nongenus

Nongenus is a historical or encyclopedic term used in some taxonomic writings to denote taxa that are not assigned to any particular genus. In this usage, nongenus functions as a provisional label indicating that the taxon’s genus-level placement has not been determined, is uncertain, or is awaiting further study. It is not recognized as a formal rank within modern nomenclature.

In practice, nongenus appears mainly in older literature or catalog entries as a temporary designation attached to a species entry until a genus can be established or confirmed. It is distinct from incertae sedis, which is the current standard term for uncertain higher-level placement, and it is not commonly used in current codes of nomenclature. When encountered, the use of nongenus reflects historical uncertainty rather than a formally defined rank.

Historical notes suggest that nongenus fell out of favor as taxonomic practices evolved toward explicit genus-level assignment or clearly labeled categories such as incertae sedis or unplaced taxa. Today, the term is largely obsolete in formal descriptions, though it may appear in retrospective discussions, catalogs, or databases that preserve older classifications for reference.

Etymology of the term traces to the Latin non-genus, literally “not a genus.” The concept underscores the practical need in taxonomy to acknowledge uncertain placement, even as modern practice relies on more standardized terminology.

See also: genus, taxonomy, incertae sedis, placeholder taxon.