Pyrenodesmia rugosa differs from P. micromontana by thicker thallus (125–200 μm vs. 95–125 μm), rugose areoles (vs. flat areoles), larger apothecia (0.2–0.7 mm diam. vs. 0.2–0.4 mm diam.), shorter hymenium (60–70 μm vs. 80–100 μm), shorter hypothecium (50–55 μm vs. 80–100 μm) and narrower tip cells of paraphyses (3–4.5 μm vs. 5–6 μm).

South Korea, Gangwon Province, Gangneung, Okgye-myeon, Mt. Seokbyung (summit), 37°35.21'N, 128°53.87'E, 1,072 m alt., on calcareous rock, 17 June 2020, B.G.Lee & H.J.Lee 2020-000902, with Athallia cf. vitellinula (Nyl.) Arup, Frödén & Søchting, Bagliettoa baldensis (A. Massal.) Vězda, Catillaria lenticularis (Ach.) Th. Fr. and Staurothele aff. succedens (Rehm) Arnold (holotype: BDNA-L-0001102!); same locality, on calcareous rock, 17 June 2020, B.G.Lee & H.J.Lee 2020-000899, with Athallia cf. holocarpa (Hoffm.) Arup, Frödén & Søchting and Staurothele cf. rupifraga (A. Massal.) Arnold (paratype: BDNA-L-0001099; GenBank MW832828 for ITS, MW832825 for mtSSU and MW832804 for LSU).

Thallus saxicolous (calcicolous), crustose, mainly areolate or slightly rimose, rugose, greyish-brown to pale brown, often with orange spots, margin indeterminate or determinate when placodioid areoles are arranged around edge, vegetative propagules absent, areoles 0.4–1.0 mm diam., 125–200 μm thick; cortex hyaline with pale brown pigment layer, pale brown pigment K+ purple, 10–40 μm thick, cortical cells granular, 5–10 μm diam., with epinecral layer, 5–7 μm thick; medulla 60–110 μm thick below algal layer or inconspicuous and algal layer shown just above substrate; photobiont coccoid, cells globose to oval, 5–15 μm diam., algal layer 50–70 μm thick. Small crystals present between algal cells, not dissolving in K. Prothallus absent.

Apothecia abundant, scattered or concentrated in centre, rounded, often contiguous or even coalescent when mature, emerging on the surface of thallus, immersed or adnate, slightly constricted at the base, 0.2–0.7 mm diam. Disc flat when young and flat or concave when mature, often white pruinose, black, 200–300 μm thick; zeorine, margin persistent, slightly prominent, generally entire or rarely slightly crenulate, thalline margin paler to disc and showing brown colour, often inconspicuous due to locating below proper margin, proper margin concolorous to disc. Amphithecium present, with small crystals between algal cells, not dissolving in K, 80–130 μm wide laterally, algal layers continuous to the base and underlying the hypothecium, algal cells 5–15 μm diam., cortical layer hyaline with pale brownish pigment at periphery, 10–40 μm thick. Parathecium well-developed, hyaline, but grey with slightly brown pigment concolorous to epihymenium at periphery, 20–40 μm wide laterally and 50–90 μm wide at periphery. Epihymenium grey with slightly brown pigment, K+ purple, tiny granules abundant on surface, not dissolving in K, 5–10 μm high. Hymenium hyaline, 60–70 μm high. Hypothecium hyaline, base open and extending downwards, 50–55 μm high. Oil droplets present in upper hypothecium, but absent in hymenium. Paraphyses septate, often anastomosing, 2–2.5 μm wide, generally simple, but occasionally branched at tips, tips slightly swollen, not pigmented, 3.0–4.5 μm wide. Asci oblong to narrowly clavate, 8-spored, 52–60 × 14–18 μm (n = 5). Ascospores ellipsoid, 1-septate, polarilocular when mature or narrow septum remaining, hyaline permanently, 11–18 × 5.5–11 μm (mean = 14.1 × 7.6 μm; SD = 1.6(L), 1.0(W); L/W ratio 1.5–2.5, ratio mean = 1.9, ratio SD = 0.3; n = 105), septum 1.5–3.0 μm. Pycnidia not detected.

