Description: Thallus attached by prostrate axes giving rise to erect delicate filamentous axes to 2 cm long. Branched in opposite pairs, each pair at right angles to the previous pair. Final branchlets alternate or secund. Usually without gland cells.

Habitat: Relatively common. Epiphytic or epilithic from low littoral to 26 m depth.

Distribution: Widely distributed on the south-west coasts of Britain and Ireland and including the Isle of Man. Europe: France and Sweden. Atlantic coast of North America: North Carolina.

Similar Species: Other Antithamnion species.

Key Identification Features:

• Paired branches at right angles to the branches below. Final branches alternate or secund.

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

iNaturalist: Antithamnion villosum at iNaturalist World Species Observations database.

WoRMS: Antithamnion villosum at World Register of Marine Species.