Mid-Cretaceous coastal amber forest palaeoenvironment revealed by exceptionally preserved ostracods from an extant lineage Author Wang, He https://orcid.org/0000-0002-5822-3309 Nanjing Institute of Geology and Palaeontology Chinese Academy of Sciences, 39 East Beijing Road, Nanjing 210008, China wanghe0701@163.com Author Matzke-Karasz, Renate https://orcid.org/0000-0002-8010-2028 Department of Earth and Environmental Sciences, Palaeontology and Geobiology, Ludwig-Maximilians-Universitaet Muenchen, Richard-Wagner-Strasse 10, 80333 Muenchen, Germany r.matzke@lrz.uni-muenchen.de Author Horne, David J. https://orcid.org/0000-0002-2148-437X School of Geography, Queen Mary University of London, Mile End Road, London E 1 4 NS, UK text Fossil Record 2022 2022-06-02 25 1 147 172 http://dx.doi.org/10.3897/fr.25.e84604 journal article http://dx.doi.org/10.3897/fr.25.e84604 2193-0074-1-147 91C70EDD7ACE492EAA7F1CE884018AE6 78E78880F4095BA2B0F947505C456D99 Electrocypria burmitei sp. nov. Figs 8 , 9 , 10 , 11 , 12 , 13 Etymology. Referring to 'burmite' , which is one of the names of amber from Myanmar. Material. Seven specimens enclosed in one amber piece (BA19005-6, 7, 37-41) (Fig. S1 ), two of which (male holo- and female paratype ) were analyzed using 3D X-ray microscopy. The species description is based on the tomographic data. Type locality and stratigraphy. Hukawng Valley, Kachin Province, northern Myanmar; upper Albian-lower Cenomanian. Types. Holotype: BA19005-6 (male); Paratype: BA19005-7 (female). Repository. Lingpoge Amber Museum (Shanghai). Dimensions. L = 470 μm , H = 200 μm , W ≈ 160 μm (male, holotype); L = 470 μm , H = 217 μm , W ≈ 145 μm (female, paratype). Diagnosis. see diagnosis of the currently monospecific genus. Description (The species description is based on the tomographic data, NIGP175852). Carapace (Figs 8 , 9 ): LV overlaps RV along the dorsal and ventral margins. Dorsal margin with greatest height at about 1/3rd of length, tapering down in straight line and same angle to anterior and posterior ends. Hinge well-developed, straight, between highest point and posterior end. Both anterior and posterior margins nearly equicurvate, with the latter curved much narrower than the former, but lacking an acute angle or pointed tip. Fusiform in dorsal view with greatest width at mid-length. Ventral margin slightly concave at mid-length. Calcified inner lamella relatively narrow at free margin, slightly broader at posterior end, and broadest at anterior end. Central muscular scars not visible. Normal pores scattered over smooth surface. Figure 8. Microtomographic reconstruction of Electrocypria burmitei gen. et sp. nov., surface rendering. A-E. Male, BA19005-6; F-J. Female, BA19005-7. First (uppermost) row: RV externally; second row: RV internally; third row: LV externally; fourth row: LV internally; fifth row: dorsal view of carapace, anterior to right. Figure 9. Microtomographic reconstruction of Electrocypria burmitei gen. et sp. nov., volume rendering. A. Male, BA19005-6, anterior view, with solidified body liquid extruding from breakage of RV; B. Cross section of same specimen, showing extrusion along the breakage in detail. Scale bar: 100 µm . Soft Body (Figs 10 - 13 ): A1 (Figs 10B , 12A, B, N, O , 13A ) with eight segments. Segments 1 and 2 fused forming large base, with two long setae originating ventro-distally on segment 2. Segment 3 short and asymmetric, sub-triangular, with ventral extension. Segment 4 connected to segment 3 with ventral inclination. Segments 4 to 8 all separate (not fused) and rectangular, with decreasing widths. Presence of setae confirmed for segments as figured. Setae on segment 8 at least as long as figured, possibly longer. Figure 10. Drawings of appendages of Electrocypria burmitei gen. et sp. nov., based on data of adult male (BA19005-6) and adult female (BA19005-7). A. A2; B. A1; C. Mxl; D. Md; E. male L5; F. female L5; G. L6; H. L7. Scale bar: 50 µm . A2 (Figs 10A , 12 C, D, P , 13A ) Segment 1 (coxa) subrectangular, segment 2 (basis) elongate and carrying long ventro-apical seta. Knee between segment 2 and 3. Segment 3 (first endopodal segment) very similar to segment 2 in shape and length, also carrying ventro-apical seta. Exopod not confirmed, but aesthetasc Y present. Natatory setae not observed in male, but at least 2 natatory setae present in one of the female's A2 (Fig. 12P ); their exact point of origin at segment 3 is unclear. Segments 4 and 5 possibly fused, since clear segmental boundary could not be confirmed. Their length approximately half the length of segment 3. Apically with at least three claws (G1, G2, G3). Segment 6 small with at least one claw apically (GM or Gm). Md (Figs 10D , 12E, F, Q , 13B ) Masticatory process of coxa with teeth (total number uncertain). Palp consisting