[Italy] ad saxa dolomitica in opp. Auronzo (Col della Favola) (VER!).

Prothallus not visible. Thallus pale brownish grey to pale greyish brown, rarely medium brown, continuous to rimose, rarely areolate, up to 0.2 mm thick, in one specimen surrounded by one dark line, algal cells c. 6–11 μm. Perithecia 0.21–0.38 mm in diam., 1/2–3/4-immersed, not leaving pits to leaving shallow pits; c. 60–160 perithecia / cm². Ostiole dark, plane to depressed, c. 20–50 μm wide, ostiolar depression up to 120 μm wide. Involucrellum apical, exceeding half of the exciple to rarely to the exciple base level, 30–80 μm thick, appressed to the exciple or to clearly diverging from it. Exciple 0.16–0.29 mm, wall pale to dark brown (usually brown), c. 17–20 μm thick. Periphysoids c. 20–40(–50) × 1.5–2 μm. Asci c. 62–72 × 26–32 μm, 8-spored. Ascospores 0–1-septate, (20.3–)24.5–26.9–29.2(–32.1) × (9.2–)10.6–11.5–12.4(–13.3) μm (n = 86).

The species occurs in northern Finland in Enontekiö, Kuusamo and Salla parishes on dolomite rock outcrops, boulders, stones and pebbles. Several collections come from the calcareous fells of Saana and Toskalharji in Enontekiö. In the biogeographical province Koillismaa, the species is very rare, and it has been confirmed only from two localities (one in Kuusamo and one in Salla). The species grows mostly on dry sun-exposed calcareous rocks. However, some localities on river and brook shores are probably periodically submerged.

The Finnish specimens are included in T. auruntii, because no clear morphological differences between the type of T. auruntii and the Finnish specimens were found. However, the type has slightly shorter spores: 20–26 × 10–14 μm. The type of T. auruntii is from the Dolomites in northern Italy. It is possible that T. auruntii is an arctic-alpine species. Sequences from the Dolomites are needed to confirm whether the Finnish specimens are conspecific with T. auruntii.

Pykälä (2007) reported the species as T. pyrenophorum (Ach.) Körb. from Finland, but the specimens differ morphologically from T. pyrenophorum (type: Helvetia, H-ACH-685!). The type of T. pyrenophorum differs in larger perithecia: 0.35–0.7 mm. According to our ITS phylogeny, the two species are rather closely related (Fig. 1) if the GenBank specimen of T. pyrenophorum from Sweden is correctly identified. Thelidium methorium (Nyl.) Hellb. is characterised by large perithecia, thick involucrellum, larger spores (mean 34 × 14 μm) and occurrence on siliceous rocks (Thüs and Nascimbene 2008; Orange 2013). Thelidium pertusatii (Garov.) Jatta resembles T. methorium but has a very thick involucrellum (110–170 μm thick) (Thüs and Nascimbene 2008). The differences between closely related T. pseudoauruntii and T. sallaense are discussed below.

Several other Thelidium species are morphologically rather similar to T. auruntii. Thelidium incinctum (Vain.) Vain. (Finland, Kuusamo, Porontimajärvi, 12.8.1867, F.Sileń (H!, H-NYL6941, syntypes)) differs in thicker involucrellum (70–80 μm thick), larger spores (25–38 × 12–15 μm) and occurrence on siliceous rock. It is only known from the type collection. Thelidium bubulcae (A.Massal.) Arnold described from Italy (ad saxa ipocretacea (Preapura) M. Bolca (M. Colle), 1854, A.Massalongo (VER!); Veneto; ad saxa arenacea oppidi Bolca (M. Colle) in prov. Veronensi Massalongo, Anzi: Lich. Rar. Veneti 136 (UPS-L-686416!, syntypes?) is rather similar to T. auruntii but may possibly differ by shorter, apical involucrellum and areolate thallus. Thelidium lacromense Zschacke ([Croatia] ins. Lacroma: An frei liegenden Gestein, c. 10 m, Kalk, 11.9.1907, A.Latzel (PRM-858048!, syntype)) is morphologically similar to T. auruntii, but the type locality is close to sea level in Croatia and thus not likely to belong to the same species as the Finnish material of T. auruntii. Thelidium athallinum Servít (Slovakia, Vysoké Tatry, monte Tokárna, supra saxa conglom., 1100–1200 m, 1925, Suza (PRM-858571!, syntype)) differs in thicker involucrellum (c. 80–100 μm thick).

