Subandine and high Andean forests are often dominated by oak trees and these are recognized as suitable phorophytes for diverse epiphyte communities. Among the latter, lichens in the upper strata appear to be understudied. Here, we report the discovery of two new species of Astrothelium (Trypetheliaceae), a diverse genus of tropical crustose lichens, both with the unusual feature of muriform, amyloid ascospores. Astrothelium mordonialensis is characterized by an olive-green thallus with solitary ascomata producing muriform and amyloid ascospores with tightened center and A. rogitamae by a light brownish to greenish grey thallus with yellow pigmented solitary ascomata, producing muriform and amyloid ascospores.