Abstract
The lichenized fungus Verrucaria hunsrueckensis (Verrucariaceae, Ascomycota) is described and distinguished from similar lichens by ascospores with an exceptionally large length to width ratio, brown and small exciple, distinct involucrellum, goniocyst-like thallus structure, growth on acidic siliceous rocks and characteristic motives in sequences of the nuclear ribosomal internal transcribed spacer region. The new species is known from only one site in the Hunsrück-Hochwald National Park (Rhineland Palatinate, Germany), where it grows on quartzitic rocks in half shaded situations at the margin of rock screes in an old growth forest. Its discovery supports the view that within the Verrucariaceae some well recognizable species may be naturally rare and their sites worthy of protection.