The (Poecilostomatoida) - order

(Abrsiidae)
- family

(Anchimolgidae)
- family

(Anomoclausiidae)
- family

(Antheacheridae)
- family

(Anthessiidae)
- family

(Bomolochidae)
- family

(Bradophilidae)
- family

(Catiniidae)
- family

(Chondracanthidae)
- family

(Clausidiidae)
- family

(Clausiidae)
- family

(Corycaeidae)
- family

(Echiurophilidae)
- family

(Entobiidae)
- family

(Erebonasteridae)
- family

(Ergasilidae)
- family

(Eunicicolidae)
- family

(Euniciolidae)
- family

(Gastrodelphyidae)
- family

(Herpyllobiidae)
- family

(Intramolgidae)
- family

(Kelleriidae)
- family

(Lamippidae)
- family

(Lernaeosoleidae)
- family

(Lichomolgidae)
- family

(Lubbockiidae)
- family

(Macrochironidae)
- family

(Mesoglicolidae)
- family

(Oncaeidae)
- family

(Philichthyidae)
- family

(Philoblennidae)
- family

(Phyllodicolidae)
- family

(Pionodesmotidae)
- family

(Polyankyliidae)
- family

(Pseudanthessiidae)
- family

(Rhynchomolgidae)
- family

(Sabelliphilidae)
- family

(Saccopsidae)
- family

(Sapphirinidae)
- family

(Serpulidicolidae)
- family

(Shiinoidae)
- family

(Spiophanicolidae)
- family

(Splanchnotrophidae)
- family

(Synapticolidae)
- family

(Synaptiphilidae)
- family

(Taeniacanthidae)
- family

(Tegobomolochidae)
- family

(Telsidae)
- family

(Thamnomolgidae)
- family

(Tuccidae)
- family

(Umazurcolidae)
- family

(Urocopiidae)
- family

(Vahiniidae)
- family

(Ventriculinidae)
- family

(Xarifiidae)
- family

(Xenocoelomatidae)
- family