Wastebasket taxon (also called awastebin taxon,^[1]dustbin taxon^[2] orcatch-all taxon^[3]) is a term used by sometaxonomists to refer to ataxon that has the 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 theirlack of one or more distinctcharacter states or by theirnot belonging to one or more other taxa. Wastebasket taxa are by definition eitherparaphyletic orpolyphyletic, and are therefore not considered valid taxa under strictcladistic rules of taxonomy. The name of a wastebasket taxon may in some cases be retained as the designation of anevolutionary grade, however.

There are many examples of paraphyletic groups, but true "wastebasket" taxa are those that are known not to, and perhaps not intended to, represent natural groups, but are nevertheless used as convenient groups of organisms. Theacritarchs are perhaps the most famous example. Wastebasket taxa are often old (and perhaps not described with the systematic rigour and precision that is possible in the light of accumulated knowledge of diversity) and populous.^[4]

• TheFlacourtiaceae, a now-defunct family offlowering plants^[5] – theAngiosperm Phylogeny Group has placed itstribes and genera in various other families, especially theAchariaceae andSalicaceae.
• The obsolete kingdomProtista is composed of alleukaryotes that are notanimals,plants orfungi, leaving to the protists all single-celled eukaryotes.^[6]
• TheTricholomataceae is a fungal group, at one point composed of the white-, yellow-, or pink-spored genera in theAgaricales not already classified as belonging to theAmanitaceae,Lepiotaceae,Hygrophoraceae,Pluteaceae, orEntolomataceae.^[7]
• Carnosauria andThecodontia 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 withinPerissodactyla orCetartiodactyla were traditionally shoved. Many of these groups, likeMeridiungulata orProtungulatum, may not representlaurasitherian mammals, while others likephenacodontids have been clearly established as early odd-toed ungulates.^[8][9]
• The orderInsectivora has traditionally been used as a dumping ground for placental insectivorous mammals (and similar forms such ascolugos), usually aligned withcarnivorans,ungulates andbats. While the core components (moles,shrews,hedgehogs and their close relations) do in fact form a consistent clade,Eulipotyphla, that is part ofLaurasiatheria with the aforementioned clades, other mammals historically placed in the order have been found to belong to other branches of the placental tree:tree shrews and colugos areeuarchontans related toPrimates and sometimes grouped inSundatheria, whiletenrecs,golden moles andelephant shrews are allafrotheres, probably forming the cladeAfroinsectiphilia. Both of these clades have at times been accused of being wastebasket taxa themselves, grouping superficially similar animals in Euarchonta and Afrotheria, respectively, but they have been more strongly supported by genetic studies.^{[citation needed]}
• Vermes is an obsolete taxon of worm-like animals. It was a catch-all term used byCarl Linnaeus andJean-Baptiste Lamarck for non-arthropod invertebrate animals.
• The genusMamenchisaurus is sometimes considered a wastebasket taxon for large, long-neckeddinosaurs.^[10]

Fossil groups that are poorly known due to fragmentary remains are sometimes grouped together on gross morphology orstratigraphy, only later to be found to be wastebasket taxa, such as the crocodile-likeTriassic groupRauisuchia.^[11]

One of the roles of taxonomists is to identify wastebasket taxa and reclassify the content into more natural units. Sometimes, during taxonomic revisions, a wastebasket taxon can be salvaged after doing thorough research on its members, and then imposing tighter restrictions on what continues to be included. Such techniques "saved" Carnosauria andMegalosaurus. Other times, thetaxonomic name contains too much unrelated "baggage" to be successfully salvaged. As such, it is usually dumped in favour of a new, more restrictive name (for example,Rhynchocephalia), or abandoned altogether (for example,Simia).^{[citation needed]}

A related concept is that ofform taxon, "wastebasket" groupings that are united by gross morphology. This is often result of a common mode of life, often one that isgeneralist, leading to generally similar body shapes byconvergent evolution.^{[citation needed]}

The term wastebasket taxon is sometimes employed in a derogatory fashion to refer to anevolutionary grade taxon.^{[citation needed]}

• Lazarus taxon
• Elvis taxon
• Incertae sedis
• Glossary of scientific naming
• Not Otherwise Specified

• Obsolete taxa
• Taxonomy (biology)
• Paraphyletic groups
• Polyphyletic groups

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