Monotypic

Monotypic is an adjective used in biology and taxonomy to describe a taxon that contains only one subordinate taxon at the next lower rank. The most common usage is for a genus with a single species, but the term can also apply to higher levels when, for example, a family consists of only one genus. In practice, monotypic genera are those that have not diversified into multiple species, or in which other species have gone extinct or have yet to be discovered.

For example, the giant panda belongs to the genus Ailuropoda, which contains only one living species, Ailuropoda melanoleuca, making the genus monotypic. Ginkgo is another well-known example: Ginkgo comprises a single living species, Ginkgo biloba, and is placed in the monotypic family Ginkgoaceae.

Monotypicity may reflect an ancient lineage with little recent diversification, extremely specialized ecology, or past extinctions that left a lone surviving lineage. Taxonomic revisions, new data, or discoveries can change a monotypic taxon into a polytypic one, or vice versa. The concept is widely used in systematics, conservation biology, and biodiversity studies to summarize patterns of diversity and evolutionary history.