Pachnolepia pruinata Frisch & G.Thor

The extensive thallus is white to pale olive grey, cracked to fissured-areolate, and has a matt to powdery surface. It is up to 0.3 mm thick and developed mainly on the surface of the bark. The margin is not determinate or delimited by a thin brown line when in contact with other lichens. The photobiont is a species of the family Trentepohliaceae.

The apothecia are usually level with the thallus surface but can be raised. They are rounded, angular or star-shaped, and colored pale brown to brown beneath a thick white pruina. They are 0.2–1 mm in size and 100–160(–250) μm tall. The disc is flat to slightly convex.

The epithecium is 10–20 μm tall, reddish brown in color, and densely interspersed with or overlain by calcium oxalate crystals.

The hymenium is colorless and 45–60 μm tall.

The hypothecium and the hymenium can be unpigmented or a pale reddish brown, and 50–170 μm tall.

The paraphysoids are 1–1.5 μm wide. Their tips are mainly perpendicular to the surface, partly free, and slightly widened to 2.5 µm. Sparse reddish brown pigment is usually deposited on the outer walls.

The asci are clavate, with stipe, 32–50 × 10–20 μm in size, and 8-spored.

The spores are persistently colorless, narrow obovate, are 13–17(–20) × 4.5–7 μm in size and divided by (3–)4–5 transverse septa. The apical cell is not enlarged.

The pycnidia are pale to reddish brown, 0.1–0.2 mm in size, and either immersed in the thallus or slightly raised. The wall is either colorless or a pale reddish brown. The conidia are 10–14 × 0.5–0.8 μm in size, short threadlike, and usually curved.

The thallus in most specimens reacts C+ red, K–, KC–, Pd–, or UV–. Arthoniaic acid is detected by TLC.

The hymenium reacts I+ blue then red and KI+ deep blue. A KI+ blue ring structure is present in the tholus of the asci. Calcium oxalate crystals are common in thallus and apothecia.

The brown pigment in the epithecium and in the wall of the pycnidia changes to pale green in K solution.