Mycotaxon 90, 2: 301 (2004).

Protolog: Thallus arcte adnatus, subcrustaceus, superne griseus vel griseo-albidus, diameter usque 2 cm, subtus pallidus, rhizinae sparsissimus vel plus minusve absens. Lobi 0.2-0.6 mm lati, lineari-elongati, plus minusve contigua, superficies superior sorediati-isidiati.

Protolog type data: United States of America. South Dakota. Marshall Co.: along Hwy 25 about 0.4 km S of junction with Hwy 10, just of Lake City. 45°42.9'N, 97°24.58'W. Esslinger 16030-2 (Holotype. DUKE: Isotypes. US. S. Herb. Essl.)".

Type locality: USA, South Dakota, Marshall County, along Highway 25 about 0.4 km south of junction with Highway 10, just of Lake City, T. Esslinger 16030-2 (DUKE - holotype; US, S, Esslinger - isotypes).

Type locality coordinates: 45°42.9'N, 97°24.58'W.

Molecular barcode: Data lacking.

Thallus: foliose to subcrustose, gray to gray-white, often noticeably darkened on the very lobe-tips; commonly orbicular, most often 1-2 cm in diameter, occasionally larger or appearing larger by coalescent thalli. Lobes flat at the ends, often becoming weakly convex inward, narrow, (0.1) 0.2-0.6 mm in width, more or less linear-elongate and broadening slightly at the tips, often confluent or occasionally somewhat imbricate toward the ends, closely appressed and adnate except right at the tips. Upper surface developing irregular small soralia on internal lobe ends or edges, at first scattered but sometimes becoming abundant, the soredia coarsly granular or becoming more or less upright and strongly isidioid. Medulla white. Lower surface more or less white where visible on the lobe ends, but elsewhere closely appressed to the substrate; rhizines sparse and very poorly developed or essentially absent, usually occurring only as occasionally small and irregular pegs. Upper cortex paraplectenchymatous, the medulla mostly hyphal, lower cortex poorly defined from the medulla or missing, except on the lobe ends where it seems to be little more than compacted hyphae intergrading with the medulla. Apothecia relatively frequent in well developed thalli and sometimes common, up to 0.9 mm in diameter, sessile, more or less flat to weakly concave, the disk black, the exciple entire or occasionally becoming granular isidioid on larger ones; hymenium 80-100 µm thick, ascospores (10) 11-14 (16) x (5.5) 6.5-10 µm, indistinctly Physcia-type, the lumina not strongly angular except at an early stage. Pycnidia frequent, often large and conspicuous, partly exposed on the thallus surface; conidia (3.5)4-5.5 (6.5) x <1-1 µ, more or less rod-shaped, occasionally with a slight bend (Esslinger 2004: 301).

Photobiont: Green alga.

Chemistry: Cortex K+ yellow; medulla K- (the medulla is very thin and must be tested very carefully to avoid confusion with the K+ test in the cortex); producing atranorin (identified by TLC) (Esslinger 2004: 302).

Ecology: On exposed granite or similar acidic rock in prairies, pastures and other very open areas (Esslinger 2004: 302), e.g. piles of field stones. Rarely on timber.

Distribution: Great Plains in North America.

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