Astrothelium lucidomedullatum
Scientific classification
Domain:	Eukaryota
Kingdom:	Fungi
Division:	Ascomycota
Class:	Dothideomycetes
Order:	Trypetheliales
Family:	Trypetheliaceae
Genus:	Astrothelium
Species:	A. lucidomedullatum
Binomial name
Astrothelium lucidomedullatum Aptroot (2016)

Astrothelium lucidomedullatum is a species of corticolous (bark-dwelling), crustose lichen in the family Trypetheliaceae.^[1] Found in Ecuador, it was formally described as a new species in 2016 by Dutch lichenologist André Aptroot. The type specimen was collected by Harrie Sipman from the Reserva Biológica San Francisco (Cordillera Numbala, Zamora-Chinchipe) at an altitude of 2,025 m (6,644 ft); there, it was found in a rainforest growing on smooth bark. The lichen has a quite smooth and shiny, pale ochraceous-green thallus with a cortex but lacking a prothallus, covering areas of up to 5 cm (2 in) in diameter. The medulla contains lichexanthone, a lichen product that causes its tissue to fluoresce when lit with a long-wavelength UV light.^[2] The main characteristics of the lichen distinguishing it from others in Astrothelium are its ascospores, which number four per ascus and have dimensions of 80–115 by 25–35 μm; the presence of lichexanthone in the medulla; and the structure of the immersed ascomata, which have separate ostioles and are covered by the thallus.^[3]

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