Rhabdodiscus albodenticulatus Weerakoon, Lücking & Lumbsch sp. nov.
MycoBank number: MB 815550, Facesoffungi number: FoF 02028, Fig. 1c, d
Etymology: Referring to the white teeth-like apothecial columella.
Holotype: G. Weerakoon 880 (PDA).
Diagnosis: Differing from Rhabdodiscus integer by the thicker, verrucose thallus and the smaller, more immersed apothecia.
Thallus corticolous, up to 5 cm diam., continuous, olivegrey to olive – green, uneven – verrucose; prothallus not observed. Thallus in section 200 – 300 μm thick, with prosoplectenchymatous cortex 10 – 20μm thick, photobiont layer 50 – 70 μm thick, and medulla 150 – 200 μm thick, strongly encrusted with numerous large crystals of calcium oxalate, forming clusters that cause the verrucae. Photobiont Trentepohlia; cells rounded to irregular in outline, in irregular groups, pale green, 7 – 11 × 4 – 6 μm. Apothecia erumpent, 0.8 – 1.2 mm diam.; disc partially covered by 0.2 – 0.4 mm wide pore, rim around the pore whitish to pale yellowish, pore mostly filled by columella. Columella present, broad-stump-shaped but becoming ruptured in to 3 – 6 irregular teeth, 100 – 200 μm broad, carbonized but with whitish top. Excipulum 30 – 50μm broad, carbonized; periphysoids absent. Hymenium 120 μm high, clear. Paraphyses unbranched. Asci 100 × 20 μm, fusiform. Ascospores 8 per ascus, submurifom, 3 transverse septa and 0 – 1 longitudinal septa, 15 – 18 × 7 – 8 μm, ellipsoid, with thick septa and lens-shaped lumina, brown, I+ violet-blue (amyloid). Secondary chemistry: Psoromic, subpsoromic and 2′-O-demethylpsoromic acids.
Material examined: SRI LANKA, Central Province, Matale district, Siyabalabokka-Rattota, 7° 31′ N, 80° 40′ E, 360 m, low altitude, on tree bark of home garden; January 2015, G. Weerakoon 880 (PDA holotype and F Isotype); Along Karagastanna road, 7° 34′ N, 80° 42′ E, 990 m, mid elevation, January 2015, G. Weerakoon 205, 237 (F); Meepiliyamana -Nuwaraeliya, 6° 56′ N, 80° 47′ E, 1350 m, high elevation, January 2015, Weerakoon 732 (F).
Distribution and ecology: The new species was collected in high elevation disturbed montane forest patches.
Notes: This new species is most similar to Rhabdodiscus integer (Müll. Arg.) Rivas Plata & Lumbsch, which which it shares the submuriform, brown ascospores, the columella rupturing into teeth, and the psoromic acid chemistry. However, R. integer has a thinner, smooth to uneven thallus and much larger, strongly prominent apothecia. Rhabdodiscus marivelensis (Vain.) Rivas Plata & Lumbsch differs in the minutely grainy thallus caused by columnar clusters of calcium oxalate crystals, the thicker apothecial margin, and the larger ascospores (20 – 30 × 8 – 18 μm).

Fig. 1 Ocellularia arachchigei (holotype) a Thallus with ascomata. Ocellularia ratnapurensis (holotype) b Thallus with ascomata. Rhabdodiscus albodenticulatus (c holotype, d paratype) c, d Thallus with ascomata. Scale bars: a – d = 1 mm.