Taxonomic Remarks. Knudsen et al. (2017) previously cited records of A. leavitii as Acarospora gyrocarpa (= Polysporina gyrocarpa), but subsequently state that that taxon appears to be restricted to Asia and that, pending further revisions, the Asian species is best considered to belong to Sarcogyne, as S. gyrocarpa.
Description.Thallus crustose, endolithic, causing no discoloring of rock, hyphae thinwalled, mostly 2–3 μm thick, with cells 4–6 μm in length, I,- spreading to 6 cm, usually continuous between apothecia, apothecia usually dispersed. Algal layer not readily apparent beneath apothecia but discontinuous throughout the endolithic thallus in scattered clumps of lichenized green algal cells to 10 μm epruinose, rugulose, distinctly superficial, round to irregular especially after division of apothecia, (0.4–)1.0–1.5(–2.0) mm in diam., plane to convex, margin smooth or knobby or crenulate, disc surface rough, black, carbonized, with distinct ridges, umbos, and/or knobs, irregular, uncarbonized furrows. Apothecia becoming partitioned by distinct carbonized abscission fissures, splitting apart, replicating by division, and forming independent apothecia in small groups. Exciple of radiating hyphae 2–3 μm in diam., 50–80 μm wide, with black carbonized outer layer, reddish orange inner layer. Hymenium (80–) 100–140 μm high, epihymenium 10 μm thick, conglutinate, reddish brown, hymenial gel IKI+ blue turning red (hemiamyloid). Paraphyses 1.5–2.0 μm wide at midlevel, infrequently branching and anastomosing, apices unexpanded or expanded to 3 μm. Asci 70–90 × 18–25 μm, 50–100 ascospores per ascus. Ascospores hyaline, simple, (3.5–) 4.0–5.0 (–7.0) × (2.0–) 2.5–3.0 (– 4.0) μm, usually ellipsoid to broadly ellipsoid, sometimes subglobose Subhymenium to 60 μm thick, IKI+ blue Hypothecium thin, usually 10 μm, but continuous with parathecium and attaching hyphae, IKI–. Conidiomata not observed.
Chemistry. no secondary metabolites detected.
Distribution and Ecology. In western North America on siliceous rock, sandstone and decaying granite, especially in the Mojave Desert and Colorado Plateau where it is frequent (California, Colorado, Idaho, Nevada, New Mexico, Utah, Wyoming)
Literature. Knudsen, K., Lendemer, J.C., Schultz, M., Kocourková, J., Sheard, J.W., Pigniolo, A., Wheeler, T. (2017) Lichen biodiversity and ecology in the San Bernardino and San Jacinto Mountains in southern California (U.S.A.). Opuscula Philolichenum16: 15-138. Polysporina gyrocarpa and Acarospora gyrocarpa).