A new species of Baiera from the Early Cretaceous ...

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David L. Dilchera,b,c,∗∗. , Yu-Ling .... Zhou and Zhang (1992) reviewed B. hallei Sze 82 ..... et al., 1963), Baiera kidoi Yabe et Ôishi from Jilin (Sze et al., 313.
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A new species of Baiera from the Early Cretaceous Jehol Biota of southeastern Jilin, China

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Miao Zhao a,b,c , Chun-Lin Sun a,b,∗ , David L. Dilcher a,b,c,∗∗ , Yu-Ling Na a,b , De-He Xing d

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Key Laboratory for Evolution of Past Life and Environment in Northeast Asia, Ministry of Education, Changchun 130026, Jilin, China b Research Center of Paleontology and Stratigraphy, Jilin University, Changchun 130026, Jilin, China c Department of Geology and Biology, Indiana University, Bloomington, IN 47405, USA d Shenyang Institute of Geology and Mineral Resources, Shenyang 110034, Liaoning, China Received 4 July 2014; received in revised form 30 September 2014; accepted 8 January 2015

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Abstract

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The Early Cretaceous Yingzuilazi Formation is exposed in the Baishan Basin, Baishan region of the southeastern Jilin Province, China. So far, no reports on fossil plants from this formation have been published. During recent field excursions, abundant faunal remains belonging to the Early Cretaceous Lycoptera–Ephemeropsis–Eosestheria assemblage of the Jehol Biota and numerous fossil plants were collected from the lacustrine beds of the lower part of this formation. A new species of Ginkgoales from this formation, Baiera baishanensis n. sp., is described based upon the leaf morphology and epidermal characters. This is the first report about fossil plants from the Yinzuilazi Formation, the easternmost distribution area of the Jehol Biota. The discovery of the new species extends significantly the stratigraphic and geographic distribution of Baiera in the Early Cretaceous Jehol Biota as well as the Eurasia. It also shows that Baiera was a common member of Ginkgophytes once lived in the Early Cretaceous deciduous forest of Northeast China. The new species also improves our knowledge on understanding the leaf morphology, epidermal features, and diversity of Baiera during the Early Cretaceous. Analysis of the epidermal characters of the new species and other associated plants reveals that the plants grew in a warm and humid climate in the temperate zone. The presence of some deciduous plants, including gingkgoaleans, czekanowskialeans, and some conifers, demonstrates a climate with seasonal fluctuations and precipitation. © 2015 Published by Elsevier B.V. on behalf of Nanjing Institute of Geology and Palaeontology, CAS.

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Keywords: Baiera; Early Cretaceous; Jehol Biota; Yingzuilazi Formation; Jilin; China

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1. Introduction

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The Early Cretaceous Jehol Biota is traditionally marked by the assemblage of Lycoptera–Ephemeropsis–Eosestheria. It is distributed generally in the non-marine basins of eastern Asia, including northern China, Mongolia, Siberia, Korea, Japan (Gu, 1962, 1982, 1983, 1995; Chen, 1988; Ji, 2002;



Corresponding author at: Key Laboratory for Evolution of Past Life and Environment in Northeast Asia, Ministry of Education, Changchun 130026, Jilin, China. Tel.: +86 431 8850 2189; fax: +86 431 8850 2189. ∗∗ Corresponding author at: Department of Geology and Biology, Indiana University, Bloomington, IN 47405, USA. Tel.: +1 812 856 0618; mobile: +1 734 239 5248. E-mail addresses: [email protected] (C.-L. Sun), [email protected] (D.L. Dilcher).

Chang et al., 2003; Ji et al., 2004). Among these fossil areas, western Liaoning of Northeast China is regarded as a fascinating region for studying the Jehol Biota because of abundant and extremely well-preserved fossils, including branchiopod crustaceans, ostracods, bivalves, gasteropods, insects, fish, amphibians, reptiles, birds, mammals, and plants that have been reported from this region since the early 1990s. The most notable discoveries include early birds, “feathered” dinosaurs, pterosaurs, early mammals, amphibians, pollinating insects, early angiosperms, and insect oviposition on plant leaves (Na et al., 2014). The new discoveries have not only provided direct and strong evidences for explaining the evolutionary history of many important groups of organisms, but also significantly expanded our knowledge on the biodiversity in the Early Cretaceous terrestrial ecosystem (Ji et al., 2001; Zhou, 2006; Ji et al., 2007; Benton et al., 2008; Zhou and Wang, 2010).

http://dx.doi.org/10.1016/j.palwor.2015.01.001 1871-174X/© 2015 Published by Elsevier B.V. on behalf of Nanjing Institute of Geology and Palaeontology, CAS.

