Thallus of minute, finely pruinose, ivory to beige, corticate squamules with marginal or laminal soredia, occasionally aggregating into minute placodioid rosettes; containing atranorin, chloroatranorin, alectoronic acid, diploicin and unidentified secalonic acid derivates.

Type: Ecuador, Galapagos, Isabela, Volcán Darwin, ca. 1.5 km from the south-western crater rim, 0˚12’20.5''S, 91˚18’52.8 W, 1280 m alt., high altitude dry zone, basalt outcrop for the most part bare of vegetation, on rock below W-exposed overhang of basalt outcrop, shaded, wind- and rain-sheltered, 14 November 2007, Bungartz 7597 (CDS 38093).

Thallus saxicolous, squamulose to minutely placodioid, of scattered sorediate squamules [(273–)303–394(–455) µm wide] that, when well developed, aggregate into minute rosettes [2–5 mm in diam.]; prothallus indistinct; surface pale cream to pale beige, dull with a ± roughened texture, moderately covered by farinose pruina, which is more pronounced and slightly coarser along the edges of the squamules; cortex phenocorticate, prosoplectenchymatous, indistinctly delimited, interspersed with dead photobiont cells, the upper part disintegrating into an indistinct epinecral layer, densely interspersed throughout by minute crystals most of which dissolve in K, but some are persistent and remain irregularly dispersed; medulla of densely interwoven, white hyphae, typically dirty orange brown near the substrate (unidentified secalonic acid derivates), IKI-, filled with minute crystals that dissolve in K and sparse, large crystals insoluble in K, no needles forming in H₂SO₄ (calcium oxalate absent); soralia convex, erumpent, circular to irregular, occasionally ±confluent, forming at the lobe apices, along the margin or on the thallus surface, soredia white (distinctly paler than the thallus surface), granular compact, ecorticate with sparse, short protruding hyphae [(61–)91–110(–150) µm in diam.]. Apothecia not known. Pycnidia not known. Photobiont green, trebouxioid, 7–10 μm in diam.

Chemistry: Thallus P+ yellow, K+ yellow, C−, KC−, UV- (dull yellowish); medulla P-, K-, KC-, C-, UV- (dull yellowish); atranorin (major), chloroatranorin (major or minor), alectoronic acid (major), diploicin (major or minor) and unknown secalonic acid derivates (major or minor).

Etymology: Named for its thalline squamules.

Ecology and distribution: Currently known only from shaded, sheltered rocks in the upper transition zone and high altitude transition zone on the western slope of Volcán Darwin on Isabela Island.

Notes: Diploicia squamulosa is most similar to D. leproidica. This is the only species of Diploicia in the Galapagos known to occur at high altitudes, in dry, sheltered habitats.