Astrothelium megeustomurale

Astrothelium megeustomurale is a species of corticolous lichen in the family Trypetheliaceae. Found in Brazil, it was formally described as a new species in 2017 by Marcela Eugenia da Silva 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 ; here it was found growing on tree bark in old-growth rainforest. The lichen has a dull olive-greenish thallus lacking a prothallus, with spherical to pear-shaped ascomata that are either immersed in or on top of the thallus surface, typically arranged in groups of 5 to 15. The pseudostromata contain lichexanthone, a secondary chemical. The ascospores number four per ascus, are muriform, and measure 95–120 by 30–33 μm. The species epithet refers to the large ascospores, the resemblance to A. eustomum, and the muriform ascospores.