The areoles of R. timdalii are small, brown to greyish and convex. The prothallus is black and well-developed. The apothecia are black, convex when old and scattered. It produces hyaline ellipsoid muriform spores. The epithecium is green-blue and gives a red reaction with nitric acid. No secondary metabolites have been found in the thallus, except an unidentified fatty acid, which was present in about half of Scandinavian specimens (Ihlen & Fryday 2002).
The species grows on silicates, preferring humid sites, e. g., in oceanic areas, lake surroundings or screes with a persisting snow cover. It is rare and scarcely recorded. It is more common in Scandinavia and Great Britain (Ihlen & Fryday 2002). The lichen is not known in the Alps and is one of the rarest Rhizocarpon species in central Europe. In the Czech Republic, it has been found on siliceous screes in the Novohradské hory Mts and Brdy Hills.
Literature: Ihlen P. G. & Fryday A. M. (2002): Rhizocarpon timdalii, a new lichen species from north-west Europe and north-east North America. – Lichenologist 34: 95–100. Malíček J., Palice Z. & Vondrák J. (2014): New lichen records and rediscoveries from the Czech Republic and Slovakia. – Herzogia 27: 257–284.taxonomic classification:
All records: 2, confirmed 2. One click on a selected square displays particular record(s), including their source(s).