Arthopyrenia is a genus of fungi in the family Trypetheliaceae. It was formerly classified in the eponymic family Arthopyreniaceae, but molecular phylogenetics studies showed that the type species, Arthopyrenia cerasi, was a member of the Trypetheliaceae. Arthopyrenia fungi typically form inconspicuous films embedded within tree bark and produce tiny, flask-shaped fruiting bodies covered by dark, shield-like caps. The genus includes both lichen-forming species (those that partner with algae) and non-lichenized species, with about 100 currently recognized species found primarily on bark and wood substrates.

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