Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2007. Lichen Flora of the Greater Sonoran Desert Region. Vol 3.
Life habit: lichenicolous, slightly parasitic, non-lichenized Ascomata: punctiform to shortly lirelliform, black, epruinose, single or grouped by 2-10, 0.15-0.23 mm in diam. when punctiform, 0.3-0.35 x 0.13-0.15 mm when lirelliform; disc: usually slit-like, rarely narrowly exposed, black, epruinose exciple: closed, 20-35 µm laterally, 20-50 µm at base, K+ olivaceous hymenium: hyaline, 60-75 µm, I+ blue turning greenish-brownish to reddish; subhymenium: pale brown, 10-13 µm; paraphysoids: 2 µm, apically indistinctly swollen asci: ellipsoid to clavate, 4-6-spored, 45-60 x 12-16 µm (Varia-type) ascospores: oblong, with rounded ends, 3-septate, straight, not constricted at septa, upper half slightly wider than the lower one, 15-19 x 5-6.5 µm (Parasitica-type); perispore hyaline, becoming brown granulose when over-mature, 1-1.5 µm wide Pycnidia: not observed. Host and ecology: slightly parasitic on thallus of corticolous Haematomma species, including Haematomma hilare World distribution: New Zealand and Mexico Sonoran distribution: Baja California Sur. Notes: Opegrapha physciaria differs by 8-spored asci, slightly shorter and wider ascospores (14-16 x 6-7 µm), longer ascomata (0.15-0.7 mm) and a different host genus (Xanthoria). Opegrapha brevissima was known so far only from the type locality in New Zealand. This fungus is therefore new to America.