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Wastebasket taxon (also called a wastebin taxon, dustbin taxon or catch-all taxon) is a term used in some taxonomic circles to refer to a taxon that has the sole purpose of classifying organisms that do not fit anywhere else. They are typically defined by either their designated members' often superficial similarity to each other, or their ''lack'' of one or more distinct character states or by their ''not'' belonging to one or more other taxa. Wastebasket taxa are by definition either paraphyletic or polyphyletic, and are therefore not considered to be valid taxa under strict cladistic rules of taxonomy. The name of a wastebasket taxon may in some cases be retained as the designation of an evolutionary grade, however. ==Examples== * The familiar category of invertebrates is an "everything-else" category, comprising all animals without backbones. * The kingdom Protista is composed of all eukaryotes that are not animals, plants or fungi, leaving to the protistans all single-celled eukaryotes. * The Tricholomataceae is a fungal group, composed of the white-, yellow-, or pink-spored genera in the Agaricales not already classified as belonging to the Amanitaceae, Lepiotaceae, Hygrophoraceae, Pluteaceae, or Entolomataceae.〔Young AM. (2002) (Brief notes on the status of Family Hygrophoraceae Lotsy. ) Australasian Mycologist 21(3):114–116.〕 * Carnosauria and Thecodontia are fossil groups, banded together back when the limited fossil record did not allow for a more detailed scheme. * Condylarthra is an artificial clade into which ungulate mammals not clearly within Perissodactyla or Cetartiodactyla were traditionally shoved. Many of these groups, like Meridiungulata or ''Protungulatum'', may not represent laurasithere mammals, while others like phenacodontids have been clearly established as early odd-toed ungulates. * The order Insectivora has traditionally been used as a dumping ground for placental insectivorous mammals (and similar forms, such as colugos), usually aligned with carnivorans, ungulates and bats. While the core components (moles, shrews, hedgehogs and close relations) do in fact form a consistent clade, Eulipotyphla, that is part of Laurasiatheria with the aforementioned clades, other mammals historically placed in the order have been found to belong to othe branches of the placental tree: tree shrews and colugos compose the euarchontan Sundatheria, while tenrecs, golden moles and elephant shrews are all afrotheres, probably forming the clade Afroinsectiphilia. Both of these clades have at times been accused of being wastebasket taxons themselves, grouping superficially similar animals in Euarchonta and Afrotheria respectively, but they have been more strongly supported by genetic studies. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「wastebasket taxon」の詳細全文を読む スポンサード リンク
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