Species description: A small bright red to red-brown seaweed up to 3 cm in height. It forms distinctive springy clumps of tangled "pom-poms" attached by a large number of scattered holdfast pads, and can also form loose mats mixed with other seaweeds. The pom-poms are made up of several cylindrical main branches with short, curved side branches that have a thorn-like appearance.

Habitat: Middle to low shore in rocky areas or exposed shores. Also reported growing on other red seaweeds and mussels.

Distribution: Scattered records from all around Britain and Ireland, especially on north coast of Ireland and south coast of Britain.

Similar Species: Could be confused with other species of red algae but the cylindrical main branches coupled with the distinctive pom-poms should help distinguish from other species.

Key Identification Features:

• Distinctive "pom-poms" with cylindrical main axes.

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

iNaturalist: Caulacanthus okamurae at iNaturalist World Species Observations database.

WoRMS: Caulacanthus okamurae at World Register of Marine Species. Accepted name: Caulacanthus okamurae Yamada, 1933. AphiaID: 496188.

Classification: Biota; Plantae; Biliphyta; Rhodophyta; Eurhodophytina; Florideophyceae; Rhodymeniophycidae; Gigartinales; Caulacanthaceae; Caulacanthus