Scapania marsupelloides, Mamontov & Vilnet & Potemkin, 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 : 62

Key to differentiate S. marsupelloides from selected Scapania species with sheathing leaf bases

1. Lobes subequal, usually spreading from each other, leaf margins entire or with a few distal angulate projections..........................2

- Dorsal lobe smaller than ventral, ca.0.6–0.9 the ventral. Leaf margins ± denticulate.......................................................................3

2. Plants 5–25(–30) mm long × 1–2.5(–3) mm wide, green or brownish. Leaves without dark brown border.Ventral leaf base ± bleached, devoid chloroplast and oil bodies and distinct from the other part of leaf, with strogly elongated basal marginal cells. Dorsal leaf base subtransversely inserted. Gemmae common ............................ S. cuspiduligera (except its var. diplophyllopsis R. M. Schust. )

- Plants larger, 30–35 mm long × (1.5–) 2–2.5 mm wide, yellowish brown. Leaves usually with darker brown border.Ventral leafbase never bleached, not differentiated from the other part of leaf, with subisodiamentric basal marginal cells. Dorsal leaf base arcuately inserted.Gemmae unknown ..................................................................................................................................... S. marsupelloides

3. Ventral lobe bordered by fuscous brown marginal teeth and often cells, ± strap-like, mostly rounded at apex; marginal teeth ± spinose, extending to proximal third of ventral lobe, their terminal cells 1.2–2.5(–3) × as long as wide. Dorsal lobes basally broader than ventral, normally extending beyond farther edge of the stem ........................................................................................... S. contorta

- Ventral lobe not bordered, with ± similarly pigmented marginal and median sectors, distally mostly triangularly narrowed in sharp apex; marginal teeth not spinose, extending at most to median third of ventral lobe, their terminal cells 1.0–1.8 × as long as wide. Dorsal lobes about as wide as ventral, not or sporadically extending beyond farther edge of the stem............................................4

4. Plants 2–3.5 mm wide, fuscous to (in apical sectors) deep purple (blackish when dry); leaf cells with smooth surface and deeply pigmented middle lamellae, coarse and nodulose, with often confluent parietal thickenings; teeth with terminal cells 1.2–1.8 × as long as wide; marginal denticulations spread at most to middle third of postical leaf margin ............................... S. pseudocontorta

- Plants 1–1.7 mm wide, green, brown or purple; leaf cells with usually regularly coarsely papillose surface, never with deeply pigmented middle lamellae and coarse nodulose often confluent parietal thickenings; teeth with terminal cells 1–1.5 × as long as wide; marginal denticulations chiefly in distal third of ventral lobe....................................................................................... S. hians