After Parker, 1982 [Slightly modified after Martin & Davis, 2001]

<==o Harpacticoida Sars, 1903 (ryömijähankajalkaiset)
   |?- Adenopleurellidae Huys, 1990
   |-- Aegisthidae Giesbrecht, 1893
   |?- Ambunguipedidae Huys, 1990
   |-- Ameiridae Monard, 1927
   |-- Ancorapolidae Sars, 1909 [Ancorbolidae Sars, 1909]
   |?- Argestidae Por, 1986
   |-- Balenophilidae Sars, 1910
   |?- Cancrincolidae Fiers, 1990
   |-- Canthocamptidae Sars, 1906
   |-- Canuellidae Lang, 1944
   |-- Cerviniidae Sars, 1903
   |-- Chappuisiidae Chappuis, 1940
   |-- Cletodidae Scott, 1905
   |?- Cletopsyllidae Huys & Williams, 1989
   |?- Clytemnestridae Scott, 1909 [from Martin & Davis, 2001, not recognized by Parker, 1982]
   |?- Cristacoxidae Huys, 1990
   |-- Cylindropsyllidae Sars, 1909
   |-- Darcythompsoniidae Lang, 1936
   |-- Diosaccidae Sars, 1906
   |-- Ectinosomitidae Sars, 1903
   |?- Euterpinidae Brian, 1921 [from Martin & Davis, 2001, not recognized by Parker, 1982]
   |-- Geleyellidae Rouch & Lescher-Moutoué, 1977 [placed in its own order by Martin & Davis, 2001]
   |?- Hamondiidae Huys, 1990
   |-- Harpacticidae Dana, 1846
   |?- Huntemanniidae Por, 1986
   |-- Laophontidae Scott, 1905
   |?- Laophontopsidae Huys & Willems, 1989
   |-- Latiremidae Bozic, 1969
   |?- Leptastacidae Lang, 1948 [from Martin & Davis, 2001, not recognized by Parker, 1982]
   |?- Leptopontiidae Lang, 1948 [from Martin & Davis, 2001, not recognized by Parker, 1982]
   |-- Longipediidae Sars, 1903
   |-- Louriniidae Monard, 1927
   |-- Metidae Sars, 1910
   |-- Miraciidae Dana, 1846
   |-- Neobradyidae Oloffson, 1917
   |?- Normanellidae Lang, 1944 [from Martin & Davis, 2001, not recognized by Parker, 1982]
   |?- Novocriniidae Huys & Iliffe, 1998
   |?- Orthopsyllidae Huys, 1990
   |-- Paramesochridae Lang, 1944
   |-- Parastenheliidae Lang, 1936
   |-- Parastenocarididae Chappuis, 1933
   |-- Peltidiidae Sars, 1914
   |-- Phyllognathopodidae Gurney, 1932
   |-- Porcellidiidae Boeck, 1865
   |-- Pseudopeltidiidae
   |?- Pseudotachidiidae Lang, 1936 [from Martin & Davis, 2001, not recognized by Parker, 1982]
   |?- Rhizothricidae Por, 1986
   |?- Rotundiclipeidae Huys, 1988
   |?- Styracothoracidae Huys, 1993
   |?- Superornatiremidae Huys, 1997
   |-- Tachidiidae Boeck, 1865
   |-- Tegastidae Sars, 1904
   |-- Tetragonicipitidae Lang, 1944
   |-- Thalestridae Sars, 1905
   |?- Thompsonulidae Lang, 1944 [from Martin & Davis, 2001, not recognized by Parker, 1982]
   `-- Tisbidae Stebbing, 1910

Reference(s):