Life habit: lichenized, not lichenicolous Thallus: crustose to squamulose, attached by the whole lower surface or ascending areoles/squamules: up to 1 mm diam., orbicular to elongated, entire to deeply lobate, plane to weakly convex, scattered, contiguous or overlapping, often forming isidia or lacinules (constricted apical parts of squamules); hypothallus: often well developed, first white, later becoming reddish brown in many species upper surface: pale gray to dark green, rarely brownish green, dull or shiny, epruinose or rarely pruinose, smooth margin: concolorous with upper side, often fibrillose lower surface: white, ecorticate upper cortex: 5-80 µm thick, composed of rather thin-walled, more or less anticlinally oriented hyphae with angular to round lumina, often containing lichens substances; algal layer 5-30 mm thick, horizontally continuous photobiont: primary one a chlorococcoid alga, secondary photobiont absent; algal cells 10-15 µm in diam. medulla: white, of intricately interwoven hyphae, I-, often containing lichen substances Ascomata: apothecial, biatorine, laminal, sessile, with a constricted base, up to 2(-3) mm in diam., simple or aggregated, plane and more or less distinctly marginate when young, later usually becoming moderately to strongly convex and often immarginate disc: pale to dark brown, epruinose, dull to slightly shiny Ascoma margin: concolorous with the disc or darker, often finely fibrillose exciple: annular, pale brown to dark reddish brown, composed of thick-walled, strongly conglutinated, radiating hyphae with thin, narrowly cylindrical lumina epithecium: colorless to pale brown, K- hymenium: hyaline, I+ blue, 40-60 µm high paraphyses: straight, sparingly branched and anastomosing, conglutinated, apical cell not or only slightly swollen hypothecium: pale brown to dark reddish brown, K- or K+ faintly purple, strongly conglutinated, not clearly separable from exciple, sometimes containing lichen substances, I- asci: clavate, surrounded by a gelatinous, amyloid sheet, with a well-developed, amyloid tholus containing a ±conical axial body (Bacidia-type), 8-spored ascospores: colorless, simple or rarely uniseptate, ellipsoid to fusiform, bacilliform or rarely acicular, smooth, 5-20(-55) x 2-5 µm, without a halo Conidiomata: pycnidial, immersed in the thallus or protruding, with short, sparingly branched conidiophores conidia: acrogenous, bacilliform, 5-10 x c. 1 µm Secondary metabolites: ß-orcinol depsidones (mainly argopsin, norargopsin, pannarin, phyllopsorin, and chlorophyllopsorin), dibenzofurans (furfuracein), atranorin, zeorin, and other terpenoids and unknowns, in many species no secondary metabolites detected Geography: pantropical, with an extension to oceanic, temperate parts of Europe Substrate: primarily on bark, sometimes growing on rock or over bryophytes, mainly in humid, somewhat shady tropical to subtropical (-temperate) forest. Notes: A comparison of Phyllopsora with 4 other squamulose (to subfoliose) genera (Bacidiopsora, Eschatogonia, Physcidia and Squamacidia) with Bacidia-type asci is provided in Brako (1991) and Kalb and Elix (1995). All have biatorine apothecia except Physcidia, which has partly zeorine and partly biatorine apothecia. All have thin-walled, simple to indistinctly 1 (-3)- sepate, narrow spores (2-5 µm wide), except Bacidiopsora which has thick-walled, pluriseptate spores. Some of the ß-orcinol depsidones and the dibenzofuran listed above appear to be unique to Phyllopsora. The apothecial type, which is composed of highly gelatinized hyphae with no clear distinction between the exciple and hypothecium, is characteristic to the core of Phyllopsora species and also occur in Eschatogonia. Eschatogonia has a characteristic cortex formed by a single layer of rounded or cuboid cells with a thick cell wall; the cortex covers both the upper and lower sides of the squamule and is continuous over the margin. The 4 other genera are all tropical, and have thus far not been reported in the Sonoran region. Collections of Phyllopsora of rock have been made by J. Hafellner in Chihuahua (near the base of Cascada de Basaseachic) and just across the border of Sonora under a large boulder in a moist, forested gully. Unfortunately the specimens have been misplaced and were not available for investigation at the time of this publication. Brako (1991) lists the following species for Mexico: P. buettneri (Müll. Arg.) Zahlbr., P. corallina (Eschw.) Müll. Arg., P. furfuracea (Pers.) Zahlbr., P. glabella (Nyl.) G. Schneider and P. parvifolia (Pers.) Müll. Arg.. Whether the collections belong to one or more of these species or a different taxon is thus impossible to assess currently.