Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2004. Lichen Flora of the Greater Sonoran Desert Region. Vol 2.

Thallus: crustose, rimose to distinctly areolate, 0.3-1 mm thick surface: cream-colored to brownish gray, smooth or uneven, esorediate Apothecia: initially immersed but becoming adnate, scattered, 0.5-1.5 mm in diam. disc: cinnabar red to brick-colored, epruinose, several discs often confluent margin: concolorous with thallus, persistent, smooth, often not distinct from thallus, often thick exciple: red, thin epihymenium: bright red (K+ red or magenta to purple) hymenium: hyaline, 70-110 µm tall; paraphyses: strongly branched and reticulate, gelatinous, with only slightly swollen apices; hypothecium: hyaline asci: clavate, 8-spored ascospores: hyaline, transversely 3-7 septate, slightly curved to S-shaped, 20-30 x 3-5 µm Pycnidia: immersed conidia: filiform, curved, 13-18 x 0.9-1 µm Spot tests: thallus K+ yellow, C-, KC-, P+ yellow or P- Secondary metabolites: atranorin, russulone, plus in chemotype a sphaerophorin and isosphaeric acid, or in chemotype b sphaerophorin, isosphaeric acid and psoromic acid, or rarely in chemotype c psoromic acid. Substrate and ecology: on siliceous rocks (granite and rhyolite) in pine-oak forest World distribution: pantropical to subtropical or Mediterranean in southwestern North America, South America, Europe, South Africa, and Australasia Sonoran distribution: Arizona at 1200-2200 m, Chihuahua at 1950 m, and Sonora at 900-1525 m. Notes: Haematomma fenzlianum is characterized by its smooth, rimose to areolate, cream-colored, pale to brownish gray thallus, +immersed apothecia with cinnabar red discs, 3-7-septate spores, and usually containing sphaerophorin in addition to russulone.