Pterygoneurum volgense Ignatov & Fedosov, 2025

Fedosov, V. E., Fedorova, A. V., Ignatova, E. A. & Ignatov, M. S., 2025, On the genus Pterygoneurum (Pottiaceae, Bryophyta) in Russia, Arctoa 34 (1), pp. 31-43 : 36-40

Pterygoneurum volgense Ignatov & Fedosov sp. nov., Figs. 2, 3.

Diagnosis: The species is similar to Pterygoneurum lamellatum (Lindb.) Jur. in having leaves with recurved margins, papillose laminal cells and lamellae, operculae with cells in oblique rows, and rudimentary peristome falling off with opercula, but differs from it in having dense, forked papillae on both leaf surfaces and lamellae, and lacking lateral outgrowths on lamellae.

Type: Russia, Volgograd Province, Pallasovka District, Elton Nature Park, 49°12'58"N – 45°40'19"E, 0 m a.s.l., steep slope on the right bank of Chernavka Creek (north of Elton Lake), on soil among Spiraea , 2.V.2023 (loc. 13). Coll. M. Ignatov, E. Ignatova, N. Stepanova & S. Suragina #23-141 (Holotype MHA9063026). DNA: isolates OK4186 & OK4194.

Etymology: The species name refers to the Volga Riv- er: the species is described from its lower course, not far from the Caspian Sea.

Description: Plants small, in dense or loose tufts, greyish-green to brownish-black. Stems from hardly reaching 1 mm to 3 mm long, simple, without central strand, with cortex composed of homogeneous, thin-walled cells. Leaves 0.5–1.4× 0.4–0.6 mm, broadly ovate or lingulate, concave, acute, with hyaline hair-points 0.5– 1.1 mm long, smooth or nearly so, curved to flexuose; margins entire to serrulate above, recurved nearly from the base, in upper leaf portion recurved or broadly revolute, rarely narrowly recurved; costa single, strong, with dorsal stereid band, in upper leaf portion with dorsal epidermis, with large, inflated, thin-walled cells on ventral surface, smooth in basal leaf portion, covered by numerous branched or looking as C-shaped papillae distally, in distal 1/5–1/3 with 1–2(–3) simple lamellae to 6 cells high; upper and median laminal cells rounded-quadrate, short rectangular to transverse-rectangular, (12–)15– 21(–25)×15–19 µm, moderately thick-walled, with 3–8 branched papillae, looking as C-shaped from above; basal leaf cells short rectangular, 20–32×18–25 µm, thin-walled, smooth. Autoicous. Perichaetial leaves to 1.6 mm long, with almost plane margins and lower ventral lamellae. Setae ca. 5 mm. Capsules exserted, cylindric, ca. 1.2 mm long. Opercula differentiated, conic-rostrate with cells in oblique rows. Peristome rudimentary, observed through translucent opercula and usually falling with them. Spores 19–24(–27) µm. Calyptrae cucullate.

Variation: Collections referred to the new species are heterogeneous, likely because of the habitat conditions, and probably also because of the age of plants. The Volgograd plants were collected in a meso-xeric conditions: at base of steep slope to a narrow valley of small creek, under Spiraea hypericifolia shrubs, associated with the moss species characteristic for dry steppes of this region: Encalypta vulgaris , Pterygoneurum ovatum , P. subsessile , Pseudocrossidium hornschuchianum , Microbryum curvicollum , Acaulon triquetrum, Entosthodon hungaricus, and E. pulchellus . Plants of P. volgense formed loose tufts, mostly possessing sporophytes (Fig. 2). In their leaves, hair-points are short or as long as the lamina; margins are slightly recurved to almost revolute (Fig. 3A, H, J); papillae are bifurcate on a relatively narrow stalk, scattered (Figs. 2F, G, 3D).

The Kalmykian plants were collected in more xeric conditions, with the only associated species being P. subsessile . Plants formed a more compact tufts, lacked sporophytes, but had unfertilized archegonia, probably indicating that they started development shortly before being collected. Leaves have long hyaline hair-points that exceed the lamina length and are strongly flexuose. Leaf margins are ranging from slightly recurved (Fig. 3K) to distinctly so (Fig. 3B) and to revolute (Fig. 3C, L). Papillae are simple or forked, the latter are most common in leaf transverse sections (Fig. 3K, L). However, they are mostly low, and in frontal leaf views are of various shape (bifid, solid, and C-shaped) in Z-stacked photographs (Fig. 3E), while look mostly C-shaped or O-shaped in single-shoot photographs (Fig. 3F). The difference in papillae between Volgograd and Kalmykian plans is probably explained by a more xeric, harsh environments in Kalmykia.

