Arthopyrenia analepta (Ach.) A. Massal., a non-lichenized fungus, rediscovered in Flanders after more than 150 years but threatened already. This species has recently been found for the second time in Flanders after more than 150 years. It was discovered on February 22, 2020 on Quercus in a former clay pit at Rumst (Terhagen, province of Antwerp, Belgium). Morphology, ecology, habitat and distribution of the species are described.