Description: Thallus small polysiphonous. Prostrate axes form erect tufts to 10 cms long, terete and complanate with 10 - 12 pericentral cells, ecorticate. Branches alternate and fine.

Habitat: Rare. Epilithic or epiphytic in low rock pools to 20 m in the low littoral and sublittoral.

Distribution: Known from only a few sites in the British Isles: Cornwall in England, Pembroke in Wales and Clare in Ireland. Europe: Mediterranean and Portugal.

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

iNaturalist: Pterosiphonia ardreana at iNaturalist World Species Observations database.

WoRMS: Pterosiphonia ardreana at World Register of Marine Species. Accepted name: Xiphosiphonia ardreana (Maggs & Hommersand) Savoie & G.W.Saunders, 2016. AphiaID: 1027800.

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