Finland, Koillismaa, Salla, Oulanka National Park, 400 m N of Savilampi, shore of river Savinajoki, dolomite rock outcrop, on NE-slope, 177 m a.s.l, 66°25'N, 29°10'E, 13 August 2009, J.Pykälä 36339 (H); Kuusamo, Oulanka National Park, Mataraniemi, shore of Oulankajoki river, treeless stony river shore, on dolomite stones, 145 m a.s.l, 66°22'N, 29°20'E, 26 August 2011, J.Pykälä 45171 (H); Enontekiön Lappi, Enontekiö, Porojärvet, Toskalharji, Toskaljärvi N, fell, dried old brook bottom, stony bottom, on dolomite pebbles, 707 m a.s.l., 69°11'N, 21°26'E, 3 August 2011, J.Pykälä 43414 (H); Enontekiö, Porojärvet, Toskalharji, Toskaljärvi N, fell, brook, W-shore, dolomite rock, outcrop, on N-slope, 710 m a.s.l, 69°11'N, 21°26'E, 3 August 2011, J.Pykälä 43446 (H); Enontekiö, Porojärvet, Toskalharji, Toskaljärvi N, fell, brook, W-shore, dolomite rock outcrop, on dolomite stones, 710 m a.s.l, 69°11'N, 21°26'E, 3 August 2011, J.Pykälä 43470 (H); Enontekiö, Porojärvet, Toskalharji, Toskaljärvi N, gentle SE-slope, alpine grassland, on dolomite boulder, 705 m a.s.l, 69°11'N, 21°26'E, 3 August 2011, J.Pykälä 43829 (H); Enontekiö, Kilpisjärvi, Saana, nature reserve, W-part, fell, dolomite rock outcrop, on SW-facing wall, 695 m a.s.l, 69°03'N, 20°48'E, 9 August 2011, J.Pykälä 43905 (H).

Differing from T. incavatum by the perithecia often less immersed in rock, the involucrellum present in most perithecia and the exciple wall is thicker, most difficult to separate from T. mendax but the involucrellum on average is shorter.

Finland, Koillismaa, Salla, Oulanka National Park, 400 m N of Savilampi, shore of river Savinajoki, dolomite rock outcrop, on NE-slope, scarce, 178 m a.s.l, 66°25'N, 29°10'E, 13 August 2009, J.Pykälä 36334 (H-9204893, holotype, UPS, isotype, GenBank accession number: OP901851).

Prothallus not visible. Thallus white, grey or pale brown, endolithic to rarely thinly epilithic, algal cells c. 5–8 μm, in one specimen (type) surrounded by dark lines. Perithecia 0.12–0.44 mm in diam., 1/2–1-immersed, often surrounded by thalline collar, leaving shallow to usually deep pits; c. 20–80 perithecia / cm². Ostiole pale to dark, plane to depressed, c. 20–50 μm wide. Involucrellum absent, apical or covering half of the exciple, 0–70 μm thick, appressed to the exciple or clearly diverging from it. Exciple 0.22–0.38 mm, wall dark brown to black, c. 25–40 μm thick, apex may be thickened to 50–70 μm thick. Periphysoids c. 30–50 × 1.5–2.5 μm. Asci c. 91–132 × 31–48 μm, 8-spored. Ascospores (1–2–)3-septate, few spores submuriform with 5–6(–8) cells, (32.3–)35.3–37.8–40.4(–44.4) × (12.6–)14.0–15.0–16.1(–17.3) μm (n = 69).

Figure 2. 

A Thelidium declivum (holotype) B T. huuskonenii (holotype) C T. mendax (holotype) D T. pseudoauruntii (holotype) E T. sallaense (holotype) F T. toskalharjiense (holotype). Scale bars: 1 mm (A–C, E, F); 0.5 mm (D).

The species occurs in NE Finland, in the parishes of Kuusamo and Salla, on dolomite rock outcrops and boulders. The species may prefer rather shady habitats. Most localities are close to river shores.

The species prefers steep rock outcrops.

This species was previously reported from Finland as T. larianum A. Massal. (Pykälä 2010b). The type specimen of T. larianum A. Massal. (in calcaris ubique, Garovaglio, VER!) is in poor condition, and thus, the identity of the species cannot be solved. According to Zschacke (1934), the spore size of T. larianum is smaller: 25–36 × 11–15 μm than the size in the Finnish specimens. The protologue (Massalongo 1855): “in circa Larium Lacum ad saxa calcareo-bituminosa Clar. Prof. Garov.”, i.e., the locality is close to Lake Como, and the collector is S. Garovaglio. Thus, the climatic conditions of the type locality are likely to strongly differ from those in NE Finland, and it is likely that the Finnish specimens do not belong to T. larianum. Based on the Finnish distribution, it could be assumed that T. declivum may be an eastern species, which has its main distribution in Russia and/or in North America.

