Description: Formerly in Catapyrenium, the thallus of this species consists of heaps of large, leathery, overlapping, pale to dark brown, crowded squamules, some to 10mm diam. The edges of the squamules are dotted with pycnidia (containing the conidia). It grows on dry calcareous rocks and soil. P. lachneum has narrower spores (6-8&

371;m against 7.5-9.5&

371;m) and larger conidia (5-7&

371;m long compared with 3-5&

371;m in P. rufescens). In Ireland, it is known from the west coast of Counties Mayo and Sligo.

Key Identification Features:

• Large leathery brown to dark red-brown squamules low down on limestone rock ledges, soil or sand; spores broad, conidia large
• On dry, calcareous rocks and rocks protruding through blown sand.

Original text submitted by Vince J. Giavarini

Distribution Map from NBN: Placidium rufescens at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Placidium rufescens at iNaturalist World Species Observations database.