• Aaptos aaptos (Schmidt, 1864): 2.0 - 200 mm
• Aaptos alphiensis Samaai & Gibbons, 2005: 2.0 - 200 mm
• Aaptos bergmanni de Laubenfels, 1950: 2.0 - 200 mm
• Aaptos ciliata (Wilson, 1925): 2.0 - 200 mm
• Aaptos conferta Kelly-Borges & Bergquist, 1994: 2.0 - 200 mm
• Aaptos duchassaingi (Topsent, 1889): 2.0 - 200 mm
• Aaptos durissima (Carter, 1882): 2.0 - 200 mm
• Aaptos globosa Kelly-Borges & Bergquist, 1994: 2.0 - 200 mm
• Aaptos glutinans Moraes, 2011: 2.0 - 200 mm
• Aaptos hajdui Carvalho, da Silva & Pinheiro, 2013: 2.0 - 200 mm
• Aaptos horrida (Carter, 1886): 2.0 - 200 mm
• Aaptos hoshinoi Van Soest, 2024: 2.0 - 200 mm
• Aaptos incrustans Payne, Samaai & Gibbons, 2025: 2.0 - 200 mm
• Aaptos kanuux Lehnert, Hocevar & Stone, 2008: 2.0 - 200 mm
• Aaptos laxosuberites (Sollas, 1902): 2.0 - 200 mm
• Aaptos lobata Calcinai, Bastari, Bertolino & Pansini, 2017: 2.0 - 200 mm
• Aaptos nuda (Kirkpatrick, 1903): 2.0 - 200 mm
• Aaptos papillata (Keller, 1880): 2.0 - 200 mm
• Aaptos pernucleata (Carter, 1870): 2.0 - 200 mm
• Aaptos potiguarensis Carvalho, da Silva & Pinheiro, 2013: 2.0 - 200 mm
• Aaptos robustus Plotkin & Janussen, 2008: 2.0 - 200 mm
• Aaptos rosacea Kelly-Borges & Bergquist, 1994: 2.0 - 200 mm
• Aaptos simplex (Lambe, 1893): 2.0 - 200 mm
• Aaptos suberitoides (Brøndsted, 1934): 2.0 - 200 mm
• Aaptos tenta Kelly-Borges & Bergquist, 1994: 2.0 - 200 mm
• Aaptos vannamei de Laubenfels, 1935: 2.0 - 200 mm
• Aatolana rapax Bruce, 1993: 2.0 - 200 mm
• Aatolana schioedtei (Miers, 1884): 2.0 - 200 mm
• Aatolana springthorpei Keable, 1998: 2.0 - 200 mm
• Abacion lactarium (Say, 1821): 2.0 - 200 mm
• Abacion magnum (Loomis, 1943): 2.0 - 200 mm
• Abacion tesselatum Rafinesque, 1820: 2.0 - 200 mm
• Abacion texensis (Loomis, 1937): 2.0 - 200 mm
• Abacion wilhelminae Shelley, McAllister & Hollis, 2003: 2.0 - 200 mm
• Abakana macrospina (Schoenmann, 1926) †: 2.0 - 200 mm
• Abakaniella globosa (B. I. Chernyshev, 1937) †: 2.0 - 200 mm
• Abakaniella jangotoika Betekhtina, 1986 †: 2.0 - 200 mm
• Abakaniella magna (B. I. Chernyshev, 1930) †: 2.0 - 200 mm
• Abakaniella obrutschewi (B. I. Chernyshev, 1937) †: 2.0 - 200 mm
• Abakaniella ornata (Tokareva, 1970) †: 2.0 - 200 mm
• Abakaniella rectangulata (Lapshina, 1958) †: 2.0 - 200 mm
• Abakaniella rugosa (B. I. Chernyshev, 1937) †: 2.0 - 200 mm
• Abakaniella tatarica (B. I. Chernyshev, 1930) †: 2.0 - 200 mm
• Abakaniella tungusensis (B. I. Chernyshev, 1937) †: 2.0 - 200 mm
• Abatetia robusta (Parent, 1933): 2.0 - 200 mm
• Abatodesmus chilensis Silvestri, 1903: 2.0 - 200 mm
• Abatodesmus simplicior Golovatch, 2014: 2.0 - 200 mm
• Abatodesmus velosoi Demange & Silva, 1971: 2.0 - 200 mm
• Abatus (Pseudabatus) nimrodi (Koehler, 1911): 2.0 - 200 mm
• Abatus agassizii Mortensen, 1910: 2.0 - 200 mm
• Abatus beatriceae (Larrain, 1986): 2.0 - 200 mm