Differentiation: By morphology, Pterygoneurum volgense is similar to P. lamellatum and P. arcticum : these three species have recurved to revolute leaf margins, ranging from rather indistinct to quite conspicuous; they are also similar in having long capsules with conic opercula with the counterclockwise spiral rows of cells, and occasional presence of rudimentary peristome, sometimes vestigal, formed of fragments attached to the inner surface of opercula or sometimes wanting.

Pterygoneurum volgense differs from P. arcticum and the Central European P. lamellatum s.str. in having cells with dense, branched papillae. In P. arcticum , papillae are observed on both leaf surfaces, but they are usually very low, simple, and scarce. In European P. lamellatum s.str., papillae are restricted to the dorsal leaf surface, and they are simple, sparse, and low.

The distinction of P. volgense from the undescribed North American species commented by Zander (2007) un- der P. lamellatum , remains unclear, but the occasional absence of lamellae in American plants (vs. always present in P. volgense ), and their occurrence in so distant areas call for their additional comparison, ideally with molecular markers.

Recently described European P. papillosum Oesau possesses similar to P. volgense furcate papillae, but only on dorsal leaf surface ( Fig. 4); in addition, its hair-points are shorter, capsules are short, cupulate (cylindric in P. volgense ), and its spores are larger (30–38 µm vs. 19– 24(–27) µm in P. volgense ). Also, the upper edge of ventral lamellae in this species is sharply serrate, at least at places ( Fig. 4A).

Distribution: Pterygoneurum volgense is known from few localities in xeric Caspian Lowland, in salted areas of Volgograd and Astrakhan Provinces, and Kalmykia Republic.

Other specimens examined: Republic of Kalmykia, Iki-Burul Settl. 45.817°N, 44.617°E, on soil, 23.V.2010, G . Ya. Ukrainskaya Kl 134 ( LE). Astrakhan’ Province, Bogdo-Baskunchak Nature Reserve, 48.266°N, 46.799°E, Bogdo Mt., Kristal’naya Cave , bottom of the karst depression, 5.V.2002, S. A . Suragina ( MHA9046879 ) .

Pterygoneurum arcticum Steere, Bryologist 62: 217,

f. 1–18. 1959. Fig. 5 .

This species was described in details and illustrated by Steere (1959) based on plants from Arctic Alaska (type of P. arcticum ) and by Abramova et al. (1973) based on specimens from the Western Taimyr. Although these descriptions and illustrations differ in several details of papillae distribution, peristome development, and position of opercula, more detailed analysis of the species variability led Abramova et al. (1973) to the conclusion that actually they represent the same species. After the revision of herbarium collections in LE and MW, additional specimens from different areas of Taimyr, and also from Severnaya Zemlya Archipelago and from two localities on Chukotka were referred to this taxon. The lat- er records fulfilled the gap between Siberian and North American partitions of the species distribution, suggesting its probable occurrence also in Arctic Yakutia. We presume that this species may have a continuous distribution along the Beringian Arctic shore, but might have been overlooked or misidentified due to having extremely small size (as experienced based on specimens from the Dikson area ) and growing sunken in silt .

A light yellow-green color of awn and distal part of leaf is suggestive for the species identification ( Fig. 5 ). Unlike most other species of the genus, the dark-brown or blackish pigmentation was not observed in it.

