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

Astrothelium sexloculatum is a species of corticolous (bark-dwelling), crustose lichen in the family Trypetheliaceae.^[1] Found in Guyana and Papua New Guinea, it was formally described as a new species in 2016 by Dutch lichenologist André Aptroot. The type specimen was collected by Harrie Sipman on the Dadadanawa ranch (Rupununi savannah, Upper Takutu-Upper Essequibo, Guyana) at an altitude of 120 m (390 ft); there, it was found growing on smooth tree bark in a savanna. The lichen has a smooth and somewhat shiny, pale yellowish-grey thallus with a cortex and a thin (up to 0.1 mm wide) black prothallus line. It covers areas of up to 9 cm (3.5 in) in diameter. Both the thallus and the pseudostromata contain lichexanthone, a lichen product that causes these structures to fluoresce yellow when lit with a long-wavelength UV light.^[2] The combination of characteristics of the lichen that distinguish it from others in Astrothelium are the indistinctly pseudostromatic ascomata, with erumpent to prominent pseudostromata that are covered by thallus.^[3] The species epithet sexloculatum refers to the ascospores, which are divided into six chambers (locules) by five transverse septa.^[2]

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