Hypotrachyna paracitrella

The lichen forms loose rosettes about 5 cm across on bark. Lobes are narrow and almost straight (2–3 mm wide), branching dichotomously and ending in blunt, slightly up-turned tips. The upper surface is greenish yellow, faintly shiny, rimmed in black and completely free of powdery or wart-like propagules. No soredia, isidia or lobules are produced. At, or just behind, the tips develop pale-yellow soralia whose granular soredia (roughly 60 μm) darken with age. The lower surface is black, grading to pale brown at the lobe ends, but carries no rhizines. Instead, the margins sprout tree-like black cilia 1–2 mm long and up to 0.2 mm thick at the base, each forking at wide angles. Apothecia (fruiting bodies) are common: 2–5 mm wide, strongly stalked at the base, with shiny brown discs and crenulate, inward-curving rims; the ellipsoid spores measure 12–13 × 6–7 μm. Standard spot tests show KC+ (yellow) in the cortex (due to a trace of usnic acid) and a medulla that is K+ (yellow turning red) and P+ (orange-red), indicating salazinic acid with minor amounts of consalazinic, norstictic and protocetraric acids.

The species is only to occur in its type locality, a humid, dwarf forest on an east-facing slope at 3,750–3,800 m in the Cordillera Llanganates, Tungurahua Province, Ecuador. It grew on tree branches in bright light just below the páramo.

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