• Abacella cornuta Shuysky, 1973 †: siphonous
• Abacella delicatula J.H.Johnson, 1964 †: siphonous
• Abacella dentata Shuysky, 1973 †: siphonous
• Abacella pertusa Maslov, 1956 †: siphonous
• Abacella pustulata Shuysky, 1973 †: siphonous
• Abacella stellata Shuysky, 1991 †: siphonous
• Abedinium dasypus (Cachon & Cachon-Enjumet) Loeblich Jr & Loeblich III, 1966: unicellular
• Abratopdinium cardioforme S.Mao & B.A.R.Mohr †: unicellular
• Abratopdinium kerguelense S.Mao & B.A.R.Mohr †: unicellular
• Acanthodinium caryophyllum Kofoid, 1907: unicellular
• Acanthogonyaulax acanthosphaera (Sargeant) Sargeant †: unicellular
• Acanthogonyaulax paliuros (Sargeant) Sargeant †: unicellular
• Acanthogonyaulax spinifera (Murray & Whitting) H.W.Graham, 1942: unicellular
• Acetabularia acetabulum (Linnaeus) P.C. Silva, 1952: siphonous
• Acetabularia caliculus J.V.Lamouroux, 1824: siphonous
• Acetabularia chiavonica Squinabol, 1902 †: siphonous
• Acetabularia crenulata J.V. Lamouroux, 1816: siphonous
• Acetabularia crenulata J.V.Lamouroux, 1816: siphonous
• Acetabularia dentata Solms-Laubach, 1895: siphonous
• Acetabularia dentata Solms-Laubach, 1895: siphonous
• Acetabularia farlowii Solms-Laubach, 1895: siphonous
• Acetabularia farlowii Solms-Laubach, 1895: siphonous
• Acetabularia haemmerlingii H.G.Schweiger & Berger, 1975: siphonous
• Acetabularia jalakanyakae Sani, Madhu, R.K.Kohli, K.Gupta & Bast, 2021: siphonous
• Acetabularia kilneri J.Agardh, 1887: siphonous
• Acetabularia major G.Martens, 1866: siphonous
• Acetabularia moldavica Barattolo, Ionesi & Ţibuleac, 2019 †: siphonous
• Acetabularia peniculus (R.Brown ex Turner) Solms-Laubach, 1895: siphonous
• Acetabularia ryukyuensis Okamura & Yamada, 1932: siphonous
• Acetabularia schenckii K. Möbius, 1889: siphonous
• Acetabularia schenckii Möbius, 1889: siphonous
• Achomosphaera alcicornu (Eisenack) R.J.Davey & G.L.Williams, 1966 †: unicellular
• Achomosphaera antleriformis P.Schiøler †: unicellular
• Achomosphaera argesensis E.Demetrescu †: unicellular
• Achomosphaera gralliforme (Brosius) R.J.Davey & G.L.Williams, 1969 †: unicellular
• Achomosphaera hirundo (Eisenack) R.J.Davey & G.L.Williams, 1969 †: unicellular
• Achomosphaera improcera M.A.Islam, 1983 †: unicellular
• Achomosphaera linifera (Cookson & Eisenack) Stover & Evitt, 1978 †: unicellular
• Achomosphaera neptuni (Eisenack) R.J.Davey & G.L.Williams, 1966 †: unicellular
• Achomosphaera recurvata K.P.Jain, S.C.D.Sah & R.Y.Singh †: unicellular
• Achomosphaera sagena R.J.Davey & G.L.Williams, 1966 †: unicellular
• Achomosphaera triangulata (Gerlach) R.J.Davey & G.L.Williams, 1969 †: unicellular
• Acicularia alaica Maslov, 1956 †: siphonous
• Acicularia albrightii Johnson & Kaska: siphonous
• Acicularia americana Konishi & Epis: siphonous
• Acicularia andrusovii Livental, 1946 †: siphonous
• Acicularia antiqua Pia, 1936 †: siphonous
• Acicularia archiacii L.Morellet & J.Morellet, 1922 †: siphonous
• Acicularia azerbaidganica Livental, 1946 †: siphonous
