos|this Wikispecies link]] and clicking on "Expand".

The name of a clade is conventionally a plural, where the singular refers to each member individually. A unique exception is the reptile clade [[Dracohors]], which was made by [[haplology]] from Latin "draco" and "cohors", i.e. "the [[dragon]] [[Cohort (taxonomy)|cohort]]"; its form with a suffix added should be e.g. "dracohortian".