Thallus K–, KC–, C–, Pd–. Epihymenium K+ purple. Hymenium I+ blue. UV–. No lichen substance was detected by TLC.

The species occurs on the calcareous rock. The species is currently known from the type collections.

The species epithet indicates the lichen’s thallus texture, rugose or wrinkled, which is the key characteristic distinguished from closely-related calcicolous species in the genus Pyrenodesmia.

The new speices is similar to P. micromontana, P. microstepposa and Caloplaca micromarina Frolov, Khodos. & Vondrák in having epilithic thallus without vegetative propagules, small apothecia generally less than 0.5 mm diameter and the substrate preference to calcareous rocks. The new species differs from P. micromontana by thicker thallus (125–200 μm vs. 95–125 μm), rugose areoles (vs. flat areoles), larger apothecia (0.2–0.7 mm diam. vs. 0.2–0.4 mm diam.), shorter hymenium (60–70 μm vs. 80–100 μm), shorter hypothecium (50–55 μm vs. 80–100 μm) and narrower tip cells of paraphyses (3–4.5 μm vs. 5–6 μm) (Frolov et al. 2016).

The new species is different from P. microstepposa by darker thallus (greyish-brown to pale brown vs. ochre, grey or grey-white), rugose thallus (vs. flat thallus), thinner thallus (125–200 μm vs. 85–370 μm), smaller algal cells (5–15 μm diam. vs. 13.5–20.5 μm diam.), presence of pruina on disc (vs. absence of it), absence of oil droplets in hymenium (vs. presence of it), greyish epihymenium (vs. brownish epihymenium), wider ascospores (11–18 × 5.5–11 μm with the L/W ratio of 1.5–2.5 vs. 13.6–18.4 × 6–7.9 μm with the ratio of 1.9–2.9) (Frolov et al. 2016).

The new species is distinguished from C. micromarina by darker thallus (greyish-brown to pale brown vs. ochre to grey), rugose thallus (vs. flat thallus), absence of pruina on thallus (vs. presence of it), shorter hymenium (60–70 μm vs. 90–100 μm), shorter septum (1.5–3 μm vs. 2.6–3.4 μm) and the habitat preference to mountain rocks (vs. coastal rocks) (Frolov et al. 2016).

Additional specimens examined: South Korea, Gangwon Province, Okgye-myeon, Mt. Seokbyung (summit), 37°35.21'N, 128°53.87'E, 1,072 m alt., on calcareous rock, 17 June 2020, B.G.Lee & H.J.Lee 2020-000889, with Bagliettoa baldensis, Catillaria lenticularis, Fulgogasparrea decipioides (Arup) S.Y. Kondr., M.H. Jeong, Kärnefelt, Elix, A. Thell & Hur and Laundonia flavovirescens (Wulfen) S.Y. Kondr., Lőkös & Hur (BDNA-L-0001089); same locality, on calcareous rock, 17 June 2020, B.G.Lee & H.J.Lee 2020-000909, with Bagliettoa baldensis, Rusavskia elegans (Link) S.Y. Kondr. & Kärnefelt and Verrucaria nigrescens Pers. (BDNA-L-0001109); same locality, on calcareous rock, 17 June 2020, B.G.Lee & H.J.Lee 2020-000910, with Bagliettoa baldensis, Catillaria lenticularis and Laundonia flavovirescens (BDNA-L-0001110); same locality, on calcareous rock, 17 June 2020, B.G.Lee & H.J.Lee 2020-000911, with Athallia cf. vitellinula, Bagliettoa baldensis, Lichenella sp. and Rusavskia elegans (BDNA-L-0001111); same locality, on calcareous rock, 17 June 2020, B.G.Lee & H.J.Lee 2020-000913, with Athallia cf. vitellinula, Bagliettoa baldensis, Endocarpon sp., Laundonia flavovirescens, Lichenella sp. and Rusavskia elegans (BDNA-L-0001113); same locality, on calcareous rock, 17 June 2020, B.G.Lee & H.J.Lee 2020-000916, with Caloplaca sp., Endocarpon sp., Lichenella sp. and Rusavskia elegans (BDNA-L-0001116).

