Cora arachnodavidea

The thallus is terrestrial, forming a foliose rosette up to 7 cm across on soil between bryophytes or at plant bases. It consists of three to five semicircular lobes, each 1–3 cm long and wide, sparsely branched and lacking obvious radial sutures. Fresh lobes are olive-brown to olive-grey with pale concentric zones; rolled-in (involute) margins bear conspicuous white pilose hairs. When dry the upper surface becomes rugose and broadly arachnoid, while the lower surface—lacking a cortex (it is ecorticate)—shows a whitish, felty medulla.^[1]

In section the thallus is 350–450 micrometres (μm) thick. A diffusely viaduct-shaped upper cortex (30–50 μm) overlies a 100–150 μm zone of spaced, anticlinal hyphae. Tufts of agglutinated hyphae form stout setae, 200–300 μm long and 30–50 μm broad at the base. The photobiont layer is 100–200 μm thick (orange-brown above, olive-green below).^[1] The photobiont is Rhizonema andinum, a filamentous cyanobacterium in the family Nostocaceae.^[3] The medulla is 70–100 μm thick and emits coralloid hyphae 3–5 μm wide. No clamp connections are present.^[1]

The hymenophore is cyphelloid: rounded to irregular, sessile depressions 3–5 mm in diameter with cream- to pale orange-brown surfaces and felty, involute margins. Sections show a 200–250 μm thick structure supported by a thickened medullary base; the hymenium contains abundant palisade-like basidioles (40–50 × 5–7 μm) and scattered four-spored basidia (25–35 × 5–7 μm). Basidiospores have yet to be observed, and thin-layer chromatography has detected no secondary metabolites.^[1]

The species is known only from the páramo of Guasca, Cundinamarca Department, Colombia (roughly 3,220 m elevation). It grows on the ground in lightly sheltered microsites among bryophytes and herbaceous plants, where frequent mist and rapid drying cycles characterise the high-Andean environment.^[1]