Lecanoromycetes, Lecanoromycetidae, Lecanorales, Mycoblastaceae

Thallus crustose, usually grey: photobiont green, Chlorococcaceae.
Ascomata apothecia, large, conspicuous, immarginate, typically black or dark-coloured.
Proper exciple thin and soon excluded
Hymenium colourless I+ blue; epihymenium usually bright blue, sometimes vivid purple.
Hamathecium richly branched, anastomosing paraphyses.
Hypothecium hyaline to yellow-brown.
Asci cylindrical, Lecanora-type; ascospores one or two/ascus, relatively large, hyaline, usually simple.
Conidiomata pycnidia, rare (often not seen), immersed in the thallus, scattered, resembling minute, black, apothecial initials;conidia, bacilliform, 68 x 1 m.

Mycoblastus is characterised by a crustose thallus containing a green coccoid photobiont, large, conspicuous, typically black or dark-coloured, immarginate apothecia, frequently rich in colourful pigments, richly branched, anastomosing paraphyses, and lecanoralean asci, typically containing either one or two relatively large, hyaline, usually simple ascospores. The genus was accommodated within its own family, Mycoblastaceae, by Hafellner (1984) and is retained there, together with Tephromela, by Lumbsch & Huhndorf (2007).

Mycoblastus species occur mostly on organic substrata, such as bark, humus or peaty turf, in cool moist environments. The genus consists of approximately 20 species, with roughly equal representation in both hemispheres. Whereas many species are widespread in their particular hemisphere, no species are shared between Northern and Southern temperate zones.

The southern hemisphere species of the genus were revised by Kantvilas (2009), and this account is taken from that work with the kind permission of the author.