Spirotaenia is a genus of basal unicellular green algae that may be sister to the Chlorokybophyceae.[1][2] It was previously considered to be part of the Zygnemataceae. It is sexually conjugating, a mode of reproduction that was previously only known in the Zygnemataceae/Mesotaeniaceae, the sister groups to the land plants. This is surprising, as Spirotaenia is much more basal. The conjugating process is substantially aberrant.[further explanation needed][3][4]Spirotaenia may actually be more than one distinct lineage which may not be closely related.[5]
