Type: Venezuela. Táchira: Páramo de Tamá, El Cobre Chiquito, 2700 m., 28-Mar-1975, Hale, H.E. 45557 & López, M. (US – holotype, MERF – isotype, fide Hale 1986).
Description.Thallus saxicolous; upper surface pale greenish yellow, dull to ± shiny, mostly emaculate, but typically distinctly wrinkled, in older thallus parts these wrinkles often breaking into reticulate cracks; abundantly sorediate; soralia marginal, ± convex-capitate; soredia farinose to ± granular, initially concolorous with the thallus surface, but often discolored by a ± brownish tinge, pale inside; lobes small to moderate-sized, 2–5 mm wide, rotund, axils incised, margins eciliate to sparsely or abundantly ciliate; cilia stout, short, 0.5–1 mm long, black, mostly simple, rarely branched; lowersurface with an erhizinate, ~ 1–2 mm wide margin, this margin either deep brown or, more often, pitch black (like the whole lower surface), the black pigmentation frequently visible from above, delimiting the lobe edge with a conspicuous black rim, the lower side of the thallus often as conspicuously wrinkled as the upper surface and densely rhizinate towards the center; rhizines short, stout, black, simple to sparsely branched; medulla white. Apothecia and pycnidia not observed among the Galapagos specimens.
Chemistry. Cortex with both usnic acid and atranorin [P+ yellow, K+ yellow, KC–, C–, UV–]; medulla with protocetraric acid [P+ yellow turning orange, K+ dirty yellowish brown, KC–, C–, UV–].
Ecology and distribution. Previously reported from Ecuador and Venezuela (Hale 1986). New for Galapagos; the only two specimens known were both collected on exposed basalt at El Mango, in the lower transition zone of Volcán Sierra Negra, on Isabela Island; the site is unusually exposed, barren, open gravel, the ground in large parts covered by the endemic Stereocaulon azulense.
Notes. At a cursory glance the saxicolous yellowish P. virescens could be mistaken for the similarly colored P. flavescens, which also grows on rock. However, the two species are otherwise not easily confused. Parmotrema virescens is sorediate, while P. flavescens is isidiate. These species also differ in their chemistry: P. virescens contains protocetraric, P. flavescens stictic and norstictic acid. Like P. virescens, the corticolous P. dominicanum also contains protocetraric acid, but it occasionally also contains traces of echinocarpic acid and its medulla reacts KC+ rosé to faintly orange.