It contains only a single species, Crowsoniella relicta, and is the only member of the monotypic family Crowsoniellidae.

It is known only from three male specimens collected in 1973 in the Lepini mountains of central Italy by Roberto Pace.

In a degraded pasture, the beetles were found among the roots of a large hawthorn tree, in deep calcareous soil.

[2] At only 1.5 mm (1⁄16 in) in length, this species is comparatively small for this suborder.

They also feature several unusual morphological features such as missing alae, modified and reduced mouth parts, and smooth elytra (lacking window punctures characteristic of this suborder).