Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2007. Lichen Flora of the Greater Sonoran Desert Region. Vol 3.

Thallus: crustose, rimose, flat to verruculose; prothallus: black surface: white, smooth, esorediate medulla: white, lacking calcium oxalate (H2SO4- Apothecia: lecideine, abundant, 0.2-1.2 mm in diam., soon sessile disc: black, epruinose, concave to flat or ±convex margin: black, persistent, enclosing disc in young apothecia proper exciple: 60-105 µm thick, with norstictic acid; differentiated into a dark brown outer part, a pale central part and a dark brown, inner part with carbonized cells (<3 µm, HNO3-, K+ orange, needle-shaped crystals), transient with the brown, <220 µm thick hypothecium (HNO3-) epihymenium: brown, pigmentation continuous with the outer exciple (HNO3-) hymenium: hyaline, not inspersed with oil droplets, 85-110 µm tall; tips of paraphyses: ±4.5 µm wide with distinct apical caps asci: clavate, Bacidia-type, 76-82 x 14-26 µm, 8-spored ascospores: soon brown, submuriform to muriform, with 5-11 cells in optical section, occasionally with oblique septa, ellipsoid, (19-)20.4-[23.4]-26.4(-29.5) x (8-)8.5-[9.3]-10.1(-11.5) µm (n=20), walls and septa lacking uneven thickenings, proper wall c. 0.2 µm thick, perispore c. 0.35 µm thick, ornamentation: rugulate Pycnidia: not seen Spot tests: thallus and medulla K+ yellow turning red (crystals), C-, P+ yellow-orange fluorescence: UV- iodine reaction: medulla non-amyloid Secondary metabolites: atranorin, norstictic acid and connorstictic acid; norstictic acid also present in proper exciple. Substrate and ecology: bark of deciduous trees in subtropical, montane forests World and Sonoran distribution: currently known from a single locality in Sinaloa (Cerro Solida above El Cajon). Notes: Buellia morsina is characterized by its submuriform to muriform spores and the presence of norstictic acid in the proper exciple. Thallus morphology, secondary chemistry and exciple anatomy are similar to B. lauricassiae, but B. morsina has larger, submuriform spores.