Polyblastia torrentis Servít (Sweden. Torne Lappmark: Jukkasjärvi par., Abisko, Regio subalpina by the torrent, alt. 400 m, 29.7.1921, A.H.Magnusson; UPS!, syntype) differs in less immersed perithecia (1/4–1/2-immersed) leaving shallow pits. Exciple may also be smaller (in studied perithecia c. 0.2–0.22 mm), but according to Servít (1953) the size of the exciple is c. 0.3 mm.

Thelidium declivum is difficult to separate from T. incavatum and the closely related T. mendax. Thelidium incavatum has predominantly fully immersed perithecia, and 3/4-immersed perithecia are usually overmature, whereas T. declivum has predominantly 3/4–immersed perithecia. Furthermore, the involucrellum is absent from most specimens of T. incavatum, whereas the involucrellum occurs in most perithecia, and in all studied specimens of T. declivum. Thelidium incavatum also has a thinner exciple wall: c. 15–25 μm thick. Thelidium mendax may differ in longer involucrellum, but more material is needed to determine whether this character can be used to separate the species from T. declivum.

Finland, Koillismaa, Kuusamo, Oulanka, Putaanoja, 500 m W-NW of Hautala, dolomite rock outcrop, beneath N-facing wall, on boulder, 228 m a.s. l., 66°22'N, 29°25'E, 9 August 2009, J.Pykälä 35996 (H); Salla, Oulanka National Park, Savikoski 300 m N, shore of lake Savilampi, calciferous (dolomite) schistose rock outcrop, on N-facing wall, 175 m a.s.l, 66°25'N, 29°10'E, 10 August 2010, J.Pykälä 39640 (H); Salla, Oulanka National Park, Savilamminniemi, shore of lake Savilampi, cliff, calciferous (dolomite) schistose rock outcrop, on S-facing wall, 172 m a.s.l, 66°25'N, 29°10'E, 12 August 2010, J.Pykälä 39780b (H); Kuusamo, Oulanka, Putaanoja, 500 m W-NW of Hautala, dolomite rock outcrop, on NE-facing wall, 230 m a.s.l., 66°22'N, 29°25'E, 15 August 2010, J.Pykälä 39997 (H), 40037 (H), 40047 (H); Kuusamo, Oulanka National Park, Taivalköngäs, shore of Oulankajoki river, Picea abies-dominated herb-rich forest, dolomite rock outcrop, NE-slope, on dolomite boulder, 174 m a.s.l, 66°24'N, 29°11'E, 20 August 2011, J.Pykälä 44554 (H); Kuusamo, Oulanka National Park, Taivalköngäs, shore of Oulankajoki river, dolomite rock outcrop, on NW-facing wall, 165 m a.s.l, 66°24'N, 29°11'E, 25 August 2011, J.Pykälä 45123 (H).

Species morphologically rather similar to T. auruntii, but the spores smaller, perithecia often leaving deep pits, and the thallus predominantly endolithic.

Holotype. Finland, Enontekiön Lappi, Enontekiö, Kilpisjärvi, Saana, fell, steep NE-slope, dolomite rock outcrop, on NE-facing wall, abundant, 820 m a.s.l, 69°02'N, 20°51'E, 11 August 2011, J.Pykälä 44167 (H9204900, GenBank accession number: OP901862).

Prothallus not visible. Thallus white to grey, endolithic to thinly epilithic, only surrounding perithecia, algal cells, c. 4–7 μm, in one specimen surrounded by one dark line. Perithecia 0.18–0.32 mm in diam., (1/2–)3/4–1-immersed, leaving shallow to deep pits; c. 80–120 perithecia / cm². Ostiole pale to dark, plane to depressed, c. 20–40 μm wide. Involucrellum absent, apical or covering half of the exciple, 0–60 μm thick, appressed to the exciple or clearly diverging from it. Exciple 0.20–0.28 mm, wall dark brown to black, c. 15–20 μm thick, apex may be thickened to 50–80 μm thick. Periphysoids c. 20–45 × 1.5–2 μm, branching. Asci c. 58–74 × 22–25 μm, 8-spored. Ascospores (0–)1-septate, (16.4–)18.2–20.7–23.2(–27.6) × (8.0–)8.6–9.9–11.2(–14.4) μm (n = 69).

