Fossil Coniferous Wood from the Middle Jurassic of Liaoning Province, China ⁎ Hong-En Jiang A,B, David K

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Review of Palaeobotany and Palynology 150 (2008) 37–47 www.elsevier.com/locate/revpalbo

Fossil coniferous wood from the Middle Jurassic of Liaoning Province, China ⁎ Hong-En Jiang a,b, David K. Ferguson c, Cheng-Sen Li a,d, , Ye-Ming Cheng e

a State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China b Academia Turfanica of Xinjiang Uygur Autonomous Region, Turpan 838000, China c Institute of Palaeontology, University of Vienna, Althanstraβe 14, A-1090 Vienna, Austria d Beijing Museum of Natural History, Beijing 100050, China e Geological Museum of China, Beijing 100034, China Received 20 April 2006; received in revised form 8 January 2008; accepted 15 January 2008 Available online 1 February 2008

Abstract

Silicified coniferous wood was collected from the Lanqi Formation (late Middle Jurassic in age) at Shebudaigou Village, Liaoning Province, China. Three taxa are identified, namely Pinoxylon dacotense Knowlton, Xenoxylon phyllocladoides Gothan, and Araucariopitys sp. Based on these new data, and those of other fossil plants reported previously from the same formation, we consider the climate during the deposition of the Lanqi Formation was subtropical, humid and seasonal. In this respect the Lanqi flora differs from the coeval Shimengou and Longmen floras from North China. The Longmen flora was deposited during more humid, subtropical conditions, while the Shimengou Formation indicates that the climate was warm temperate and dry. Our data would suggest that the Late Jurassic climatic pattern was initiated as early as the late Middle Jurassic. © 2008 Elsevier B.V. All rights reserved.

Keywords: Lanqi Formation; Middle Jurassic; fossil wood; palaeoclimate; wood anatomy

1. Introduction bryophytes, ferns, cycads, ginkgos, and conifers (Table 1) from Beipiao. Later, a fern rhizome was discovered from the Mesozoic strata are well developed in the western part of same formation in Fuxin (Zhang and Zheng, 1991). Original- Liaoning Province, China. The Lanqi Formation, which belongs ly described as Millerocaulis liaoningensis Zhang et Zheng to the upper part of the Middle Jurassic, contains abundant (Osmundaceae), it was later transferred to Ashicaulis liaonin- and diverse plant fossils. Outcrops of the Lanqi Formation are gensis (Zhang et Zheng) Tidwell (Tidwell, 1994). Recently, two mainly located in Beipiao County, but they also occur spo- osmundaceous fern rhizome, Millerocaulis sinica Cheng et Li, radically in Fuxin County, an area adjacent to Beipiao. To date, and Millerocaulis preosmunda Cheng et al., were reported from 92 plant taxa have been recorded from the Lanqi Formation (see Beipiao (Cheng and Li, 2007; Cheng et al., 2007). Table 1) of which 91 are from Beipiao and one from Fuxin. The Lanqi Formation is the main stratigraphic unit containing Zhang and Zheng (1987) first reported 79 taxa (they listed 75 fossil wood in North China. In contrast to compression taxa, but there are actually 79 according to the original data) of plant fossils, the fossil wood has not been well studied yet. To date, seven species are known from Beipiao: Protopiceoxylon chaoyangense Duan, Araucarioxylon batuense Duan, Xenoxylon hopeiense Chang, X. latiporosum Gothan, Haplomyeloxylon ⁎ Corresponding author. State Key Laboratory of Systematic and Evolutionary tiaojishangense Zhang et Wang, Sahnioxylon rajmahalense Botany, Institute of Botany, Chinese Academy of Sciences, No. 20, Nan xin cun, Xiangshan, Beijing, 100093, China. Tel.: +86 10 62836436; fax: +86 10 (Sahni) Bose et Sah, and Lixylon liaoningense Zhang et al. 62593385. (Duan, 2000; Ding et al., 2000; Zheng et al., 2005; Zhang et al., E-mail address: [email protected] (C.-S. Li). 2006; Wang, Y.D. et al., 2006a).

