Form taxon

Form taxon (plural form taxa) is a biological term with two uses:

In general taxonomy, it is a kind of wastebasket taxon, either a taxon that is not a natural (monophyletic) group but united by shared plesiomorphies, or a presumably artificial group of organisms whose true relationships are not known, being obscured by ecomorphological similarity. Well-known form taxa of this kind include "ducks", "fish", "reptiles" and "worms".