The family Speleoithonidae, recently described by Rocha & Iliffe (1991), includes small copepods, close to Oithonidae, at present known only for anchialine waters of the Bahamas and Bermuda Islands.

Speleoithonidae is considered to be a sister group of Oithonidae. It is believed that Speleoithona evolved in its "restricted habitat, developing very characteristic features, while retaining some primitive traits" (Rocha and Iliffe, 1991) (left: S. bermudensis).