Thelocarpon citrum (Wallr.) Rossman

Syn.: Sphaeria citrum Wallr., Thelocarpon arenicola Vain., Thelocarpon herteri J. Lahm, Thelocarpon vicinellum Nyl.
Lichenised.
Substrate: siliceous rocks
Altitudinal range: from the montane belt (potential vegetation: deciduous forests dominated by Fagus sylvatica and closed coniferous forests with Picea abies) to the subalpine belt (potential vegetation: open, taiga-like forests dominated by Larix decidua and/or Pinus cembra and Rhododendron)
Note: an ephemeral species of disturbed habitats, with optimum near treeline; so far only reported from the Eastern Alps (Austria, Italy).
Austria: Niederösterreich (incl. Wien); Italy: Trentino Alto Adige;