Hedwigia 31: 34 (1892).
Basionym: Verrucaria actinostoma Pers. ex Ach., Lich. Univ.: 288 (1810).
Protolog: Data lacking.
Protolog type data: Data lacking.
Type locality: Data lacking.
Type locality coordinates: Data lacking.
Molecular barcode: Available by Kraichak,E., Parnmen,S., Luecking,R. and Lumbsch,H.T. Gintarasia and Xalocoa, two new genera to accommodate temperate to subtropical species in the predominantly tropical Graphidaceae (Ostropales, Ascomycota). Austr. Syst. Bot. 26: 466-474 (2014).
Thallus: rimose-areolate, areoles 0.5-1.5 mm in diameter, plane, thin. Upper surface whitish gray to gray, smooth, shiny or dull, epruinose. Perithecia immersed, up to 3 mm in diameter, disc blackish, plane, proper exciple up to 70 µm thick, hymenium 120-160 µm high. asci cylindrical to subclavate, ascospores 4 - 8 in the ascus, brown, muriform, ellipsoid, 16-32 x 10-20 µm, transverse septa 4-6, longitudinal septa 1-3 per transverse segment. Pycnidia immersed. Conidia bacilliform, 4-7 x 1.0 µm (Lumbsch 2002: 174).
Photobiont: Green alga.
Chemistry: Lecanoric acid, diploschistesic acid, more or less atranorin in some samples (Culberson & Culberson 1971: 424 material from France). Lecanoric acid (major), diploschistesic acid (major), orsellinic acid (minor), + gyrophoric acid (minor) (Guderley & Lumbsch 1996: 272). Lecanoric acid (Lumbsch 1993: 228). Spot tests: K-, C+ red, KC-, P-, UV- Secondary metabolites: lecanoric acid (major), diploschistesic and orsellinic acids, both minor (Lumbsch 2002: 174).
Ecology: On exposed siliseous rocks usually in maritime or humid places (Guderley & Lumbsch 1996: 272).
Distribution Type: Subcosmopolitan in relatively open habitats in arid, semi-arid and Mediterranean areas. Sonoran distribution: scattered in mountains at c. 500- 2400 m in Arizona, Chihuahua, and Sonora, and about sea level at the coast in Baja California and California (Lumbsch 2002: 174).
Taxonomy: Diploschistes actinostomus is characterized by the perithecioid ascomata, the presence of lecanoric acid and the whitish gray to gray thallus. A similar species is D. caesioplumbeus which differs in having larger ascospores and darker thallus. Poorly developed thalli of D. actinostomus may be similar to D. euganeus which is readily distinguished by the absence of secondary metabolites and the broadly ellipsoid ascospores (Lumbsch 2002: 174).
Note: Diploschistes actinostomus "(Pers.)" Zahlbr. by Nash (1975: 122)