Huriella aeruginosa differs from ‘Squamulea’ chelonia by dark greenish-grey to grey thallus without pruina (vs. yellow orange to deep orange thallus with white pruina), gold to yellow-brown epihymenium (vs. orange epihymenium), larger ascospores (7.5–12 × 4.5–7.5 μm vs. 8–10.4 × 4.7–6.0 μm) and the chemistry (thallus K–, KC– and no substance vs. thallus K+ purple, KC± purplish and the presence of parietin, teloschistin, fallacinal, parietinic acid and emodin).

South Korea, Gangwon Province, Gangneung, Okgye-myeon, Mt. Seokbyung (summit), 37°35.21'N, 128°53.87'E, 1,072 m alt., on calcareous rock, 17 June 2020, B.G.Lee & H.J.Lee 2020-000872, with Bagliettoa baldensis, Catillaria lenticularis, Endocarpon subramulosum Y. Joshi & Hur, Laundonia flavovirescens, Rusavskia elegans and Verrucaria nigrescens (holotype: BDNA-L-0001072!; GenBank MW832829 for ITS).

Thallus saxicolous (calcicolous), crustose, mainly areolate or slightly rimose, placodioid around edge, but without distinct lobes, thin, dark greenish-grey to grey, occasionally pale yellowish-grey when young, margin indeterminate or determinate when placodioid areoles are arranged around edge, vegetative propagules absent, areoles 0.3–0.7 mm diam., 150–200 μm thick; cortex hyaline with dark green pigment layer, 15–25 μm thick, cortical cells granular, coarsely anticlinally arranged, 5–10 μm diam., with epinecral layer, up to 5 μm thick; medulla 80–100 μm thick, below algal layer, with large crystals (materials of substrate possibly) and brown cells (dead algal cells possibly); photobiont coccoid, cells globose to oval, 5–25 μm. Small crystals in cortex, medulla and between algal cells, dissolving in K. Prothallus absent.

Apothecia abundant, scattered and not concentrated in centre, rounded, often contiguous when mature, emerging on the surface of thallus, immersed, adnate or rarely sessile, constricted at the base, 0.2–0.4 mm diam. Disc flat when young and flat or slightly convex when mature, not pruinose, orange from the beginning, 110–230 μm thick; margin persistent, even to disc or slightly prominent, generally entire or slightly crenulate, thalline margin concolorous to disc, proper margin inconspicuous. Amphithecium well-developed, with small crystals between algal cells, dissolving in K, 50–55 μm wide laterally, algal layers continuous to the base or solitarily remaining in amphithecium, algal cells 5–25 μm diam., cortical layer hyaline with gold to yellow-brown pigment concolorous to epihymenium at periphery, 15–20 μm thick. Parathecium inconspicuous, hyaline but gold to yellow-brown at periphery, ca. 10 μm wide laterally and ca. 20 μm wide at periphery. Epihymenium gold to yellow-brown, granular, pigment K+ wine red and dissolved, 10–20 μm high. Hymenium hyaline, 45–55 μm high. Hypothecium hyaline, 35–45 μm high. Oil droplets present, small, along paraphyses and more in the base of hymenium and hypothecium. Paraphyses septate, anastomosing, 2–3 μm wide, simple or branched at tips, tips swollen or slightly swollen, not pigmented, 3.5–5.5 μm wide. Asci clavate, 8-spored, 35–48 × 14–17 μm (n = 5). Ascospores generally ellipsoid, occasionally globose, 1-septate, polarilocular or narrow septum remaining, hyaline permanently, 7.5–12 × 4.5–7.5 μm (mean = 9.9 × 5.7 μm; SD = 0.9(L), 0.6(W); L/W ratio 1.2–2.3, ratio mean = 1.8, ratio SD = 0.2; n = 104), globose spores 7.5–9 × 7.0–9.2 μm (mean = 8.0 × 7.7 μm; SD = 0.8(L), 0.9(W); L/W ratio 1.0–1.1, ratio mean = 1.0, ratio SD = 0.1; n = 11). Pycnidia not detected.

