Description: Grows as flattened thalli rising from a discoid holdfast to a length of 15 cms as narrow tapering blades more than 5 cms broad.

Habitat: Common. Epilithic in shallow pools of the lower littoral.

Distribution: Widely distributed around the British Isles. Europe: Mediterranean, Azores, Portugal,Atlantic coast of Spain and France, Netherlands, Denmark, Germany, Baltic Sea, Sweden, Norway, Faroes and Iceland. Atlantic coast of North America: Canada, Maine, New Hampshire, Massachusetts, Rhode Island, Connecticut and Long Island, New Jersey, Delaware, Maryland, Virginia, North Carolina and Florida. Further afield: Canary Islands, Arctic Seas: Murman Sea, White Sea, American Arctic Sea and Cumberland Sound and Greenland, Caribbean, Atlantic and Pacific coasts of America from Alaska, Canada, California and Chile, Japan, Senegal, West and South Africa, Australia and New Zealand.

Similar Species: Punctaria and young Laminaria.

Key Identification Features:

• Flat, not twisted blades rising from a discoid holdfast.

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

iNaturalist: Petalonia fascia at iNaturalist World Species Observations database.

WoRMS: Petalonia fascia at World Register of Marine Species. Accepted name: Petalonia fascia (O.F.Müller) Kuntze, 1898. AphiaID: 145863.

Classification: Biota; Chromista; Harosa; Heterokonta; Ochrophyta; Phaeophyceae; Fucophycidae; Ectocarpales; Scytosiphonaceae; Scytosiphoneae; Petalonia