Gyrotrema papillatum is a little-known species of corticolous (bark-dwelling), crustose lichen in the family Harpidiaceae. It is known from a single collection in a lowland rainforest region of Costa Rica.
Gyrotrema papillatum was described as new to science in 2011 by the German lichenologist Robert Lücking. The type specimen of this lichen was collected by the author in Costa Rica, in the Los Patos section of Corcovado National Park (Puntarenas Province). This location is part of the Osa Conservation Area on the Osa Peninsula, situated approximately southeast of San José and west-southwest of Golfito; there, in a lowland rainforest zone, at an elevation between, it was found growing on the bark of a partially shaded lower tree trunk. At the time of its original publication, the lichen was only known from the type locality. It species epithet alludes to the nature of its thallus (i.e., covered with papillae, which are small, conically rounded growths).
Gyrotrema papillatum has a grey-green to olive-green thallus adorned with numerous white . The cortex is –made of a dense, tightly interwoven layer of fungal hyphae. The and the medulla beneath often contain clusters of calcium oxalate crystals. The apothecia of G. papillatum are prominent, with a rounded to shape, measuring 1–1.5 mm in diameter. The exposed of the apothecia is a cinnabar-red colour. Around this disc, the margin is to and fused, sharing the same cinnabar-red hue on the inside. This species lacks a, but instead has concentric rings of tissue that separate rings of old hymenia. The youngest hymenium ring is situated closest to the margin. The excipulum is prosoplectenchymatous and, and lacks . The hymenium stands 80–100 μm high, and the are unbranched.
Each ascus contains eight that have between 5 and 9 septa (internal partitions), measuring 25–30 by 6–8 μm. These ellipsoid spores have thick septa and lens-shaped, are colourless, and has a violet-blue reaction when treated with iodine (amyloid reaction). The apothecial disc contains an unidentified type of anthraquinone substance.