Thelidium decussatum (Kremp.) Zschacke

Syn.: Acrocordia decussata Kremp., Involucrothele decussata (Kremp.) Servít
Lichenised. Poorly known taxon.
Substrate: calciferous rocks
Altitudinal range: from the submediterranean/colline belt (potential vegetation: mixed deciduous forests dominated by Quercus and Carpinus) to the montane belt (potential vegetation: deciduous forests dominated by Fagus sylvatica and closed coniferous forests with Picea abies)
Note: a species of the Th. pyrenophorum-group with a thin, greyish thallus surrounded and crossed by black lines, somewhat protruding ascomata (less than 0.5 mm in diam.) with an involucrellum reaching down c. half the perithecium, and 1-septate ascospores (less than 30 µm long); on sandstone or calcareous rocks, ecology otherwise poorly known; rare in Central Europe, including the Eastern Alps (Austria).
Austria: Steiermark;