Melanohalea peruviana

The thallus of M. peruviana is foliose (leaf-like) but tightly appressed to the twig, forming rosettes up to about 1.5 cm across. Lobes are narrow (0.4–1.0 mm), mostly flat, and become weakly convex toward the center. Their upper surface is brown to olive-brown, shiny—especially at the lobe tips—and develops low wrinkles (a rugose texture) with age; conspicuous vegetative outgrowths such as soredia or isidia are absent. Tiny, same-colored pseudocyphellae (pin-prick pores that aid gas exchange) are sparse and hard to see. The lower surface is dark brown and distinctly trabeculate (marked by raised ridges) and carries matching brown rhizines that anchor the thallus.^[2]

Rounded to slightly convex apothecia are common; they are sessile, up to 2 mm wide, and bordered by an entire or weakly scalloped margin. The spore-bearing layer (hymenium) is 55–60 μm tall; asci hold eight colorless, broadly ellipsoid ascospores witgh dimensions of 6–8 × 5–7 μm. Immersed black pycnidia produce slender conidia 6–7 × about 1 μm. Standard spot tests are negative and thin-layer chromatography fails to detect any lichen substances.^[2]

The only known specimen grew on angiosperm twigs in open, high-Andean scrub at 4400 m in the Cordillera Blanca of Peru. No additional populations have been recorded, making the species apparently endemic to its type locality.^[2]