Odontoschisma dimorpha (Casp.) Heinrichs, K.Feldberg, Váňa & Schäf.

Odontoschisma dimorpha (Casp.) Heinrichs, K.Feldberg, Váňa & Schäf. View in CoL -Verw. ( Figs. 3 View Figure 3 , 4 View Figure 4 ).

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-18d, SIZK-Be-18e, SIZK-Be-18f (Schmalhausen Institute of Zoology in Kiev). Baltic amber: GZG. BST.22048 (Geoscientific Collections of the University of Göttingen, Germany).

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. 3A View Figure 3 ), 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. 3A View Figure 3 ). 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 3a, 3b, as Cylindrocolea dimorpha ) and Feldberg et al. (2017: 150, fig. 2a, 2b). For comparison a shoot fragment from Baltic amber (GZG.BST.22048) is pictured in Fig. 4D, 4E View Figure 4 . 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. 4E View Figure 4 ) and in the shoot imaged in Feldberg et al. (2017: 150, fig. 2a) some leaves are bilobed up to 0.2 the length and are very similar to the leaves of the Rovno plants ( Fig. 3A, 3D View Figure 3 ). 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. 3F View Figure 3 ). Another character that aligns it with typical O. dimorpha is the tapering shoot with the leaves becoming successively smaller and more distant ( Fig. 4A, 4D View Figure 4 ). 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 144a): type from Baltic amber ( Feldberg et al. 2017: 149, fig. 1a–d); Gröhn 2038: mat with creeping and ascending shoots from Baltic amber ( Feldberg et al. 2017: 150, fig. 2f); GZG.BST.21958: ascending shoot with underleaf from Bitterfeld amber ( Feldberg et al. 2017: 150, fig. 2a–d), rather similar to the new fossil.

General discussion

With the new records provided in this paper, the Rovno amber liverwort flora includes 19 species, namely Acrolejeunea ucrainica Mamontov, Heinrichs & Schäf. -Verw., Anastrophyllum rovnoi Mamontov, Heinrichs & Váňa , Cephaloziella nadezhdae Mamontov, Heinrichs & Váňa , Frullania ekaterinae Mamontov, Ignatov & Perkovsky , F. pycnoclada Grolle , F. riclefgrollei Mamontov, Heinrichs, Schäf. -Verw., Ignatov & Perkovsky, F. rovnoi Mamontov, Hentschel, Konstant., Perkovsky & Ignatov , F. schmalhausenii Mamontov, Ignatov & Perkovsky , F. vanae Mamontov, J.J.Atwood, Perkovsky & Ignatov , F. varians Casp. , F. zerovii Mamontov, Ignatov & Perkovsky , Jubula polessica Mamontov, J.J.Atwood & Perkovsky , Lejeunea aristovii , Leptoscyphus davidii , Nipponolejeunea rovnoi Mamontov, Schäf. -Verw. & Perkovsky, N. solodovnikovii , Odontoschisma dimorpha , Radula oblongifolia , and R. tikhomirovae Mamontov & Perkovsky ( Feldberg et al. 2021; Mamontov et al. 2024a, 2024b, 2024c, 2024d). All genera that are found in Rovno amber are commonly epiphytic, and many have been preserved in Baltic and Bitterfeld amber together, so we have another small excerpt of an epiphyte community in the studied amber piece.