Please cite this article in press as: Zhao, M., et al., A new species of Baiera from the Early Cretaceous Jehol Biota of southeastern Jilin, China. Palaeoworld (2015), http://dx.doi.org/10.1016/j.palwor.2015.01.001

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Baishan region is the easternmost extent of the Jehol Biota in China (Gu, 1962). More recently, many fossil remains, including bivalves, ostracoda, branchiopod crustaceans, insects, fish, amphibians, and plants, have been collected from the Early Cretaceous Yingzuilazi Formation of this area by Prof. Chun-Lin Sun and his colleagues. Fossil plants of the new collections mainly include horsetails (Equisetites longevaginatus Wu, Equisetostachys sp.), ferns (Gleichenites sp., Coniopteris angustiloba Brick, C. burejensis (Zalessky) Seward, C. spp., Cladophlebis sp.), ginkgoaleans (Ginkgo sp., Baiera sp., Eretmophyllum sp.), czekanowskialeans (Phoenicopsis sp., Solenites spp.), and conifers (Pityostrobus sp., Pityospermum sp., Pityophyllum lindstroemi Nathorst, Schizolepis sp., Podozamites sp.). Preliminary study of bivalves, ostracoda, branchiopod crustaceans, insects, and fishes indicates that this biota belongs to Lycoptera–Ephemeropsis–Eosestheria assemblage of the Jehol Biota, commonly found in the Early Cretaceous Yixian Formation of western Liaoning. It represents a new, easternmost fossil locality of the Jehol Biota. No fossil plants from the Yingzuilazi Formation have been formally published and described except for the fossil records in geological survey reports. In this paper, a new species of the genus Baiera (Ginkgoales), Baiera baishanensis n. sp., is described based on the leaf morphology and epidermal characters. Baiera Braun is a common member of Ginkgophytes in the Mesozoic floras of Eurasia. A large number of species have been reported since the establishment of this genus in the 19th century (Braun, 1843). According to Zhou (2006) and Zhou and Wu (2006), 31 species have been already reported from different localities of the Late Triassic–Early Cretaceous in China. However, most species were described based mainly upon poorly preserved fossil leaves and the gross morphology.

Although epidermal features are important in identifying Baiera, only a small number of species was studied in detail based on both gross morphology and epidermal structures from Chinese records. Zhou and Zhang (1992) reviewed B. hallei Sze and associated ovule-bearing organs from the Middle Jurassic of Henan. Wu (1993) studied B. furcata (L. et H.) Braun from the Early Cretaceous of Shangxian, southern Shaanxi. Deng (1995) and Deng et al. (1997) reported B. furcata (L. et H.) Braun from the Early Cretaceous of the Huolinhe and Hailar basins, Inner Mongolia. Wu et al. (2006) described the Baiera-type leaves associated with Ginkgoalean ovulate organs and seeds from the Middle Jurassic of Qinghai. Yin et al. (2008) reported a new species, B. bifurcata, from the Early Cretaceous in the Wujiu Basin of the northeastern Inner Mongolia. Wang et al. (2013) reconstructed the Mesozoic paleoatmospheric CO2 on the basis of the stomatal parameters of B. furcata (L. et H.) Braun. Aside from China, Baiera was also excavated from other places of the world. The more detailed report about Baiera furcata (L. et H.) Braun and related flora is from Yorkshire, England (Harris et al., 1974). B. furcata (L. et H.) Braun was also described from the Middle Jurassic of Afghanistan by Schweitzer and Kirchner (1995). Furthermore, B. muensteriana Heer associated with isolated ovules (seeds) and juvenile organs was found from the basal Liassic of Franconia, Germany by Kirchner (1992). In addition, it is necessary to mention that the Baiera-type leaves were regarded as vegetative leaves of Yimaia because they were most often found associated with Yimaia-type ovulate organs and seeds which appear to form a regular combination in the Mesozoic ginkgoaleans (Wu et al., 2006; Zhou, 2007, 2009). Baiera and Yimaia are members of Yimaiaceae, a family of Ginkgoales (Zhou, 1997, 2000). Yimaiaceae possibly is distributed widely in the Mesozoic of China and the Eurasia.

