Abacum M.A.Fombella, 1978 † (basis of record)
Abbottella Hollenberg, 1967 (extant flag source)
Abbottella Hollenberg, 1967 (basis of record)
Abratopdinium S. Mao & B.A.R. Mohr, 1992 † (basis of record)
Abrotanifolia Stackhouse, 1809 accepted as Cystoseira C.Agardh, 1820 (basis of record)
Abrotanifolia Stackhouse, 1809 accepted as Cystoseira C.Agardh, 1820 (extant flag source)
Acanthocerataceae Round, Crawford & Mann, 1990 (extant flag source)
Acanthocerataceae Round, Crawford & Mann, 1990 (basis of record)
Acanthococcus J.D. Hooker & W.H. Harvey, 1845 (extant flag source)
Acanthococcus J.D. Hooker & W.H. Harvey, 1845 (basis of record)
Acanthocodium W.F.R. Suringar, 1867 (basis of record)
Acanthocodium W.F.R. Suringar, 1867 (extant flag source)
Acanthocodium W.F.R. Suringar, 1867 (current name source)
Acanthodinium Kofoid, 1907 (extant flag source)
Acanthodinium Kofoid, 1907 (basis of record)
Acanthoecaceae accepted as Acanthoecidae Norris, 1965 (extant flag source)
Acanthoecaceae accepted as Acanthoecidae Norris, 1965 (basis of record)
Acetabulum Boehmer in Ludwig, 1760 (extant flag source)
Acetabulum Boehmer in Ludwig, 1760 (basis of record)
Achnantheiopsis Lange-Bertalot, 1997 (basis of record)
Achnantheiopsis Lange-Bertalot, 1997 (extant flag source)
Achnanthidiaceae D.G. Mann (basis of record)
Achnanthidiaceae D.G. Mann (extant flag source)
Achomosphaera Evitt, 1963 † (basis of record)
Achradina Lohmann, 1902 (basis of record)
Achradina Lohmann, 1902 (extant flag source)
Acinetosporaceae Hamel ex J. Feldmann, 1937 (basis of record)
Acinetosporaceae Hamel ex J. Feldmann, 1937 (extant flag source)
Aclistochara R.E. Peck, 1937 † (basis of record)
Aclistocharaceae † accepted as Characeae Agardh, 1824 (basis of record)
Acritarcha (awaiting allocation) † (basis of record)
Acrocarpus Kützing, 1843 accepted as Gelidiella Feldmann & G. Hamel, 1934 (basis of record)
Acrocarpus Kützing, 1843 accepted as Gelidiella Feldmann & G. Hamel, 1934 (extant flag source)
Acrosymphytaceae S.C. Lindstrom (basis of record)
Acrosymphytaceae S.C. Lindstrom (extant flag source)
Acrosymphytonema C.F. Boudouresque, M. Perret-Boudouresque & M. Knoepffler-Peguy, 1984 (basis of record)
Acrosymphytonema C.F. Boudouresque, M. Perret-Boudouresque & M. Knoepffler-Peguy, 1984 (extant flag source)
Actinochloridaceae (extant flag source)
Actinochloridaceae (basis of record)
Actinodictyon Pantocsek, 1889 † (basis of record)
Actinodiscus Greville, 1863 † (basis of record)
Actinophaenia Shadbolt, 1854 (basis of record)
Actinophaenia Shadbolt, 1854 (extant flag source)
Actinosphaenia G. Shadbolt, 1854 (basis of record)
Actinosphaenia G. Shadbolt, 1854 (extant flag source)
Actinostephanos G.K. Khursevich, 1989 (extant flag source)
Actinostephanos G.K. Khursevich, 1989 (basis of record)
Acutochara L. Ya. Sajdakovskij, 1993 † (basis of record)
Adamsiella L.E. Phillips & W.A. Nelson in L.E. Phillips, 2002 (basis of record)
Adamsiella L.E. Phillips & W.A. Nelson in L.E. Phillips, 2002 (extant flag source)
Adenocystaceae F. Rousseau, B. de Reviers, M.-C. Leclerc, A. Asensi & R. Delépine (basis of record)
