taxonID	type	description	language	source
03D887D6681BFFC94998019DFB599A59.taxon	materials_examined	Type material: Holotype. SIZK-Be- 18 c, Rovno amber, late Eocene (Schmalhausen Institute of Zoology in Kiev). Syninclusions: Leptoscyphus davidii, Nipponolejeunea solodovnikovii, Odontoschisma dimorpha (see below), Plagiochila sp., and Radula oblongifolia.	en	Mamontov, Yuriy S., Schäfer-Verwimp, Alfons, Feldberg, Kathrin, Vasilenko, Dmitry V., Legalov, Andrei A., Perkovsky, Evgeny E. (2024): Hepatics from Rovno amber (Ukraine). 14. Lejeunea aristovii sp. nov. and Odontoschisma dimorpha from Belokorovychi. Ecologica Montenegrina 80: 230-243, DOI: 10.37828/em.2024.80.21, URL: https://doi.org/10.37828/em.2024.80.21
03D887D6681BFFC94998019DFB599A59.taxon	diagnosis	Diagnosis: The Lejeunea gametophyte is characterized by elliptic-ovate, apiculate to obtuse or narrowly rounded leaf lobes, reduced to absent leaf-lobules, and bilobed underleaves, and differs from the Paleogene Cheilolejeunea latiloba by the less falcate and longly inserted leaf lobes, reduced or absent leaf lobules, and underleaves that are longer than wide and widest in their upper third.	en	Mamontov, Yuriy S., Schäfer-Verwimp, Alfons, Feldberg, Kathrin, Vasilenko, Dmitry V., Legalov, Andrei A., Perkovsky, Evgeny E. (2024): Hepatics from Rovno amber (Ukraine). 14. Lejeunea aristovii sp. nov. and Odontoschisma dimorpha from Belokorovychi. Ecologica Montenegrina 80: 230-243, DOI: 10.37828/em.2024.80.21, URL: https://doi.org/10.37828/em.2024.80.21
03D887D6681BFFC94998019DFB599A59.taxon	description	Description: Shoot yellow-brownish, 1.5 mm long and 0.36 – 0.48 mm wide, creeping, unbranched. Rhizoids not observed. Stem straight, colourless, up to 64 – 68 μm in diameter (where observable). Epidermis of ventral merophytes at least 3 cells wide, cells with equally somewhat thickened walls, rounded-rectangular, (17.3 –) 18 – 32 (– 49) µm long × (9.8 –) 10.2 – 13.5 μm wide, from 1.64 – 1.92 to 3.3 – 3.8 × as long as wide. Cells of dorsal stem cortex with equally somewhat thickened walls, ± rectangular, 13 – 21 µm long × 8 – 11 μm wide, ca 1.6 – 2.5 × as long as wide. Leaves with a very long, J-shaped insertion, insertion line ca. (0.61 –) 0.66 – 0.85 of leaf width, incubous, usually planodistichous, remote to loosely imbricate, dorsally almost not interlocking, not reaching beyond the farther edge of stem. Lobe diverging at an angle of 40 – 80 ° to stem, usually almost flat, sometimes slightly elevated, slightly convex dorsally, shape widely to narrowly ovate or almost oblong, 181 – 255 μm long × 100 – 214 μm wide, ca 1.07 – 1.81 × as long as wide, free margin entire. Dorsal margin semilunate to strongly arcuate in basal half, not ampliate at base. Apex sometimes decurved, ± rounded or obtuse or apiculate with a single acute protruding cell. Free ventral margin in proximal half straight to slightly incurved, near the end of the keel-like part gradually curved, not forming a part of the ventral lobule opening, in distal half slightly to strongly incurved. Cells in upper middle ± isodiametric, hexagonal, 13 – 26 μm long × 12 – 21 μm wide, ca 1.04 – 1.25 × as long as wide, in lower middle 14 – 25 μm long × 12 – 19 μm wide, with brownish slightly thickened walls and distinct trigones. Ocelli absent. Keellike part (where present) 0.24 – 0.45 (– 0.55) length of lobe, smooth, convex to almost straight, with gradual transition into free margin of lobe. Lobule (if present) not available for observation. Underleaves with shallowly arcuate insertion, remote, the only available evident underleaf (Figs. 2 E, 2 G) flat, 167 μm long × 145 μm wide, ca. 2.5 × wider than the stem, obovate, widest in its upper third, ± cuneate at base, bilobed to 0.39 – 0.43 × the length, sinus acutangular with U-shaped base, lobes slightly converging, triangular, ca. 4 cells long, ca. 4 – 5 cells wide at base, moderately acute, formed by a single rounded cell, subterminally with 2 cells side by side, lateral margin in the upper half unidentate because of a protuberant cell, in the lower half somewhat sinuous. Asexual reproduction, gynoecia, and androecia not observed.	