Table 1 Table 1 (continued) Fossil floras of the Lanqi, Longmen, and Shimengou Formations of upper Class Lanqi Formation Longmen Shimengou Middle Jurassic in North China Formation Formation Class Lanqi Formation Longmen Shimengou Nilssonia Formation Formation qaidamensis Coniferopsida ⁎⁎Araucariopitys sp. Nilssonia tenuicaulis Araucarioxylon batuense Nilssonia sp. Brachyphyllum Nilssoniopteris obesum vittata Elatocladus ⁎⁎Pseudoctenis oleosa manchurica ⁎⁎Pterophyllum baotum Elatiescf.ovalis ⁎⁎Pterophyllum burejense Elatocladus sp. Elatocladus sp. Pterophyllum festum Haplomyeloxylon ⁎⁎Pterophyllum tiaojishangense liaoxiense ⁎⁎Pinoxylon dacotense Ptilophyllum cf. Pinoxylon chaoyangense pectinoides (Syn. Protopiceoxylon Sahnioxylon chaoyangense) rajmahalense Tyrmia pachyphylla Pityocladus taizishanensis (Syn. Tyrmia pachyphyllus) ⁎⁎Pityophyllum lindstroemii Tyrmia petrophylloides Pityophyllum longifolium Pityophyllum Pityophyllum Tyrmia taizishanensis longifolium cf. longifolium Tyrmia valida Pityophyllum cf. Tyrmia sp. nordenskiöldi ⁎⁎Williamsonia? cf. Podozamites shebudaiensis distans ⁎⁎Williamsoniella sinensis Podozamites lanceolatus Podozamites Williamsoniella? lanceolatus exiliforma Podozamites sp. ⁎⁎Zamiophyllum Schizolepis dabangouensis buchianum ⁎⁎Xenoxylon hopeiense ⁎⁎Zamites gigas ⁎⁎Xenoxylon latiporosum Zamites tosanus ⁎⁎Xenoxylon Zamites sp. phyllocladoides Filicopsida Ashicaulis liaoningensis Yuccites decus ⁎⁎Cladophlebis acuta Cycadopsida ⁎⁎Anomozamites angulatus ⁎⁎Cladophlebis asiatica Cladophlebis ⁎⁎Anomozamites kornilovae asiatica Anomozamites cf. Cladophlebis cf. major gigantea Anomozamites sinensis Cladophlebis haiburnensis ⁎⁎Anomozamites thomasi Anomozamites Cladophlebis aff. thomasi scariosa Anomozamites ⁎⁎Cladophlebis ulanensis shansiensis Anomozamites sp. Cladophlebis spinellosus Bennetticarpus sp. Cladophlebis tarsus Ctenis ananastomosans Cladophlebis cf. ⁎⁎Ctenis chinensis tschagdamensis Ctenis leeiana Cladophlebis ⁎⁎Ctenis pontica vasilevskae ⁎⁎Ctenis sulcicaulis Cladophlebis sp. Cycadolepis nitens Clathropteris Cycadolepis speciosus pekingensis (Syn. Cycadolepis speciosa) ⁎⁎Coniopteris burejensis Coniopteris Cycadolepis spheniscus burejensis Cycadolepis szei ⁎⁎Coniopteris Coniopteris Cycadolepis sp. hymenophylloides hymenophylloides Jacutiella denticulata Coniopteris Lioxylon liaoningense spectabilis Nilssonia compta Coniopteris ⁎⁎Nilssonia liaoningensis tatungensis Nilssonia orientalis Nilssonia ex gr. Coniopteris cf. orientalis tatungensis Nilssonia ⁎⁎Coniopteris pterophylloides tyrmica H.-E. Jiang et al. / Review of Palaeobotany and Palynology 150 (2008) 37–47 39