• Acicularia clapei Jaffrezo: siphonous
• Acicularia clavata L.Morellet & J.Morellet, 1922 †: siphonous
• Acicularia cornigera L.Morellet & J.Morellet, 1922 †: siphonous
• Acicularia dubossariensis Maslov, 1961 †: siphonous
• Acicularia dyumatsenae Pia: siphonous
• Acicularia endoi Praturlon, 1964 †: siphonous
• Acicularia eocaenica Munier-Chalmas ex L.Morellet & J.Morellet, 1922 †: siphonous
• Acicularia ferganensis Maslov, 1956 †: siphonous
• Acicularia hebertii L.Morellet & J.Morellet, 1922 †: siphonous
• Acicularia indica Varma: siphonous
• Acicularia intermedia Dragastan, 1967 †: siphonous
• Acicularia jurassica J.H.Johnson: siphonous
• Acicularia mediopora Munier-Chalmas: siphonous
• Acicularia michelinii Munier-Chalmas ex L.Morellet & J.Morellet, 1922 †: siphonous
• Acicularia micropora Munier-Chalmas ex L.Morellet & J.Morellet, 1922 †: siphonous
• Acicularia munieri L.Morellet & J.Morellet, 1913 †: siphonous
• Acicularia parvula Munier-Chalmas ex L.Morellet & J.Morellet, 1922 †: siphonous
• Acicularia pavantina d'Archiac, 1846 †: siphonous
• Acicularia transylvana Bányai & Morellet: siphonous
• Acicularia valetii Segonzac, 1971 †: siphonous
• Acicularia weisswasserensis Schlagintweit & D.Sanders, 2010 †: siphonous
• Aciculella bacillum Pia, 1930 †: siphonous
• Aciculella ogilvie-gordoniae G.F.Elliott, 1971 †: siphonous
• Acroporella anceps Segonzac, 1976 †: siphonous
• Acroporella bacilliformis (Sokač) I.I.Bucur et al., 2012 †: siphonous
• Acroporella cairensis A.Mancinelli, 2006 †: siphonous
• Acroporella occidentalis Johnson & Kaska †: siphonous
• Acroporella prisca (Pia) Grgasović, 2022 †: siphonous
• Actiniscus canadensis Bursa ex Carty, 2014: unicellular
• Actiniscus elongatus Dumitrică, 1968 †: unicellular
• Actiniscus flosculus S.Locker & E.Martini, 1986 †: unicellular
• Actiniscus laciniatus S.Locker & E.Martini, 1986 †: unicellular
• Actiniscus pentasterias (Ehrenberg) Ehrenberg, 1844: unicellular
• Actiniscus squamosus S.Locker & E.Martini, 1986 †: unicellular
• Actinodinium apsteinii Chatton & Hovasse: unicellular
• Actinoporella cretacica Raineri, 1922 †: siphonous
• Actinoporella krymensis Maslov, 1958 †: siphonous
• Actinoporella kukociorum Radoičić, 1975 †: siphonous
• Actinoporella maslovii Praturlon, 1964 †: siphonous
• Actinoporella podolica (Alth) C.Gümbel, 1881 †: siphonous
• Adenoides eludens (Herdman) Balech, 1956: unicellular
• Adenoides sinensis H.Gu, X.Li & Z.Luo, 2018: unicellular
• Adinimonas oviformis J.Schiller, 1928: unicellular
• Ailadinium reticulatum Saburova & Chomérat, 2014: unicellular
• Ajakmalajsoria rotunda Korde, 1958 †: siphonous
• Akashiwo sanguinea (K.Hirasaka) Gert Hansen & Moestrup, 2000: unicellular
• Alasphaera caudata H.Keupp, 1979 †: unicellular
• Alatosphaera hermosillae (Carbonell-Moore) Nézan, Carbonell-Moore, K.N.Mertens & Chomérat, 2023: unicellular
• Albertaporella involuta Johnson, 1966 †: siphonous
• Alexandrium affine (H.Inoue & Y.Fukuyo) Balech, 1995: unicellular
• Alexandrium andersonii Balech, 1990: unicellular