Four specimens have been confirmed by sequencing, but more than twenty morphologically similar specimens have been collected from the calcareous fells of Saana and Toskalharji. The species seems to occur only in northern Finland, in Enontekiö on fells on dolomite rock outcrops, boulders, stones and pebbles. It grows on southern and northern slopes and on rather flat surfaces. The altitudinal range is 705–890 m a.s.l.

Figure 3. 

Drawn anatomical features of the newly described Thelidium species. Represented perithecial features are similar between T. huuskonenii and T. toskalharjiense, as well as between T. declivum and T. mendax; therefore, they are shown combined. Spores are represented as intermediate size for all species A perithecia of T. huuskonenii and T. toskalharjiense combined B spores of T. huuskonenii C spores of T. toskalharjiense D perithecium of T. pseudoauruntii E spores of T. pseudoauruntii F perithecium of T. sallaense G spores of T. sallaense H perithecia of T. declivum and T. mendax combined I spores of T. declivum J spores of T. mendax. Scale bars for perithecia are 100 μm, and for spores 20 μm. Illustration: A. Kantelinen

The species is named after A.J.Huuskonen, the Finnish amateur lichenologist, who most intensively collected lichens from the Enontekiö area.

The species differs from T. auruntii in smaller spores, perithecia often leaving deep pits and thinner, predominantly endolithic, thallus. The species has been previously reported from Finland as T. decussatum (Pykälä 2010a). The Finnish specimens have similar perithecia and involucrellum as T. decussatum. However, T. decussatum ([Germany] Trier, 1862, Mezler, Rabenhorst Lichenes Europaei 646 (UPS!, syntype)) has a rimose thallus and the spores may be slightly larger (20–25 × 10–11 μm). Furthermore, the type locality is in a temperate zone in lowland Germany. Phytogeographically, it is unlikely that such species would occur only in fells in the northwestern most part of Finland. Thelidium stenosporum Servít (Slovakia: Bielské Tatry: in rup. calc. in convalle Dominův důl, … m. Havran … norg, 1700 m, 1937, Suza (PRM-858497!, syntype)) has smaller perithecia and narrower spores. Thelidium bubulcae (A.Massal.) Arnold (syntypes: VER, UPS-L-686416!)) has larger rimose to areolate thallus, larger perithecia (0.2–0.37 mm) and larger spores: 20–27 × 9–13 μm. Thelidium polycarpum Servít (Montenegro, Lovčen, Ljubin potok, 1230 m, 1929, Servít (PRM-858491!, holotype)) has smaller perithecia (0.13–0.23 mm) and spores (15–23 × 8–9 μm). Thelidium klementii Servít has rather thick rimose to areolate thallus and slightly larger spores and is only known from a temporarily inundated calcareous rock (Thüs and Nascimbene 2008).

Finland. Enontekiön Lappi, Enontekiö, Kilpisjärvi, Saana fell, Saana nature reserve, low arctic zone, on SW-facing wall of dolomite rock outcrop, 880 m a.s.l., 69°02'N, 20°51'E, 27 July 2007, J.Pykälä 31576 (H); Enontekiö, Porojärvet, Toskalharji, Toskaljärvi N, fell, dolomite rock outcrop, on S-slope, 730 m a.s.l, 69°12'N, 21°26'E, 2 August 2011, J.Pykälä 43243 (H); Enontekiö, Porojärvet, Toskalharji, Toskaljärvi N, fell, dolomite rock outcrop, on dolomite pebbles, 735 m a.s.l, 69°12'N, 21°26'E, 2 August 2011, J.Pykälä 43246 (H).

[England] 282. Bilsdale, Yorkshire, W.Mudd (M-0207325!, syntype?).

Prothallus not visible. Thallus white to grey, endolithic, in two specimens partly epilithic, slightly rimose, up to 0.1–0.15 mm thick, algal cells c. 4–6 μm. Perithecia 0.06–0.36 mm in diam., (1/2–)3/4–1-immersed, often thalline covered except apex, leaving deep pits; c. 20–160 perithecia / cm². Ostiole pale to dark, plane, c. 20–40 μm wide. Involucrellum absent or apical, c. 30–60(–90) μm thick. Exciple 0.16–0.39 mm, wall dark brown to black, c. 15–25 μm thick, often with ostiolar neck, often pear-shaped. Periphysoids c. 40–50 × 1.5–2 μm. Asci c. 93–122 × 33–52 μm, 8-spored. Ascospores 3-septate, few spores submuriform with 5–7 cells, (32.3–)37.5–40.9–44.3(–49.4) × (12.2–)13.7–14.9–16.2(–18.1) μm (n = 78), rarely with a perispore c. 1 μm thick.