Fig. 1. Map showing fossil locality. The inset map shows the Baishan region in the southeastern Jilin, Northeast China.

Please cite this article in press as: Zhao, M., et al., A new species of Baiera from the Early Cretaceous Jehol Biota of southeastern Jilin, China. Palaeoworld (2015), http://dx.doi.org/10.1016/j.palwor.2015.01.001

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The new species is significant because it is the first fossil plant documented from the Early Cretaceous Yingzuilazi Formation of the Baishan Basin of southeastern Jilin and the locality is the easternmost extent of the Early Cretaceous Jehol Biota, China. It also reveals that Baiera is an important member of ginkgoaleans that lived in the Early Cretaceous deciduous forest of Northeast China. The discovery of the new material not only extends the stratigraphic and geographic distribution of Baiera in northern China and Eurasia, but also improves our understanding of the leaf morphology, epidermal structure, and diversity of Baiera during the Early Cretaceous.

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2. Materials and methods

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The specimens reported here were collected from the Baishan Basin in Baishan region of southeastern Jilin, Northeast China (Fig. 1). This Early Cretaceous basin is the easternmost extent of the Jehol Biota in China (Gu, 1962) and in ascending order contains the Early Cretaceous Yingzuilazi Formation and Linzitou Formation. The Yingzuilazi Formation is a set of deposits with thin coal layers in fluvial-lacustrine-swamp environments. It is about 437 m thick and composed of conglomerate, sandstone, siltstone, mudstone, shale, and coal. It overlies the Upper Proterozoic Badaojiang Formation unconformably, and is conformably overlain by the Early Cretaceous Linzitou Formation (Fig. 2). The geological age of the Yingzuilazi Formation was previously attributed to the Late Jurassic (Bureau of Geology and Mineral Resources of Jilin Province, 1988, 1997). However, the flora and fauna composition of the biota is very similar to that of the Early Cretaceous Yixian Formation in western Liaoning, China, based upon our preliminary study. The age of Yingzuilazi Formation is probably Early Cretaceous. The plant fossils were found in dark gray siltstones from the lower part of the type section of the Yingzuilazi Formation near Yingzuilazi Village, Baishan region (41◦ 58 28.3 N, 126◦ 25 46.8 E). Twenty compression specimens of Baiera are examined. Hand specimens are observed under stereoscopic microscope (Olympus SZX10). The images were obtained by the reflected light using a Canon digital camera (Canon 5D Mark II) and Keyence digital microscope with a camera attachment (Keyence VHX-1000). Cuticular preparations are made by using standard procedures (Dilcher, 1974; Kerp, 1990). Treated cuticle samples for SEM are mounted on the stubs using double-sided adhesive tape, coated with gold, then observed and photographed with a JSM-6700 CF scanning electron microscope at an acceleration voltage of 8 kV at the Research Center of Paleontology and Stratigraphy of Jilin University, Changchun, China. All specimens and preparations are stored in the Research Center of Paleontology and Stratigraphy of Jilin University, Changchun, China.

3. Systematics Order Ginkgoales Genus Baiera Braun, 1843, emend. Florin, 1936

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Fig. 2. Measured section of the Early Cretaceous Yingzuilazi Formation in the Baishan Basin of southeastern Jilin, Northeast China. 1. Conglomeratic sandstone; 2. Arkose; 3. Silty mudstone; 4. Shale; 5. Calcareous mudstone; 6. Coal seam; 7. Silty shale; 8. Limestone; and 9. Plant-bearing horizon.

Baiera baishanensis n. sp. (Figs. 3–7) Etymology: The specific epithet “baishanensis” refers to the Baishan region, Jilin, China, where the fossil was collected. Holotype: YZB001A (Fig. 3A) and YZB001B (Fig. 4C, the counterpart of the lower half of YZB001A). Paratype: YZB002, YZB003 (Fig. 4E), YZB004 (Fig. 4D), YZB005 (Fig. 4A), YZB006, YZB007, YZB008A (Fig. 3D), YZB008B (the counterpart of YZB008A), YZB009, YZB010, YZB011 (Fig. 4B), YZB012, YZB013, YZB014, YZB015, YZB016, YZB017, YZB018. Repository: The Research Center of Paleontology and Stratigraphy of Jilin University, China. Type locality: Yingzuilazi Village, Baishan, Jilin, China. Stratum typicum: Dark gray siltstones from the lower part of the Yingzuilazi Formation. Diagnosis: Leaf with a long and slender petiole, lamina as a whole broadly wedge-shaped. Lamina firstly divided into two segments at an angle about 30◦ –40◦ , each segment subdivided by three to four successive dichotomies at an angle around 25◦ –30◦ , resulting in at least 16 ultimate lobes. Ultimate lobes more or less linear, usually about 1.5 mm wide with subacute or obtuse apices. Vein visible, regularly 4 in ultimate lobe. No resin bodies between veins.

