Cylindroleberidoidea

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.

Species of the Cylindroleberididae are found in marine areas, from shallow waters to depths of more than 4,500 metres (14,800 ft). Most species are approximately 2 millimetres (0.08 in) long. In 2006, there were 219 described species.