Monotypic taxon

In biology, for ranks such as genus or family, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate extant taxon. In the case of genera, the term "unispecific" or "monospecific" is sometimes preferred. In botanical nomenclature, a monotypic genus is a genus in the special case in which a genus and a single extant species are simultaneously described. The term monotypic may be used somewhat differently for species, where a monotypic species may be the only extant species in its genus.