Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2002. Lichen Flora of the Greater Sonoran Desert Region. Vol 1.
Life habit: non-lichenized, saprophytic Thallus: crustose, mostly immersed in the substrate, inconspicuous, causing a slight bleaching of the bark surface photobiont: absent Ascomata: perithecial, circular, ellipsoid or irregular in outline, usually aggregated in pseudostromata ascomatal wall: black, not continuous below the hamathecium hamathecium: composed of branched pseudoparaphyses, not anastomosing, non-amyloid asci: bitunicate, pyriform to clavate, with tholus, non-amyloid, 8-spored ascospores: hyaline or pale brown, clavate to ellipsoid, 1-3-septate with eusepta, 15-26 x 3-8 µm; walls: not ornamented Conidiomata: pycnidial, black conidia: bacilliform, simple, colorless Secondary metabolites: absent Geography: cosmopolitan, but most common in the tropics Substrate: mostly on bark, but also on wood or palm roots. Notes: Sonoran species of this genus have recently been classified in two different genera in two different families (Harris 1995), but the differences between species of Tomasellia are not very discrete and do not warrent a separation at the generic (let alone family) level. The genus is characterized by the usually aggregated perithecioid ascomata and large-celled, never anastomosing, pseudoparaphyses. It is often confused with Arthonia, which has apothecia with roundish asci that may somewhat resemble compound perithecia.