A red seaweed (Xiphosiphonia pennata)

Distribution data supplied by the Ocean Biodiversity Information System (OBIS). To interrogate UK data visit the NBN Atlas.Map Help



Xiphosiphonia pennata is a small brownish-red seaweed up to 8 cm high, with a rigid texture. Erect thalli are flattened in one plane, with several short lateral branches and occasional long branches arranged on each side of the frond giving a triangular outline. Usually 1.5-2 mm wide and it is up to 6 mm wide when main axes are branched. It has regular alternate lateral branching on every second axial segment.

Recorded distribution in Britain and Ireland

Recorded from scattered localities in southwest Britain and Ireland.

Global distribution

British Isles to Atlantic France and Spain; Mediterranean.


Xiphosiphonia pennata prefers moderately exposed to extremely wave-sheltered sites, often with moderate to strong currents. It grows on muddy bedrock, pebbles, crustose corallines and maerl, usually growing amongst other turf-forming algae in the littoral and sublittoral.

Depth range


Identifying features

  • Brownish-red colour.
  • Rigid texture.
  • Up to 8 cm height.
  • Regular alternate branching on every second axial segment.

Additional information

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Listed by

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  1. Hardy, F.G. & Guiry, M.D., 2003. A check-list and atlas of the seaweeds of Britain and Ireland. London: British Phycological Society

  2. Hiscock, S., 1986b. A field key to the British Red Seaweeds. Taunton: Field Studies Council. [Occasional Publication No.13]

  3. JNCC (Joint Nature Conservation Committee), 1999. Marine Environment Resource Mapping And Information Database (MERMAID): Marine Nature Conservation Review Survey Database. [on-line] http://www.jncc.gov.uk/mermaid

  4. Maggs, C.A. & Hommersand, M.H., 1993. Seaweeds of the British Isles: Volume 1 Rhodophycota Part 3A Ceramiales. London: Natural History Museum, Her Majesty's Stationary Office.

  5. Picton, B.E. & Costello, M.J., 1998. BioMar biotope viewer: a guide to marine habitats, fauna and flora of Britain and Ireland. [CD-ROM] Environmental Sciences Unit, Trinity College, Dublin.


  1. NBN (National Biodiversity Network) Atlas. Available from: https://www.nbnatlas.org.

  2. OBIS (Ocean Biodiversity Information System),  2024. Global map of species distribution using gridded data. Available from: Ocean Biogeographic Information System. www.iobis.org. Accessed: 2024-07-14


This review can be cited as:

Edwards, R.V. 2003. Xiphosiphonia pennata A red seaweed. In Tyler-Walters H. and Hiscock K. Marine Life Information Network: Biology and Sensitivity Key Information Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 14-07-2024]. Available from: https://www.marlin.ac.uk/species/detail/1963

Last Updated: 31/07/2003