The species occurs in many localities in SW Finland on calcareous rocks and in lime quarries. It occurs on south- as well as on north-facing walls and on gentle slopes. More rarely, it grows on boulders, stones and pebbles. At present, more than 50 localities are known. Most localities are in the hemiboreal vegetation zone, a few in the southern boreal vegetation zone, only some tens of kilometres north of the limit of the hemiboreal zone. However, one separate locality occurs in Kuopio (former Juankoski) in eastern central Finland. Thelidium incavatum may be the most common species of Thelidium in SW Finland, together with T. minutulum Körb.

The observed syntype of Polyblastia sepulta is somewhat similar to T. incavatum, and P. sepulta may be the oldest name available for the species. However, better material of P. sepulta is needed to confirm it. Furthermore, it is uncertain whether T. incavatum is the correct name for the Finnish specimens. The syntype in M differs in rimose thallus. However, several localities have been included in the protologue, and the specimen in M may be untypical for T. incavatum. The Finnish specimens fit well with the description of T. incavatum by Orange (2013).

If the Finnish specimens do not belong to T. incavatum, there are two other putative younger names available for them. Thelidium decipiescens was described from SW Finland (Vainio 1921) and is morphologically similar to the sequenced Finnish specimens of T. incavatum. Already Vainio (1921) considered T. decipiescens to be similar to some material of T. incavatum. Thelidium anisomerum Hellb., described from Sweden, is also similar to T. incavatum.

Thelidium bavaricum Dalla Torre & Sarnth. has broader spores (Germany, Bavaria, an den aus den begrasten Boden hervorstehenden Dolomitblöcken oberhalb des Tiefenthales bei Eichstätt, April 1859, Arnold, in Arnold: Lich.. Exs. 87 (UPS-L-165297!, syntype): 30–48 × 15–20 μm, and submuriform spores may be more frequent.

The ITS sequence of the T. incavatum specimen, collected in the separate locality in eastern Finland, differs from the other sequenced specimens (98.5% similarity). The specimen also differs morphologically from the other specimens by less immersed perithecia (1/4–1/2-immersed) and thicker involucrellum (c. 70–90 µm thick). The spores may also be slightly shorter: 28.1–35.7 x 12.8–15.4 µm (n=15). It may represent a separate species but is now included in T. incavatum, awaiting more material.

Finland, Varsinais-Suomi, Parainen (Korppoo), Åfvensår, Kälklot island, calcareous rock outcrop on shore of the Baltic Sea, E-slope, on pebbles, 5 m a.s.l., 60°18'N, 21°31'E, 27 July 2009, J.Pykälä 35282 (H); Salo (Särkisalo), Förby, 200 m S of lime factory, calcareous rock outcrop, on SW-slope, 60°05'N, 22°52'E, 8 September 2009, J.Pykälä 36857 (H); Salo (Särkisalo), Förby, 200 m S of lime factory, abandoned lime quarry, on 40 cm high NW-facing wall, 18 m a.s.l, 60°05'N, 22°52'E, 8 September 2009, J.Pykälä 36867 (H); Parainen (Iniö), Söderby, Biskopsö island, calcareous rock outcrop on shore of the Baltic Sea, on N-slope, 8 m a.s.l, 60°20'N, 21°28'E, 9 June 2010, J.Pykälä 37971 (H); Parainen (Korppoo), Elfsjö, Stora Limskär island, shallow abandoned lime quarry, on N-facing wall, 6 m a.s.l., 60°09'N, 21°26'E, 21 June 2010, J.Pykälä 38227 (H); Parainen (Houtskari), Björkö, Östra Långholm, Norrnäs, siliceous rock outcrop on shore of the Baltic Sea, NW-slope, on narrow calcareous vein, scarce, 9 m a.s.l., 60°15'N, 21°26'E, 29 June 2010, J.Pykälä 38399 (H); Parainen, Petteby, Kalkudden, abandoned lime quarry, on W-facing wall, 18 m a.s.l., 60°17'N, 22°10'E, 5 October 2011, J. Pykälä 46459 (H); Uusimaa, Hyvinkää, Myllykylä, Kalkkikallio, abandoned lime quarry, on N-facing wall, 100 m a.s.l, 60°36'N, 25°03'E, 7 July 2009, J.Pykälä 34722 & H. Rämä (H); Pohjois-Karjala, Kuopio (Juankoski), Siikajärvi, Huosiaisniemi, nature reserve, dolomite rock outcrop on shore of lake Ala-Siikajärvi, on gentle NE-slope, scarce, 97 m a.s.l., 63°12'N, 28°21'E, 26 July 2011, J.Pykälä 42871(H).