Table 1 (continued) Table 1 (continued) Class Lanqi Formation Longmen Shimengou Class Lanqi Formation Longmen Shimengou Formation Formation Formation Formation Dicksonia Equisetum aff. changheyingziensis multidentatus ⁎⁎Dicksonia charieisa ⁎⁎Equisetum naktongense ⁎⁎Eboracia lobifolia Eboracia lobifolia Equisetum sp.1 ⁎⁎Hausmannia Equisetum sp.2 shebudaiensis Neocalamites Marattia hoerensis haifanggouensis ⁎⁎Millerocaulis Neocalamites preosmunda nathorstii ⁎⁎Millerocaulis sinica Neocalamitessp. ⁎⁎Raphaelia stricta Unclear Allicospermum Todites denticulate Todites denticulate ovoidus Todites williamsonii Todites Carpolithus sp. Carpolithus sp. williamsonii Desmiophyllum Ginkgopsida Czekanowskia haixizhouense speciosa Taeniopteris sp. Czekanowskia Total species 92 27 39 stenophylla The authors of the original data in the table have been referred in the text. Czekanowskia ⁎⁎Fossils found from the Shebudaigou Village. sp. Ginkgo huttonis Ginkgo lepida In the present study we describe three species of coni- Ginkgo sibirica Ginkgo cf. sibirica fer wood, namely, Pinoxylon dacotense Knowlton, Xenoxylon Ginkgo cf. phyllocladoides Gothan, and Araucariopitys sp. The fossil wood whitbiensis specimens are silicified and display anatomical details. These Ginkgo sp. arborescent taxa are new for the Lanqi flora and enable in- Ginkgoites lepidus terpretions of the palaeoclimate during late Middle Jurassic in Ginkgoites tasiakouensis Ginkgoites sp. Northeast China. Ixostrobus groenlandicus Ixostrobus schmidtianus 2. Materials and methods Ixostrobus sp. Ixostrobus sp. ⁎⁎ Phoenicopsis speciosa The fossil wood was collected from sediments of the Lanqi Phoenicopsis ′ decorate Formation near the village of Shebudaigou (41° 43.9 N, 121° Phoenicopsis 03.8′ E), Changgao Town, Beipiao County, Liaoning Province enissejensis (Fig. 1). The Lanqi Formation is composed of intermediate lavas Phoenicopsis cf. and pyroclastic rocks, with intercalations of basic volcanic rocks taschkessiensis and tuffs. The fossiliferous beds, considered to be deposited in a Pseudotorellia longilancifolia lacustrine environment, consist of fine-grained sandstones and Pseudotorellia silty shales (Wang, Y.D. et al., 2006b; Cheng and Li, 2007). The qinghaiensis Lanqi Formation (=Tiaojishan Formation) lies between the Solenites vimineus Tuchengzi Formation (above) and the Haifanggou Formation Sphenarion (below) and is generally regarded as being late Middle Jurassic dicrae Sphenobaiera colchica in age based on the flora (Zhang and Zheng, 1987; Wang, Y.D. Sphenobaiera et al., 2006b; Cheng and Li, 2007). However, K–Ar isotopic ginkgooides dating has indicated that at least some of the volcanics of Sphenobaiera paucipartita the Lanqi Formation are as young as 156.3±8.5 Ma (Diao and Sphenobaiera Li, 1983), or 158 Ma (Wang, 1983), i.e. early Late Jurassic spectabilis Sphenobaierasp. (Gradstein and Ogg, 2004). Hepaticae ⁎⁎Hepaticites Pieces of large branches or trunks were scattered in the shebudaiensis sediments at the site. However, some standing stumps were Lycopsida Lycopodites Lycopodites also found in situ. Altogether, 95 specimens were collected. falcatus falcatus Transverse, radial longitudinal and tangential longitudinal Sphenopsida Equisetum beani Equisetum cf. gracile sections were prepared using conventional cutting, grinding and ⁎⁎Equisetum laterale Equisetum polishing methods. The slides were studied under a microscope laterale (Olympus 60). The terminology for the description follows the Equisetum cf. published wood identification keys and fossil wood descriptions laterale (e.g. Medlyn and Tidwell, 1979; Falcon-Lang and Cantrill, 2000; (continued on next page) 40 H.-E. Jiang et al. / Review of Palaeobotany and Palynology 150 (2008) 37–47

Fig. 1. Map showing fossil localities of Shebudaigou, Western Hills and Dameigou. A. The locations of Shebudaigou (1), Western Hills (2), and Dameigou (3). B. Detailed locality of Shebudaigou in Liaoning Province of China (triangle marks fossil locality).