• Abatus cavernosus (Philippi, 1845): 2.0 - 200 mm
• Abatus cordatus (Verrill, 1876): 2.0 - 200 mm
• Abatus curvidens Mortensen, 1936: 2.0 - 200 mm
• Abatus ingens Koehler, 1926: 2.0 - 200 mm
• Abatus kieri McKinney, McNamara & Wiedman, 1988 †: 2.0 - 200 mm
• Abatus koehleri (Thiéry, 1909): 2.0 - 200 mm
• Abatus philippii Lovén, 1871: 2.0 - 200 mm
• Abatus shackletoni Koehler, 1911: 2.0 - 200 mm
• Abderos minotaurus Schüller & Jirkov, 2013: 2.0 - 200 mm
• Abditoconus anselli (Harvey, 1996): 2.0 - 200 mm
• Abditoconus brava (Romano, Pérez-Portela & D. Martin, 2014): 2.0 - 200 mm
• Abditoconus heterosiphon (Voight, 2007): 2.0 - 200 mm
• Abditoconus investigatoris MacIntosh & Voight, 2021: 2.0 - 200 mm
• Abditoporella dimorpha Sosa-Yañez, Vieira & Solís-Marín, 2015: 2.0 - 200 mm
• Abditoporella turrita (Osburn, 1952): 2.0 - 200 mm
• Abdomenopora schumacheri Voigt, 1995 †: 2.0 - 200 mm
• Abebaioscia troglodytes Vandel, 1973: 2.0 - 200 mm
• Aberomysis muranoi Bacescu & Iliffe, 1986: 2.0 - 200 mm
• Aberrantidrilus cuspis (Erséus & Dumnicka, 1988): Macrobiota
• Aberrantidrilus stephaniae Martin, 2015: Macrobiota
• Aberrapex arrhynchum (Brooks, Mayes & Thorson, 1981) Jensen, 2001: 2.0 - 200 mm
• Aberrapex catarinensis Quadros, 2024: 2.0 - 200 mm
• Aberrapex ludmilae Menoret, Mutti & Ivanov, 2017: 2.0 - 200 mm
• Aberrapex manjajiae Jensen, 2006: 2.0 - 200 mm
• Aberrapex panamensis Quadros, 2024: 2.0 - 200 mm
• Aberrapex sanmartini Menoret, Mutti & Ivanov, 2017: 2.0 - 200 mm
• Aberrapex senticosus Jensen, 2001: 2.0 - 200 mm
• Aberrapex vitalemuttiorum Menoret, Mutti & Ivanov, 2017: 2.0 - 200 mm
• Aberrapex weipaensis Koch, Jensen & Caira, 2012: 2.0 - 200 mm
• Aberrodomus candidus Gordon, 1988: 2.0 - 200 mm
• Aberrodomus pocillifer (Harmer, 1957): 2.0 - 200 mm
• Aberrodomus sinuatus (Harmer, 1957): 2.0 - 200 mm
• Abertella aberti (Conrad, 1842) †: 2.0 - 200 mm
• Abertella cazonesensis (Kew in Dickerson & Kew, 1917) †: 2.0 - 200 mm
• Abertella dengleri Osborne & Ciampaglio, 2010 †: 2.0 - 200 mm
• Abertella gualichensis Martínez, Reichler & Mooi, 2005 †: 2.0 - 200 mm
• Abertella habanensis (Sanchez Roig, 1949) †: 2.0 - 200 mm
• Abertella kewi Durham, 1957 †: 2.0 - 200 mm
• Abertella miskellyi Kroh, Mooi, del Rió & Neumann, 2013 †: 2.0 - 200 mm
• Abertella palmeri Durham, 1957 †: 2.0 - 200 mm
• Abertella pirabensis (Marchesini Santos, 1958) †: 2.0 - 200 mm
• Abeskunus brusinianus (Clessin & W. Dybowski, 1887): 2.0 - 200 mm
• Abeskunus depressispira (Logvinenko & Starobogatov, 1969): 2.0 - 200 mm
• Abeskunus exiguus (Eichwald, 1838): 2.0 - 200 mm
• Abgrallaspis cyanophylli (Signoret, 1869): 2.0 - 200 mm
• Abiella arta Papin, 1996 †: 2.0 - 200 mm
• Abiella beloserskiensis Ivanova, 1963 †: 2.0 - 200 mm
• Abiella burussensis (Ragozin, 1964) †: 2.0 - 200 mm
• Abiella chejagica Kanev, 1989 †: 2.0 - 200 mm