Astrothelium dimidioinspersum is a species of corticolous (bark-dwelling) lichen in the family Trypetheliaceae. Found in Brazil, it was formally described as a new species in 2017 by Marcela Cáceres and André Aptroot. The type specimen was collected by the authors along a trail near a field station in the Adolfo Ducke Forest Reserve (Manaus); there it was found growing on tree bark in old-growth rainforest. It has a dull, pale greenish thallus lacking a , and spherical to pear-shaped ascomata immersed in and on the thallus. Ascospores number two per ascus, are (divided into regular chambers), and measure 155âÂÂ170 by 30âÂÂ40 üm. The species epithet refers to the characteristic that occurs in the upper half of the . The lichen lacks any secondary chemicals detectable with thin-layer chromatography.