Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2007. Lichen Flora of the Greater Sonoran Desert Region. Vol 3.
Thallus: crustose, effuse, up to 10 cm wide and up to 0.8 mm thick, epixylic, warted-areolate or granular-areolate areoles: up to 1 mm wide but warts or granules 0.1-0.4 mm wide, irregularly rounded but sometimes with incised margins and constricted bases, rarely hollow centrally, often coalescing into a crust with an uneven upper surface, lacking a cortex or epinecral layer surface: light to moderately yellowish brown, or light to dark grayish brown, dull, epruinose but with crystals forming a layer up to 80 µm thick, turning somewhat greenish gray when wet medulla: not developed; algal layer: continuous, up to c. 140 µm thick Apothecia: abundant, 0.2-0.5(-0.6) mm wide, rounded to somewhat irregular, rarely with a flexuose margin, mostly single, sometimes crowded or in small groups, broadly adnate to sessile, sometimes constricted at base, often uneven disc: pale to dark reddish brown, plane or slightly convex, epruinose margin: persistently rather thick, 0.05-0.2 mm wide, mostly verruculose to crenulate, clearly raised, concolorous with the thallus, slightly shiny amphithecium: ecorticate, with algal cells (5-17 µm in diam.) filling almost the entire margin, hyphae intricate with fine, dispersed, with hyaline to yellowish granules, laterally 50-200 µm wide, basally up to 100 µm thick but often irregular to confluent with the thallus below parathecium: not developed or thin and up to 10 µm wide, filled with fine hyaline to pale yellow granules epihymenium: yellowish brown to reddish brown, with pale yellowish granules, K-, N- hymenium: hyaline, 40-60 µm tall, with amorphous brownish orange granules; paraphyses: numerous, densely septate, branched, occasionally anastomosing especially at base, immersed within a gelatinous matrix, K/I-; cells: 2.5-5 x 2.5-3.5 µm, not or rarely slightly widened at the apices up to 4 µm wide, hyaline or yellowish brown to rarely with an internally olive black apical cap, K-, N-, K/I- hypothecium: colorless, up to 100 µm thick, with unoriented hyphae asci: oblong-clavate, 30-40 x 9-12 µm, Lecanora-type, 8-spored ascospores: hyaline, simple or sometimes 1-septate, ellipsoid to ovoid, sometimes slightly curved, 9-11 x (2.5-)3-4.5 µm Pycnidia: abundant, present on most thallus warts, 100-200(-250) µm in diam., 100-180 µm high, at the top pale to dark brown, hyaline below, somewhat raised on thallus warts conidia: 4.5-6 x (1.5-)2-2.5 µm, narrowly oblong-ellipsoid to sometimes ovoid, straight to rarely slightly curved, sometimes extruding as white blobs Spot tests: thallus K-, C-, KC-, P- Secondary metabolites: isousnic acid (major), 7-O-methylnorascomatic acid (minor), atranorin trace) and usnic acid (trace). Substrate and ecology: on dead wood of a fence post, accompanied by Cyphelium tigillare; only known from the type locality in Mexico in the Sierra Madre Occidental Mountains above 2000 m World and Sonora distribution: western Chihuahua. Notes: Lecanora crassithallina is easily mistaken for L. albellula, L. coniferarum or L. saligna (see Vol. II). However, the very conspicuous thallus of L. crassithallina is thicker and more warted, and the margin of the apothecia more strongly developed. At least in comparison with L. coniferarum, the ascospores are narrower. The conspicuous gelatinous matrix of L. crassithallina, in which the paraphyses are bound, is not observed in other species of the L. saligna group. The chemistries of L. albellula, L. conifer-arum and L. saligna are all different from the chemistry of L. crassithallina: L. albellula and L.coniferarum contain isousnic and usnic acids and L. saligna contains isousnic acid only. Two compounds in the new species, atranorin and 7-O-methylnorascomatic acid are not reported for any other species of the L. saligna group from the Sonoran area. An important character of Lecanora crassithallina is the occurrence of many macropycnidia, present in most of the thallus granules which are ±raised and thus easily observed. However, macropycnidia in L. saligna are also very common, but its macroconidia are longer than those in L. crassithallina.