• Neosiphonia M.-S.Kim & I.K.Lee, 1999
• Neosiphonia Sollas, 1888
• Neosiphonia apiculata (Hollenberg) Masuda & Kogame, 2003 accepted as Melanothamnus apiculatus (Hollenberg) Díaz- Tapia & Maggs, 2017
• Neosiphonia bajacali (Hollenberg) Mamoozadeh & Freshwater, 2011 accepted as Melanothamnus bajacali (Hollenberg) Díaz-Tapia & Maggs, 2017
• Neosiphonia baliana D.E.Bustamante, B.Y.Won & T.O.Cho, 2013 accepted as Melanothamnus balianus (D.E.Bustamante, B.Y.Won & T.O.Cho) Díaz-Tapia & Maggs, 2017
• Neosiphonia beaudettei (Hollenberg) M.-S.Kim & I.A.Abbott, 2006 accepted as Polysiphonia beaudettei Hollenberg, 1961
• Neosiphonia cheloniae (Hollenberg & J.N.Norris) J.N.Norris, 2014 accepted as Melanothamnus cheloniae (Hollenberg & J.N.Norris) Díaz-Tapia & Maggs, 2017
• Neosiphonia collabens (C.Agardh) Díaz-Tapia & Bárbara, 2013 accepted as Melanothamnus collabens (C.Agardh) Díaz-Tapia & Maggs, 2017
• Neosiphonia concinna (Hollenberg) J.N.Norris, 2014 accepted as Melanothamnus concinnus (Hollenberg) Díaz-Tapia & Maggs, 2017
• Neosiphonia confusa (Hollenberg) J.N.Norris, 2014 accepted as Eutrichosiphonia confusa (Hollenberg) Savoie & G.W.Saunders, 2019
• Neosiphonia decumbens (T.Segi) M.-S.Kim & I.K.Lee, 1999 accepted as Melanothamnus decumbens (T.Segi) Díaz-Tapia & Maggs, 2017
• Neosiphonia eastwoodiae (Setchell & N.L.Gardner) S.-D.Xiang, 2004 accepted as Melanothamnus eastwoodiae (Setchell & N.L.Gardner) Díaz-Tapia & Maggs, 2017
• Neosiphonia echinata (Harvey) N.Mamoozadeh & D.W.Freshwater, 2011 accepted as Acanthosiphonia echinata (Harvey) Savoie & G.W.Saunders, 2018
• Neosiphonia elongata (Hudson) Xiang Si-duan, 2004 accepted as Carradoriella elongata (Hudson) Savoie & G.W.Saunders, 2019
• Neosiphonia elongella (Harvey) M.S.Kim & I.K.Lee, 1999 accepted as Carradoriella elongella (Harvey) Savoie & G.W.Saunders, 2019
• Neosiphonia ferulacea (Suhr ex J.Agardh) S.M.Guimarães & M.T.Fujii, 2004 accepted as Melanothamnus ferulaceus (Suhr ex J.Agardh) Díaz-Tapia & Maggs, 2017
• Neosiphonia flaccidissima (Hollenberg) M.S.Kim & I.K.Lee, 1999 accepted as Neosiphonia sertularioides (Grateloup) K.W.Nam & P.J.Kang, 2012 accepted as Polysiphonia sertularioides (Grateloup) J.Agardh, 1863
• Neosiphonia flavimarina M.-S.Kim & I.K.Lee, 1999 accepted as Melanothamnus flavimarinus (M.-S.Kim & I.K.Lee) Díaz-Tapia & Maggs, 2017
• Neosiphonia fruticosa (Wilson, 1925)
• Neosiphonia gorgoniae (Harvey) S.M.Guimarães & M.T.Fujii, 2004 accepted as Melanothamnus gorgoniae (Harvey) Díaz-Tapia & Maggs, 2017
• Neosiphonia harlandii (Harvey) M.S.Kim & I.K.Lee, 1999 accepted as Melanothamnus harlandii (Harvey) Díaz-Tapia & Maggs, 2017
• Neosiphonia harveyi (Bailey) M.-S.Kim, H.-G.Choi, Guiry & G.W.Saunders, 2001 accepted as Melanothamnus harveyi (Bailey) Díaz-Tapia & Maggs, 2017
• Neosiphonia harveyi var. arietina (Harvey) M.J.Wynne, 2005 accepted as Melanothamnus harveyi var. arietina (Harvey) M.J.Wynne, 2017
• Neosiphonia harveyi var. olneyi (Harvey) A.C.Mathieson & Dawes, 2017
• Neosiphonia hawaiiensis (Hollenberg) M.-S.Kim & I.A.Abbott, 2006 accepted as Melanothamnus hawaiiensis (Hollenberg) Díaz-Tapia & Maggs, 2017
• Neosiphonia howei (Hollenberg) Skelton & G.R.South, 2007 accepted as Wilsonosiphonia howei (Hollenberg) D.Bustamante, Won & T.O.Cho, 2017
• Neosiphonia japonica (Harvey) M.-S.Kim & I.K.Lee, 1999 accepted as Melanothamnus japonicus (Harvey) Díaz-Tapia & Maggs, 2017
• Neosiphonia johnstonii (Setchell & N.L.Gardner) J.N.Norris, 2014 accepted as Melanothamnus johnstonii (Setchell & N.L.Gardner) Díaz-Tapia & Maggs, 2017
