Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2002. Lichen Flora of the Greater Sonoran Desert Region. Vol 1.

Thallus: squamulose squamules: up to 1.0 mm diam., adnate or irregularly ascending, concave, plane or weakly convex upper surface: grayish green or greenish to dark brown, dull or shiny; margin: entire, crenulate or incised, not upturned, concolorous with upper side; soredia absent upper cortex: up to 30 µm thick, composed of thin-walled hyphae Apothecia: up to 1.0 mm diam., marginal or laminal, plane; disc: black, epruinose, egyrose; margin: remaining prominent, entire or flexuose; exciple: composed of closely conglutinated hyphae, olivaceous in inner part, brownish black in the rim, not containing crystals, K+ brown, N- or N+ violet; hypothecium: dark brown; epithecium: dark brown, not containing crystals, K+ brown, N-; paraphyses: without swelling or pigment cap in apical cell asci: with a poorly developed tholus not containing visible structures, or remaining immature ascospores: rare, broadly to narrowly ellipsoid, simple, 6-8 x 3-4 µm Pycnidia: sessile, black, attached marginally to the squamule conidia: bacilliform, 7-9 x c. 1 µm Spot tests: upper cortex K+ yellow, C+ red (rarely C-), KC+ red (rarely KC-), P+ yellow Secondary metabolites: alectorialic acid and usually thamnolic acid, rarely thamnolic acid only. World distribution: Asia and North America Sonoran distribution: Arizona and Chihuahua, fairly common. Notes: The species is morphologically very similar to H. friesii. It differs in forming mainly immature asci, having longer conidia, and in the chemistry. In H. friesii the apothecial disc is often gyrose, but never in H.oligospora.