Thallus: tightly adnate to adnate, appressed, foliose, up to 4 cm diam. but sometimes coalescing into larger patches, lobate lobes: short and rounded to more elongate or ir-regularly sublinear, subdiscrete to contiguous or slightly imbricate, 0.5-2.5 mm broad, flat to somewhat convex upper surface: dark olive-green to greenish black, mostly smooth at the periphery, inward becoming fissured or rugose-areolate; dull throughout or slightly shiny on the lobe ends isidia: becoming numerous, cylindrical or sometimes knobbed at the end, simple or branched, up to c. 0.6 (-1) mm long and 0.1-0.15 mm in diam. lower surface: black, ± smooth and flat, dull to slightly shiny; moderately to somewhat sparsely rhizinate, the rhizines simple and concolorous with the lower surface Apothecia: frequent, up to 4 mm diam., sessile, concave when young, flattening to weakly convex, the margin at first entire, becoming papillate-crenate and sometimes isidiate asci: clavate, 8-spored ascospores: ellipsoid to subglobose, 7-8 x 4.5-6.5 µm Pycnidia: infrequent, immersed conidia: bifusiform, 4.5-6 x c. 1 µm Spot tests: cortex K+ and HNO3+ violet, C-, KC-, P-; medulla K+ yellow turning orange-red, C-, KC-, P+ orange Secondary metabolites: stictic acid, (major), norstictic acid (minor), constictic acid (accessory). Substrate: rocks World distribution: SW North America, including west Texas Sonoran distribution: mountains of Arizona and Chihuahua, from c. 1,000 to 2,000 m. Notes: This is the most distinctive species of Neofuscelia in the study area. The closely appressed, isidiate thallus, and unusual greenish-black upper surface with a K+ violet spot test, make this species difficult to confuse with any other. Other isidiate species in the genus have the more typical HNO3+ blue-green reaction on the cortex, and those occurring in the Sonoran region all have pustular rather than the distinctly cylindrical isidia of N. chiricahuensis. The only closely related species is N. atroviridis, a species from southern Africa with similar cortical and medullary spot tests, which lacks isidia. A few saxicolous and isidiate species in the related genus Melanelia might be initially confusable, but they lack positive cortical spot tests and medullary spot tests are either negative or only C+.