Please cite this article in press as: Zhao, M., et al., A new species of Baiera from the Early Cretaceous Jehol Biota of southeastern Jilin, China. Palaeoworld (2015), http://dx.doi.org/10.1016/j.palwor.2015.01.001

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Fig. 3. The leaves of Baiera Baishan n. sp. (A) YZB001A, holotype, a well-preserved leaf; arrows indicate the positions where cuticle was removed for preparation. (B) Enlarged from (A) showing the apices of ultimate lobes. (C) Enlarged from (A) showing the conspicuous veins in the ultimate lobes (indicated by arrows). (D) YZB008A, specimen showing a long and narrow petiole. Scale bar = 1 cm. 185 186 187 188 189 190 191 192 193 194 195 196 197 198

Leaves amphistomatic. Both sides of cuticle very thin. Stomata density higher on lower cuticle. Upper cuticle with veins usually marked by strips of elongated cells arranged in longitudinal rows (length mostly 5–7 times as long as the width). Cells between veins rectangular, often shorter near stomata. Anticlinal cell walls straight, fairly thick. Periclinal cell walls not thickened. Trichomes absent. Stomata unevenly distributed between veins, sometimes forming short longitudinal files. Stomatal pit longitudinally orientated. Lower cuticle with veins either indistinguishable or poorly defined by a few rows of rectangular cells. Cells between veins isodiametric or rectangular arranged in longitudinal files. Anticlinal walls straight, medium width (about 2–3 ␮m wide). Periclinal cell walls smooth, not thickened. Trichomes

absent. Numerous stomata occurring between veins, scattered, or occasionally arranged in short longitudinal files. Stomatal pit longitudinally orientated. Guard cells with thin surface wall except for thickened strip along aperture. Guard cells surrounded by a group of subsidiary cells arranged in an oval pattern. Subsidiary cells thickening varied, but often with thickening band adjacent to guard cells, forming a complete rim around the stomata pit. Rim usually bulging, forming papillae projecting upwards, or slightly over guard cells. Surface of subsidiary cells with thickening or small solid papilla in addition to fused with bulging rim of thickening around stomata pit. Description: Seven specimens are shown in Figs. 3 and 4. The holotype of Baiera baishanensis n. sp. is over 90 mm long (Fig. 3A). The entire lamina is wedge-shaped, with a basal

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Fig. 4. The leaves of Baiera baishanensis n. sp. (A, B, D, E) paratypes; (A) YZB005; (B) YZB011; (D) YZB004; (E) YZB003. (C) holotype, YZB001B; the counterpart of the lower half of (A); specimen showing incomplete leaves of Baiera baishanensis n. sp. Arrows indicate the position where cuticle was removed for preparation. Scale bar = 1 cm.

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angle about 30◦ –40◦ . The lamina is firstly divided into two primary division extending to the petiole, and then each division is subdivided into 16 ultimate lobes at least by three successive dichotomies at an angle around 25◦ –30◦ . The ultimate lobes are narrow and more or less linear with straight lateral margins, usually about 1.5 mm wide (Figs. 3 and 4C–E). The petiole is over 22 mm long and 1.5–2.5 mm wide (Fig. 3A, D). The apices are obtuse or somewhat acute (Fig. 3B). Veins are visible, regularly 4 in ultimate lobes and 6–8 in the lower segments (Figs. 3C, 4A). No resin bodies are presented between veins. The leaf is amphistomatic. On the upper cuticle the stomata density is obviously lower than that on the lower cuticle. Both upper and lower cuticles normally lack trichomes. The stomata are longitudinally orientated and unevenly distributed between veins, but they are sometimes arranged in short longitudinal files (Fig. 5A). The epidermal cells between the stomata are elongated cells arranged in longitudinal rows (mostly 50–70 long

