• [non-Uristidae] albinus (K.H. Barnard, 1932)
• [non-Uristidae] georgianus (Schellenberg, 1931)
• Aaptos robustus Plotkin & Janussen, 2008
• Abarenicola affinis (Ashworth, 1903)
• Abarenicola affinis affinis (Ashworth, 1902) represented as Abarenicola affinis (Ashworth, 1903)
• Abarenicola assimilis (Ehlers, 1897)
• Abarenicola assimilis assimilis (Ehlers, 1897) accepted as Abarenicola assimilis (Ehlers, 1897)
• Abatus (Pseudabatus) nimrodi (Koehler, 1911)
• Abatus agassizii Mortensen, 1910
• Abatus beatriceae (Larrain, 1986)
• Abatus bidens Mortensen, 1910 accepted as Abatus cavernosus bidens Mortensen, 1910
• Abatus cavernosus (Philippi, 1845)
• Abatus cavernosus bidens Mortensen, 1910
• Abatus cordatus (Verrill, 1876)
• Abatus curvidens Mortensen, 1936
• Abatus elongatus (Koehler, 1908) accepted as Abatus koehleri (Thiéry, 1909)
• Abatus ingens Koehler, 1926
• Abatus koehleri (Thiéry, 1909)
• Abatus nimrodi (Koehler, 1911) accepted as Pseudabatus nimrodi Koehler, 1911 accepted as Abatus (Pseudabatus) nimrodi (Koehler, 1911)
• Abatus philippi Lovén, 1871 accepted as Abatus philippii Lovén, 1871
• Abatus philippii Lovén, 1871
• Abatus shackletoni Koehler, 1911
• Abietinaria abietina (Linnaeus, 1758)
• Abietinella operculata (Jäderholm, 1903)
• Abraliopsis (Micrabralia) gilchristi (G. C. Robson, 1924) represented as Abraliopsis gilchristi (G. C. Robson, 1924)
• Abraliopsis gilchristi (G. C. Robson, 1924)
• Abyssaster diadematus (Sladen, 1883)
• Abyssaster planus (Sladen, 1883)
• Abyssocladia antarctica Buskowiak & Janussen, 2021
• Abyssocladia leverhulmei Goodwin, Berman, Downey & Hendry, 2017
• Abyssocladia symmetrica (Ridley & Dendy, 1886)
• Abyssoclymene annularis Hartman, 1967
• Abyssocucumis abyssorum (Théel, 1886)
• Abyssocucumis liouvillei (Vaney, 1914) Gutt, 1988 accepted as Staurocucumis liouvillei (Vaney, 1914) Ekman, 1927
• Abyssocucumis tourqueti (Vaney, 1906) accepted as Staurocucumis turqueti (Vaney, 1906)
• Abyssocypris atlantica (Maddocks, 1977)
• Abyssocythere antarctica (Neale, 1967) accepted as Austrotrachyleberis antarctica (Neale, 1967)
• Abyssocythere bensoni Brandão, Stuhlmann, Vital & Brandt, 2016
• Abyssogyra vemae A. H. Clarke, 1961 accepted as Moelleriopsis vemae (A. H. Clarke, 1961)
• Abyssoninoe abyssorum (McIntosh, 1885)
• Abyssophilos ktis Jellinek & Swanson, 2003
• Abyssorchomene charcoti (Chevreux, 1912)
• Abyssorchomene nodimanus (Walker, 1903)
• Abyssorchomene plebs (Hurley, 1965) represented as Pseudorchomene plebs (Hurley, 1965)
• Abyssorchomene rossi (Walker, 1903) represented as Pseudorchomene rossi (Walker, 1903)
• Abyssorchomene scotianensis (Andres, 1983)
• Abyssorchomene shannonae Hendrycks & De Broyer, 2022
• Abyssorhynchia craneana (Dall, 1895)
• Abyssothyris wyvillei (Davidson, 1878)
• Abyssotrophon drygalskii (Thiele, 1912) accepted as Trophon drygalskii Thiele, 1912
