Cylindroleberididae is a family of ostracods that shows remarkable morphological diversity.

The defining feature is the possession of gills: 7–8 leaf-like pairs at the posterior of the body.

Other features common to all species in the family include a "baleen-comb" on both the maxilla and the fifth limb, a sword-shaped coxal endite on the mandible, and the triaenid bristles on the basal endites of the mandible.

[2] Species of the Cylindroleberididae are found in marine areas, from shallow waters to depths of more than 4,500 metres (14,800 ft).

[5] The fossil appears to have gills and is thought to date from 425 million years ago.