Haplopoma impressum is distributed southwards from the west of Scotland. It is not known from the north-east. Outside of the UK, the species is known from the Mediterranean.
Haplopoma impressum is an encrusting bryozoan. Colonies typically form small patches with a glass-like appearance. Autozooids are hexagonal to oval and often taper proximally. They are 0.5-0.55 by 0.3-0.35 mm.
The species is most commonly found on red algae in shallow water just offshore. It may also colonise Posidonia seagrass.
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