Scapania marsupelloides Potemkin, Vilnet et Mamontov, 2018

Mamontov, Yuriy S., Vilnet, Anna A. & Potemkin, Alexey D., 2018, Scapania marsupelloides sp. nov. (Scapaniaceae, Marchantiophyta), a remarkable new species near the base of Scapania phylogeny, Phytotaxa 385 (2), pp. 55-66 : 59-62

Scapania marsupelloides Potemkin, Vilnet et Mamontov , sp. nov. Figs 2 , 3 , 4 , 5

Type. — CHINA. Yunnan: Fugong County, Lumadeng Xiang, Yaping Cun , E slope of Gaoligong Shan (Nu Jiang catchment), east slope of Burma / Yunnan border ridge beside ‘ Twin Lakes’ south of ‘ Yaping Pass’ , ca. 3610 m a. s. l., 27°12′01.1″N, 98°41′40.1″E, alpine lake shore with marshy slopes, boulders and tall herbs ; on flushed slope, 5 October 2007, D. G. Long & J. Shevock 37350 det. as Marsupella sphacelata, MO (Holotype), LE, MHA, KPABG, VBGI (isotypes) .

Diagnosis:— Brownish green to yellowish brown Marsupella sphacelata -like plants with coarsely papillose leaf surface in median part of lobes. The species furthermore characterized by 1–2-stratose cortex with indistinct and only locally expressed areas of ± larger ± thick-walled to thin-walled cells situated often side by side with smaller cells or in one part of stem ( Figs. 2 : 5, 3: 4, 4: 1). The leaves are sheathing the stem and not keeled, 0.5–0.6 mostly equally bilobed with oval, ovate or lingulate falcate lobes, rounded to obtuse or rarely angulate at apex, spreading from each other, ± arcuately inserted and ± decurrent on both dorsal and ventral sides. The marginal leaf cells usually darker brown pigmented, ± evenly thick-walled, without distinct trigones.

Description: —Plants brownish green to yellowish brown, robust, 30–35 mm long and (1.5–) 2–2.5 mm wide, sporadically with innovations from broken shoot tips, rare with microphyllous terminal branches, apparently Radula - type, originating from postical shoot sectors not in leaf axils but below upper leaf insertion. Stem 250–300 mm in diam., deep brown, reddish-brown or brownish green, in upper part sometimes green. Cortex 1–2-stratose, with outer cortical cells partially larger than internal, moderately thick-walled to thin-walled, ± finely papillose when observed in cross section, with finely grooved surface in SEM images; middle lamellae in cortical cells invisible to ± distinct. Leaves 0.5–0.6 bilobed, broadly sheathing the stem, hardly broadened to the base; keel lacking or hardly developed distally, lobes oval, ovate or lingulate falcate, often with subparallel margins, rounded to obtuse or rarely angulate at apex, reaching but usually not extending beyond the farther edge of stem, entire or very rare with single blunt marginal tooth-like projections of subisodiametric cells, slightly arcuately inserted on dorsal and ventral sides, with indistinct short to rather long decurrency below the level of keel insertion; leaf insertion often indistinct on dark stem. Dorsal lobe mostly equal in area the ventral lobe or a bit smaller, identical to it in shape, ca. × 0.6–0.7(–0.8) as wide as long, ca. 625–1125 μm wide × 1000–1625 μm long, similarly falcate or moderately divergent with it, obtuse or rarely angulate at apex, entire or with a few tooth-like marginal angulations of subisodiametric cells. Leaves distinctly bordered with 1(–2) rows of evenly thick-walled mostly subquadrate marginal cells with yellowish or brownish almost always deeply pigmented walls, sometimes slightly elongated perpendicular to margin, (8–)10–15(–20) × 7–12(–15) μm; only some basal marginal cells elongated along margin; marginal area deeper brown pigmented than median part of leaves. Median lobe cells with yellow walls, (12–)17–20(–25) × 20–25 μm or 25–27 × 25–37 μm, usually with acute to sometimes ± bulging trigones, in mod. leptoderma -viridis trigones may be vestigial. Median cells below sinus occasionally strongly elongated, 20–27 × 50–70(–80) μm, with acute to bulging elongated trigones and yellowish walls. Basal cells elongated at median part of leaf base close to the place of its insertion, (15–)17(–20) × (35–)40– 60(–75) μm, thin- to ± evenly thin-walled, with slighter developed papillae. Cell surface irregularly densely coarsely papillose in distal part of leaves with chiefly hemispherical and partly elongated papillae in median part of lobes and often minute papillae near margins; cell surface in proximal part of leaves below sinus moderately papillose, with elongated papillae; leaf margins smooth or sometimes with distinct flattened papillae. Gemmae not seen.

