Thelotrema amazonicum

The thallus grows on bark and is light gray-green, continuous, and finely powdery (farinose), lacking a cortex. It can reach about 10 cm across and is about 30–50 μm thick. The photosynthetic partner photobiont is the green alga Trentepohlia, and the medulla is indistinct and white.^[2]

The fruiting bodies (apothecia) are sunken in the thallus (immersed) and angular to rounded, about 0.25–0.4 mm in diameter, with a pale brown disc lightly frosted with white (white-pruinose) and partly covered by the outer wall (excipulum). The apothecial margin appears "double", with a visible gap separating the inner fungal rim (proper margin) from the outer thallus-derived rim (thalline margin). A central column (columella) is absent. Each ascus contains eight colorless, oval (ellipsoid) ascospores that are divided into 10–14 cells (9–13-septate) and measure 40–50 × 7–8 μm; the spores stain violet-blue with iodine (I+ violet-blue). No secondary metabolites were detected by thin-layer chromatography (P–, K–).^[2]

The species is known from the type locality in the Department of Madre de Dios, Peru, in tropical lowland rainforest at about 270 m elevation, where it was found on tree bark in secondary forest.^[2]