Melanelia stygia (L.) Essl.

    Foliose thallus formed of closely imbricated lobes 1-5 mm long and 1-2 mm wide, convex but with flattened and more or less upturned ends, arranged in a rosette 3-10 cm in diameter, upper surface smooth and shiny, dark greenish-brown when wet, dark brown to blackish-brown, blackish when dry. Presence of numerous pseudocyphellae especially towards the margin, rounded to oval, whitish with a grayish to blackish margin. Underside dark brown to blackish with simple, black rhizines. Apothecia infrequent, lecanorine, sessile and more or less pedunculated, 4-6 mm in diameter, disc flat, dark brown, margin crenate-nodular with pseudocyphellae. Ascospores simple, broadly elliptic, 7-12 x 4-6 µm. Frequent and numerous pycnidia, laminal, buried in the thallus and visible as black dots with an ostiole, dumbbell-shaped conidia, 3-5 x 1 µm. Photobiont: chlorococcoid. Cortex: C-, K-, KC-, P-; medulla: C-, K+ yellow → reddish-brown, KC-, P+ reddish-orange. Arctic or alpine species occurring on exposed rocks.

Cf. Melanelia disjuncta without pycnidia and P-.

N.B. Species associated with yellow Rhizocarpons and mountain Umbilicaria.