Meijer, 2000; Falcon-Lang et al., 2001; IAWA Committee, 2004; usually tangentially and horizontally flattened, somewhat squarish Kim et al., 2005; Harland et al., 2007). All the specimens or araucaroid, 18 μm in diameter; if triseriate, pits circular and and slides are housed in the National Museum of Plant History alternate; crassulae present between the two adjacent pits (Fig. 2B); of China, Institute of Botany, Chinese Academy of Sciences, late wood tracheids 1–3 cells wide, mostly elliptical, thick walled, Beijing, China. 40 μm in tangential diameter, 15 μm in radial diameter; bordered pits on radial walls uniseriate, round, mostly separate; tangential 3. Wood description and identification pits absent or not preserved. Wood parenchyma — Axial wood parenchyma cells not Family: ?Protopinaceae Kräusel abundant, 189 μm long, 36 μm wide, terminal walls pitted (Fig. Genus: Pinoxylon Knowlton 2C, arrows). Species: Pinoxylon dacotense Knowlton Wood rays — Prominent, usually uniseriate, seldom partly Fig. 2A–F biseriate, 2–16 (commonly 3–7) cells high; rays consisting Material: FWLX017, collected as a piece of fragmented trunk, only of ray parenchyma with pitted horizontal and tangential 20.3×12.0×5.6 cm in size. walls (Fig. 2F, arrows); cross-field having 1 to 4 (commonly 2) 1900 Pinoxylon dacotense Knowlton, 20th Ann. Rep. U.S. rounded and simple pits, very rarely taxodioid (Fig. 2D); ray Geol. Survey, part 2, p. 420, pl. 179, figs. 1–6. tracheids absent. 1919 Pinoxylon dacotense Knowlton, by Kräusel, Palaeontogr. Resin canals — Vertical, present in all annual rings, mostly 62, p. 226. in early wood, commonly occurring singly along rays, seldom 1932 Pinoxylon dakotense Knowlton, by Read, Bot. Gaz. 93, in pairs; resin canals usually elliptical (Fig. 2A), seldom round, p. 175, figs. 1–12. 49–220 μm in diameter, with 8–12 thick walled epithelial cells; 1937 Pinoxylon dakotense (Knowlton) Read, by Shimakura, traumatic and horizontal resin canals absent. Sci. Rep. Toh. Imp. Univ., ser. 2 (Geol.) 18, p. 22, pl. 5, figs. 1– Comparison: 6, text-fig. 6. The genus Pinoxylon was established by Knowlton (1900), 1963 Protopiceoxylon dakotense (Knowlton) Sze, by Sze, Fossil based on wood remains from the Lower Cretaceous (?) of woods of gymnosperm, p. 330, pl. 112, figs. 1–4, text-fig. 62. South Dakota, USA. The genus was named as Pinoxylon because 1979 Protopiceoxylon dacotense (Knowlton) Vogellehner, by Knowlton (1900) initially thought it might have affinity to modern Medlyn and Tidwell, Can. J. Bot. 57, p. 1454, figs. 25–30. Pinus. Later, another genus, Protopiceoxylon, was established 1995 Pinoxylon dakotense Knowlton emend. Read, by Nishida by Gothan (1907), for fossil wood discovered in König Karls and Nishida, J. Plant Res. 108, p. 167, fig 4. E–I. Land. Based on studies of the holotype of Pinoxylon dacotense by Description: Read (1932), Bailey (1933) and Medlyn and Tidwell (1979), Tracheids — Growth rings distinct, 0.3 to 3.1 mm wide, Pinoxylon was found to share similar traits with Protopiceoxylon. transition from early to late wood abrupt (Fig. 2A); early wood cells According to the International Code of Botanical Nomenclature rectangular, squarish, elliptical to round, 19–53 μm in tangential (e.g. McNeill et al., 2006), Protopiceoxylon should be regarded diameter, 13–39 μminradialdiameter;1to8(commonly2to5) as a synonym of Pinoxylon: the latter taxon having priority rows of regular aligned tracheids between vascular rays; bordered (Art. 11.3) (Read, 1932; Shimakura, 1936a, 1937; Kräusel, 1949; pits on radial walls of tracheids uniseriate to biseriate, very seldom Nishida and Nishida, 1995). triseriate; if uniseriate, pits usually circular and separate, sometimes The wood of Pinoxylon possesses araucarian and abietinean slightly contiguous, 19 μm in diameter; if biseriate, pits usually pitting on the radial walls of the tracheids, axial resin canals, opposite (Fig. 2B), sometimes sub-opposite to alternate (Fig. 2E), and pits in the horizontal and tangential walls of the ray H.-E. Jiang et al. / Review of Palaeobotany and Palynology 150 (2008) 37–47 41

