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]