Synonyms: Callopisma fallax Bagl.; Caloplaca conversa var. fallax (Bagl.) Wunder; Caloplaca fallax (Bagl.) Jatta; Caloplaca oreadum (Stizenb.) Jatta; Pisutiella conversa (Kremp.) S. Y. Kondr., L. Lőkös & E. Farkas; Placodium conversum (Kremp.) Anzi
Distribution: N - Frl (TSB 2795), TAA, Lomb, Piem, VA (Piervittori & Isocrono 1999, Isocrono & al. 2008, Favero-Longo & Piervittori 2009, Matteucci & al. 2015c), Emil (Fariselli & al. 2020), Lig. C - Sar (Rizzi & al. 2011, Giordani & al. 2013). S - Cal (Herb. Vondrák 10812), Si.
Description: Thallus crustose, mostly thinly episubstratic, continuous to usually rimose-areolate, pale to dark grey or brown, usually without a distinct prothallus. Apothecia immersed to adnate, 0.2-0.6(-0.7) mm across, with a yellow-orange to dark brown, sometimes black, flat, epruinose disc, and a persistent proper margin. Thalline exciple filled by algae at least at the base, ecorticate throughout; proper exciple grey-brown in outer part, paraplectenchymatous, K+ violet, N+ red; epithecium brownish orange or grey, the epipsamma K+ red (K- in speciments without anthraquinones), the upper part of paraphyses K+ violet, C+ violet or K-, C-; hymenium colourless, 60-90 µm tall; paraphyses slightly branched in upper part, the uppermost cells slightly swollen; hypothecium colourless to brownish. Asci 8-spored, cylindrical-clavate, Teloschistes-type. Ascospores 1-septate, polarilocular, hyaline, ellipsoid, 10-14.5 x (4-)6-9 µm, the septum 4-8.5 µm thick. Spot tests: thallus K- or K+ violet, C- or C+ violet, KC-, P-; apothecial margin and epithecium K+ violet, C+ violet or K-, C-; epipsamma K+ purple or K- in specimens without anthraquinones. Chemistry: apothecia and sometimes thallus with the Sedifolia-grey pigment (blackened parts); apothecia with or without anthraquinones.
Note: a mild-temperate to subtropical-montane lichen found on calciferous or basic siliceous rocks (especially basalt) in sunny sites with short periods of water seepage, often on colonies of cyanobacteria. An earlier record from Venezia Giulia (Nimis 1993: 162) has been excluded, being far from the Italian border. According to Vondrák (in litt.) the species, which is related to C. conglomerata, is heterogeneous, and more species are involved, some of them fully lacking anthraquinones. It does not belong to Caloplaca s.str.
Growth form: Crustose
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly sexual
On otherwise dry surfaces with short periods of water seepage after rain