Abstract
A taxonomic and biogeographic overview of the genus Myrionora is provided. Two species are recognized, M. albidula (Willey) R.
C. Harris and M. pseudocyphellariae (Etayo) S.
Ekman & Palice comb. nov. The genus is characterized by polysporous asci, the presence of crystals in the hymenium and proper exciple that partly consist of lobaric acid, and a photobiont with large cells (mostly in the range 12-20 mu m).
Myrionora albidula is currently known from Germany, Norway, Sweden, the Russian Federation (Altayskiy Kray, Chelyabinskaya Oblast', Khabarovskiy Kray and Zabaykal'skiy Kray), and the United States (Alaska, Connecticut, Maine and Massachusetts). It inhabits bark of deciduous trees and shrubs and conifers over a wide range of latitudes.
Myrionora pseudocyphellariae is known from Chile and Ecuador, where it has been encountered on lichens and decaying bark. Based on morphological characteristics, we conclude that Myrionora belongs in the Ramalinaceae.