Mesostigma is a genus of unicellular biflagellate freshwater green algae, with a single species Mesostigma viride, covered by an outer layer of basket‐like scales instead of a cell wall.[4][1] It is the only known genus in the class Mesostigmatophyceae[5] (and thus, the only genus in the family Mesostigmataceae[2] and the order Mesostigmatales[3]).
Earlier studies were unable to resolve the position of the species, and it was often placed as a sister to all other green algae, as one of the basal members of the Streptophyta, close to Chaetosphaeridium.[6][7][8] More recent studies agree that Mesostigma and Chlorokybus form a clade, being the earliest diverging of the green plants, specifically within Charophytes.[9][10][11][12]
^ abGuiry, M.D.; Guiry, G.M. "Mesostigma". AlgaeBase. World-wide electronic publication, National University of Ireland, Galway.
^ abGuiry, M.D.; Guiry, G.M. "Mesostigmataceae". AlgaeBase. World-wide electronic publication, National University of Ireland, Galway.
^ abGuiry, M.D.; Guiry, G.M. "Mesostigmatales". AlgaeBase. World-wide electronic publication, National University of Ireland, Galway.