A lichen with a light grey-green, mostly immersed thallus and black perithecia. The species is macroscopically very similar to Acrocordia gemmata but has different anatomy. Lithothelium phaeosporum may be also mistaken for the non-lichenized fungus Requienella fraxini which, however, differs in perithecia with a beak-shaped protrusion around ostiolum.
The lichen grows on rough bark of deciduous trees (often on ash trees) in lowland forests with humid mesoclimate (such as scree and floodplain forests). In Europe, it has been reported only from a few countries so far. In the Czech Republic, it was repeatedly recorded at the confluence of the Morava and Dyje rivers in South Moravia and in the Křivoklát region (Týřov).taxonomic classification:
All records: 5, confirmed 5. One click on a selected square displays particular record(s), including their source(s).