Thallus K–, KC–, C–, Pd–. Apothecia K+ wine red. Epihymenium K+ wine red. Epihymenium and hymenium I+ blue. UV–. No lichen substance was detected by TLC.

The species occurs on the calcareous rock. The species is currently known from the type collection.

The species epithet indicates the lichen’s thallus colour, dark green, which is the key characteristic distinguished from all the species in the genus Huriella.

The morphological classification of the new species is not clear between Huriella and Squamulea because the new species has some characteristics for the former genus and others for the latter, i.e. the new species represents mainly areolate thallus without lobed margin and smaller apothecia for the former, whilst showing some squamulose thallus and wider ascospores for the latter (Table 2). The molecular results concluded the new species classification into the former genus, Huriella.

The new species is unique with the key characteristics of green pigmented thallus (with a distinct green layer in a section) and the substrate preference to calcareous rocks amongst all Huriella species.

The new species is similar to ‘Squamulea’ chelonia, Squamulea galactophylla,‘Squamulea’ humboldtiana, S. parviloba and S. subsoluta in the substrate preference to calcareous rocks. However, the new species is different from ‘Squamulea’ chelonia by dark greenish-grey to grey thallus without pruina (vs. yellow orange to deep orange thallus with white pruina), gold to yellow-brown epihymenium (vs. orange epihymenium), larger ascospores (7.5–12 × 4.5–7.5 μm vs. 8–10.4 × 4.7–6.0 μm) and the chemistry (thallus K–, KC– and no substance vs. thallus K+ purple, KC± purplish and the presence of parietin, teloschistin, fallacinal, parietinic acid and emodin) (Bungartz et al. 2020).

The new species differs from S. galactophylla by thallus colour (dark greenish-grey to grey vs. dirty white to yellowish-brown), flat to convex disc (vs. flat disc only), yellowish-orange apothecia (vs. cinnamon-brown apothecia), smaller ascospores (7.5–12 × 4.5–7.5 μm vs. 10–15 × 5–7 μm) (Fink 1935; Arup 2013).

The new species is distinguished from‘Squamulea’ humboldtiana by dark greenish-grey to grey thallus without pruina (vs. yellow-orange to deep orange thallus with pruina), absence of prothallus (vs. presence of prothallus), larger ascospores (7.5–12 × 4.5–7.5 μm vs. 8.1–9.9 × 4.8–5.9 μm) and the chemistry (thallus K–, KC– and no substance vs. thallus K+ purple, KC± purplish and the presence of parietin, teloschistin, fallacinal, parietinic acid and emodin) (Bungartz et al. 2020).

The new species differs from S. parviloba by dark greenish-grey to grey thallus (vs. yellow-orange to orange thallus), absence of lobes (vs. short narrow elongated lobes around edge), convex and yellow-orange disc (vs. flat and deep orange disc), smaller ascospores (7.5–12 × 4.5–7.5 μm vs. 11–14 × 5.5–7 μm) and the chemistry (thallus K– vs. thallus K+ red) (Wetmore 2003; Nash III TH et al. 2007).

The new species is different from S. subsoluta by dark greenish-grey to grey thallus (vs. yellow-orange, orange to reddish-orange thallus), absence of prothallus (vs. black prothallus), flat to convex, yellow-orange apothecia (vs. flat to concave, deep orange apothecia) and the chemistry (thallus K– and no substance vs. thallus K+ red, the presence of parietin, fallacinal, emodin and teloschistin) (Wetmore 2003; Nash III TH et al. 2007).

The most distinctive characteristic of the new species is the thallus colour, i.e. dark greenish-grey to grey, which is different from all comparable calcicolous species in the genus Squamulea.