Schizoporella unicornis (Johnston, 1874)

Diagnostic description: 

Colony encrusting, multiserial, unilamellar or multilamellar, generally less than 5 cm in diameter. Colour normally pink or whitish pink.

Autozooids large but variable in size, length 0.387–0.715 mm (mean 0.529 mm, SD 0.0844 mm, n = 35), width 0.273–0.537 mm (mean 0.383 mm, SD 0.05914 mm, n = 35), on average about 1.4 times longer than wide, broadening before row bifurcations, generally rectangular in shape with wide, squared distal end accommodating single or paired adventitious avicularia. Frontal shield convex, covered with numerous irregularly arranged pseudopores and deep marginal areolar pores. Umbo stout, congruent with boundary between pseudoporous and non-pseudoporous frontal shield. Pseudopores have small openings not changing in size or shape during secondary calcification. Primary orifice broader than long, length (including sinus) 0.115–0.145 mm (mean 0.131 mm, SD 0.00832 mm, n = 25), width 0.143–0.186 mm (mean 0.1635 mm, SD 0.010 mm, n = 25), anter forming a wide D-shape, sinus (poster) a broad U-shape. When the operculum is removed, orifice edge adjacent to condyles runs proximally from sinus to proximolateral corners (i.e. slopes downwards). condyles prominent, fully visible above proximal edge of primary orifice, tips rounded and directed distally; viewed from within, condyles are clearly constructed from calcified oral rim.

Adventitious avicularia either single or paired, directed distolaterally from centre-line. Occasional additional adventitious avicularia developed on frontal shield proximal to primary orifice. In early ontogeny avicularia appear raised but are subsumed into frontal shield during secondary calcification. Rostrum acute with concave sides and upturned tip. Opesia rounded, D-shaped; crossbar without columella. Mandible with an acutely pointed distal tip curved upwards. Rostrum length 0.102–0.181 mm (mean 0.131 mm, SD 0.017 mm, n = 26), width of crossbar 0.056–0.083 mm (mean 0.068 mm, SD 0.0075 mm, n = 26).

Ovicells found in localized clusters or more widely distributed, prominent, round and globular, recumbent on frontal shield of distal zooid, large, 0.247–0.356 mm (mean 0.292 mm, SD 0.029 mm, n = 26) long by 0.318–0.452 mm (mean 0.372 mm, SD 0.032 mm, n = 26) wide. Ooecial surface cryptocystal, bearing radially aligned, scalloped grooves around edges; pores few in number, present only at the periphery, centre imperforate.

Tompsett et al., 2009


Schizoporella unicornis is an encrusting bryozoan that develops pink or white sheets, normally less than 5 cm in diameter. Colonies are composed of a single or multiple layers of autozooids. Autozooids are rectangular to polygonal and convex. They are large, commonly 0.4-0.7 by 0.3-0.5 mm.


Schizoporella unicornis is distributed throughout the northeast Atlantic, from northwest Africa and Spain to the Faroes and western Norway


The species is able to colonise a wide range of substrates including stones, shells, Laminaria holdfasts and the underside of the button-like thali of Himanthalia. It is commonly found on the underside of flat stones. It ranges from the lower shore to shallow sublittoral waters.


The larvae of S. unicornis 
are non-feeding coronate larvae, which lack a shell and have a
densely ciliated belt (the corona) for locomotion.

Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith