Thalloidima sedifolium (Scop.) Kistenich, Timdal, Bendiksby & S. Ekman

Thalloidima sedifolium thallus consists of convex to irregularly lobed, olive-green, grey or brown squamules. The thalli and apothecia are very variable in the extent of their pruinosity. It is difficult to distinguish from T. opuntioides and T. physaroides in the field. In many cases, the distinction can only be made based on the analysis secondary metabolites by TLC or by studying microscopic characters.

The species grows on calcareous soil and rock, often associated with bryophytes or cyanolichens, especially when young. It occurs in cracks of sun-exposed natural rocks, but also on early successional soils developing after, e.g., limestone mining. It can be found from lowlands to high mountains. In Europe and in the Czech Republic, it is the most abundant species of Toninia sensu lato. The lichen is distributed all over the continent, in the Czech Republic mainly in karst areas but also known from calcareous insertions in volcanic rocks.

Ascomycota → Lecanoromycetes → Lecanorales → Ramalinaceae → Thalloidima