• Acanthodasys aculeatus Remane, 1927: no
• Acanthodasys algarvense Hummon, 2008: no
• Acanthodasys arcassonensis Kisielewski, 1987: no
• Acanthodasys australis Bosco, Lourenço, Guidi, Balsamo, Hochberg & Garraffoni, 2020: no
• Acanthodasys caribbeanensis Hochberg & Atherton, 2010: no
• Acanthodasys carolinensis Hummon, 2008: no
• Acanthodasys comtus Lee, 2012: no
• Acanthodasys ericinus Lee, 2012: no
• Acanthodasys fibrosus Clausen, 2004: no
• Acanthodasys flabellicaudus Hummon & Todaro, 2009: no
• Acanthodasys lineatus Clausen, 2000: no
• Acanthodasys paurocactus Atherton & Hochberg, 2012: no
• Acanthodasys silvulus Evans, 1992: no
• Acanthophora aokii Okamura, 1934: no
• Acanthophora dendroides Harvey, 1855: no
• Acanthophora muscoides (Linnaeus) Bory de Saint-Vincent, 1828: no
• Acanthophora nayadiformis (Delile) Papenfuss, 1968: no
• Acanthophora pacifica (Setchell) Kraft, 1979: no
• Acanthophora ramulosa Lindenberg ex Kützing, 1843: no
• Acanthophora spicifera (M.Vahl) Børgesen, 1910: no
• Acrodiscus vidovichii (Meneghini) Zanardini, 1868: no
• Acrosorium acrospermum (J.Agardh) Kylin, 1938: no
• Acrosorium amphiroae Jaasund, 1976: no
• Acrosorium ciliolatum (Harvey) Kylin, 1924: no
• Acrosorium cincinnatum M.J.Wynne, 1986: no
• Acrosorium decumbens (J.Agardh) Kylin, 1929: no
• Acrosorium deformatum (Suhr) Papenfuss, 1943: no
• Acrosorium flabellatum Yamada, 1930: no
• Acrosorium fragile W.R.Taylor, 1945: no
• Acrosorium krishnamurthyi M.Umamaheswara Rao, 2002: no
• Acrosorium maculatum (Sonder ex Kützing) Papenfuss, 1940: no
• Acrosorium minus (Sonder) Kylin, 1924: no
• Acrosorium odontophorum M.A.Howe & W.R.Taylor, 1931: no
• Acrosorium papenfussii W.R.Taylor, 1945: no
• Acrosorium polyneurum Okamura, 1936: no
• Acrosorium procumbens E.Y.Dawson, 1961: no
• Acrosorium venulosum (Zanardini) Kylin, 1924: no
• Acrosorium yendoi Yamada, 1930: no
• Acrosymphyton brainardii Vroom & I.A.Abbott, 2004: no
• Acrosymphyton caribaeum (J.Agardh) Sjöstedt, 1926: no
• Acrosymphyton firmum M.W.Hawkes, 1982: no
• Acrosymphyton purpuriferum (J.Agardh) G.Sjöstedt, 1926: no
• Acrosymphyton taylorii I.A.Abbott, 1962: no
• Acrosymphyton tenax A.J.K.Millar & Kraft, 1984: no
• Aeodes dilatata Yamada: no
• Aeodes nitidissima J.Agardh, 1876: no
• Agardhiella coulteri (Harvey) Setchell, 1897: no
• Agardhiella floridana (Kylin) P.W.Gabrielsen ex Guimarães & Oliviera, 1996: no
• Agardhiella mexicana E.Y.Dawson, 1944: no
• Agardhiella ramosissima (Harvey) Kylin, 1932: no
• Agardhiella subulata (C.Agardh) Kraft & M.J.Wynne, 1979: no
• Aiolocolax pulchellus Pocock, 1956: no
• Alaria angusta Kjellman, 1889: no
• Alaria cordata Tilden, 1898: no
• Alaria costata Fallis: no
• Alaria crassifolia Kjellman, 1885: no
• Alaria crispa Kjellman, 1889: no
• Alaria dolichorachis: no
• Alaria elliptica Kjellman, 1883: no
• Alaria esculenta (Linnaeus) Greville, 1830: no
• Alaria flagellaris Strömfelt, 1886: no
• Alaria fragilis De A.Saunders, 1901: no
• Alaria longipes (Ruprecht) De Toni, 1895: no
• Alaria macrophylla Miyabe, 1902: no
• Alaria marginata Postels & Ruprecht, 1840: no
• Alaria musifolia (De la Pylaie) J.Agardh, 1872: no
• Alaria oblonga Kjellman, 1883: no
• Alaria ochotensis Yendo, 1919: no
• Alaria paradisea (Miyabe & Nagai) Widdowson, 1972: no
• Alaria praelonga Kjellman, 1889: no
• Alaria pylaiei (Bory) Greville, 1830: no
• Alaria remotifolia (De la Pylaie) Widdowson nom.prov.: no
• Alaria striata J.Agardh ineditae: no
• Anacanthoderma paucisetosum (Marcolongo, 1910): no
• Anacanthoderma punctatum Marcolongo, 1910: no
• Anadyomene cladophoroides (W.J.Gilbert) Guiry & A.R.Sherwood, 2023: no
• Anadyomene crispa Chevallier: no
• Anadyomene eseptata Gilbert, 1961: no
• Anadyomene gigantodictyon M.M.Littler & D.S.Littler, 2012: no
• Anadyomene howei D.S.Littler & Littler, 1991: no
• Anadyomene lacerata D.S.Littler & Littler, 1991: no
• Anadyomene leclancheri Decaisne, 1844: no
• Anadyomene lenormandii J.E.Gray: no
• Anadyomene linkiana D.S.Littler & M.M.Littler, 1991: no
• Anadyomene menziesii (J.E.Gray) J.Agardh, 1887: no
• Anadyomene muelleri Sonder: no
• Anadyomene pavonina (J.Agardh) Wille, 1910: no
• Anadyomene plicata C.Agardh, 1823: no
• Anadyomene reticulata Askenasy, 1888: no
• Anadyomene rhizoidifera A.B.Joly & Pereira, 1973: no
• Anadyomene saldanhae A.B.Joly & E.C.Oliveira, 1969: no
• Anadyomene stellata (Wulfen) C.Agardh, 1823: no
• Anadyomene wrightii Harvey ex J.E.Gray, 1866: no
• Anandrodasys agadasys (Hochberg, 2003): no
• Anotrichium anthericephalum (E.Y.Dawson) Baldock, 1976: no
• Anotrichium barbatum (C.Agardh) Nägeli, 1862: no
• Anotrichium crinitum (Kützing) Baldock, 1976: no
• Anotrichium elongatum (Harvey) Baldock, 1976: no
• Anotrichium furcellatum (J.Agardh) Baldock, 1976: no
• Anotrichium gracile (J.Agardh) Baldock, 1976: no