Rimularia austrolimborina Coppins & Fryday
Lichenologist 38: 105. 2007.

Thallus effuse, or weakly delimited, only occasionally partly delimited by a narrow prothalline zone, deeply rimose areolate, with areoles (0.1)0.20.5(0.6) mm wide, whitish buff, matt. In section to 300 m tall; cortex c. 2430 m tall, hyaline to dilute straw-brown, composed of vertically arranged compacted hyphae c. 2.5 m wide, sometimes overlain by a c. 5 m tall epinecral layer; algal layer poorly delimited from the medulla, c. 6075 m tall; medulla whitish, containing many mineral fragments from the substratum, I. Photobiont cells globose, 712 m diam.
Apothecia arising from between the areoles, often remaining level with the surface of the thallus, but sometimes emergent or even sessile, rounded or irregularly angular in outline, black, 0.61.1(1.3) mm diam.; margin prominent, radially, deeply cracked, c. 0.150.2 mm wide; disc concave, but usually mostly obscured by a raised, convex central umbo; some apothecia becoming irregularly gyrose-contorted. Exciple cupulate, dark reddish brown [blackish in thick sections], K+ brown-red pigment going into solution, N, 70300 m thick at base, 4050 m laterally and 120200 m thick at the apex [margin, or labium]. Hymenium 98170 m tall, hyaline or dilute brown-red in uppermost part, I+ blue; epihymenium absent. Hypothecium c. 2025 m tall, poorly delimited from the hymenium, dilute brown-red, I. Asci [few healthy examples seen] clavate, c. 95110 2427 m, 8-spored; in K/I with an amyloid outer wall, and an apparently non-amyloid tholus [few good preparations obtained]. Ascospores simple, hyaline or contents dilute brown, ellipsoid, 2227 1216.5 m; without an obvious perispore. Paraphyses richly branched, distinctly septate but not moniliform, c. 11.5 m wide.
Conidiomata: no healthy pycnidia seen.

Chemistry. Thallus K+ yellow, C, KC, P+ orange, UV; stictic (major), norstictic (minor) and constictic (minor) acids by TLC.

Ecology and distribution. Known from only two localities near the coast in southern Chile between latitudes 4952 and 5039S. The holotype specimen has accompanying thalli of Lithographa graphidioides.

Notes. With regard to the general appearance of the apothecia, and of ascospore size, Rimularia austrolimborina closely resembles the Northern Hemisphere R. limborina Nyl. However, the latter has somewhat smaller apothecia (0.30.8 mm diam.), and a thinner, more darkly coloured, grey or brown thallus, which lacks lichen substances or rarely contains gyrophoric acid.

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Thallus and apothecia