Monotypic

A monotypic taxon is one that contains only a single subordinate taxon. A monotypic genus contains only one species; a monotypic family contains only one genus. Monotypic taxa often represent highly distinct lineages with no close living relatives — evolutionary "singletons." Examples in fish include: Latimeria (coelacanth — the only genus in its family and order, a lone survivor of a once-diverse lineage), Arapaima gigas (recently shown to be one of several valid Arapaima species), and Electrophorus electricus (electric eel — now comprising three species). Monotypic status flags high taxonomic distinctiveness and often conservation significance.