en	Mamontov, Yuriy S., Schäfer-Verwimp, Alfons, Feldberg, Kathrin, Vasilenko, Dmitry V., Legalov, Andrei A., Perkovsky, Evgeny E. (2024): Hepatics from Rovno amber (Ukraine). 14. Lejeunea aristovii sp. nov. and Odontoschisma dimorpha from Belokorovychi. Ecologica Montenegrina 80: 230-243, DOI: 10.37828/em.2024.80.21, URL: https://doi.org/10.37828/em.2024.80.21
03D887D6681BFFC94998019DFB599A59.taxon	etymology	Etymology: The species is named in honor of Dr. Daniil Sergeevich Aristov, an eminent paleoentomologist. Comparison: Lejeunea aristovii differs from Cheilolejeunea latiloba by its yellow-brownish colour (red-brown in C. latiloba), less falcate leaf lobes, much less prominent and frequently reduced leaf lobules, and an apiculate leaf apex with a single acute cell (if apiculate in C. latiloba, then with a single protruding rounded cell). It is therefore obvious that L. aristovii cannot be identical with C. latiloba. Lejeunea aristovii is a very small species, but possibly only a less developed branch is at hand. The ovate to almost oblong and often apiculate leaf lobes with partly (or completely?) reduced lobules in combination with the remote and distinctly bilobed (to ca. 0.4), obovate (to ovate) underleaves seem to be very characteristic. It is possible that the majority of leaf lobes were apiculate, but the apiculus might be hidden because it is incurved and therefore not (well) visible, especially when the plant is enclosed in amber and cannot be examined like an extant species. Other fossil species of Cheilolejeunea can be easily excluded either by undivided underleaves (C. antiqua W. Ye & R. L. Zhu and C. suzannensis (Grolle) Grolle & R. L. Zhu, both from Dominican amber) or by rather different shapes of leaf lobes and underleaves (C. lamyi (Casp.) Grolle, also from Dominican amber). Fossil Lejeunea species are only known from the Miocene Dominican and Mexican amber. Dominican amber includes the species L. hamatiloba G. E. Lee, Schäf. - Verw., M. A. M. Renner & Heinrichs, L. miocenica Heinrichs, Schäf. - Verw., M. A. M. Renner & G. E. Lee, L. resinata G. E. Lee, Schäf. - Verw., M. A. M. Renner & Heinrichs and L. urbanoides G. E. Lee, Schäf. - Verw., M. A. M. Renner & Heinrichs (Lee et al. 2017). Recently, a small specimen of Lejeunea sp. was discovered in Mexican amber (Feldberg et al. in press). None of these species are similar to L. aristovii. There are some small extant species of Lejeunea and Cheilolejeunea with which L. aristovii may be compared. Lejeunea apiculata Sande Lac. is easily distinguished by a much more prominent apiculus, while L. cocoes Mitt. and L. malaysiana G. E. Lee & Pócs differ by their narrowly rounded to sometimes obtuse leaf lobe apex. Moreover, these Lejeunea species all have shorter leaf lobe insertion lines, ca. 0.38 – 0.67 of leaf width (according to our measures of the leaves imaged in Lee 2013). One of the smallest Lejeunea species in Asia, L. exilis (Reinw., Blume & Nees) Grolle, has distant, ovatelanceolate leaf lobes with a leaf lobe insertion line ca. 0.44 – 0.74 of leaf width, with mostly well-developed leaf lobules, and small, deeply divided or undivided lanceolate underleaves, which are not or only slightly wider than the stem. Another small species, L. tuberculosa Steph., has ovate-orbicular, broadly rounded leaf lobes without apiculus, a leaf lobe insertion line ca. 0.44 – 0.74 of leaf width, rarely reduced leaf lobules and underleaves that are mainly as long as