Thallus: moderately to somewhat loosely adnate, appressed, foliose, up to 8.5 cm diam., lobate lobes: short and rounded or somewhat elongate and sublinear, ± contiguous or imbricate, (0.5-) 1-2 mm broad, ± flat upper surface: olive- to yellowish brown or dark brown, smooth near the periphery, inward becoming moderately fissured or fissured-rugose, occasionally somewhat warted; dull throughout or slightly shiny on the lobe ends lower surface: pale tan to pale brown; ± smooth and dull; moderately rhizinate, the rhizines concolorous with the lower surface or darkening Apothecia: common, up to 3 mm diam., sometimes rather crowded inward, sessile, flat to concave or sometimes irregularly convex; the margin entire to somewhat crenulate asci: clavate, 8-spored ascospores: ellipsoid to broadly ovoid, 7-9.5 x 4.5-5.5 µm Pycnidia: common, immersed conidia: bifusiform to unequally bifusiform or weakly clavate, 4.5-5.5 x 1 µm Spot tests: cortex K-, C-, KC-, P-, HNO3- blue-green; medulla K-, C-, KC-, P+ yellow to orange-red, especially near the upper cortex, occasionally P- in some parts Secondary metabolites: fumarprotocetraric and often caperatic acids (both major), protocetraric acid (minor or trace), virensic acid (accessory). Substrate: rocks World distribution: SW North America in Mexico and U.S.A. Sonoran distribution: from 1350 to 2750 in the mountains of Arizona, Chihuahua and Sonora. Notes: This species has been found to be more chemically variable than originally reported. Fumarprotocetraric acid is constant, but caperatic acid, in somewhat variable amounts, was detected in only 60-70% of the specimens. Protocetraric acid and virensic acid also occur in relatively low frequency and low concentration. The medullary spot test with P is variable, and specimens with caperatic acid often have only a slight P reaction in the medulla, but a stronger reaction near and in the upper cortex. The cortical P reaction is also visible on the surface, at least in some of the paler lobe ends. Specimens with a weak P reaction in the medulla might be mistaken for N. atticoides, but that species usually has a fairly distinctive K+ yellow turning red-orange reaction.