Until now, only three of the liverwort species discovered in Rovno amber, namely Frullania pycnoclada , F. varians and Radula oblongifolia are also known from Baltic and/or Bitterfeld amber ( Grolle & Meister 2004). The record of Odontoschisma dimorpha in Rovno amber brings the floras closer together, but the other 15 species endemic to Rovno amber suggest that environmental conditions were different between the Baltic and Rovno amber forests. The close phylogenetic relationship of O. dimorpha to the pantropical section Iwatsukia of the genus Odontoschisma hypothesized in Feldberg et al. (2017) together with the previous record of Leptoscyphus davidii suggest a warmer climate in the area of the Rovno amber forests. Many arthropod records also point to at least frost-free winters on the Volhynian Uplift (e.g., Baranov et al. 2016; Matalin et al. 2021; Yamamoto et al. 2022; Telnov et al. 2021, 2023; Anisyutkin & Perkovsky 2023; Belokobylskij et al. 2023; Legalov et al. 2023 a, 2023b; Loktionov et al. 2023; Lyubarsky et al. 2023; Nabozhenko & Perkovsky 2023; Turbanov et al. 2024; Jenkins Shaw et al. 2024; Perkovsky et al. 2024; Sokolov et al. 2024; Chemyreva et al. 2024b). The shoot of Lejeunea aristovii is partly attached to a defoliated stem of the Plagiochila species preserved in the same amber piece, and it is typical for Lejeunea to grow on larger liverworts in the subtropics and tropics. Despite the fact that the majority of the Lejeunea species are restricted to the tropics, the record of L. aristovii , however, cannot provide additional information to support the assumptions about the climatic conditions in the discussed area this time. The phylogenetic relationships of L. aristovii can currently hardly be determined on the basis of morphological characters, which makes it impossible to assume the climatic preferences of this species based on comparison of the climatic preferences and distribution of its closest extant relatives. The new species is similar to representatives of the former genera Neopotamolejeunea M.E.Reiner and Taxilejeunea (Spruce) Steph. , both currently considered synonyms of Lejeunea subgen. Lejeunea , in its stem anatomy (the width of the ventral merophytes), the length of its leaf insertion and the alleged reduction of its leaf lobules. However, the circumscription of Lejeunea taxa is still problematic and the morphology of Lejeunea and Taxilejeunea largely overlapping ( Reiner-Drehwald 2005a; Heinrichs et al. 2013), as reflected in the phylogeny obtained in Heinrichs et al. (2013: 3, fig. 1) with Taxilejeunea elements in nearly all lineages of Lejeunea .

The incomplete understanding of the morphology of L. aristovii includes the lack of data on sexual organs and the shape of leaf lobules (if they were present in this species). In fact, no obvious lobules have been found in L. aristovii , although some of its leaf lobes are well visible against the light as they are neither attached to a substrate, nor fouled by organic residues. In comparison, the leaf lobules in the holotype of Nipponolejeunea solodovnikovii , which is preserved in the same amber piece and was also studied mainly from the dorsal side, could be seen quite clearly through the lobes ( Mamontov et al. 2024a). In the case of N. solodovnikovii , viewing of the leaves against the light was sufficient to see the shape of the leaf lobules, including the shape of their marginal teeth. As the lobules in Lejeunea aristovii are not visible against the light, it is possible that they are strongly or completely reduced, similarly to what is known for some extant Lejeunea , including those formerly belonging to the genus Taxilejeunea , for example L. asthenica Spruce ( Bastos & Gradstein 2020: 68, fig. 2A–C), L. pulverulenta (Gottsche ex Steph.) M.E.Reiner ( Reiner-Drehwald 2005b: 60, fig. 1, 2), and to the genus Neopotamolejeunea M.E.Reiner (= Lejeunea subg. Neopotamolejeunea (M.E.Reiner) Gradst. & M.E.Reiner ), including L. juruana Gradst. & M.E.Reiner ( Reiner-Drehwald 2000: 453, fig. 2N, 2O, 2Q, 2R, 2S, as Neopotamolejeunea uleana (Steph.) M.E.Reiner ), L. tenera (Sw.) Gottsche, Lindenb. & Nees ( Reiner-Drehwald 2000: 457, fig. 3F, 3I), and L. topoensis Gradst. & M.E.Reiner ( Gradstein & Reiner-Drehwald 2007: 489, fig. 1:1, 1:7).

The variability of underleaf shape in L. aristovii is also open to question, because only a single evident underleaf was available for study and a structure similar to a half of a Lejeunea underleaf was found ( Fig. 2B, 2C View Figure 2 ), which differs in its shape from the underleaf described above. If the mentioned structure is a part of an underleaf of L. aristovii , this underleaf could be similar to those in L. adpressa Nees ( Schuster 1980: 1021, fig. 709:4, as L. caespitosa Lindenb ; Reiner-Drehwald 2009: fig. 1–2, 11– 12, 20), thus it was ovate in outline, widest below the middle, up to 0.66 bifid, with lobes erect, divaricate or incurved, triangular at the base and then linear-lanceolate. Lejeunea adpressa is otherwise readily distinguished from L. aristovii by ovate leaf lobes with broadly rounded to subacute, never apiculate apices.

