''Spirotaenia'' is a genus of basal

green algae The green algae (singular: green alga) are a group consisting of the Prasinodermophyta and its unnamed sister which contains the Chlorophyta and Charophyta/ Streptophyta. The land plants ( Embryophytes) have emerged deep in the Charophyte alg ...

that may be sister to the

Chlorokybophyceae ''Chlorokybus'' is a multicellular (sarcinoid) genus of basal green algae or charophyte, a soil alga Algae ( , ; : alga ) are any of a large and diverse group of photosynthetic, eukaryotic organisms. The name is an informal term for a pol ...

. It was previously considered to be part of the

Zygnemataceae The Zygnemataceae are a family of Algae#Morphology, filamentous or unicellular, uniseriate (unbranched) green algae. The filaments are septum, septated and reproduction is by Sexual conjugation, conjugation; ''Spirogyra'' is commonly used in scho ...

. It is sexually conjugating, a mode of reproduction that was previously only known in the

Mesotaeniaceae The Mesotaeniaceae are a small family of unicellular green algae known as the "saccoderm desmids". The Mesotaeniaceae appear to be sister or ancestral to the Zygnemataceae. The desmids are a deep branching group of Zygnemataceae. ''Spirotaenia ...

, the sister groups to the

land plants The Embryophyta (), or land plants, are the most familiar group of green plants that comprise vegetation on Earth. Embryophytes () have a common ancestor with green algae, having emerged within the Phragmoplastophyta clade of green algae as sist ...

. This is surprising, as ''Spirotaenia'' is much more basal. The conjugating process is substantially aberrant. ''Spirotaenia'' may actually be more than one distinct lineage which may not be closely related.

Phylogeny

References

Green algae {{Alga-stub