Subdomain

Based on Evolutionary systematics or Evolutionary taxonomy, which is itself based on the Linanean system of ranking but with the addition of phylogeny, the rank of "subdomain" was coined by Ernst Mayr as an alternative to Carl Woese's three domains. It refers to the rank intermediate between Domain and Kingdom. Mayr 1990 divided the Eukaryote domain into two subdomains, a paraphyletic Protista for mostly single celled organsisms, and a possibly monophyletic Metabionta for mostly multicelled organisms. This seems to be the only context in which the term "Subdomain" is used in biology.