Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2007. Lichen Flora of the Greater Sonoran Desert Region. Vol 3.
Life habit: not lichenized photobiont: not present Ascomata: dispersed, ±round to lirellate, 0.5-1 mm wide, 130-160 µm tall disc: black plane to slightly convex epihymenium: olivaceous brown, 30-40 µm; hyphal tips: c. 2 µm wide, free or intermingled with hyaline particles of substrate remains hymenium: hyaline, 80-100 µm tall, paraphosoids: strongly reticulate, sinuous and c. 1 µm wide, denser around the asci; subhymenium: hyaline, 20-40 µm thick asci: subglobose, 90-100 x 70-90 µm, lateral walls thick, with distinct stipe, (6-)8-spored ascospores: hyaline, muriform, with 9-11 straight transverse septa and 1-3 longitudinal septa, septation starting from the center, ellipsoid, 48-52 x 21-25 µm Chemical reactions: ascomatal gels I+ immediately red, KI+ blue, without KI+ ring-structure in tholus, with faint KI+ bluish epispore. Substrate and ecology: on smooth bark or woody substrates Sonoran distribution: Baja California along the Pacific coast. Note: Arthonia brucei is superficially similar to A. beccariana, A. orbillifera, and A. subastroidea, but differs in having much larger ascospores and the differently shaped asci. So far, only two specimens are placed in this species, and therefore I refrain from providing a validating description at this stage. The anticipated name is dedicated to the memory of Dr. Bruce Ryan, and for his substantial contributions to the lichenological exploration of the Sonoran Desert.