Specimens examined: RUSSIA: Krasnoyarsk Territory, Severnaya Zemlya Archipelago, Bol’shevik Island, ancient terrace in the middle course of Lagernaya River, 78°22'N, 103°31'E, 8.VII.2000, Matveeva s.n. (LE). Taimyr Distr., vicinity of Dickson village, Bol’shoy Arctichesky State Reserve, 2 km southwards Lemberova River Mouth, 73.403°N, 80.655°E, on eroded slope, 30.VII.2019, Fedosov & Koltysheva (MW9113999, MW9114127); Pyasina River middle course near Tareya settl., 73°17’N, 90°49’E, steep slope, Dryas & herb dominated tundra, on loamy ground, 28.VII.1968, Blagodatskikh & Afonina s.n. (LE); same locality: grass & herb dominated tundra, on loamy ground, 31.VII.1968, Blagodatskikh & Afonina s.n. (LE), S-faced slope, with Tortula leucostoma and Bryum sp. , 31.VII.1968, Blagodatskikh s.n. (LE), herb & moss dominated tundra, 3.VIII.1969, Blagodatskikh s.n. (LE), dwarf-shrub & herb & moss dominated tundra, 23.VIII.1969, Blagodatskikh s.n. (LE), spotty tundra, on bare spots, 8.VII.1970, Blagodatskikh s.n. (LE), upper part of steep S-faced slope, Dryas & herb dominated tundra, 1.VIII.1970, Blagodatskikh s.n. (LE); Kotuyskoe Plateau, vicinity of Ereechka River mouth, variegate deposits outcrops, 71.150°N, 102.580°E, on salty soil, 21.VIII.2011, Fedosov 11-1219 (MW9061139); same area: calcareous rock outcrops Kysyl-Khaya, 71.000°N, 102.696°E, rock ledge, on finesoil, 15.VIII.2007 Fedosov 07-848 (MW9075003); North periphery of Anabar Plateau, rocky slope of hill with altitudinal mark 386 m to Fomich River ca. 15 km above its mouth, 72.06°N, 110.210°E, on finesoil, 13.VII.2008, Fedosov 08-99 (MW9061137); same area: rock outcrops along Rossokha River 27 km upstream its mouth, 71.7509°N, 110.234°E, on finesoil, 27.VII.2008, Fedosov 08-185 (MW9061138), rock outcrops along Popigai River 4 km downstream Popigai abandoned village, 71.9221°N, 110.735°E, on fine soil, 28.VII.2008, Fedosov 08-165 (MW9061140). Chukotsky Autonomous District, vicinities of Valkumey settl., dry seashore with steppe vegetation, 10.VII.1983, Afonina s.n. (LE); NW spurs of Pekulney Range, vicinities of Baran’e Lake, 66°54'N, 176°15'E, rock outcrops along a creek, 31.VII.1980, Afonina s.n. (LE).

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An unusual Pterygoneurum specimen from North Siberia ( Russia, Krasnoyarsk Territory, Taimyr Autonomous Distr., rocky canyon of Kotuy River valley 1 km downstream Kotuykan River mouth, steep rocky slope, on calcareous fine soil, 11.VIII.2011, Fedosov 11-1128, MW9061193) ( Fig. 6) represented by tiny P. sampaianum - like plants without hyaline hair points and with large, 38–48 µm spores was proved to belong to the sympatrically distributed P. ovatum , but appeared distinct in plastid sequences both from the European accessions of this species and from a single involved specimen of typical P. ovatum from the area, where P. sampaianum -like plants were collected. Although weak molecular justification of the aberrant morphology of this specimen might indicate the need for its taxonomical recognition, it is postponed until additional similar specimens could be studied. Morphologically, it may represent a lineage parallel to P. arcticum and P. sampaianum , adopted to a very short growth season due to cold or/and xeric environments. Deeper sampling of reduced epilose morphotypes of P. ovatum , as well as those with the very short setae sometimes considered as P. medium , and also those with an abundant lateral lamellae outgrowths sometimes considered as P. crossidioides , is needed to complete the comprehensive revision of this group in the Holarctic region.

Figures

Fig. 5. Pterygoneurum arcticum (A–B, D–E, G–H from Taimyr, MW9061137; C, F from Chukotka, Afonina, 30.VII.1980, LE). A–B: leaf distal parts, ventral views, showing short concolorous awns and low ventral lamellae sometimes looking as rows of inflated papillose cells on costa, ‘A’, or they are 2–3 cells high, ‘B’; C: habit of plant with cylindric capsule and high conic operculum; D: leaf transverse section; E: a relatively tall ventral lamella, 5–6 cells high, showing a somewhat undulate arrangement on costa; F: habit of plant with juvenile sporophyte; G–H: leaves.