Crypthonia, a new genus of byssoid Arthoniaceae (lichenised Ascomycota)

Crypthonia with 11 species is described as belonging to the Arthoniaceae. The new genus is characterised by (1) white to pale carneous, maculiform ascomata lacking a distinct exciple, (2) a weakly gelatinised, hydrophobic hymenium of paraphysoids, (3) a discontinuous layer of branched ascogenous hyphae in the hypothecium, (4) small, clavate to broadly clavate asci of the Arthonia-type lacking a hemiamyloid ring structure in the tholus, (5) eight small, hyaline, 1-3-septate, thin-walled ascospores per ascus, (6) loosely attached thalli with a byssoid, coloured hypothallus, and (7) a chemistry of mainly beta-orcinol depsidones and tridepsides including psoromic, norstictic, and gyrophoric acids. Rugulosin occurs in C. bella and C. citrina. Crypthonia athertoniensis Frisch & G. Thor, C. bella Frisch & G. Thor, C. brevispora Frisch & G. Thor, C. citrina Frisch & G. Thor, C. olivacea Frisch & G. Thor, C. palaeotropica Frisch & G. Thor, and C. vandenboomii Frisch & G. Thor are described. C. albida (F,e) Frisch & G. Thor, C. biseptata (Aptroot & Wolseley) Frisch & G. Thor, C. mycelioides (Vain.) Frisch & G. Thor, and C. polillensis (Vain.) Frisch & G. Thor are new combinations. The delimitation from similar genera and the position within the Arthoniaceae is discussed.