After Martin & Davis, 2001

<==o Poecilostomatoida Thorell, 1859
   |-- Anchimolgidae Humes & Boxshall, 1996
   |-- Anomoclausiidae Gotto, 1964
   |-- Antheacheridae Sats, 1870
   |-- Anthessiidae Humes, 1986
   |-- Bomolochidae Sumpf, 1871
   |-- Catiniidae Bocquet & Stock, 1957
   |-- Chitonophilidae Avdeev & Sirenko, 1991
   |-- Chondracanthidae Milne Edwards, 1840
   |-- Clausidiidae Embleton, 1901
   |-- Clausiidae Giesbrecht, 1895
   |-- Corallovexiidae Stock, 1975
   |-- Corycaeidae Dana, 1852
   |-- Echiurophilidae Delamare-Deboutteville & Nunes-Ruivo, 1995
   |-- Entobiidae Ho, 1984
   |-- Erebonasteridae Humes, 1987
   |-- Ergasilidae von Nordmann, 1832 [Amazonicopeidae Thatcher, 1986; Vaigamidae Thatcher & Robertson, 1984]
   |-- Eunicicolidae Sars, 1918
   |-- Gastrodelphyidae List, 1889
   |-- Herpyllobiidae Hansen, 1892
   |-- Intramolgidae Marchenkov & Boxshall, 1995
   |-- Kelleriidae Humes & Boxshall, 1996
   |-- Lamippidae Joliet, 1882
   |-- Lernaeosoleidae Yamaguti, 1963
   |-- Lichomolgidae Kossmann, 1877
   |-- Lubbockiidae Huys & Böttger-Schnack, 1997
   |-- Macrochironidae Humes & Boxshall, 1996
   |-- Mesoglicolidae de Zulueta, 1911
   |-- Micrallectidae Huys, 2001
   |-- Myicolidae Yamaguti, 1936
   |-- Mytilicolidae Bocquet & Stock, 1957
   |--o Nereicolidae Claus, 1875 [Anomopsyllidae]
   |  `-- Anomopsyllus
   |-- Nucellicolidae Lamb, Boxshall, Mill & Grahame, 1996 [jr. syn. of Chitonophilidae?]
   |-- Octopicolidae Humes & Boxshall, 1996
   |-- Oncaeidae Giesbrecht, 1893
   |-- Paralubbockiidae Boxshall & Huys, 1989
   |-- Pharodidae Illg, 1948
   |-- Philichthyidae Vogt, 1877
   |-- Philoblennidae Izawa, 1976
   |-- Phyllodicolidae Delamare-Deboutteville & Laubier, 1961
   |-- Polyankylidae Ho & Kim, 1997
   |-- Pseudanthessiidae Humes & Stock, 1972
   |-- Rhynchomolgidae Humes & Stock, 1972
   |-- Sabelliphilidae Gurney, 1927
   |-- Saccopsidae Lützen, 1964
   |-- Sapphirinidae Thorell, 1860
   |-- Serpulidicolidae Stock, 1979
   |-- Shiinoidae Cressey, 1975
   |-- Spiophanicolidae Ho, 1984
   |-- Splanchnotrophidae Norman & Scott, 1906
   |-- Synapticolidae Humes & Boxshall, 1996
   |-- Synaptiphilidae Bocquet, 1953
   |-- Taeniacanthidae Wilson, 1911
   |-- Tegobomolochidae Avdeev, 1978
   |-- Telsidae Ho, 1967
   |-- Thamnomolgidae Humes & Boxshall, 1996
   |-- Tuccidae Vervoort, 1962
   |-- Urocopiidae Humes & Stock, 1972
   |-- Vahiniidae Humes, 1967
   |-- Ventriculinidae Leigh-Sharpe, 1934
   |-- Xarifiidae Humes, 1960
   `-- Xenocoelomatidae Bresciani & Lützen, 1966

Reference(s):