Wastebasket taxon

Wastebasket taxon (also called a wastebin taxon, dustbin taxon or catch-all taxon) is a term used by some taxonomists to refer to a taxon 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 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 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. The term was coined in a 1985 essay by Steven Jay Gould. 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. The acritarchs 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; further characteristics are reviewed by. The Flacourtiaceae, a now-defunct family of flowering plants – the Angiosperm Phylogeny Group has placed its tribes and genera in various other families, especially the Achariaceae and Salicaceae. The obsolete kingdom Protista is composed of all eukaryotes that are not animals, plants or fungi, leaving to the protists all single-celled eukaryotes. The Tricholomataceae is a fungal group, at one point 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. Carnosauria and Thecodontia are fossil groups, banded together back when the limited fossil record did not allow for a more detailed scheme.