Acknowledgements

The authors are deeply grateful to S. Robbert Gradstein for his fair and helpful criticism, suggestions, and improvements of the paper. The study by Evgeny Perkovsky was supported by the Scholars at Risk Ukraine (SARU) program jointly funded by the Villum Foundation, Carlsberg Foundation and the Novo Nordisk Foundation. Financial support from the German Research Foundation (DFG, project 428174246) to Kathrin Feldberg is gratefully acknowledged.

References

Anisyutkin, L.N. & Perkovsky, E.E. (2023) Two new cockroaches (Dictyoptera: Ectobiidae) from Rovno amber. Biologia, 78 (6), 1721–1730. https://doi.org/10.1007/s11756-023-01333-6

Aranda, S.C., Gradstein, S.R., Patiño, J., Laenen, B., Désamoré, A., & Vanderpoorten, A. (2014) Phylogeny, classification and species delimitation in the liverwort genus Odontoschisma (Cephaloziaceae). Taxon, 63, 1008–1025. https://doi.org/10.12705/635.12

Baranov, V.A., Kvifte, G.M. & Perkovsky, E.E. (2016) Two new species of fossil Corethrella Coquillett from Late Eocene Rovno amber, with a species-level phylogeny for the family based on morphological traits (Diptera: Corethrellidae). Systematic Entomology, 41 (2), 531–540.

https://doi.org/10.1111/syen.12172

Bastos, C.J.P. & Gradstein, S.R. (2020) The genus Lejeunea Lib. (Lejeuneaceae, Marchantiophyta) in Brazil. Phytotaxa, 453, 055–107. https://doi.org/10.11646/phytotaxa.453.2.1

Belokobylskij, S.A., Simutnik, S.A., Vasilenko, D.V. & Perkovsky, E.E. (2023) First record of the parasitoid subfamily Doryctinae (Hymenoptera, Braconidae) in Rovno amber: description of a new genus and species with stigma-like enlargement on the hind wing of the male. Journal of Hymenoptera Research, 95, 59–72. https://doi.org/10.3897/jhr.95.96784

Chemyreva, V.G., Legalov, A.A. & Perkovsky, E.E. (2024 a) A new genus of Ambositrinae (Hymenoptera, Diapriidae) from Rovno amber and remarks on the Eocene distribution of the subfamily. Ecologica Montenegrina, 79, 104–112. https://doi.org/10.37828/em.2024.79.9

Chemyreva, V.G., Vasilenko, D.V. & Perkovsky, E.E. (2024 b) ‘ Where there are many cattle’ in the Eocene amber of Ukraine: Review of Ambositra Masner (Hymenoptera, Diapriidae, Ambositrinae) from Rovno amber, with the description of three new species. Zootaxa, 5446 (4), 499–516. https://doi.org/10.11646/zootaxa.5446.4.3

Dunlop, J.A. (2010) Bitterfeld amber. In: Penney, D. (Ed.), Biodiversity of fossils in amber from the major world deposits. Siri Scientific Press, Manchester, pp. 57–68.

Dunlop, J.A., Kotthoff, U., Hammel, J.U., Ahrens, J. & Harms, D. (2018) Arachnids in Bitterfeld amber: a unique fauna of fossils from the heart of Europe or simply old friends? Evolutionary Systematics, 2, 31–44. https://doi.org/10.3897/evolsyst.2.22581

Feldberg, K., Gradstein, S.R., Gröhn, C., Heinrichs, J., von Konrat, M., Mamontov, Yu.S., Renner, M.A.M., Roth, M., Schäfer-Verwimp, A., Sukkharak, P. & Schmidt, A.R. (2021) Checklist of fossil liverworts suitable for calibrating phylogenetic reconstructions. Bryophyte Diversity & Evolution, 043, 014–071. https://doi.org/10.11646/bde.43.1.6

Feldberg, K., Kaasalainen, U., Mamontov, Yu.S., Gradstein, S.R., Schäfer-Verwimp, A., Divakar, P.K. & Schmidt, A.R. (2024) Extending the fossil record of Miocene neotropical epiphyte communities. Fossil Record, in press.

