Thallus: thin to thick, superficial, membranous, rimose to deeply cracked-areolate upper surface: yellow-gray to pink or red-brown, fading to pale gray or gray in the herbarium; smooth to uneven-warted prothallus: absent Perithecia: dispersed; ostiole dark-brown; involucrellum: absent; exciple: colorless below, brownish above; hamathecium: composed of persistent paraphyses, richly branched and anastomosed; periphysoids towards the inner side of the ostiole; periphyses absent asci: cylindrical, 4- to 8-spored ascospores: colorless, rarely becoming pale yellow-brown when overmature, muriform, with 7-9 lateral and 2-3 longitudinal septa, ellipsoid to narrowly ellipsoid, 25-42 x 11-17 µm Pycnidia: immersed conidia: filiform, colorless, 11-14 x 0.6-0.8 µm Spot tests: all negative Secondary metabolites: none detected. Substrate and ecology: bark (on smooth bark of Quercus agrifolia and Juglans californica in southern California) World distribution: temperate and mediterranean Europe, mediterranean northern Africa, North America and Australia Sonoran distribution: San Gabriel Mountains and the Santa Monica Range in southern California. Notes: This species is characterized by its rimose to deeply cracked-areolate, yellow-gray to pink or red-brown thallus and muriform colorless ascospores. Thelenella hassei is distinguished by its brown ascospores.