Type: Argentina. Córdoba: Departamento Sobremonte, Cerro Colorado, 30°08′S, 63°54′W, on rock, Nov-1996, Estrabou s.n., (BAFC 37878 – holotype, Estrabou Herbarium 1500 – isotype, fide Estrabou & Adler 1998).
Description.Thallus saxicolous; upper surface whitish gray to ivory, dull, epruinose, emaculate, occasionally cracked, but not forming a distinctly reticulate pattern; abundantly sorediate; soralia submarginal, forming conspicuous cauliflower-like outgrowths; soredia ± granular, ± concolorous or slightly paler than the thallus, pale inside; lobes small to moderate-sized, 1–5(–6) mm wide, ± angular, axils incised, margins eciliate; lower surface with an erhizinate, ~ 1–2(–2.5) mm wide, pale brown margin, moderately to densely rhizinate and blackened 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 atranorin [P+ yellow, K+ yellow, KC–, C–, UV–]; medulla with fatty acids [P–, K–, KC–, C–, UV–].
Ecology and distribution. Argentina, Brazil (Estrabou & Adler 1998; Canêz 2005). New for Galapagos and Ecuador; currently only two specimens known, both from the same locality (Volcán Darwin, above Tagus Cove), one from a ± shaded and sheltered basalt ledge, the other from an exposed basalt rock.
Notes. The cauliflower-like submarginal soralia of this saxicolous species with angular lobes are quite conspicuous and in the Galapagos P. soredioaliphaticum is thus not easily confused with any other species. Parmotrema mordenii and P. praesorediosum typically have ± linear to crescent-shaped marginal soralia, which occasionally may become subcapitate, but not distinctly cauliflower-like. Parmotrema dilatatum and P. weberi can have similar cauliflower-like soredia, but these originate from abundant lobules, which are absent from P. soredioaliphaticum. All these species are clearly distinguished by their chemistry, with P. soredioaliphaticum containing only fatty acids in its medulla.