polyphyletism (adj. polyphyletic) The occurrence in taxa of members that have descended via different ancestral lineages. True polyphyletism has traditionally been distinguished from errors of classification, especially at the higher taxonomic levels, where organisms, as a result of convergent or parallel evolution, have been placed wrongly in the same natural group; but modern phyletic taxonomists would hold that any taxon found to be polyphyletic is unnatural, and so an ‘error’, and must be disbanded.

polyphyletism The occurrence in taxa of members that have descended via different ancestral lineages. True polyphyletism has traditionally been distinguished from errors of classification, especially at the higher taxonomic levels, where organisms, as a result of convergent or parallel evolution, have been placed wrongly in the same natural group; but some modern phyletic taxonomists would hold that any taxon found to be polyphyletic is unnatural, and so an ‘error’, which must be disbanded.