Cora fimbriata forms small, leaf-like rosettes that cling to tree bark in the humid spaces between moss cushions. Each thallus (the overall lichen body) is seldom more than 3 cm across and typically consists of one to three semicircular lobes. Individual lobes measure 1–2.5 cm in width and 1–1.5 cm in length; they fork once to three times, and fine "sutures" run between the branches like seams in fabric. When moist the upper surface is a dark olive-grey, drying to a plain grey in the herbarium. It is smooth to the touch but shows faint concentric wrinkles. Along the lobe margins and within the sutures the lichen bears a fringe of short, white cilia—fine, hair-like projections that give the species its name. The lower surface is patterned with alternating white and grey rings, a feature that remains visible whether the specimen is fresh or dry.[2]
A thin vertical slice through a lobe reveals a three-layered structure 0.22–0.30 mm thick. The outer cortex, measuring 110–130 micrometres (μm) thick, acts like a protective skin; its fungal threads (hyphae) are arranged first parallel to the surface (periclinal) and then, in a deeper sub-layer, roughly perpendicular (anticlinal). Beneath lies the photobiont layer (75–100 μm), where cyanobacteria occur in tight emerald-green clusters 25–30 μm across. Each bacterial cell is 10–15 μm wide and enveloped by a sheath of interlocking fungal cells, with additional hyphae 5–7 μm thick weaving through the layer. The innermost medulla (55–75 μm) is a looser mesh of mostly periclinal hyphae 1–3 μm in diameter. No hymenophore—the spore-bearing tissue typical of many basidiolichens—has yet been observed in this species, and thin-layer chromatography detects no secondary metabolites in the thallus.[2]