wide. In fact, all other extant Lejeunea species known to us are clearly different from L. aristovii. There are no small-sized extant Cheilolejeunea species with ovate-oblong leaf lobes and an apiculate leaf apex combined with underleaves as in Lejeunea aristovii (not even among the Neotropical Cheilolejeunea species). Cheilolejeunea subopaca (Mitt.) Mizut. differs from L. aristovii by its ovate-triangular, acute leaf lobes and small underleaves, which are entire-margined and nearly orbicular, as long as wide or wider than long. Other small or tiny species have either almost orbicular, broadly rounded leaf lobes like C. intertexta (Lindenb.) Steph. or ovate to ovate-triangular leaf lobes with obtuse or acute apices like C. osumiensis (S. Hatt.) Mizut. or C. obtusifolia (Steph.) S. Hatt.	en	Mamontov, Yuriy S., Schäfer-Verwimp, Alfons, Feldberg, Kathrin, Vasilenko, Dmitry V., Legalov, Andrei A., Perkovsky, Evgeny E. (2024): Hepatics from Rovno amber (Ukraine). 14. Lejeunea aristovii sp. nov. and Odontoschisma dimorpha from Belokorovychi. Ecologica Montenegrina 80: 230-243, DOI: 10.37828/em.2024.80.21, URL: https://doi.org/10.37828/em.2024.80.21
03D887D6681CFFC44998074EFB7D9AE5.taxon	materials_examined	Type material: MB. Pb. 1979 / 687 (Museum für Naturkunde, Leibniz Institute for Evolution and Biodiversity Science in Berlin; holotype). Additional specimens examined: Rovno amber: SIZK-Be- 18 d, SIZK-Be- 18 e, SIZK-Be- 18 f (Schmalhausen Institute of Zoology in Kiev). Baltic amber: GZG. BST. 22048 (Geoscientific Collections of the University of Göttingen, Germany).	en	Mamontov, Yuriy S., Schäfer-Verwimp, Alfons, Feldberg, Kathrin, Vasilenko, Dmitry V., Legalov, Andrei A., Perkovsky, Evgeny E. (2024): Hepatics from Rovno amber (Ukraine). 14. Lejeunea aristovii sp. nov. and Odontoschisma dimorpha from Belokorovychi. Ecologica Montenegrina 80: 230-243, DOI: 10.37828/em.2024.80.21, URL: https://doi.org/10.37828/em.2024.80.21
03D887D6681CFFC44998074EFB7D9AE5.taxon	description	Description: Shoots greyish or yellowish, prostrate, creeping, up to 1.5 mm long and (0.13 –) 0.25 – 0.44 mm wide, not branched. Stem straight to curved, not or slightly translucent, (70 –) 80 – 105 μm in diameter. Epidermis not hyalodermatic, cells hardly visible, square or mostly short rectangular, 11.2 – 17.8 × 10.5 – 14.5 μm. Rhizoids not seen. Leaves with straight insertion line, distinctly succubous, subtransverse to very oblique or almost horizontal, reaching or nearly reaching the dorsal midline (Fig. 3 A), neither dorsally nor ventrally decurrent, remote to contiguous in the same shoot, erect to spreading or leaning on the stem, usually somewhat elevated to the dorsal side, slightly to rather distinctly concave (in dorsal view), variable in size and shape, sometimes reduced, scaly, if well-developed ovate to ovate-oblong to rectangular, ca. (70 –) 147 – 287 μm long (including lobes), (86 –) 135 – 245 μm wide, ca. 0.81 – 1.21 × as long as wide, widest in or slightly below the middle and narrowing towards apex, not or slightly narrowing towards base, subsymmetric, margins entire, bilobed to 0.15 – 0.33 the length, sinus acute or rectangular, with rounded angular base, lobes equal in size, sometimes ventral one slightly larger, directed forward or mostly ± converging, broadly triangular to triangular, (2 –) 3 – 6 cells wide at base, apex acute, usually formed by a single long triangular cell, sometimes by two uniseriate cells, dorsal and ventral margin strongly arcuate or almost straight or somewhat angulate (Fig. 3 A). Cells hardly visible, 14.9 – 18.2 µm long × 13.1 – 16.2 μm wide, with strongly incrassate walls. Underleaves, asexual reproduction, and gametangia not observed. Comparison: Odontoschisma dimorpha has seen significant taxonomical changes over the years. First it