The thallus of R. ferax consists of yellow areoles regularly scattered on a black prothallus. They usually have a half-moon shape and embrace the black apothecia with a proper margin.
The species usually grows on acidic and hard siliceous rocks in montane and alpine habitats. It prefers the microclimate of rock overhangs and exposed vertical surfaces. The thalli are usually small, only about 1 cm. Sometimes, mainly under rock overhangs, the thalli are quite close to each other giving the impression of a larger continuous crust. In the Czech Republic, it has been recorded in Obří důl in the Krkonoše Mts and in the glacial cirques of Plešné jezero and Černé jezero in the Šumava Mts.
Literature: Bouda F. (2017): Nové druhy žluté skupiny rodu Rhizocarpon v České republice. – Bryonora 59: 24–29.taxonomic classification: most frequented synonyms:Rhizocarpon drepanodes
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