The Mesostigmatophyceae are a class of basal green algae found in freshwater.

[3][4][5] In a narrow circumscription, the class contains a single genus, Mesostigma.

[6] AlgaeBase then places the order within its circumscription of Charophyta.

[1] A clade containing Chlorokybus and Spirotaenia may either be added,[7][8][9][10][11][12] or treated as a sister, with Chlorokybus placed in a separate class, Chlorokybophyceae.

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