Life habit: lichenized, lichenicolous Thallus: squamulose, attached by the whole lower surface or basal end of squamule squamules: adnate and dispersed when young, later becoming ascending and imbricate, up to 2 (-3) mm wide, plane to concave, rounded to elongate, lacking vegetative dispersal units upper surface: dark olivaceous brown, slightly shiny, epruinose, smooth upper cortex: 30-50 µm thick, containing remnants of algae (chlor-zinc-iodine!), not containing crystals, consisting of a thin upper epinecral layer and a thicker lower stainable layer; stainable layer containing a brown pigment zone in the upper part, composed of rather thin-walled, anticlinally oriented hyphae with rounded lumina; algal layer: 50-100 µm thick, horizontally continuous margin: entire or lobed, often slightly raised, dark brown to black medulla: thin or sometimes absent, white, of intricately interwoven hyphae, I-, not containing lichen substances or calcium oxalate photobiont: primary one a chlorococcoid, secondary photobiont absent, but occurring on Spilonema revertens, a cyanolichen often thought to be a free-living cyanobacterium; algal cells: 10-15 µm diam. lower cortex: 20-40 µm thick, greenish black, often mixed with dark brown pigment, composed of anticlinally to periclinally oriented thick-walled hyphae with narrow lumina, not containing calcium oxalate lower surface: dark green or brown to black Ascomata: apothecial, marginal, sessile, with a constricted base, up to 1 mm diam., black, slightly shiny, epruinose, simple or more rarely a few agglomerated, plane to weakly convex, with a narrow and often disappearing margin; exciple: annular, not continuous with upper cortex, greenish black in the rim, dark reddish brown in inner part, composed of thick-walled, strongly conglutinated, radiating hyphae with shortly cylindrical to rounded lumina; hypothecium: dark reddish brown, composed of strongly conglutinated hyphae, lacking crystals, I-; epithecium: dark green, often with a brown tinge, not containing crystals, K-; hymenium: hyaline to faintly green, I+ blue, 60-80 µm high; paraphyses: straight, sparingly branched and anastomosing, strongly conglutinated, apical cell not or only slightly swollen asci: clavate, with a well developed, amyloid tholus containing a deeper amyloid tube and lacking an ocular chamber (Porpidia-type), 8-spored ascospores: colorless, simple, ellipsoid, smooth, without halo, 9-12 x 5-7 µm Conidiomata: pycnidial, marginal, sessile, black, with a dark green to brown wall and short-celled, intricately branched conidiophores conidia: pleurogenous, narrowly ellipsoid, 3-5 x c. 1.5 µm Spot tests: all negative Secondary metabolites: none. Substrate and ecology: on a filamentous cyanolichen (Spilonema revertens) over acidic rock in open habitats, up to 2350 m alt. World distribution: widely distributed in arid and semi-arid areas in the temperate region in the northern hemisphere Sonoran distribution: rather common in Arizona, Baja California, Baja California Sur, Chihuahua and Sonora; not known from southern California. Notes: Psorula rufonigra is morphologically rather similar to Toninia submexicana de Lesd., but differs in anatomical feature of the apothecia, including the spores. Psorula rufonigra is associated with the cyanolichen Spilonema revertens and the Toninia usually grows independently.