by 10–15 ␮m wide, a few up to 100–120 ␮m by 10–15 ␮m wide). The epidermal cells between veins are commonly rectangular or quadrangular and often become shorter near the stomata (mostly 20–30 long by 10–20 ␮m wide). Anticlinal cell walls are straight, fairly thick (Fig. 5A). Periclinal cell walls are smooth and not thickened. More stomata are unevenly distributed in the lower cuticle (Fig. 6A and D). The epidermal cells between the stomata are clearly different from those of the upper cuticle. They are generally rectangular or isometric in the lower cuticle (20–30 ␮m long and 10–20 ␮m wide) (Fig. 6D). Most characters of stomata are similar on both upper and lower cuticles. The haplocheilic stomatal apparatuses are elliptical, averaging ca. 40–50 ␮m long and 20–30 ␮m wide. The pit of stomata is 20–30 ␮m long and longitudinally oriented. The guard cells have thin surface walls except for thickened strip along the pit and slightly sunken below the epidermal surface

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Fig. 5. The upper cuticlar SEM images of B. baishanensis n. sp., showing leaf epidermal features. (A) YZB001A-005-1-3, the inner surface showing the distribution of stomata (indicated by arrows). (B) YZB001A-005-2-2, the outer surface showing a few stomata (indicated by arrows). (C) YZB001A-006-2-5 and (D) YZB001A007-4-5, the inner surface showing the characters of stomatal apparatus. (E) YZB001A-002a-2 and (F) YZB001A-002a-4, the outer surface showing the entire rim or slight papillae of subsidiary cells around stomata pit. For (A, B), scale bar = 100 ␮m; for (C–F), scale bar = 10 ␮m.

Please cite this article in press as: Zhao, M., et al., A new species of Baiera from the Early Cretaceous Jehol Biota of southeastern Jilin, China. Palaeoworld (2015), http://dx.doi.org/10.1016/j.palwor.2015.01.001

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Fig. 6. The lower cuticlar LM and SEM images of B. baishanensis n. sp., showing leaf epidermal features. (A) YZB001A-G-005, showing uneven distribution of stomata. (B) YZB001A-G-013, showing slight papillae of subsidiary cells around stomata pit. (C) YZB001A-007-3-1, the outer surface showing distribution of the stomata (indicated by arrows). (D) YZB001A-007-2-9, the inner surface showing more stomata unevenly arranged (indicated by arrows). (E) YZB001A-007-1-4 and (F) YZB001A-007-2-11, the inner surface showing the characters of stomatal apparatus. (G) YZB001A-007-2-13, the inner surface showing two stomata which are close to each other. (H) YZB001A-007-3-3, the outer surface of the lower cuticle showing slight papillae of subsidiary cells around stomata pit. For (A, C, D), scale bar = 100 ␮m; for (B, E-H), scale bar = 10 ␮m. 247 248 249 250

(Figs. 5C and D and 6E–G). They are surrounded by the group of subsidiary cells which arranged in an oval pattern. The number of subsidiary cells varies from six to eight, and they often unevenly thickened and form irregular papillae. These small solid papil-

lae make up of an entire rim around the stomata pit, slightly covering the guard cells (Figs. 5B, E and F and 6B, C and H). Both cuticular surfaces of the petiole contain longitudinal files of similar elongate epidermal cells, 20–30 ␮m long and

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Fig. 7. The SEM images showing the epidermal features of leaf petiole of B. baishanensis n. sp. (A) YZB001B-004-4-7, the inner surface of the upper cuticle showing two stomata and the shape of the epidermal cells. (B) YZB001-004-3-4, the inner surface of the upper cuticle showing the distribution of the stomata (indicated by arrows). (C) YZB001A-004-5-1, the outer surface of the lower cuticle showing smooth and slightly thickened periclinal walls of the epidermal cells. (D) YZB001B-004-3-12, the inner surface of the upper cuticle showing the character of stomatal apparatus. (E) YZB001A-004-4-8, the inner surface of the

