Underenheterna

Underenheterna, or subkingdoms, is a taxonomic rank that has been used in some classification schemes to subdivide a kingdom into major, traditionally recognizable lineages. The rank sits below the kingdom and above the phylum (or division in older terminology). Its practical purpose is to group large, evolutionarily related groups within a kingdom.

Historically, subkingdoms were more common in 19th- and early 20th-century systematics, when researchers sought stable, morphologically distinct divisions to organize the diversity of life. The criteria for recognizing subkingdoms varied among authors and over time, and different classification schemes often placed the same organisms into different subkingdoms. This lack of standardization contributed to inconsistent usage across disciplines and countries.

In modern taxonomy, the use of subkingdoms has declined. Advances in phylogenetics and a shift toward rank-free, clade-based frameworks have reduced reliance on traditional, named ranks such as subkingdom. When subkingdoms are mentioned today, they are typically within the context of historical classifications or as part of a specific, non-universal scheme rather than as a universally accepted standard.

Because the term is not standardized, contemporary treatments generally describe subkingdom as a historical concept or as an annotation within a particular system rather than as a universally adopted level of the taxonomic hierarchy. The term may still appear in older textbooks, regional classifications, or discussions of the history of taxonomy.

See also: Taxonomy, Hierarchy of biological classification, Phylum, Clade, Kingdom.