This rather conspicuous lichen is very similar to the better-known P. hypnorum. It differs in a chestnut brown thallus, lacerate apothecium margins without squamules, perispore with small warts and the presence of porphyrillic acid methyl ester and pannaric acid in the thallus. Phylogenetically, it is related to the arctic-alpine P. tenue (Elvebakk 2012).
The species grows on slightly acidic to calcareous soil in open habitats, such as heathlands, road banks, open forests and their edges. Its distribution area is little known; it has only been recorded in several European countries and Turkey. However, the latest European collection is dated 1945 (Elvebakk 2022). All its localities lie at lower altitudes of quite dry regions. In the Czech Republic, it was confirmed in a single locality near Třebíč, where it was collected and published as exsiccate by J. Suza. Possibly some of the records of P. hypnorum f. campestre from Silesia (Stein 1879) refer to P. femsjonense and the area of the Czech Republic. Interestingly, J. Suza collected P. hypnorum near Třebíč as well (Elvebakk 2022).
The species was long considered a synonym of P. hypnorum, from which it is distinguished by various characters and partly by its ecology, too. In northern Europe, it used to be distinguished as a variety campestris (Elvebakk 2012). Its resurrection at the species level was recently done by Elvebakk (2022).
Literature: Elvebakk A. (2012): An overlooked Psoroma in Denmark and southern parts of Sweden. – Graphis Scripta 24: 45–48. Stein B. (1879): Flechten. – In: Cohn F. (ed.), Kryptogamen-Flora von Schlesien, 2(2): 1–400, J. U. Kern’s Verlag, Breslau. Elvebakk A. (2022): Psoroma femsjonense (Fr.) Trevis., a misunderstood species possibly extinct from Europe. – Graphis Scripta 34: 22–35.taxonomic classification:
Ascomycota → Lecanoromycetes → Peltigerales → Pannariaceae → Psoroma
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