Extending the diversity of the bryoflora in Kachin amber (Myanmar), with the description of Radula patrickmuelleri, sp. nov. and R. tanaiensis, sp. nov. (Jungermanniopsida, Porellales, Radulaceae) Author Feldberg, Kathrin Department of Geobiology, University of Goettingen, Goldschmidtstrasse 3, 37077 Goettingen, Germany kathrin.feldberg@uni-goettingen.de Author Schaefer-Verwimp, Alfons Mittlere Letten 11, 88634 Herdwangen-Schoenach, Germany Author Li, Ya Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China Author Renner, Matt A. M. https://orcid.org/0000-0003-2286-7257 Wildland Consultants, 99 Sala Street, Whakarewarewa, Rotorua, New Zealand text Fossil Record 2022 2022-06-16 25 1 213 230 http://dx.doi.org/10.3897/fr.25.82362 journal article http://dx.doi.org/10.3897/fr.25.82362 2193-0074-1-213 45048AF336F04E93AB9607BE0F9258D9 459456B3E21956818C00FAA8B4DD7F26 Radula tanaiensis K.Feldberg, Schaef .-Verw. & M.A.M.Renner sp. nov. Fig. 5A-E Holotype. GZG.BST.22042 ( Mueller BuB4329) , Geoscience Centre (GZG) at the University of Goettingen , Germany. Etymology. The specific epithet refers to the village of Tanai, where Kachin amber is mined. Locality and horizon. Amber mines southwest of the village of Tanai ca. 105 km north of Myitkyina in Kachin State, northern Myanmar, fossil enclosed in upper Albian-lower Cenomanian Kachin amber. Diagnosis. Gametophyte irregularly branched, branches similar to main shoot, Radula -type. Lateral leaves complicate bilobed; dorsal lobe oval to ovate with rounded apex, deeply emarginated at end of keel; free exterior wall of marginal cells distinctly thickened; ventral lobules Lejeunea -type, up to 0.4 x as big as dorsal lobes, ovate to rounded trapezoid, insertion longitudinal, antical free margin often reaching antical margin of lobe. Description. Branched gametophyte fragment ca. 4 mm long [tip of main shoot broken off], yellowish to reddish brown (Fig. 5A-C ); main shoot up to 2.12 mm wide with leaves. Branching irregular, Radula -type (Fig. 5A, C ); three intact branches with reduced leaves near their base, becoming main shoot-like, 2.6-2.72 mm long and 1.2-2.1 mm wide with leaves. Stem dark reddish brown, straight to slightly zig-zagged, on main shoot ca. 70-90 µm wide [strongly decomposed], on branches ca. 60 µm wide; surface cells not visible; ventral and dorsal leaf-free strips not visible. Rhizoids not seen. Foliation incubous, lateral leaves alternate, complicate bilobed, divided into large dorsal lobe and smaller ventral Lejeunea -type lobule enclosing the ventral leaf surface and forming a sharp postical keel (Fig. 5B ). Dorsal lobes imbricate, oval to ovate, insertion longitudinal, flat, spreading, not obliquely patent, riding onto dorsal stem surface; margin entire, postical margin deeply curved along inner half, first nearly straight then evenly curved towards apex along outer half, lobe apex broadly rounded, exterior antical margin evenly curved, interior margin curved and slightly ampliate, overlapping the stem up to 1 x the stem width beyond the father edge of the stem; lobes on main shoot 600-610 µm long x 440-510 µm wide, length:width ratio 1.2-1.4:1, length exterior to keel 390-400 µm , length of stem insertion not clearly visible; lobes on branches 390-520 µm long x 300-360 µm wide, length exterior to keel 180-320 µm , length of stem insertion not visible. Marginal lobe cells quadrate to rectangular, 10-20 µm long x 15-25 µm wide, long axis either perpendicular or parallel with leaf margin (Fig. 5E ); medial cells (sub)isodiametric to slightly elongated, 15-30 µm long x 12.5-25 µm wide (Fig. 5D ); basal cells not visible; cell surfaces appearing smooth, but possible ornamentation visible in some parts (Fig. 5D ) [cells generally indistinct]; cell walls moderately thickened, with small triangular to subnodulose trigones, free exterior wall of marginal cells distinctly thickened (Fig. 5E ). Ventral lobules ovate to rounded trapezoid, up to 0.4 x as big as lobe, free antical margin often reaching antical margin of lobe (Fig. 5B ), insertion longitudinal, free exterior and antical margins nearly straight to curved, apex narrowly rounded to rounded, interior margin ampliate, ventrally extending up to 1 x the stem width beyond the farther edge of stem; keel emerging at an angle of ca. 45° from the stem, lobe deeply emarginated at end of keel; lobules on main stem 290-310 µm long x 340-370 µm wide, length:width ratio ca. 0.9:1, keel length 210-230 µm , length of stem insertion not visible; on branches 270-330 µm long x 300-340 µm wide, length:width ratio 0.8-1:1. Underleaves lacking. No asexual reproduction. Sterile. Remarks. The new fossil material consists of a short shoot fragment with the apex broken off and three main shoot-like Radula -type branches. It is not very well preserved, and many branches and leaves are broken (Fig. 5A-E ). The lobules are generally very large in relation to the lobes (Fig. 5A, B ) and differentiate this fossil clearly from R. patrickmuelleri as well as the much smaller R. cretacea whose lobules are less than 0.2 x the lobe size (Figs 3 , 4F ). Superficially the new species looks similar to R. heinrichsii (Fig. 5F, G ; compare descriptions in Feldberg et al. 2021b ), but the lobules of R. tanaiensis are up to 0.4 x the lobe size and their antical margin often reaches the antical margin of the lobe (Fig. 5B ), while the lobules of R. heinrichsii remain smaller and are more rounded (Fig. 5F ). The lobe cells are somewhat indistinct, but it is clearly visible that the outer walls of the marginal cells are distinctly thickened (Fig. 5E ) whereas those of R. heinrichsii are thinner (Fig. 5G ). Figure 5. Radula tanaiensis sp. nov. and R. heinrichsii Feldberg et al. A-E. R. tanaiensis , GZG.BST.22042 ( Mueller BuB4329), holotype; A. Gametophyte, ventral; B. Lobe and lobule, ventral (lobule indicated by black arrow); C. Lower part of Radula -type branch; D. Medial lobe cells; E. Marginal lobe cells with thickened free exterior walls (indicated by white arrow); F, G. R. heinrichsii , GZG.BST.22023 ( Mueller BuB3683), holotype; F. Gametophyte with microphyllous (amentulose) branches (indicated by asterisks), ventral; G. Lobe cells with central mamillae.