Hyphal strands: superficial, dark brown, spreading over the host thallus and rarely also on the apothecial discs; strands 1-cell wide, septate, ramified to net-like, hyphae connecting also the ascomata, slightly constricted at the septa, hyphal cells 6-10 x 4-7 µm, surface coarsely ornamented with punctiform elements, less than 1 µm wide, sometimes with short longitudinal rows, additional deeper cracks sometimes present Ascomata: superficial, dark brown to black, scattered, subglobose or ellipsoid, rough but without setae, 60-100 wide and 30-45 tall, opening apically with +round to irregular ruptures internal structure: wall of the external cells: dark brown, with a granular pigment, hyaline in the internal ones, cells 3-6 µm in diam. centrum: usually I+ orange-red, K/I+ blue asci: broadly clavate to subglobose, 15-20 x 12-15 µm, 8-spored; wall: K/I+ bluish around the apex of the ocular chamber but this reaction difficult to see in mature asci ascospores: hyaline, sometimes becoming brown with age, 1-septate, narrowly obovate, halonate, 8-11 x 3-5 µm. Hosts: on the thallus and rarely on the apothecia of Xanthoparmelia spp. World distribution: all continents except Antarctica Sonoran distribution: Arizona, California, and Baja California. Notes: Lichenostigma cosmopolites has frequently been misinterpreted as Echinothecium reticulatum, the ascomata of which are provided with septate seta-like hyphae, and that seems to be restricted to Parmelia s. str. Lichenostigma cosmopolites ascomata are rough but lack seta-like hyphae, and the species is well characterized by its ramified to net-like, single stranded hyphal strands spreading over the thallus (rarely on the apothecia) of Xanthoparmelia species. Also distinctive features are its hyaline and relatively small ascospores, and usually I+ orange-red centrum.