Acarospora carbonacea J. X. Wang, F. H. Liang & L. Hu sp. nov.Fig. 2Type.China • Gansu Province: Jiuquan City, Aksay Kazakh Autonomous County, Dangjin Mountain pass, 39°19'38"N, 94°15'54"E, alt. 3719 m, on calcareous rock, 5 Aug. 2022, L. Hu et al. 20222137 (SDNU, holotype).Diagnosis.Similar to Sarcogyne plicata (Knudsen and Kocourková 2011) but differs by its round apothcia (vs. lirellate apothecia), disc with carbonized epihymenial accretions (vs. without carbonized epihymenial accretions), lower hymenium 60–90 μm (vs. 100–140 μm), hymenial gel IKI + red or blue turning red (vs. IKI + blue), and only occurs on the calcareous rocks in arid and high-altitude areas, rather than on granite in drainages, washes and flood plains.Etymology.Its name derives from the characteristic carbonization of its apothecia.Description.Thallus endolithic, algal cells 6–10 μm wide, scattered clusters in the substrate, sometimes developing white epilithic ecorticate thallus. Apothecia lecideine, round to irregular, 0.2–1 mm wide, 0.2–0.4 mm thick, usually contiguous, small apothecia usually emerging from mycelial base, sometimes compound with two hymenia, disc black usually round or irregular with carbonized epihymenial accretions, sometimes forming one umbo, slightly lower than margin. Margin segmented, usually in short linear sections at joints, 50–100 μm wide. Parathecium 40–70 μm wide, outer layer carbonized, 20–40 μm wide, inner layer hyaline, 20–30 μm wide. Hymenium 60–90 μm tall, epihymenium reddish brown, 15–25 μm tall, paraphyses 1–2 μm wide, apices expanded up to 4 μm wide in brown caps, hymenial gel IKI + red or blue turning red, hemiamyloid. Asci clavate, 60–80 × 20–25 μm, ascospores several hundred per ascus, ellipsoid, 4–5 × 2–3 μm, usually with two oil drops. Subhymenium 40–50 μm tall, IKI + blue to dark blue, euamyloid. Hypothecium indistinct to 10 μm thick. Pycnidia not observed. Not producing secondary metabolites.Habitat and distribution.This new species is currently known only from Jiuquan city in Gansu Province, and occurs on calcareous rocks in arid regions at an elevation of 3719 m.Additional specimens examined.China • Gansu Province: Jiuquan City, Aksay Kazakh Autonomous County, Dangjin Mountain pass, 39°19'38"N, 94°15'54"E, alt. 3719 m, on calcareous rock, 5 Aug. 2022, L. Hu et al. 20222137, 20222151 (SDNU).Note.This species is similar to Acarospora brodoana in having carbonized accretions on the disc surface, but is distinguished by a white thallus with epilithic and ecorticate, smaller apothecia 0.2–1 mm (vs. 1–1.5 mm), lower hymenium 60–90 μm (vs. 150–170 μm), and the absence of a black hypothecium (vs. black hypothecium) (Knudsen et al. 2016). Acarospora carbonacea is also similar to A. profusa, but the latter differs in having thinner ascus 100–90 × 10–12 μm (vs. 60–80 × 20–25 μm), smaller ascospores 1–1.5 × 1 μm (vs. 4–5 × 2–3 μm), and producing low amounts of norstictic acid (vs. producing no secondary metabolites) (Knudsen et al. 2025 a).