It is a considerably recent clade, erected after molecular studies.

[1] The order Fecampiida, as currently defined, was erected based on molecular studies.

[2] They all are parasitic organisms and are united by a similar development of the basal bodies during spermiogenesis.

[3] Three families of Fecampiida were initially classified in different flatworm orders: Urastomatidae and Genostomatidae were considered prolecithophorans, while Fecampiidae was considered a rhabdocoel.

[4] Due to similarities in the protonephridial flame bulb, sperm and spermiogenesis, as well as the parasitic lifestyle, fecampiids were thought to be closely related to neodermatans,[3] but molecular studies revealed them to be more closely related to triclads and prolecithophorans.