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10–15 ␮m wide. The anticlinal walls are straight (Fig. 7A and B). The periclinal walls are evenly thickened (Fig. 7C). The stomatal density on lower cuticle is clearly greater than the upper one (Fig. 7E). They are longitudinal oriented and almost unspecialized compared with those of leaf lobe (Fig. 7D, F and G). 4. Comparison The presence of an obvious petiole can be used to distinguish Baiera from the genus Sphenobaiera according to Florin (1936) and Harris et al. (1974). Many species of Baiera have been described from the Mesozoic floras of China and some other places of the world. Baiera furcata (L. et H.) Braun (including B. gracilis Bunbury) from the Middle Jurassic flora of Yorkshire, England is similar to the new species in leaf morphological features, particularly the narrow ultimate lobe (Harris et al., 1974). However, B. furcata differs from the new species in having numerous round or oval resin bodies between veins and in that the stomata are irregularly orientated between veins. The new species is also similar to Baiera hallei Sze that may be affiliated with Yimaia-type organs from the Middle Jurassic Yima flora of Henan, the Datong flora of Shanxi and Hebei, China (Sze, 1933; Wang, 1984; Zhou and Zhang, 1992). Baiera hallei can be distinguished from the new species by having resin bodies between veins and randomly oriented stomata. A number of Baiera leaves from the Early to Middle Jurassic of northern China are comparable with the new species based on the gross morphological features. They all seem to differ in leaf size and other important characters such as the shape of leaf lobes. Their cuticular features are unknown. These species include B. asadai Yabe et Ôishi from Shandong, Liaoning, and the West Hills of Beijing (Yabe and Ôishi, 1928; Ôishi, 1933; Zhang et al., 1980; Chen et al., 1984), B. concinna (Heer) Kawasaki from Liaoning, the West Hills of Beijing, and Inner Mongolia (Zhang et al., 1980; Chen et al., 1984; Duan et al., 1986), B. gracilis Bunbury from Liaoning and the West Hills of Beijing (Zhang et al., 1980; Chen et al., 1984; Duan, 1987). It is dubious that they are really related to the present new species from the Early Cretaceous. Several distinctive Early Cretaceous Baiera leaves have been described from Northeast China. These include Baiera furcata (L. et H.) Braun from the Huolinhe, Hailar, and Dayan basins of northeastern Inner Mongolia (Deng, 1995; Deng et al., 1997) and Baiera bifurcate Yin et al. from the Wujiu Basin of northeastern Inner Mongolia (Yin et al., 2008). All of these fossils have narrower leaf lobes in leaf outline. However, B. furcata from the Huolinhe Basin is different from the new species in having one to two veins in the ultimate lobes and undeveloped papillae of the subsidiary cells. The new species resembles Baiera bifurcate in leaf lobe shape, but other characters proved that they are different species. For instance, the leaf of B. bifurcate is narrowly wedge-shaped, forks twice, and forms four ultimate

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lobes with two inconspicuous veins. The cuticles features of two species also differ from each other. The species from the Wujiu Basin is distinguished from the new species by its well -defined stomatal and non-stomatal zone and fewer stomata on both upper (3–4/mm2 ) and lower cuticles (9–11/mm2 ). Furthermore, there are some other related species of Mesozoic Baiera can be compared to the new species. These species include Baiera guilhaumati Zeiller from Jiangsu and Anhui (Sze et al., 1963), Baiera kidoi Yabe et Ôishi from Jilin (Sze et al., 1963), Baiera manchurica Yabe et Ôishi (Sze et al., 1963), Baiera minita Ôishi from Jilin (Sze et al., 1963) and Baiera multipartite Ôishi from Jilin (Sze et al., 1963). These species can be distinguished from the new species by either leaf morphological features or the epidermal structures (Table 1).

5. Discussion Baiera is a common element in the Late Triassic–Early Cretaceous floras, and is known to first occur in the Permian. However, unequivocal fossils of the Late Paleozoic Baiera are limited. A few species were recorded from several locations of the world, including Baiera digitata (Brongniart) Heer from the Permian of Hungary (Heer, 1876; Tuzson, 1909; Greguss, 1961), the Late Permian Marlslate of Middridge, England (Stoneley, 1958) and Kupferschiefer Flora of Germany (Weigelt, 1928, 1932; Schweitzer, 1960; Bauer et al., 2013); B. mansfeldensis Bauer from the German Kupferschiefer Flora (Bauer et al., 2013); Baiera plumose Hoeg et Bose from the Permian of Kisulu, Congo (Høeg and Bose, 1960); Baiera virginiana Fontaine et White, from the Permian of the Upper Barrens, West Virginia, USA (Fontaine and White, 1880); Baiera tartarica Zalessky from the Permian of Bachkire and Tatare, Russia (Zalessky, 1929); Baiera raymondii Renault from the Permian of Charmoye, France (Renault, 1888). The fossil records show that Baiera became widespread and diverse at the beginning of the Late Triassic. It was reported mainly from the Late Triassic–Early Cretaceous floras of the Eurasia (Sze et al., 1963; Zhou, 2006, 2009; Zhou and Wu, 2006). There is no record of this genus in the Cenozoic. This indicates that Baiera had died out after the mass extinction events at the end of the Cretaceous (McElwain and Punyasena, 2007). It is interesting to note that the fossil plant records in the strata, equivalent to the lower part of the Lower Cretaceous Yixian Formation, are scanty in Northeast China except for the Jianshangou flora from the western Liaoning (Sun et al., 2001). We provide here a new record of Baiera from the easternmost extent of the Early Cretaceous Jehol Biota on the basis of well-preserved specimens. Although several Baiera leaves resembling present new species have been described from the Early Cretaceous of northern China, their epidermal anatomy is usually unknown.

