Square-end hornwrack (Securiflustra securifrons)

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



Securiflusta securifrons forms a compact erect branched tuft, with a leaf-like structure (frond) that ends in a distinctive lateral flat end, which looks like they have been cut by a pair of scissors. The fronds are elongated, narrow, angular, and regularly divided. The colonies are whitish to light brown in colour and are often larger than 10 cm in height. The colour appears lighter towards the end of each frond. The individual zooids are elongated, and rectangular in shape and range from 0.7 to 1.1 mm by 0.14 to 0.2 mm in size. The zooids have a lightly calcified thin body wall with an entirely membranous frontal surface and no spines. The colony is edged with several rows of narrow specialized zooids that lack a feeding polypide (kenozooids), that branch out frequently to give out new rows of zooids. The avicularium (a specialized zooid) is around a quarter of the length of the zooids and is inserted into the zooid rows. The sides of the zooids are constricted developing brood chambers (ovicells), which gives them an irregular outline. The ovicells are globular and immersed by flattened, thinly calcified processes. The embryos are dull pinkish-orange in colour.

Recorded distribution in Britain and Ireland

Recorded off all the coasts of Britain and Ireland. 

Global distribution

It is a cold, temperate, boreal species with a circumpolar distribution. Recorded mostly in the North Sea and the Gulf of Saint Lawrence, Canada. Also recorded in northern Norway, within Franz Josef Land, to the south of the Novaya Zemlya archipelago, the White Sea, and within Prudhoe Bay in Alaska and by Foxe Basin, Nunavut, Canada.


Found in the sublittoral on hard surfaces.

Depth range

Sublittoral 0-100 m (occasional records down to 600 m)

Identifying features

  • Whitish to light brown in colour.
  • Fronds end in a lateral flat end giving the appearance of being cut.  
  • Colonies larger than 10 cm in height.
  • Forms a compact erect branched tuft. 
  • Zooids are typically 0.7 to 1.1 mm by 0.14 to 0.2 mm in size. 
  • Zooids do not have spines. 
  • Embryos are dull pinkish-orange in colour. 

Additional information


Listed by

- none -


  1. Hayward, P.J. & Ryland, J.S. 1998. Cheilostomatous Bryozoa. Part 1. Aeteoidea - Cribrilinoidea. Shrewsbury: Field Studies Council. [Synopses of the British Fauna, no. 10. (2nd edition)]

  2. Porter, J., 2012. Seasearch Guide to Bryozoans and Hydroids of Britain and Ireland.   Ross-on-Wye: Marine Conservation Society.


  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: 2024-06-22


This review can be cited as:

Burdett, E.G. 2023. Securiflustra securifrons Square-end hornwrack. In Tyler-Walters H. Marine Life Information Network: Biology and Sensitivity Key Information Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 22-06-2024]. Available from: https://www.marlin.ac.uk/species/detail/2358

Last Updated: 04/10/2023