Astrothelium gyalostiolatum

Astrothelium gyalostiolatum is a species of corticolous (bark-dwelling) crustose lichen in the family Trypetheliaceae. Found in Brazil, it was described in 2022 by the Dutch lichenologist André Aptroot. It belongs to the genus Astrothelium, sharing similarities with Astrothelium bicolor but uniquely characterized by the presence of lichexanthone exclusively around the ostioles.

Description
The lichen has a dull, dirty ochraceous gray thallus, covering up to 15 cm in diameter. The thallus resembles resin in texture and is bordered by a black prothallus line. It produces ascomata, which are immersed in groups within, and bears hyaline, with three septa (internal partitions). The unique chemical signature is the UV+ (yellow) reaction of its ostioles, indicating the presence of lichexanthone.

Habitat and distribution
Exclusive to Brazil's Mato Grosso region, A. gyalostiolatum grows on tree bark in primary rainforests.