Feldberg, K., Schneider, H., Stadler, T., Schäfer-Verwimp, A., Schmidt, A.R. & Heinrichs, J. (2014) Epiphytic leafy liverworts diversified in angiosperm-dominated forests. Scientific Reports, 4, 5974. https://doi.org/10.1038/srep05974

Feldberg, K., Váňa, J., Krusche, J., Kretschmann, J., Patzak, S.D.F., Pérez- Escobar, O.A., Rudolf, N.R., Seefelder, N., Schäfer-Verwimp, A., Long, D.G., Schneider, H. & Heinrichs, J. (2016) A phylogeny of Cephaloziaceae (Jungermanniopsida) based on nuclear and chloroplast DNA markers. Organisms Diversity & Evolution, 16 (4), 727–742.

https://doi.org/10.1007/s13127-016-0284-4

Feldberg, K., Váňa, J., Schäfer- Verwimp, A., Krings, M., Gröhn, C., Schmidt, A.R. & Heinrichs, J. (2017) Problems related to the taxonomic placement of incompletely preserved amber fossils: transfer of the Paleogene liverwort Cylindrocolea dimorpha (Cephaloziellaceae) to the extant Odontoschisma sect. Iwatsukia (Cephaloziaceae). Fossil Record, 20 (2), 147–157.

https://doi.org/10.5194/fr-20-147-2017

Gradstein, S.R. (2021) The liverworts and hornworts of Colombia and Ecuador. Memoirs of the New York Botanical Garden, 121, i–xxv, 1–723. https://doi.org/10.1007/978-3-030-49450-6

Gradstein, S.R., Aranda, S.C., & Vanderpoorten, A. (2014) Notes on Early Land Plants Today. 47. Transfer of Iwatsukia to Odontoschisma (Cephaloziaceae, Marchantiophyta). Phytotaxa, 162, 232–233. https://doi.org/10.11646/phytotaxa.162.4.6

Gradstein, S.R. & Ilkiu-Borges, A.L. (2015) A taxonomic revision of the genus Odontoschisma (Marchantiophyta: Cephaloziaceae). Nova Hedwigia, 100, 15–100.

https://doi.org/10.1127/nova_hedwigia/20014/0219

Gradstein, S.R. & Reiner-Drehwald, M.E. (2007) On the status of Neopotamolejeunea E.Reiner (Lejeuneaceae), with description of a new species. Systematic Botany, 32, 487–492.

https://doi.org/10.1600/036364407782250571

Grolle, R. (1980) Lebermoose in Bernstein 1. Feddes Repertorium, 91, 183–190.

https://doi.org/10.1002/fedr.19800910304

Grolle, R. & Meister, K. (2004) The liverworts in Baltic and Bitterfeld amber. Weissdorn, Jena, 91 pp.

Heinrichs, J., Dong, S., Schäfer-Verwimp, A., Pócs, T., Feldberg, K., Czumaj, A., Schmidt, A.R., Reitner, J., Renner, M.A.M., Hentschel, J., Stech, M. & Schneider, H. (2013) Molecular phylogeny of the leafy liverwort Lejeunea (Porellales): Evidence for a Neotropical origin, uneven distribution of sexual systems and insufficient taxonomy. PloS ONE, 8, e82547.

https://doi.org/10.1371/journal.pone.0082547

Heinrichs, J., Scheben, A., Bechteler, J., Lee, G.E., Schäfer-Verwimp, A., Hedenäs, L., Singh, H., Pócs, T., Nascimbene, P.C., Peralta, D.F., Renner, M.A.M. & Schmidt, A.R. (2016) Crown group Lejeuneaceae and pleurocarpous mosses in early Eocene (Ypresian) Indian amber. PLoS ONE, 11, e0156301. https://doi.org/10.1371/journal.pone.0156301

Ivanov, V.D., Melnitsky, S.I. & Perkovsky, E.E. (2016) Caddisflies from Cenozoic resins of Europe. Paleontological Journal, 50 (5), 485–493. https://doi.org/10.1134/S0031030116050063

Jenkins Shaw, J., Perkovsky, E.E., Ślipiński, A., Escalona, H. & Solodovnikov, A. (2024) An extralimital fossil of the genus Diagrypnodes (Coleoptera: Salpingidae: Inopeplinae). Historical Biology, 36 (7), 1196–1203. https://doi.org/10.1080/08912963.2023.2206858

Kaasalainen, U., Heinrichs, J., Renner, M.A.M., Hedenäs, L., Schäfer-Verwimp, A., Lee, G.E., Ignatov, M.S., Rikkinen, J. & Schmidt, A.R. (2018) A Caribbean epiphyte community preserved in Miocene Dominican amber. Earth and Environmental Science Transactions of the Royal Society of Edinburgh, 107, 321–331. https://doi.org/10.1017/S175569101700010X