was described as Jungermannia dimorpha Casp., based on a single specimen with androecia, and then it was transferred to the family Cephaloziellaceae as more fossil material became available. Grolle included it first in Cephaloziella (Spruce) Schiffn. (Grolle 1980, as Cephaloziella dimorpha (Casp.) Grolle) and later in Cylindrocolea R. M. Schust. (Grolle & Meister 2004, as Cylindrocolea dimorpha (Casp.) Grolle). Among the relatively rare fossils of Jungermanniales, O. dimorpha became the most frequently found, with ca. 19 inclusions in Baltic and ca. 15 in Bitterfeld amber. This allows a comparatively detailed assessment of the considerable morphological variability. The plants grow in mats of creeping and ascending shoots, the latter occasionally bearing multicellular, deeply bifid underleaves (Feldberg et al. 2017). The presence of these underleaves as well as the occurrence of ventral-intercalary branches, isodiametric leaf cells with equally thickened walls, and an androecium on an elongated branch align the fossil species with extant representatives of the pantropical Iwatsukia which is now treated as a section of Odontoschisma (Aranda et al. 2014; Gradstein et al. 2014; Gradstein & Ilkiu-Borges 2015). The plants studied here generally resemble the plants of O. dimorpha illustrated in Grolle & Meister (2004: 71, plate 3 a, 3 b, as Cylindrocolea dimorpha) and Feldberg et al. (2017: 150, fig. 2 a, 2 b). For comparison a shoot fragment from Baltic amber (GZG. BST. 22048) is pictured in Fig. 4 D, 4 E. The leaves strongly resemble those of the Rovno amber fossil and the shoot is also tapering into a flagella-like part with tiny reduced leaves. The leaf insertion that varies from nearly transversal to nearly horizontal is typical for the species. In Grolle & Meister (2004) and Feldberg et al. (2017), leaves of O. dimorpha were characterized as having a sinus descending 0.3 – 0.6 of the leaf length, whereas in the shoots studied here the leaves are bilobed to only 0.15 – 0.33 of the length. However, in the specimen GZG. BST. 22048 (Fig. 4 E) and in the shoot imaged in Feldberg et al. (2017: 150, fig. 2 a) some leaves are bilobed up to 0.2 the length and are very similar to the leaves of the Rovno plants (Fig. 3 A, 3 D). Therefore, the Rovno plants fall rather well within the morphological range of the species. In the Baltic plants, the walls of the leaf cells are evenly thickened or becoming slightly thicker towards the corners, sometimes thin-walled, while in the Rovno plants the leaf cell walls are strongly incrassate, but also becoming thicker towards the corners (Fig. 3 F). Another character that aligns it with typical O. dimorpha is the tapering shoot with the leaves becoming successively smaller and more distant (Fig. 4 A, 4 D). Another fossil species similar to some very small, creeping or tapering shoots of O. dimorpha is Cephalozia veltenii T. Katag. from Baltic amber (Katagiri 2015). The species has tiny leaves in relation to its robust stem and is differentiated by the presence of a stem hyalodermis. Additional photos: MB. Pb. 1979 / 687 (Künow amber collection 144 a): type from Baltic amber (Feldberg et al. 2017: 149, fig. 1 a – d); Gröhn 2038: mat with creeping and ascending shoots from Baltic amber (Feldberg et al. 2017: 150, fig. 2 f); GZG. BST. 21958: ascending shoot with underleaf from Bitterfeld amber (Feldberg et al. 2017: 150, fig. 2 a – d), rather similar to the new fossil.	en	Mamontov, Yuriy S., Schäfer-Verwimp, Alfons, Feldberg, Kathrin, Vasilenko, Dmitry V., Legalov, Andrei A., Perkovsky, Evgeny E. (2024): Hepatics from Rovno amber (Ukraine). 14. Lejeunea aristovii sp. nov. and Odontoschisma dimorpha from Belokorovychi. Ecologica Montenegrina 80: 230-243, DOI: 10.37828/em.2024.80.21, URL: https://doi.org/10.37828/em.2024.80.21
