Circumscription (taxonomy)

Agreement on circumscriptions is not governed by the Codes of Zoological or Botanical Nomenclature, and must be reached by scientific consensus.

A goal of biological taxonomy is to achieve a stable circumscription for every taxon.

Balancing these two goals is a work in progress, and the circumscriptions of many taxa that had been regarded as stable for decades are in upheaval in the light of rapid developments in molecular phylogenetics.

Once molecular phylogenetic data showed that chimpanzees were more closely related to humans than to gorillas or orangutans,[1] it became clear that Pongidae is a paraphyletic group, and the circumscription of Hominidae was changed to include all four extant genera of great apes.

[2] An example of a botanical group with unstable circumscription is Anacardiaceae, a family of flowering plants.