Species morphologically rather similar to T. declivum and T. incavatum, but the involucrellum is on average longer.

Holotype. Finland, Koillismaa, Salla, Oulanka National Park, Pikkuköngäs, shore of river Oulankajoki, high cliff, calciferous (dolomite) schistose rock outcrop, W-facing wall, on dolomite patch, 180 m a.s.l, 66°25'N, 29°08'E, 4 August 2010, J.Pykälä 39179 (H-9206536, GenBank accession number: OP901872).

Prothallus not visible. Thallus white to pale brown, endolithic to weakly rimose, algal cells, c. 4–7 μm. Perithecia 0.18–0.38 mm in diam., 1/2–1-immersed, often surrounded by thalline collar, leaving shallow to deep pits; c. 20–60 perithecia / cm². Ostiole pale to dark, plane, c. 20–60 μm wide. Involucrellum apical to exceeding half of the exciple, c. 40–80 μm thick, appressed to the exciple or clearly diverging from it. Exciple 0.18–0.36 mm, wall dark brown to black, rarely pale, c. 20–30 μm thick. Periphysoids c. 40–60 × 1.5–2.5 μm. Asci c. 90–128 × 31–43 μm, 8-spored. Ascospores 3-septate, (34.8–)36.1–40.1–44.1(–51.0) × (11.8–)12.8–13.4–14.0(–14.9) μm (n = 48), perispore 1–1.5 μm thick in few spores.

The species is known from three localities, two in NE Finland, in the parishes Kuusamo and Salla, and one in Juuka in central eastern Finland. Thelidium mendax grows on calcareous rocks and calciferous (dolomite) schistose rocks. Two collection sites are affected by spring flooding and may periodically be submerged.

The species is easily misidentified.

Based on the ITS phylogeny, this species is closely related to T. declivum. It is also morphologically difficult to separate from that species. Thelidium mendax has, on average, longer involucrellum than in T. declivum. Thelidium mendax is here kept separated from T. declivum because this solution received high support value in the ITS phylogeny (99%). Within the species T. declivum and T. mendax have identical ITS sequences and the species have a clear barcoding gap (3% difference).

Polyblastia torrentis (Sweden. Torne Lappmark: Jukkasjärvi par., Abisko, Regio subalpina by the torrent, alt. 400 m, 29 July 1921, A.H.Magnusson (UPS!, syntype)) differs in less immersed perithecia (1/4–1/2-immersed) and thinner involucrellum (c. 30–40 μm thick).

Finland, Koillismaa, Kuusamo, Juuma, Oulanka National Park, Jäkälävuoma, gorge, calciferous (dolomite) schistose rock outcrop, on bottom, shore of a pond, on dolomite coated stone, 200 m a.s.l., 66°15'N, 29°26'E, 16 August 2010, J.Pykälä 40152 (H); Pohjois-Karjala, Juuka, Petrovaara, Riihilahti S, calcareous rock outcrop, on W-facing wall, 190 m a.s.l, 63°09'N, 28°58'E, 13 July 2011, J.Pykälä 42502 (H), 42503 (H).

Species morphologically rather similar to T. auruntii, but the spores are smaller and the perithecia tend to be less immersed.

Holotype. Finland, Kollismaa, Kuusamo, Oulanka National Park, Mataraniemi W, shore of Oulankajoki river, small dolomite rock outcrop, on SE-slope, 147 m a.s.l, 66°22'N, 29°20'E, 28 August 2011, J.Pykälä 45374 (H9220350, GenBank accession number: OP901877).