Dioicous. Androecia intercalary of 3–5 pairs of male bracts strongly concave basally, with three distinct cavities, broadly ovate when flattened, with maximal width near the base, sometimes partly purplish in the middle; sinuses shallower than in sterile leaves, ca. 0.35–0.5 × the length; lobes broadly rounded or narrowed to the apex, 0.64–0.94 × as wide as long, ca. 700–1050 μm wide and 1100–1175 μm long; marginal cells occasionally bleached in apical area.

Antheridia in groups in the cavities, with 1(–2)–seriate stalks, 17–20 μm wide, 50–150 μm long, of ± flattened thin-walled cells; mature body oval, ca. 150 × 125 μm. Paraphyses not seen. Female plants not seen.

Ethymology: —The species name originates from its habitual resemblance to Marsupella sphacelata . Ecology. —Alpine lake shore with marshy slopes, boulders and tall herbs; on flushed slope.

Differentiation:— Scapania contorta , S. pseudocotorta Potemkin (2000: 115) and S. hians Stephani ex Müller (1905: 223) of the subgenus Ascapania as well as S. cuspiduligera ( Nees1833: 175, 180, 181) Müller (1915: 472) (except for its var. diplophyllopsis Schuster (1974: 361) that has a typical scapanioid habit) are morphologically most close to S. marsupelloides . S. marsupelloides shares with them subequal lobes spreading from each other and sheathing leaf bases.

Figures

FIGURE 2. Line drawing of Scapania marsupelloides sp. nov. 1, 2, 4—Shoots. 3—Cells of the leaf middle, showing papillose surface. 5—Stem cross section. 6–11—Leaves. Scale bars: 3 mm for 1; 4 mm for 2; 100 μm for 3; 500 μm for 5; 5 mm for 4; 1 mm for 6–11. All from D. G. Long & J. Shevock 37350 (isotype, MHA).

FIGURE 3. Line drawing of Scapania marsupelloides sp. nov.1, 2, 3, 17—Shoot sectors (1—postical aspect; 2—postical aspect with long decurrent ventral lobe; 3, 17—antical aspect). 4—Stem cross section. 5—Leaf. 6–9, 10–12, 14—Leaf cross sections. 13, 15, 16—Male bracts. Scale bars: 3 mm for 1, 3, 17; 2 mm for 2; 1.5 mm for 5, 13, 15, 16; 500 мm for 4; 300 мm for 6, 9, 10, 12, 14; 250 мm for 7, 8, 11. All from D. G. Long & J. Shevock 37350 (isotype, MHA).

FIGURE 4. Photomicrographs of Scapania marsupelloides sp. nov. 1–Stem cross section. 2, 3, 5, 6—Leaf apices. 4, 11—Marginal leaf cells. 7—Cells of leaf base. 8–10—Cells of leaf middle. Scale bars: 1, 2, 3, 5, 6 = 100 μm. 4, 7, 8, 10 = 50 μm. 9, 11= 25 μm. All from D. G. Long & J. Shevock 37350 (isotype, MHA).

FIGURE 5. SEM images of Scapania marsupelloides sp. nov. 1–3, 5, 6—Cells of leaf middle showing papillose surface. 4—Cells of leaf base. 7—Cells of stem cross section. Scale bars: 1, 4 = 30 μm. 2 = 10 μm. 3, 5 = 40 μm. 6 = 200 μm. 7 = 20 μm. All from D. G. Long & J. Shevock 37350 (isotype, LE).