• Acanthamunnopsis hystrix Schultz, 1978
• Acantharcturus acanthurus (Monod, 1925) accepted as Mixarcturus acanthurus (Monod, 1925)
• Acantharcturus acutipleon Schultz, 1981
• Acanthascus (Rhabdocalyptus) australis (Topsent, 1901)
• Acanthaspidia acanthonotus (Beddard, 1886) accepted as Iolanthe acanthonotus Beddard, 1886
• Acanthaspidia drygalskii Vanhöffen, 1914 accepted as Iolanthe drygalskii (Vanhöffen, 1914)
• Acanthaspidia iolanthoidea Vasina & Kussakin, 1982 accepted as Iolanthe iolanthoidea (Vasina & Kussakin, 1982)
• Acanthaspidia longiramosa Vasina & Kussakin, 1982 accepted as Iolanthe longiramosa (Vasina & Kussakin, 1982)
• Acanthaspidia mucronata (Menzies & Schultz, 1968) accepted as Iolanthe mucronata (Menzies & Schultz, 1968)
• Acanthaspidia pleuronotus (Menzies & Schultz, 1968) accepted as Iolanthe pleuronotus Menzies & Schultz, 1968
• Acanthaspidia porrecta Menzies & Schultz, 1968 accepted as Iolanthe porrecta (Menzies & Schultz, 1968)
• Acanthaspidia rostrata (Menzies & Schultz, 1968) accepted as Iolanthe rostrata (Menzies & Schultz, 1968)
• Acanthaspidia sulcatacornia Menzies & Schultz, 1968 accepted as Iolanthe sulcatacornia (Menzies & Schultz, 1968)
• Acanthephyra pelagica (Risso, 1816)
• Acanthephyra quadrispinosa Kemp, 1939
• Acanthina monodon (Pallas, 1774)
• Acanthocope annulatus Menzies, 1962
• Acanthocope eleganta Malyutina & Brandt, 2004
• Acanthocope galatheae Wolff, 1962
• Acanthocope spinicauda Beddard, 1885
• Acanthodraco dewitti Skóra, 1995
• Acanthogorgia incrustata Kükenthal, 1919
• Acanthogorgia laxa Wright & Studer, 1889
• Acanthomenia gaussiana Thiele, 1913
• Acanthomunna spinipes (Vanhöffen, 1914)
• Acanthonotozomella alata Schellenberg, 1926
• Acanthonotozomella barnardi Watling & Holman, 1980
• Acanthonotozomella rauscherti Coleman & Jäger, 2001
• Acanthonotozomella trispinosa (Bellan-Santini, 1972)
• Acanthonotozomoides oatesi (K.H. Barnard, 1930)
• Acanthonotozomoides sublitoralis Schellenberg, 1931
• Acanthonotozomopsis pushkini (Bushueva, 1978)
• Acanthopharynx merostomacha (Steiner, 1921) Schuurmans Stekhoven, 1943 (uncertain > taxon inquirendum)
• Acanthophragma polaris Hayward, 1993
• Acanthopolymastia acanthoxa (Koltun, 1964)
• Acanthopriapulus horridus (Théel, 1911)
• Acanthorhabdus fragilis Burton, 1929
• Acanthoserolis polaris (Richardson, 1911)
• Acanthoserolis schythei (Lütken, 1859)
• Acartia (Acartiura) ensifera Brady, 1899
• Accalathura gigantissima Kussakin, 1967
• Achelia assimilis (Haswell, 1885)
• Achelia brucei Calman, 1915 accepted as Achelia communis (Bouvier, 1906)
• Achelia communis (Bouvier, 1906)
• Achelia dohrni (Thompson, 1884)
• Achelia hoekii (Pfeffer, 1889)
• Achelia intermedia Calman, 1915 accepted as Achelia spicata (Hodgson, 1914)
• Achelia lagena Child, 1994
• Achelia megacephala Hodgson, 1914 (uncertain > nomen dubium)
• Achelia parvula (Loman, 1923)