Lecanoromycetes, Ostropomycetidae, Baeomycetales, Xylographaceae

Thallus crustose, areolate or cracked–rimose: photobiont green, Chlorococcaceae.
Ascomata apothecia, lirellate to round or somewhat angular, disc slit-like.
Proper exciple of dark-brown, conglutinate, anastomosing and radiating hyphae
Hymenium colourless I+ blue, 65–59 µm tall; epihymenium often poorly defined, brownish.
Hamathecium of paraphyses.
Hypothecium pale- to dark-brown.
Asci cylindrical, Rimularia or Trapelia -type; ascospores colourless, ellipsoidal, halonate or not, usually simple but submuriform in two species.
Conidiomata pycnidia (often not seen), black, minute, immersed;conidia, short rods.

Lithographa is a genus of seven saxicolous species that until recently was represented only by the type species (L. tesserata (DC.) Nyl.), known only from the Northern Hemisphere. However, recent work has identified a number of other species in the Southern Subpolar Region (see literature below).
The genus is closely related to Rimularia, and a recent molecular revision (Resl et al. 2015) showed that most species assigned to that genus were not con-generic with the type species, R. limborina, which belonged in the Trapeliaceae, and a new family, Xylographaceae, was erected for the species with lirellate/gyrose apothecia, along with the genera Xylographa, Ptychgrapha and Lithographa for which they resurrected the genus Lambiella. Unfortunately only L. tesserata was included in this study so the systematic position of the rest of the genus is still not resolved, although they certainly belong in the Xylographaceae.
It is also probable that the two species with submuriform ascospores (L. serpentina and L. skottsbergii) should be included in a separate genus.

Literature: Hertel & Rambold 1990, Fryday 2004a; Coppins & Fryday 2006, Fryday & Coppins 2007, Resl. et al. 2015.