1. Species Mesotaenium amaliae Schmidle
2. Species Mesotaenium berggrenii (Wittrock) Lagerheim, 1892
   1. Variety Mesotaenium berggrenii var. alaskana Kol, 1942
   2. Variety Mesotaenium berggrenii var. alaskanum Kol, 1942
3. Species Mesotaenium caldariorum (Lagerheim) Hansgirg, 1886
   1. Variety Mesotaenium caldariorum var. gracile Hansgirg, 1890
4. Species Mesotaenium chlamydosporum De Bary, 1858
   1. Forma Mesotaenium chlamydosporum f. minor West & G.S.West, 1892
   2. Variety Mesotaenium chlamydosporum var. archeri
      1. Forma Mesotaenium chlamydosporum var. archeri f. minor Nordstedt, 1879
   3. Variety Mesotaenium chlamydosporum var. curumalense (Wille) Willi Krieger ex Tomaszewicz, 1993
   4. Variety Mesotaenium chlamydosporum var. minus (West & G.S.West) West & G.S.West, 1904
   5. Variety Mesotaenium chlamydosporum var. violascens (de Bary) Willi Krieger, 1935
   6. Forma Mesotaenium chlamydosporum f. curumalense Wille accepted as Mesotaenium chlamydosporum var. curumalense (Wille) Willi Krieger ex Tomaszewicz, 1993 (synonym)
5. Species Mesotaenium degreyi W.B.Turner, 1886
   1. Forma Mesotaenium degreyi f. breve (West & G.S.West) Kossinskaja, 1952
   2. Forma Mesotaenium degreyi f. exiguum (Hansgirg) G.H.Tomaszewicz
   3. Forma Mesotaenium degreyi f. majus West & G.S.West, 1904
   4. Forma Mesotaenium degreyi f. tenue West & G.S.West, 1904
   5. Variety Mesotaenium degreyi var. borgei Willi Kreiger, 1933
   6. Variety Mesotaenium degreyi var. breve West, 1892
6. Species Mesotaenium de-greyi
   1. Forma Mesotaenium de-greyi f. exiguum (Hansgirg) G.H.Tomaszewicz
   2. Forma Mesotaenium de-greyi f. major West & West
   3. Forma Mesotaenium de-greyi f. minor Roll
   4. Forma Mesotaenium de-greyi f. tenue West & West
   5. Variety Mesotaenium de-greyi var. borgei W.Krieger, 1933 (uncertain, uncertain taxonomic status subjected to verification)
7. Species Mesotaenium dodekahedron Geitler
8. Species Mesotaenium endlicherianum Nägeli, 1849
   1. Variety Mesotaenium endlicherianum var. grande Nordstedt, 1879
   2. Variety Mesotaenium endlicherianum var. minimum (Cushman) Willi Krieger
   3. Forma Mesotaenium endlicherianum f. grande (Nordstedt) Kossinskaja, 1952 accepted as Mesotaenium endlicherianum var. grande Nordstedt, 1879
   4. Variety Mesotaenium endlicherianum var. caldariorum Lagerheim, 1886 accepted as Mesotaenium caldariorum (Lagerheim) Hansgirg, 1886 (synonym)
   5. Variety Mesotaenium endlicherianum var. exiguum Hansgirg (uncertain)
   6. Variety Mesotaenium endlicherianum var. insigne Beck-Mannagetta (uncertain)
9. Species Mesotaenium fusisporum (P.L.Crouan & H.M.Crouan) De Toni
10. Species Mesotaenium giganteum W.B.Turner, 1893
11. Species Mesotaenium hansgirgii Schmidle, 1900
12. Species Mesotaenium heimii Bourrelly, 1952
13. Species Mesotaenium kramstae Lemmermann, 1896
    1. Variety Mesotaenium kramstae var. breve West & G.S.West
    2. Variety Mesotaenium kramstae var. kneuckeri Schmidle, 1904
    3. Forma Mesotaenium kramstae f. breve (West & G.S.West) Kossinskaja, 1952 accepted as Mesotaenium kramstae var. breve West & G.S.West
14. Species Mesotaenium macrococcum (Kützing) J.Roy & Bisset, 1894
    1. Variety Mesotaenium macrococcum var. minus (De Bary) Compère, 1966
    2. Variety Mesotaenium macrococcum var. truncatum (W. West & G.S. West) Willi Krieger, 1933
    3. Variety Mesotaenium macrococcum var. micrococcum (Kützing) West & G.S.West, 1900 accepted as Mesotaenium macrococcum var. minus (De Bary) Compère, 1966 (synonym)
15. Species Mesotaenium manshuricum Skvortsov
16. Species Mesotaenium minimum J.A.Cushman, 1906
17. Species Mesotaenium mirificum W.Archer, 1864
    1. Variety Mesotaenium mirificum var. mahabaleshwarense Kamat
18. Species Mesotaenium neglectum Reinhard, 1888
19. Species Mesotaenium nivale Beck-Mannagetta, 1926
20. Species Mesotaenium obscurum Lagerheim, 1883
21. Species Mesotaenium purpureum West & G.S.West, 1898
    1. Variety Mesotaenium purpureum var. major Rabanus, 1923
22. Species Mesotaenium pyrenoidosum (P.A.Broady) O.V.Petlovany, 2015
23. Species Mesotaenium testaceovaginatum Fucikova, J.D.Hall, J.R.Johansen & R.Lowe, 2008
24. Species Mesotaenium truncatum West & G.S.West, 1904
25. Species Mesotaenium braunii De Bary, 1858 accepted as Mesotaenium macrococcum (Kützing) J.Roy & Bisset, 1894 (synonym)
    1. Variety Mesotaenium braunii var. minus De Bary, 1853 accepted as Mesotaenium macrococcum var. minus (De Bary) Compère, 1966 (synonym)
26. Species Mesotaenium micrococcum (Kützing) Kirchner, 1878 accepted as Mesotaenium macrococcum var. minus (De Bary) Compère, 1966 (synonym)
    1. Forma Mesotaenium micrococcum f. violascens Lagerheim
    2. Variety Mesotaenium micrococcum var. truncatum (West & G.S.West) W.Krieger, 1933 accepted as Mesotaenium truncatum West & G.S.West, 1904 (synonym)
    3. Variety Mesotaenium micrococcum var. lagerheimii W.Krieger, 1933 (uncertain, uncertain taxonomic status subjected to verification)
27. Species Mesotaenium scrobiculatum J.Cambra, 1989 accepted as Mougeotia austriaca Czurda, 1932 (synonym)
28. Species Mesotaenium violascens De Bary, 1858 accepted as Mesotaenium chlamydosporum var. violascens (de Bary) Willi Krieger, 1935 (synonym)
29. Species Mesotaenium aplanosporum C.E.Taft (uncertain)
30. Species Mesotaenium clepsydra (Wood) Wolle, 1884 (uncertain > unassessed, preliminary, not subjected to verification)
31. Species Mesotaenium turicense Huber-Pestalozzi (uncertain)
    1. Variety Mesotaenium turicense var. sigmoideum Huber-Pestalozzi (uncertain)

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