Pyrenomyxa Morgan, J. Cincinnati Soc. Nat. Hist. 18: 42 (1895)
MycoBank number: MB 22327; Index Fungorum number: IF 22327; Facesoffungi number: FoF 03000; 3 morphological species (Species Fungorum 2020), 2 species with sequence data.
Type species – Pyrenomyxa invocans Morgan
Notes – Stromata of Pyrenomyxa are similar too species of the H. rubiginosum complex when collected in the field, but their ascal morphology is different, since they feature subglobose asci in which phaseoliform, laterally compressed ascospores are arranged in a similar manner to the slices of an orange fruit. The ascospores are not forcibly discharged as in most other Hypoxylaceae genera aside from Phylacia, Rhopalostroma and Thamnomyces, but they are released from the mature stromata in powdery masses.
A comparison of morphological features and secondary metabolite profiles of Pyrenomyxa invocans, Hypoxylon piceum and Pulveria porrecta were evaluated by Stadler et al. (2005) and it was concluded that they are congeneric with Pyrenomyxa which is the older name and takes preference. The molecular data and the secondary metabolite profiles (rubginosins and hypomiltins as prevailing stromatal metabolites) clearly suggest that this genus has affinities with Hypoxylon.