Prothallus not visible. Thallus pale greyish brown to medium brown, endolithic to rimose, algal cells c. 5–7 μm, with one dark brown thalline line. Perithecia 0.18–0.36 mm in diam., 1/4–1/2-immersed, not leaving pits to leaving shallow pits; c. 50–140 perithecia / cm². Ostiole dark, depressed, c. 20–50 μm wide. Involucrellum covering half of the exciple, c. 40–70 μm thick, appressed to clearly diverging from the exciple. Exciple c. 0.17–0.24 mm, wall pale brown to usually dark brown, c. 15–20 μm thick. Periphysoids c. 20–25 × 2 μm. Asci c. 64–83 × 22–32 μm, 8-spored. Ascospores 0–1-septate, (21.3–)23.9–25.1–26.2(–26.6) × (8.6–)9.2–10.1–11.0(–12.2) μm (n = 23), perispore 1 μm thick present in some spores.

The species is only known from the type locality on small dolomite rock outcrop on the rivershore. The locality is likely to be under water during spring floods. Potentially suitable habitats for the species may be very rare in Finland.

The species resembles morphologically T. auruntii and is also closely related to the species based on the ITS sequences.

The species is closely related to T. auruntii and T. sallaense. Only two specimens are known and from the same locality. We prefer to treat T. pseudoauruntii as a species separate from T. auruntii because of high support value (100%) in the ITS phylogeny. Furthermore, there is a clear barcoding gap (3%) between the species. The species have also different distribution areas. Thelidium pseudoauruntii seems to be absent from the calcareous fells of NW Finland, i.e., from the main distribution area of T. auruntii in Finland. Thelidium pseudoauruntii may be an eastern species with the main distribution area in North America and/or Russia. The specimens of T. pseudoauruntii have smaller spores than in T. auruntii and T. sallaense. Furthermore, the perithecia are less immersed. However, more material is needed to determine whether the species differs unambiguously morphologically from the related species.

Finland, Koillismaa, Kuusamo, Oulanka National Park, Mataraniemi W, shore of Oulankajoki river, small dolomite rock outcrop, on dolomite stones, 145 m a.s.l., 66°22'N, 29°20'E, 28 August 2011, J.Pykälä 45371 (H).

Species morphologically rather similar to T. auruntii, but the thalli may be more brown-pigmented.

Holotype. Finland, Koillismaa, Salla, Oulanka National Park, Savilampi 1,4 km NE, shore of Savinajoki river, river shore, on dolomite stone, 185 m a.s.l., 66°26'N, 29°11'E, 23 August 2011, J.Pykälä 44902 (H9220340, GenBank accession number: OP901878).

Prothallus not visible. Thallus pale brown to medium brown, rimose, algal cells c. 5–8 μm. Perithecia 0.21–0.28 mm in diam., 3/4(–1)-immersed in thallus, not leaving pits; c. 60–80 perithecia / cm². Ostiole brown, plane to depressed, c. 20–60 μm wide. Involucrellum apical, c. 40–50 μm thick, slightly diverging from the exciple. Exciple c. 0.16–0.27 mm, wall pale to brown, K+ olive. Periphysoids c. 20–30 × 2 μm. Asci c. 67–83 × 25–32 μm, 8-spored. Ascospores (0–)1-septate, (26.3–)27.3–28.8–30.2(–31.1) × (12.0–)12.2–12.6–12.9(–13.4) μm (n = 12), perispore 1 μm thick present in some spores.

The species is only known from the type locality growing on dolomite stone on a rivershore. The species is likely to be very rare and threatened in Finland.

The name is according to the parish Salla from where the only known specimen has been collected.

More material is needed to solve whether the species can be morphologically separated from T. auruntii. It may differ from T. auruntii by a more clearly brown pigmented thallus.

Species morphologically rather similar to T. auruntii, but the spores are larger, and the involucrellum is, on average, shorter and thinner.

Holotype. Finland, Enontekiön Lappi, Enontekiö, Porojärvet, Toskalharji, Toskaljärvi N, fell, stony lake shore, on dolomite stones, 705 m a.s.l., 69°11'N, 21°26'E, 3 August 2011, J.Pykälä 43398 (H9206484, GenBank accession number: OP901882).

Prothallus not visible. Thallus grey to pale brownish grey, endolithic to thinly epilithic, rarely rimose, algal cells c. 5–8 μm, sometimes surrounded by dark lines. Perithecia 0.17–0.36 mm in diam., 1/2–3/4(–1)-immersed, leaving shallow to deep pits; c. 60–160 perithecia / cm². Ostiole pale to dark, plane, c. 20–30(–60) μm wide. Involucrellum apical to covering half of the exciple, 20–50 μm thick, appressed to the exciple or strongly diverging from it. Exciple c. 0.15–0.24 mm, wall dark brown to black, c. 20–30 μm thick. Periphysoids c. 20–30 × 2–2.5 μm. Asci c. 73–83 × 23–29 μm, 8-spored. Ascospores 1-septate, (22.4–)26.8–29.1–31.3(–35.5) × (11.8–)12.5–13.4–14.2(–16.1) μm (n = 91).