Kazantsev, S.V., Legalov, A.A. & Perkovsky, E.E. (2024) First representative of the genus Lycocerus Gorham, 1889 (Coleoptera, Cantharidae) from Rovno amber. Ecologica Montenegrina, 78, 79– 84. https://dx.doi.org/10.37828/em.2024.78.9

Katagiri, T. (2015) First fossil record of the liverwort family Cephaloziaceae (Jungermanniales, Marchantiophyta) from Baltic amber. Nova Hedwigia, 101, 247–354.

https://doi.org/10.1127/nova_hedwigia/2015/0276

Kozub, D., Khmelik, V., Shapoval, Y., Chentsov, S., Yatsenko, B., Litovchenko, B. & Starykh, V. (2008) Helicon Focus software. Available from: http://www.heliconsoft.com

Laenen, B., Shaw, B., Schneider, H., Goffinet, B., Paradis, E., Désamoré, A., Heinrichs, J., Villarreal, J. C., Gradstein, S.R., McDaniel, S.F., Long, D.G., Forrest, L.L., Hollingsworth, M.L., Crandall- Stotler, B., Davis, E.C., Engel, J., von Konrat, M., Cooper, E.D., Patiño, J., Cox, C.J., Vanderpoorten, A. & Shaw, A.J. (2014) Extant diversity of bryophytes emerged from successive post-Mesozoic diversification bursts. Nature Communications, 5, 5134.

https://doi.org/10.1038/ncomms6134

Lee, G.E. (2013) A systematic revision of the genus Lejeunea Lib. (Marchantiophyta: Lejeuneaceae) in Malaysia. Cryptogamie, Bryologie, 34 (4), 381–484.

http://dx.doi.org/10.7872/cryb.v34.iss4.2013.381

Lee, G.E., Bechteler, J., Pócs,T., Schäfer-Verwimp, A., Tang, H.Y. & Chia, P.W. (2022) Integrative taxonomy reveals a new species of the genus Lejeunea (Marchantiophya: Lejeuneaceae) from Peninsular Malaysia. Plants, 11, 1642. https://doi.org/10.3390/plants11131642

Lee, G.E., Condamine, F.L., Bechteler, J., Pérez-Escobar, O.A., Scheben, A., Schäfer-Verwimp, A., Pócs, T. & Heinrichs, J. (2020) An ancient tropical origin, dispersals via land bridges and Miocene diversification explain the subcosmopolitan disjunctions of the liverwort genus Lejeunea. Scientific Reports, 10, 14123. https://doi.org/10.1038/s41598-020-71039-1

Lee, G.E., Kolberg, L., Bechteler, J., Schäfer-Verwimp, A., Renner, M.A.M., Schmidt, A.R. & Heinrichs, J. (2017) The leafy liverwort genus Lejeunea (Porellales, Jungermanniopsida) in Miocene Dominican amber. Review of Palaeobotany and Palynology, 238, 144–150.

https://doi.org/10.1016/j.revpalbo.2016.11.013

Legalov, A.A., Vasilenko, D.V. & Perkovsky, E.E. (2023 a) From abundance to extinction: evolutionary history of European Aedemonini (Curculionidae) with a description of the first representative from Rovno amber. Diversity, 15 (3), 376. https://doi.org/10.3390/d15030376

Legalov, A.A., Vasilenko, D.V. & Perkovsky, E.E. (2023 b) New proxy for Moraceae in Priabonian of Europe: first record of the genus Demimaea Pascoe, 1870 (Coleoptera: Curculionidae) from Eocene Rovno amber. Historical Biology, 35 (8), 1322–1328.

https://doi.org/10.1080/08912963.2022.2089983

Loktionov, V.M., Lelej, A.S., Vasilenko, D.V. & Perkovsky, E.E. (2023) Discovery of a new extinct spider wasp (Hymenoptera, Pompilidae) from Eocene Rovno amber. Zootaxa, 5352 (3), 426– 432. https://doi.org/10.11646/zootaxa.5352.3.6.