lower cuticle showing unevenly distributed stomata. (F) YZB001B-004-5-3, the outer surface of the upper cuticle showing distinct papillae of the subsidiary cells around stomata pit. (G) YZB001B-004-3-17, the inner surface of the upper cuticle showing two stomata which are close to each other. For (A-C, G), scale bar = 100 ␮m; for (D–F), scale bar = 10 ␮m.

Please cite this article in press as: Zhao, M., et al., A new species of Baiera from the Early Cretaceous Jehol Biota of southeastern Jilin, China. Palaeoworld (2015), http://dx.doi.org/10.1016/j.palwor.2015.01.001

305 306 307 308 309 310 311 312 313 314 315 316 317 318

319

320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353

Lamina

Division times

Apex

Segments Shape

Width

Veins

Epidermal cells

Stomata Density (/mm2 )

Guard cells

Subsidiary cells

Arrangement

Resin bodies

Reference

Yabe and Ôishi (1928); Ôishi (1933); Zhang et al. (1980); Chen et al. (1984) Zhang et al. (1980); Chen et al. (1984); Duan et al. (1986) Yin et al. (2008)

5–6

Slight bent and linear

2 mm

Acute to acuminate















Baiera concinna

Fan-shaped

4

Oblanceolate

4 mm

Obtuse

4–5













Baiera bifurcata

Wedge-shaped

2

Linear

1–1.2 mm

Obtuse

2

Irregular rectangular. Anticlinal cell walls straight.

3–4 (upper cuticle) 9–11 (lower cuticle).

Slightly sunken

5–7 (6 is most common)



Baiera furcata

Fan-shaped to semicircular

2–6

Linear

About 1.5 mm

Subacute or acute

1–5

Rectangular or polygonal. Anticlinal cell walls straight.

10–15 (upper cuticle) 35–45 (lower cuticle).

Sunken

5–7

Baiera baishanensis n. sp.

Broad wedge-shaped

4–5

Linear

About 1.5 mm

Subacute or obtuse

Regularly 4

10–15 (upper cuticle) 25–35 (lower cuticle).

Sunken

6–8

Baiera gracilis

Fan-shaped

3–4

Linear or oblanceolate

About 3 mm

Acuminate or obtuse

2–4



Fan-shaped to inverted wedge Fan-shaped to semicircular

2–3

Oblanceolate

Up to 5 mm

Obtuse



About 10 (upper cuticle) About 35 (lower cuticle). –



Baiera guilhaumati

Rectangular or quadrangular (upper cuticle), rectangular or isodiametric (lower cuticle). Anticlinal cell walls straight. Quadrangular to rectangular. Anticlinal cell walls straight. –

Longitudinally orientated (occasionally oblique orientated). Scattered, or in short longitudinal files, irregular orientated. Unevenly distributed. Some arranged in short files. Longitudinally orientated.





2–6

Obovate, oblanceolate or linear

Up to 3 mm

Obtuse to somewhat truncate

2–4



Sunken

5–7

40–50 (lower cuticle) –



Baiera hallei

Baiera kidoi

Fan-shaped

4

Oblanceolate

Up to 3 mm



4–6

Baiera manchurica

Semicircular to almost orbicular

2–3

Oblanceolate

Up to 3 mm

Obtuse

6

Baiera minita

Fan-shaped to semlorbicular, about 1.5–2 mm tall

3 –4

Linear



Obtuse

4–5

Baiera multipartite

Fan-shaped to semicircular

6–7

Oblanceolate



Notch

2–3

Polygonal or isodiametric. Anticlinal cell walls straight to undulate. Rectangular, or polygonal. Polygonal. Anticlinal cell walls strongly wrinkling. Rectangular, to isodiametric. Anticlinal cell walls wrinkling. –

Present

Harris et al. (1974); Deng (1995); Deng et al. (1997)

Absent

Present article

Present

Zhang et al. (1980); Chen et al. (1984); Duan (1987)



Sze et al. (1963)

Randomly orientated or irregular distributed.