Adenocystaceae F. Rousseau, B. de Reviers, M.-C. Leclerc, A. Asensi & R. Delépine (extant flag source)
Adlafia G. Moser, H. Lange-Bertalot & D. Metzeltin, 1998 (basis of record)
Adlafia G. Moser, H. Lange-Bertalot & D. Metzeltin, 1998 (extant flag source)
Adnatosphaeridiaceae † (basis of record)
Adnatosphaeridium G. Williams & Downie, 1966 † (basis of record)
Adoneis G.W. Andrews & P. Rivera, 1987 (basis of record)
Adoneis G.W. Andrews & P. Rivera, 1987 (extant flag source)
Aegira Fries, 1825 accepted as Eudesme J.Agardh, 1882 (extant flag source)
Aegira Fries, 1825 accepted as Eudesme J.Agardh, 1882 (basis of record)
Aeroligeraceae † accepted as Areoligeraceae Evitt, 1963 † (basis of record)
Aeronema J.W. Snow, 1911 accepted as Heterococcus Chodat, 1908 (extant flag source)
Aeronema J.W. Snow, 1911 accepted as Heterococcus Chodat, 1908 (basis of record)
Aerosphaera Gerneck, 1907 (extant flag source)
Aerosphaera Gerneck, 1907 (status source)
Aerosphaera Gerneck, 1907 (basis of record)
Agardhia A. Cabrera, 1823 accepted as Codium Stackhouse, 1797 (basis of record)
Agardhia A. Cabrera, 1823 accepted as Codium Stackhouse, 1797 (extant flag source)
Ahnfeldtia Trevisan, 1849 accepted as Caulerpa J.V.F. Lamouroux, 1809 (extant flag source)
Ahnfeldtia Trevisan, 1849 accepted as Caulerpa J.V.F. Lamouroux, 1809 (basis of record)
Ahnfeltiaceae C.A. Maggs & C.M. Pueschel (extant flag source)
Ahnfeltiaceae C.A. Maggs & C.M. Pueschel (basis of record)
Akkesiphycaceae H. Kawai & H. Sasaki (basis of record)
Akkesiphycaceae H. Kawai & H. Sasaki (extant flag source)
Aldavemyxa Skvortzov, 1972 (basis of record)
Aldavemyxa Skvortzov, 1972 (extant flag source)
Aldorfia L.E. Stover & W.R. Evitt, 1978 (basis of record)
Algites A.C. Seward, 1894 † (basis of record)
Alisphaera Heimdal, 1973 (extant flag source)
Alisphaera Heimdal, 1973 (basis of record)
Alleynea Womersley, 2003 (extant flag source)
Alleynea Womersley, 2003 (basis of record)
Allogonium Kützing, 1843 (extant flag source)
Allogonium Kützing, 1843 (basis of record)
Alloioneis K.M. Schumann in P.T. Cleve, 1878 (extant flag source)
Alloioneis K.M. Schumann in P.T. Cleve, 1878 (status source)
Alloioneis K.M. Schumann in P.T. Cleve, 1878 (basis of record)
Alveolophora A.I. Moisseeva & T.L. Nevretdinova, 1990 † (basis of record)
Alveovallum Lange-Bertalot & Krammer, 2000 (basis of record)
Alveovallum Lange-Bertalot & Krammer, 2000 (extant flag source)
Alveus I. Kaczmarska & G.A. Fryxell, 1996 (extant flag source)
Alveus I. Kaczmarska & G.A. Fryxell, 1996 (basis of record)
Amblyochara L. Grambast, 1963 † (basis of record)
Amblypyrgus R. Gersonde & D.M. Harwood, 1990 † (basis of record)
Amicula Witkowski, Lange-Bertalot & Metzeltin, 2000 (basis of record)
Amiculosphaera R. Harland in L. Montadert et al., 1979 † (basis of record)
Amithalithina J.J. Pospichal & S.W. Wise Jr., 1990 † (basis of record)
Ammodochiaceae † accepted as Ammodochiidae Deflandre, 1950 † (basis of record)
Ammodochium Hovasse, 1932 † (basis of record)
Amoebophyraceae accepted as Amoebophryaceae (basis of record)