• Neosiphonia masonii (Setchell & N.L.Gardner) J.N.Norris, 2014 accepted as Melanothamnus masonii (Setchell & N.L.Gardner) Díaz-Tapia & Maggs, 2017
• Neosiphonia mexicana (E.Y.Dawson) J.N.Norris, 2014 accepted as Lophosiphonia mexicana E.Y.Dawson, 1944
• Neosiphonia microtriaeneae Gómez & Calderón-Gutiérrez, 2020
• Neosiphonia motukawanui Kelly, 2007
• Neosiphonia notoensis (Segi) M.S.Kim & I.K.Lee, 1999 accepted as Melanothamnus notoensis (Segi) Díaz-Tapia & Maggs, 2017
• Neosiphonia paniculata (Montagne) J.N.Norris, 2014 accepted as Eutrichosiphonia paniculata (Montagne) D.E.Bustamante & T.O.Cho, 2021
• Neosiphonia peruviensis D.E.Bustamante, B.Y.Won, M.E.Ramirez & T.O.Cho, 2012 accepted as Melanothamnus peruviensis (D.E.Bustamante, B.Y.Won, M.E.Ramirez & T.O.Cho) Díaz-Tapia & Maggs, 2017
• Neosiphonia poko (Hollenberg) I.A.Abbott, 2002 accepted as Polysiphonia poko Hollenberg, 1968
• Neosiphonia polyphysa (Kützing) Skelton & G.R.South, 2007 accepted as Melanothamnus polyphysus (Kützing) Díaz-Tapia & Maggs, 2017
• Neosiphonia porrecta (T.Segi) Y.-P.Lee, 2008 accepted as Melanothamnus porrectus (T.Segi) Díaz-Tapia & Maggs, 2017
• Neosiphonia profunda (Hollenberg) M.-S.Kim & I.A.Abbott, 2006 accepted as Polysiphonia profunda Hollenberg, 1968
• Neosiphonia ramireziae D.E.Bustamante, B.Y.Won & T.O.Cho, 2012 accepted as Melanothamnus ramireziae (D.E.Bustamante, B.Y. Won & T.O.Cho) Díaz-Tapia & Maggs, 2017
• Neosiphonia rubrorhiza (Hollenberg) M.-S.Kim & I.A.Abbott, 2006 accepted as Polysiphonia rubrorhiza Hollenberg, 1968
• Neosiphonia saccorhiza (Collins & Hervey) J.M.C.Nunes & S.M.Guimarães, 2010 accepted as Polysiphonia saccorhiza (Collins & Hervey) Hollenberg, 1968
• Neosiphonia savatieri (Hariot) M.S.Kim & I.K.Lee, 1999 accepted as Melanothamnus savatieri (Hariot) Díaz-Tapia & Maggs, 2017
• Neosiphonia schmidtii Sollas, 1888
• Neosiphonia sertularioides (Grateloup) K.W.Nam & P.J.Kang, 2012 accepted as Polysiphonia sertularioides (Grateloup) J.Agardh, 1863
• Neosiphonia silvae D.E.Bustamante, B.Y.Won & T.O.Cho, 2013 accepted as Melanothamnus silvae (D.E.Bustamante, B.Y.Won & T.O.Cho) Díaz-Tapia & Maggs, 2017
• Neosiphonia simplex (Hollenberg) Y.-P.Lee, 2008 accepted as Melanothamnus simplex (Hollenberg) Díaz-Tapia & Maggs, 2017
• Neosiphonia sparsa (Setchell) I.A.Abbott, 2002 accepted as Melanothamnus sparsus (Setchell) Díaz-Tapia & Maggs, 2017
• Neosiphonia sphaerocarpa (Børgesen) M.-S.Kim & I.K.Lee, 1999 accepted as Melanothamnus sphaerocarpus (Børgesen) Díaz-Tapia & Maggs, 2017
• Neosiphonia subtilissima (Montagne) M.S.Kim & I.K.Lee, 1999 accepted as Polysiphonia subtilissima Montagne, 1840
• Neosiphonia superstes Sollas, 1888
• Neosiphonia tepida (Hollenberg) S.M.Guimarães & M.T.Fujii, 2004 accepted as Polysiphonia foetidissima Cocks ex Bornet, 1892 accepted as Vertebrata foetidissima (Cocks ex Bornet) Díaz-Tapia & Maggs, 2017
• Neosiphonia teradomariensis (M.Noda) M.-S.Kim & I.K.Lee, 1999 accepted as Melanothamnus teradomariensis (M.Noda) Díaz-Tapia & Maggs, 2017
• Neosiphonia thailandica N.Muangmai & C.Kaewsuralikhit, 2014 accepted as Melanothamnus thailandicus (N.Muangmai & C.Kaewsuralikhit) Díaz-Tapia & Maggs, 2017
• Neosiphonia tongatensis (Harvey ex Kützing) M.-S.Kim & I.K.Lee, 1999 accepted as Melanothamnus tongatensis (Harvey ex Kützing) Díaz-Tapia & Maggs, 2017
• Neosiphonia upolensis (Grunow) M.S.Kim & Boo, 2008 accepted as Melanothamnus upolensis (Grunow) Díaz-Tapia & Maggs, 2017
• Neosiphonia yendoi (Segi) M.S.Kim & I.K.Lee, 1999 accepted as Melanothamnus yendoi (T.Segi) Díaz-Tapia & Maggs, 2017
• Neosiphonia yongpilii B.Kim & M.-S.Kim, 2016 accepted as Melanothamnus yongpilii (B.Kim & M.-S.Kim) Díaz-Tapia & Maggs, 2017