P. compressa is a subtidal species found throughout boreal-arctic zone. It extends south through the Faroe Islands, Britain and the Bay of Biscay. Colonies form large irregularly branched structures that stand erect from the substrate. When alive, the colonies are pale pinkish to bright orange, with flattened branches. They commonly reach 30 – 40 mm high, although often they can exceed 90 mm.
Colonies grow through asexual budding of new zooids at the branch tips. New laminae and branches are formed through frontal budding on the proximal regions of the colony.
Colonies consist of bilaminar flattened branches, which may become rounded in later development. Zooids have a calcified body wall and are rectangular to hexagonal in shape. The orifice is frontal and approximately semi-circular. Broad lyrula (tooth-like projections of calcification) are located on the proximal edge of the orifice, occupying almost three quarters of its total width. Condyles are small and indistinct, while the oval-shaped avicularia are large. Areolae pores mark the boundary of the zooids
Colonies often exceed 90 mm in height. Zooids dimensions vary from 0.4 to0.6 by 0.2 to 0.3
A circumpolar species distributed throughout boreal arctic zone, extending south through the Faroe Islands, Britain and the Bay of Biscay. The species is thought to be absent from the Mediterranean
P. compressa most commonly grows on coarse grounds, attached to stones, large shell debris or rock. This subtidal species occurs below the kelp belt and across much of the continental shelf
The founding zooid (ancestrula) develops into a young colony, and later into an adult colony through asexual budding. Sexually produced embryos are brooded within the colony. Larvae settle after liberation and metamorphose into an ancestrula.
Like all bryozoans, P.compressa is a suspension feeder. It feeds on small phytoplankton using ciliated tentacles of the lophophore.
Sexually-produced embryos, which are pinkish orange, are brooded in hemispherical ovicells. In Europe, embryos have been observed from December to January. The larvae of P.compressa are non-feeding coronate larvae, which lack a shell and have a densely ciliated belt (the corona) for locomotion.