of 4 separate segments and remarkably straight (i.e., not bent ventrally towards mouth). Segment 1 (basis) with vibratory (branchial) plate on dorsal edge (no setae observed), and two thick setae ventrally, one at medium-length of the segment, the other more distally, but still at a considerable distance to segment 2. Shape of this segment obliquely trapezoidal due to angulation on dorsal margin. Segment 2 nearly square-shaped, with at least three setae apically (one dorsally, two ventrally). Segment 3 more elongate, with shoulders distally towards segment 4. On these shoulders, at least 5 setae confirmed (2 dorsally, 3 ventrally). Segment 4 much thinner than proximal segments, distally at least one thick seta or claw present. Mxl (Fig. 10C ) Protopod with branchial plate (no setae confirmed), three masticatory lobes (endites 1-3) and palp. Palp possibly two-segmented, as dorsal seta might indicate. Distal claws and/or setae not confirmed. L5 Male (Figs 10E , 12G, H , 13C ): no setae on protopod confirmed. Palp (endopod) truncated, possible finger-like process of this clasping organ not observed. Masticatory process with several distal setae. Female (Figs 10F , 12R ): masticatory process and palp preserved with no detail. L6 (Figs 10G , 12I, J, S ) Walking leg. Segment 1 small, segment 2 elongate with seta e distally. Segments 3 and 4 separate, not fused. Segment 3 with seta f distally, segment 4 with no seta g observed. Segment 5 with long claw h2. L7 (Figs 10H , 12K, L, T, U , 13D ) Cleaning leg, directed dorsally. Segment 1 (basis) with setae d1 and d2 present. Segment 2 (first endopodal segment) long, with distal seta e. Segments 3 and 4 separate, not fused. Segment 3 with seta f, segment 4 with seta g distally. Segment 5 short, nearly quadrate; distally long claw h2 and long reversed seta h3 present. Ur ramus (Figs 11A, B , 12M, V , 13E ) Relatively stout and straight, with two relatively long terminal claws of similar length preserved (approx. half the length of the posterior edge of the ramus). Posterior and anterior setae not observed. UR attachment simply branched. Figure 11. Drawings of appendages of Electrocypria burmitei gen. et sp. nov., based on microtomography of adult male (BA19005-6) and adult female (BA19005-7). A. UR with proximal attachment; B. UR with female genital lobe; C. Hemipenis, ventral view. Scale bar: 50 µm . Figure 12. Microtomographic reconstruction of soft parts of male (BA19005-6) and female (BA19005-7) Electrocypria burmitei gen. et sp. nov., surface renderings. A-M. With same scale, male (BA19005-6); N-V. With same scale, female (BA19005-7). A. A1, right; B. A1, left; C. A2, right; D. A2, left; E. Md, right; F. Md, left; G. L5, left; H. L5, right; I. L6, right; J. L6, left; K. L7, right; L. L7, left; M. UR; N. A1, right; O. A1, left; P. A2, right; Q. Md, right; R. L5, left; S. L6, left; T. L7, right; U. L7, left; V. UR. Figure 13. Microtomographic reconstruction of Electrocypria burmitei gen. et sp. nov., based on data of adult male (BA19005-6) and adult female (BA19005-7), volume rendering. A. A1 (short arrow) and A2 (long arrow); B. Right Md (highlighted); C. Male L5 (highlighted); D. Left L7; E. UR (highlighted); F. Right HP, interior view; G. Female genital lobe (highlighted). Scale bars: 50 µm . HP (Figs 11C , 13F ) roughly triangular in lateral view, with no differentiation of lobes observed. Greatest length of HP nearly a quarter of carapace length. Female genital lobes (Figs 11B , 13G ) formed as spindle-shaped projections towards posterior and extending nearly to the posterior-most end of the soft body (i.e. basis of the UR). Remarks. Electrocypria burmitei gen. et sp. nov. possesses relatively long setae on A1, as well as at least 2 natatory setae on A2, however, the latter are only preserved partly, and possibly not at their full lengths. It is therefore impossible to evaluate the swimming capability of this species. The straight appearance of the Md palp results from segment 2 being nearly square-shaped and not as wedge-shaped as is often the case in other Cypridoidea . None of the L5s is completely preserved in either specimen and it remains unclear how the male claspers look in E. burmitei gen. et sp. nov. While L6 is formed as a walking leg with a long distal claw and segments 3 and 4 not fused, L7 is formed as a 5-segmented cleaning leg with setae e, f and g present, as well as long terminal h2 and h3 setae/claws. The holotype shows a linear breakage in its LV, in parallel to the dorsal margin, as well as minor breaking marks in its RV. The external pressure of the resin seems to have squeezed body liquid out of the animal on the LV into the surrounding resin (Figs 8A, B , 9A, B ). Suborder Cytherocopina Baird, 1850 Superfamily Cytheroidea Baird, 1850 Family Loxoconchidae Sars, 1925