• Abarenicola affinis (Ashworth, 1903)
• Abarenicola affinis affinis (Ashworth, 1902) represented as Abarenicola affinis (Ashworth, 1903)
• Abarenicola affinis africana Wells, 1963
• Abarenicola affinis chilensis Wells, 1963
• Abarenicola affinis clarki Wells, 1963
• Abarenicola assimilis (Ehlers, 1897)
• Abarenicola assimilis assimilis (Ehlers, 1897) accepted as Abarenicola assimilis (Ehlers, 1897)
• Abarenicola assimilis brevior Wells, 1963 accepted as Abarenicola brevior Wells, 1963
• Abarenicola assimilis devia Wells, 1963 accepted as Abarenicola devia Wells, 1963
• Abarenicola assimilis haswelli Wells, 1963 accepted as Abarenicola haswelli Wells, 1963
• Abarenicola assimilis insularum Wells, 1963 accepted as Abarenicola insularum Wells, 1963
• Abarenicola brevior Wells, 1963
• Abarenicola claparedei (Levinsen, 1884) accepted as Abarenicola claparedi (Levinsen, 1884)
• Abarenicola claparedi (Levinsen, 1884)
• Abarenicola claparedi oceanica (Healy & Wells, 1959)
• Abarenicola claparedi vagabunda Healy & Wells, 1959
• Abarenicola claparedii [auctt.] accepted as Abarenicola claparedi (Levinsen, 1884)
• Abarenicola devia Wells, 1963
• Abarenicola gilchristi Wells, 1963
• Abarenicola haswelli Wells, 1963
• Abarenicola insularum Wells, 1963
• Abarenicola pacifica Healy & Wells, 1959
• Abarenicola pusilla (Quatrefages, 1866)
• Abarenicola vagabunda Healy & Wells, 1959 accepted as Abarenicola claparedi vagabunda Healy & Wells, 1959
• Abarenicola vagabunda oceanica Healy & Wells, 1959 accepted as Abarenicola claparedi oceanica (Healy & Wells, 1959)
• Abderos minotaurus Schüller & Jirkov, 2013
• Abyssocapitella commensalis Buzhinskaja & Smirnov, 2000
• Abyssoclymene annularis Hartman, 1967
• Aciculaspio anaximanderi Blake & Ramey-Balci, 2020
• Aclymene gesae Buzhinskaja, 1995
• Acmira catherinae (Laubier, 1967) represented as Aricidea (Acmira) catherinae Laubier, 1967
• Acmira cerrutii (Laubier, 1966) represented as Aricidea (Acmira) cerrutii Laubier, 1966
• Acmira finitima (Strelzov, 1973) represented as Aricidea (Acmira) finitima Strelzov, 1973
• Acmira lopezi (Berkeley & Berkeley, 1956) represented as Aricidea (Acmira) lopezi Berkeley & Berkeley, 1956
• Acmira philbinae (Brown, 1976) represented as Aricidea philbinae Brown, 1976 represented as Aricidea (Acmira) philbinae Brown, 1976
• Acmira simplex (Day, 1963) represented as Aricidea (Acmira) simplex Day, 1963
• Acmira taylori (Pettibone, 1965) represented as Aricidea (Acmira) taylori Pettibone, 1965
• Acrocirrus aciculigerus Kudenov, 1976
• Acrocirrus bansei Magalhães & Bailey-Brock, 2012
• Acrocirrus columbianus Banse, 1979
• Acrocirrus crassifilis Moore, 1923
• Acrocirrus frontifilis (Grube, 1860)
• Acrocirrus heterochaetus Annenkova, 1934
• Acrocirrus heterochaetus okotensis Imajima, 1963 accepted as Acrocirrus okotensis Imajima, 1963
• Acrocirrus incisa Kudenov, 1975
• Acrocirrus leidyi Verrill, 1882 accepted as Macrochaeta leidyi (Verrill, 1882)
• Acrocirrus muroranensis Okuda, 1934
• Acrocirrus occipitalis Banse, 1979
• Acrocirrus okotensis Imajima, 1963
• Acrocirrus trisectus Banse, 1969
• Acrocirrus uchidai Okuda, 1934
• Acrocirrus validus Marenzeller, 1879
• Acromegalomma acrophthalmos (Grube, 1878)
• Acromegalomma adriaticum (Giangrande, Caruso, Mikac & Licciano, 2015)
• Acromegalomma bioculatum (Ehlers, 1887)
• Acromegalomma carunculatum (Tovar-Hernández & Salazar-Vallejo, 2008)
• Acromegalomma cinctum (Fitzhugh, 2003)
• Acromegalomma circumspectum (Moore, 1923)
• Acromegalomma claparedei (Gravier, 1906)
• Acromegalomma coloratum (Chamberlin, 1919)
• Acromegalomma fauchaldi (Giangrande, Licciano & Gambi, 2007)
• Acromegalomma georgiense (Tovar-Hernández & Carrera-Parra, 2011)
• Acromegalomma gesae (Knight-Jones, 1997)
• Acromegalomma heterops (Perkins, 1984)
• Acromegalomma inflatum (Capa & Murray, 2009)
• Acromegalomma interruptum (Capa & Murray, 2009)
• Acromegalomma josei Rebello, Nogueira & Carrerette, 2025
• Acromegalomma jubatum (Capa & Murray, 2015)
• Acromegalomma kaikourense (Knight-Jones, 1997)
• Acromegalomma lanigerum (Grube, 1846)
• Acromegalomma lobiferum (Ehlers, 1887)
• Acromegalomma longoventrale (Giangrande, Caruso, Mikac & Licciano, 2015)
• Acromegalomma messapicum (Giangrande & Licciano, 2008)
• Acromegalomma miyukiae (Nishi, 1998)
• Acromegalomma modestum (Quatrefages, 1866)
• Acromegalomma multioculatum (Fitzhugh, 2002)
• Acromegalomma mushaense (Gravier, 1906)
• Acromegalomma nechamae (Knight-Jones, 1997)
• Acromegalomma omenae Rebello, Nogueira & Carrerette, 2025
• Acromegalomma pacifici (Grube, 1859)
• Acromegalomma pacificum (Johansson, 1927) accepted as Megalomma pacificum Johansson, 1927
• Acromegalomma perkinsi (Tovar-Hernández & Salazar-Vallejo, 2006)
• Acromegalomma phyllisae (Capa & Murray, 2009)
• Acromegalomma pigmentum (Reish, 1963)
• Acromegalomma pseudogesae (Mikac, Giangrande & Licciano, 2013)
• Acromegalomma punctum Rebello, Nogueira & Carrerette, 2025
• Acromegalomma quadrioculatum (Willey, 1905)
• Acromegalomma roulei (Gravier, 1908)
• Acromegalomma schwindtae Tovar-Hernández, de León-González & Bybee, 2017
• Acromegalomma scutolenis Rebello, Nogueira & Carrerette, 2025
• Acromegalomma splendidum (Moore, 1905)
• Acromegalomma sumbense Tovar-Hernández, ten Hove & de León-González in Tovar-Hernández et al, 2020
• Acromegalomma suspiciens (Ehlers, 1904)
• Acromegalomma trioculatum (Reish, 1968)
• Acromegalomma vesiculosum (Montagu, 1813)
• Actaedrilus polyonyx (Eliason, 1962)
• Actaedrilus yanbarensis Jimi, Fujimoto & Imura, 2020
• Adekunbiella durhami Adegoke, 1967 †
• Adercodon pleijeli Mackie, 1994
• Aedicira alisetosa Fauchald, 1972