Thallus: crustose, bullate to verrucose-areolate; prothallus: not visible areoles: bullate, thick, opaque, ecorticate surface: yellowish gray to yellowish white, smooth, shiny, epruinose, with a distinct margin, sorediate soralia: greenish gray-black to very dark blue-green, round and discrete to elongate and edging the areoles, excavate to level, 0.5 soredia: granular, 35-50 µm in diam., K+ green Apothecia: not seen in North American material but rare in European material, sessile or slightly constricted at the base, 0.8-1.5 mm in diam., lecanorine disc: dark red-brown or grayish brown to almost strongly brown, plane, epruinose margin: concolorous with the thallus, thick, persistent, prominent, +flexuous, smooth, entire or verrucose or verruculose, without a parathecial ring amphithecium: present, with numerous algal cells, with large crystals insoluble in K, corticate; cortex: hyaline or pale yellow, distinct, uniform, inspersed, (20-)37-35(-40) µm thick parathecium: hyaline, lacking crystals epihymenium: orange-brown to yellow-brown, turning olivaceous in K, with crystals dissolving in K hymenium: hyaline; paraphyses: slightly thickened apically, pigmented, up to asci: clavate, 8-spored ascospores: hyaline, simple, broadly ellipsoid to ellipsoid, 9.5-15 x 5-7.5 µm; wall: more than 1 µm thick Pycnidia: not seen Spot tests: K+ yellow, C-, KC-, P+ pale yellow Secondary metabolites: atranorin (major), chloroatranorin (minor), gangaleoidin (major or minor), norgangaleoidin (traces), and roccellic acid. Substrate and ecology: on exposed siliceous rocks World distribution: western Europe and southwestern North America Sonoran distribution: Chihuahua. Notes: Lecanora pannonica is a very distinctive species that is hardly confused with any other Lecanora spp. in the study area, due to its bullate thallus and dark colored soralia. Lecanora pannonica may be similar to some sorediate Tephromela spp., such as T. grumosa or T. pertusarioides. However, these taxa are readily distinguished by a different chemistry: T. grumosa contains lichesterinic acid as major constituent in addition to atranorin and has coalescing soralia, while T. pertusarioides contains α-collatolic acid. This is the first record of L. pannonica outside of Europe.