Rhizochromulina is an unusual genus of marine
heterokont algae, with one species,
R. marina. They are colored amoeboids with a single flagellum, and produce distinctive spindle-shaped zoospores. These have a cell structure typical of the
axodines, and in particular
Rhizochromulina is considered to be the closest relative of the
actinodines, including various colored algae and colorless heliozoa. Before it was studied in detail,
Rhizochromulina was included among the superficially similar
Chrysamoebales, but these produce zoospores which are of typical chromulinid form.