Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2004. Lichen Flora of the Greater Sonoran Desert Region. Vol 2.

Life habit: lichenized Thallus: crustose, continuous or ±cracked, rarely areolate surface: mostly cream-colored or pale gray, rarely ochre, dull, smooth and waxy or mealy-powdery, without soralia and isidia cortex: usually present but often indistinct, and without a distinct layer of periclinal hyphae as in Fissurina, only a few species without a cortex developed photobiont: primary one a Trentepohlia green alga, secondary one absent Ascomata: apothecial, mostly oval to oblong (lirellate), fissurine, or ±raised above the thallus disc: slit-like or little opened, usually pale, flesh-colored and slightly pruinose margin: white or pale cream-colored, well developed and ±crenate or entire, inconspicuous/indistinct (±fissurine lirellae) exciple: usually not carbonized (carbonized only in A. obscura), rarely pale brown, rudimentary or poorly developed at the base, lateral exciple and excipular lips often consisting of loosely connected hyphae and granula or small crystals, in some species ±distinctly crenate/striate, basal 'edges' of the exciple often react I+ blue-violet hymenium: not inspersed (except A. obscura), 80-180 µm tall, I- paraphyses: parallel, closely packed, unbranched, with warty or spiny, hyaline or slightly brownish tips; periphysoids: usually well developed, hyaline and in most species with warty or spiny surface, usually 5-20 µm (up to 50 µm) long asci: clavate, I-, apex thickened with ±distinct ocular chamber, ("Graphis-type"), 1-8-spored ascospores: hyaline, transversely septate or muriform, oblong or oval, with a halo in some species, locules often cylindrical and not lens-shaped or globose as in most other genera of the Graphidaceae, I-, I+ pale blue-violet or I + blue-violet Conidiomata and conidia: not found so far Secondary metabolites: various ß-orcinol depsidones, isohypocrelline (red pigment, present in the ascocarps of red-fruited species), and lichexanthone Geography: tropical to subtropical Substrate: on bark or wood, exceptionally on rock (A. silicicola only). Notes: The genus Acanthothecis is usually characterized by ascocarps with white to cream-colored margins (and lacking carbonization internally), often oblong ±thinwalled ascospores (rarely ovoid and thick-walled like in Fissurina-species) and the presence of periphysoids that show as well as the paraphyses tips a warty/spiny surface.