The species occurs in the fell Toskalharji in northern Finland in Enontekiö within an area of three square kilometres and is divided into three subpopulations. It grows on dolomite boulders, stones and pebbles. Most specimens are from dolomite pebbles. It mostly grows on gentle slopes. The altitudinal range is 705–875 m a.s.l.

The species has been found only in the Toskalharji area.

The species differs from T. auruntii by larger spores, but there is a considerable overlap in the spore size. The involucrellum is, on average, shorter and thinner, but few specimens of T. auruntii may have similar involucrellum to T. toskalharjiense. Nevertheless, based on ITS phylogeny, the species is not closely related to T. auruntii.

Finland, Enontekiön Lappi, Enontekiö, Porojärvet, Toskalharji, Toskalpahta fell, SW-slope, scree, on dolomite pebbles, 790 m a.s.l, 69°11'N, 21°29'E, 1 August 2011, J.Pykälä 43090 (H); Enontekiö, Porojärvet, Toskalharji, Toskaljärvi N, fell, gentle SE-slope, on dolomite boulder, 715 m a.s.l, 69°11'N, 21°26'E, 2 August 2011, J.Pykälä 43211 (H); Enontekiö, Porojärvet, Toskalharji, Toskaljärvi N, fell, gentle SW-slope, dolomite rock outcrop, on dolomite pebbles, 715 m a.s.l, 69°11'N, 21°26'E, 3 August 2011, J.Pykälä 43364 (H); Enontekiö, Porojärvet, Toskalharji, Toskaljärvi N, close by lake shore, gentle NE-slope, alpine grassland on dolomite stone, 706 m a.s.l, 69°11'N, 21°26'E, 7 August 2011, J.Pykälä 43848 (H); Enontekiö, Porojärvet, Toskalharji, Toskaljärvi N, close by lake shore, alpine grassland, gentle SE-slope, dolomite rock outcrop, on dolomite pebbles, 706 m a.s.l, 69°11'N, 21°26'E, 7 August 2011, J.Pykälä 43861 (H).

Prothallus not visible. Thallus whitish grey, endolithic. Perithecia 0.25–0.33 mm in diam., 1/4–1/2-immersed, leaving shallow pits; c. 50 perithecia / cm². Ostiole, tiny, dark, plane. Involucrellum almost to the exciple base, 30–50 μm thick, may thicken to the base to c. 50–60 μm thick, slightly diverging from the exciple. Exciple c. 0.17–0.25 mm, wall dark brown. Periphysoids c. 25–30 × 2 μm. Asci 8-spored. Ascospores 0–1-septate, 23–28 × 10–12 μm.

The specimen has been collected from a dolomite rock outcrop on a fell in northern Finland in Enontekiö.

The specimen probably represents an undescribed species belonging to the T. auruntii complex. However, the specimen is quite small, and thus, better material is needed.

Finland, Enontekiön Lappi, Enontekiö, Porojärvet, Toskalharji, Toskaljärvi N, fell, dolomite rock outcrop, on SW-slope, 715 m a.s.l., 69°11'N, 21°26'E, 2 August 2011, J.Pykälä 43208 (H).

Prothallus not seen. Thallus whitish grey, endolithic. Perithecia 0.17–0.26 mm, 3/4–immersed, leaving deep pits; c. 40–60 perithecia /cm². Ostiole dark, plane to depressed, c. 20–40 µm wide. Involucrellum absent. Exciple c. 0.26–0.32 mm, wall black, apex thickened.

Spores 3-septate, 30–37 x 16–18 µm.

The only specimen has been collected from calcareous pebbles in a lime quarry spoil in SW Lapland.

The specimen is small. It is morphologically similar to T. incavatum and probably closely related to that species, although the relationship remains unsupported. The species may be undescribed but a better specimen is needed for type material.

Finland, Kittilän Lappi, Kolari, Äkäsjokisuu, Mannajoki, former cement factory 200 m N-NW, lime quarry spoil, on calcareous pebbles, 165 m a.s.l, 67°27'N, 23°38'E, 16 August 2018, J.Pykälä 52038 (H).