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

Astrothelium megatropicum is a species of corticolous (bark-dwelling), crustose lichen in the family Trypetheliaceae.^[1] Found in Guyana, it was formally described as a new species in 2016 by Dutch lichenologist André Aptroot. The type specimen was collected by Harrie Sipman near Paramakatoi village (Potaro-Siparuni region) at an altitude of 800 metres (2,600 ft); there, it was found growing on smooth tree bark. The lichen has a smooth and somewhat shiny, pale ochraceous-green thallus with a cortex and a thin (about 0.1 mm wide) black prothallus line. It covers areas of up to 7 cm (2.8 in) in diameter. The presence of the lichen does not induce the formation of galls in the host plant. No lichen products were detected from collected specimens using thin-layer chromatography.^[2] The combination of characteristics of the lichen that distinguish it from others in Astrothelium are its uneven to verrucose thallus; its confluent ascomata, which are erumpent to prominent and exposed, with gently to steeply sloping sides; and the dimensions of its ascospores (100–120 by 30–35 μm).^[3] The spores, which have three septa and diamond-shaped cavities, are the longest 3-septate ascospores in the Trypetheliaceae.^[2]

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