Description: Thallus polysiphonous with erect axes to 20 cms long. Branches fine and complanate. All axes of 5 pericentral cells, corticate.

Habitat: Rare. Epilithic or epiphytic in rock pools of the low littoral.

Distribution: South west shores of England, Wales, Ireland and the Channel Islands. Europe: Mediterranean, Azores, Giblaltar, Portugal, Atlantic coasts of Spain and France. Further afield: Madeira, Mauritania.

Key Identification Features:

• Cortication on all axes.

Distribution Map from NBN: Pterosiphonia complanata at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Pterosiphonia complanata at iNaturalist World Species Observations database.

WoRMS: Pterosiphonia complanata at World Register of Marine Species. Accepted name: Pterosiphonia complanata (Clemente) Falkenberg, 1897. AphiaID: 146368.

Classification: Biota; Plantae; Biliphyta; Rhodophyta; Eurhodophytina; Florideophyceae; Rhodymeniophycidae; Ceramiales; Rhodomelaceae; Pterosiphonieae; Pterosiphonia