Lyubarsky, G., Perkovsky, E.E. & Vasilenko, D.V. (2023) Unexpected diversity of Xenoscelinae in Priabonian European amber: the third xenosceline species from Rovno amber. Life, 13 (3), 636.

https://doi.org/10.3390/life13030636

Mamontov, Yu.S., Heinrichs, J., Schäfer-Verwimp, A., Ignatov, M.S. & Perkovsky, E.E. (2013) Hepatics from Rovno Amber (Ukraine), 2. Acrolejeunea ucrainica sp. nov. Arctoa, 22, 93–96.

Mamontov, Yu.S., Schäfer-Verwimp, A., Ignatov, M.S., Vasilenko, D.V., Perkovsky E.E. (2024 a) Hepatics from Rovno amber (Ukraine): Nipponolejeunea rovnoi sp. nov. and N. solodovnikovii sp. nov. Historical Biology, 1–8. https://doi.org/10.1080/08912963.2024.2370004

Mamontov, Yu.S., Ignatov, M.S., Vasilenko, D.V. & Perkovsky, E.E. (2024 b) Hepatics from Rovno amber (Ukraine): Leptoscyphus davidii sp. nov. The Bryologist, 127 (1), 88–94.

https://doi.org/10.1639/0007-2745-127.1.088

Mamontov, Yu.S., Ignatov, M.S., Vasilenko D.V., Legalov, A.A. & Perkovsky, E.E. (2024 c) Hepatics from Rovno amber (Ukraine). 11. Radula oblongifolia and R. tikhomirovae sp. nov. Ecologica Montenegrina, 72, 189–199. https://doi.org/10.37828/em.2024.72.18

Mamontov, Yu.S., Atwood, J.J., Ignatov, M.S., Vasilenko, D.V., Legalov, A.A. & Perkovsky, E.E. (2024 d) Hepatics from Rovno amber (Ukraine). 12. Jubula polessica sp. nov. Ecologica Montenegrina, 73, 1–10. https://doi.org/10.37828/em.2024.73.1

Matalin, A.V., Perkovsky, E.E. & Vasilenko, D.V. (2021) First record of tiger beetles (Coleoptera, Cicindelidae) from Rovno amber with the description of a new genus and species. Zootaxa, 5027 (2), 290–296. https://doi.org/10.11646/zootaxa.5027.2.9

Mitov, P.G., Perkovsky, E.E. & Dunlop, J.A. (2021) Harvestmen (Arachnida: Opiliones) in Eocene Rovno amber (Ukraine). Zootaxa, 4984 (1), 43–72.

https://doi.org/10.11646/ZOOTAXA.4984.1.6

Nabozhenko, M.V. & Perkovsky, E.E. (2023) Oracula campbelli sp. n. – the first fossil darkling beetle (Coleoptera: Tenebrionidae: Alleculinae) from the late Eocene Rovno amber (Ukraine). Zootaxa, 5230 (2), 245–250. https://doi.org/10.11646/zootaxa.5230.2.8

Perkovsky, E.E., Rasnitsyn, A.P., Vlaskin, A.P. & Taraschuk, M.V. (2007) A comparative analysis of Baltic and Rovno amber arthropod faunas: perspective samples. African Invertebrates, 48, 229– 245.

Perkovsky, E.E., Zosimovich, V.Y. & Vlaskin, A.P. (2010) Rovno amber. In: Penney, D. (Ed.), Biodiversity of fossils in amber from the major world deposits. Siri Scientific Press, Manchester, pp. 116–137.

Perkovsky, E.E., Legalov, A.A. & Háva, J. (2024) Trinodes puetzi Háva et Prokop (Coleoptera, Dermestidae, Trinodinae) from Klesov: first record for the Ukrainian Eocene. Ecologica Montenegrina, 73, 428–433. https://dx.doi.org/10.37828/em.2024.73.28

Radchenko, A.G., Perkovsky, E.E. & Vasilenko, D.V. (2021) Formica species (Hymenoptera, Formicidae, Formicinae) in late Eocene Rovno amber. Journal of Hymenoptera Research, 82, 237–251. https://doi.org/10.3897/jhr.82.64599

Reiner-Drehwald, M.E. (2000) On Potamolejeunea and Neopotamolejeunea gen. nov. (Lejeuneaceae, Hepaticae). Nova Hedwigia, 71, 447–464. https://doi.org/10.1127/nova/71/2000/447

Reiner-Drehwald, M.E. (2005 a) On Lejeunea rotundifolia and Dicladolejeunea (Lejeuneaceae, Jungermanniopsida). Systematic Botany, 30, 687–692.

https://doi.org/10.1600/036364405775097860

Reiner-Drehwald, M.E. (2005 b) Taxilejeunea pulverulenta (Lejeuneaceae, Jungermanniopsida), a poorly known species from the Neotropics, is transferred to Lejeunea. Cryptogamie, Bryologie, 26 (1), 59–65.

