Description.Thallus saxicolous, thick, contiguous, areolate, areoles with undulating edges, closely adjoining but not interlocked; surface white, dull, whitish pruinose, coarsely granular and roughened, lacking soredia; thallus margin delimited by a thin compact, blackened prothalline line, most pronounced where different thalli meet. Apothecia sparse to numerous, circular to weakly undulate, 0.2–1.2 mm in diam., adnate to just sessile, distinctly lecideine with a thin, shiny, epruinose, increasingly carbonized margin and a brownish to black, convex disc, densely covered by bluish grey pruina (C−, K−); hymenium hyaline, not inspersed, epihymenium with a diffuse aeruginose pigment (cinereorufa-green: intensifying in K, HCl+ bluish green, N+ reddish violet), with sparse clusters of small, dull brown granules that dissolve in K, and with few, large, irregular, hyaline crystals persistent in K, pigmentation and hyaline granules extending to the outer exciple; proper exciple initially weakly to moderately carbonized, pigmentation intensifying with age; thalline exciple absent; subhymenium and hypothecium hyaline to very faintly yellow; asci clavate, Lecanora-type, ascospores 8/ascus, simple, subglobose to globose, (5.9–)6.8–8.6(–9.3) × (4.9–)5.2–7.1(–7.8) μm (n = 25). Pycnidia not seen.
Ecology and distribution. Previously reported from Tasmania and southern New Zealand; new to Ecuador and the Galapagos, where it is known from a single specimen collected at the shore.
Notes. This species is superficially very similar to L. avium, but lacks areoles that are interlocked by their crenate margins and the thalli react C+/KC+ orange and fluoresce UV+ bright orange due to the presence of xanthones. Further, the ascospores of L. austro-oceanica are almost globose whereas those of L. avium are narrower (3.9-6.4 μm) and ellipsoid to broadly ellipsoid. Previously Hertel (1989) reported L. subcoarctata from Galapagos based on the specimen re-determined here as L. austro-oceanica (Weber 151, L-41000, COLO 190133). Weber’s handwritten annotation of this material originally identifies the specimen as Lecidea chilena Zahlbr. We compared this specimen with exsiccatae of Lecanora subcoarctata from New Zealand (Lecideaceae Exs. 146, COLO 409407, L-78791; Plantae Graecenses Lich. 405; COLO 375193, L-84332). Both differ from the Galapagos material collected by Weber. The New Zealand specimens of L. subcoarctata have an uneven verrucose to almost verruculose thallus composed of ±discrete, ±dispersed areoles whereas L. austrooceanica from the Galapagos has an even, contiguous upper surface. Lecanora subcoarctata also lacks xanthones and therefore its thallus does not fluoresce nor does it react with C or KC.