Lecanactis is a genus of crustose lichens, commonly called old wood lichens. The mycobiont (fungus partner) is in the family Roccellaceae. The photobiont is an algae in the genus Trentepohlia. These lichens typically grow as thin crusts on tree bark or rocks, producing small black fruiting bodies that may appear as round discs or elongated slits. The genus contains about 40 species found worldwide, with some species considered rare and threatened by habitat loss.

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