Reiner-Drehwald, M.E. (2009) Lejeunea adpressa Nees (Lejeuneaceae), a widely distributed species of tropical America. Cryptogamie, Bryologie, 30 (3), 329–336.

Reiner-Drehwald, M.E., Schmidt, A.R. & Heinrichs, J. (2012) The genus Lejeunea in Miocene amber from the Dominican Republic. Cryptogamie, Bryologie, 33 (1), 33–38.

https://doi.org/10.7872/cryb.v33.iss1.2012.033

Sadowski, E.-M., Schmidt, A.R., Seyfullah, L.J., Solórzano-Kraemer, M.M., Neumann, C., Perrichot, V., Hamann, C., Milke, R. & Nascimbene, P.C. (2021) Conservation, preparation and imaging of diverse ambers and their inclusions. Earth-Science Reviews, 220, 103653.

https://doi.org/10.1016/j.earscirev.2021.103653

Schuster, R.M. (1980) The Hepaticae and Anthocerotae of North America east of the hundredth meridian. Vol. 4. Field Museum of Natural History, Chicago. 1334 pp.

Sokolov, A.V., Nabozhenko, M.V., Sadyrin, E.V., Vasilenko, D.V. & Perkovsky, E.E. (2024) The second extinct microhisterid species (Coleoptera: Histeridae: Bacaniini) described from the Eocene Rovno amber using X-ray microtomography. Historical Biology.

https://doi.org/10.1080/08912963.2024.2328273

Telnov, D., Perkovsky, E.E., Vasilenko, D.V. & Yamamoto, S. (2021) The first fossil Coleoptera record from the Volyn Region, Ukraine, with description of a new Glesoconomorphus (Coleoptera, Mycteridae) in syninclusion with Winterschmidtiidae (Acari) and a key to species. ZooKeys, 1068, 189–201. https://doi.org/10.3897/zookeys.1068.75391

Telnov, D., Perkovsky, E.E., Kundrata, R., Kairišs, K., Vasilenko, D.V. & Bukejs, A. (2023) Revealing Paleogene distribution of the Ptilodactylidae (Insecta: Coleoptera): the first Ptilodactyla Illiger, 1807 records from Rovno amber of Ukraine. Historical Biology, 35 (11), 2171–2180.

https://doi.org/10.1080/08912963.2022.2136034

Turbanov, I.S., Kolesnikov, V.B., Vorontsov, D.D., Vasilenko, D.V. & Perkovsky, E.E. (2024) Chthonius marusiki sp. nov. the first pseudoscorpion of the family Chthoniidae Daday, 1889 (Arachnida, Pseudoscorpiones) from the late Eocene Rovno amber. Historical Biology, 36 (12), 2557–2564. https://doi.org/10.1080/08912963.2023.2266821

Wilson, R., Gradstein, S.R., Schneider, H. & Heinrichs, J. (2007) Unravelling the phylogeny of Lejeuneaceae (Jungermanniopsida): evidence for four main lineages. Molecular Phylogenetics and Evolution, 43, 270–282. https://doi.org/10.1016/j.ympev.2006.10.017

Wolfe, A.P., McKellar, R.C., Tappert, R., Sodhi, R.N.S. & Muehlenbachs, K. (2016) Bitterfeld amber is not Baltic amber: three geochemical tests and further constraints on the botanical affinities and succinitee. Review of Palaeobotany and Palynology, 225, 21–32.

https://doi.org/10.1016/j.revpalbo.2015.11.002

Yamamoto, S., Nazarenko, V.Yu., Vasilenko, D.V. & Perkovsky, E.E. (2022) First fossil species of ship-timber beetles (Coleoptera: Lymexylidae) from Eocene Rovno amber (Ukraine). Fossil Record, 25 (1), 65–74. https://doi.org/10.3897/fr.25.81054