Present

Sze (1933); Wang (1984); Zhou and Zhang (1992)

About 5





Sze et al. (1963)



About 5





Sze et al. (1963)

25–30 (lower cuticle)

Slightly sunken

4–6



Sze et al. (1963)







Irregular distributed, somewhat longitudinally orientated. –



Sze et al. (1963)

Longitudinally orientated or irregular orientated. –

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M. Zhao et al. / Palaeoworld xxx (2015) xxx–xxx

Baiera asadai

+Model

Species

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Please cite this article in press as: Zhao, M., et al., A new species of Baiera from the Early Cretaceous Jehol Biota of southeastern Jilin, China. Palaeoworld (2015), http://dx.doi.org/10.1016/j.palwor.2015.01.001

Table 1 Comparison between Baiera baishanensis n. sp. and other related species of Baiera from the Mesozoic.

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The new discovery has paleogeographic and paleoclimatic significance. Vakhrameev (1991) divided Palaeo-floristic Regions of Early Cretaceous into the Siberian-Canadian, Euro-Sinian, Equatorial, and Austral (or Notal). The SiberianCanadian Region was then subdivided into the Lena, Amur, and Canadian provinces based on the composition and distribution of plant groups. The Amur province includes Bureya basin, Tyl-Torom and Udsk troughs, the Transbaikal area, Northeast and North China. In this province, ginkgoaleans, czekanowskialeans, and conifers mixed with some ferns and horsetails were much more diverse, whereas Cycadophytes are rare except for Nilssonia. According to the preliminary study, the flora of the Early Cretaceous Yingzuilazi Formation is composed mainly of horsetails, ferns, ginkgoaleans, czekanowskialeans, and conifers. It is characterized by the abundance of ginkgoaleans, czekanowskialeans, and conifers, as well as the lack of Cycadophytes. Therefore, the composition of the Yingzuilazi flora is basically identical to that of Amur Province. The compositional characters of floras and epidermal characters can be used to explain the palaeoenvironmental and palaeoclimate reconstructions of the Mesozoic (Chen et al., 2001; Retallack, 2001; Royer et al., 2001; Beerling and Royer, 2002; Sun et al., 2003). The epidermal features of the new species along with consideration of associated plant and faunal assemblage suggest that regional climate was warm and moderately humid, with seasonal variations in temperature and precipitation. These characters include thinner cuticle and smooth periclinal walls of epidermal cells that lack trichomes and the absence of conifers with rigid scale-like and hooklike leaves that are considered to indicate arid climate (Deng and Lu, 2008; Kostina and Herman, 2013). The occurrence of abundant branchiopod crustaceans, ostracods, bivalves, gasteropods, insects, fish, and amphibians discovered from the mudstone, siltstone, and shale of the Yingzuilazi Formation and the analysis of sedimentary structures imply a landscape of an alluvial plain with rivers, lakes, and transitory swamps surrounded by the deciduous forest and other herbaceous vegetation in Baishan region during the Early Cretaceous. The specimens we have collected and provided in this article are well-preserved; especially the Holotype (YZB001A and YZB001B) is over 90 mm long, linear lobes, only about 1.5 mm wide, but the specimens as a whole are so completed and unbroken, and they were unlikely to experience longdistance transportation. They were probably buried in the lower energy water bodies, such as in the deposits of swamps or lakes.

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Acknowledgements

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Q4

We are thankful to China Scholarship Council (File No. 201206170100) for its financial support. We are really grateful to Mr. Chun-Tian Li for photographing the specimens, Mr. An-Ping Wang for SEM technical assistance at the Research Center of Paleontology and Stratigraphy of Jilin University, China. Special thanks are given to Dr. Hongshan Wang and another anonymous reviewer for their comments on this paper.

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This study was supported also by China Geological Survey Grant (1212011120149; 1212011085275), National Natural Science Foundation of China (41172009), Specialized Research Fund for the Doctoral Program of Higher Education grant (2010061110034), and Project “111” China.

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