Description: Thallus to 25 cms long primary axes dominant with bipinnate branches, no more than 5 mm long. Uniseriate above and polysiphonous at the base.

Habitat: Rare. Low littoral and sublittoral.

Distribution: Widespread in the British Isles. Europe: France, Baltic Sea and Norway. Atlantic coast of North America: Canada and Massachusetts. Further afield: Japan.

Similar Species: Haplospora globosa Kjellman has irregular branching unlike Tilopteris which has opposite branching.

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

iNaturalist: Tilopteris mertensii at iNaturalist World Species Observations database.

WoRMS: Tilopteris mertensii at World Register of Marine Species. Accepted name: Tilopteris mertensii (Turner) Kützing, 1849. AphiaID: 145919.

Classification: Biota; Chromista; Harosa; Heterokonta; Ochrophyta; Phaeophyceae; Fucophycidae; Tilopteridales; Tilopteridaceae; Tilopteris