Bahiaxenos relictus is the sole member

Monotypic

In biology, a monotypic taxon is a taxonomic group with only one biological type. The term's usage differs slightly between botany and zoology. The term monotypic has a separate use in conservation biology, monotypic habitat, regarding species habitat conversion eliminating biodiversity and...

 of the family Bahiaxenidae, a type of winged insect. It was only discovered and described in 2009 from relictual sand dunes associated with the Rio São Francisco in Bahia, Brazil. It is considered to be the most basal living member of the order Strepsiptera

Strepsiptera

The Strepsiptera are an order of insects with ten families making up about 600 species...

, and therefore is the sister taxon to the remaining extant species. It is known from only a single male specimen, and its biology is unknown.