Fig. 2. Pinoxylon dacotense Knowlton. A) Transverse section showing distinct growth rings and resin canals. Scale bar=400 μm. B) Radial section showing biseriate opposite bordered pits and crassulae. Scale bar=20 μm. C) Tangential section showing ray cells, and nodular end walls (arrows) of axial parenchyma cells. Scale bar=50 μm. D) Radial section showing simple cross-field pits. Scale bar=40 μm. E) Radial section showing alternate pits and distinct crassulae. Scale bar=20 μm. F) Radial section showing nodular end walls (arrows) of ray parenchyma cells. Scale bar=50 μm.

parenchyma. The new specimen described above shows 1936b; IAWA, 2004). Accordingly, we identified the specimen similarities, so we consider it to belong to this genus. Fourteen as Pinoxylon dacotense. species of Pinoxylon (Protopiceoxylon) have been reported (Knowlton, 1900; Gothan, 1907; Stopes, 1915, 1916; Seward, Genus: Xenoxylon Gothan 1919; Edwards, 1925; Walton, 1927; Read, 1932; Shimakura, Species: Xenoxylon phyllocladoides Gothan 1936a, 1937; Sze, 1963; Medlyn and Tidwell, 1979; Du, 1982; Fig. 3A–F Duan et al., 1995; Duan, 2000; Ding, 2000; Wang et al., 2000). Material: FWLX014, collected as a fragmented trunk, 8.2× Our specimen with wood parenchyma, 1–3 lines of radial pits, 6.5×5.1 cm in size. and 2–4 rounded, simple (seldom taxodioid) pits in the cross- 1906 Xenoxylon phyllocladoides Gothan, Verh. Russ.-Kais. fields displays the closest affinity to Pinoxylon dacotense Miner. Ges. 44, p. 454, fig. 4. described by Read (1932), and Nishida and Nishida (1995). 1907 Xenoxylon phyllocladoides Gothan, Kungl. Svenska Vet.- However, the height of the ray cells in our specimen (2–16) is akad. Handl. 42, No. 10, p. 10, text-figs. 3–9. lower than that in the holotype (1–24) (Read, 1932). This may 1910 Xenoxylon phyllocladoides Gothan, Kungl. Svenska Vet.- be due to the different part or age of the trunk (Shimakura, akad. Handl. 45, No. 8, p. 36, pl. 6, figs. 9–10. 42 H.-E. Jiang et al. / Review of Palaeobotany and Palynology 150 (2008) 37–47

Fig. 3. Xenoxylon phyllocladoides Gothan. A) Transverse section showing distinct and narrow growth rings. Scale bar=400 μm. B) Radial section showing window- like cross-field pits. Scale bar=100 μm. C) Tangential section showing ray cells, and resinous cells. Scale bar=100 μm. D) Tangential section showing resinous cells and pits on the tangential walls of tracheid. Scale bar=100 μm. E) Radial section showing uniseriate, compressed bordered pits and distinct crassulae. Scale bar=50 μm. F) Radial section showing biseriate, opposite bordered pits and distinct crassulae. Scale bar=50 μm.

1913 Xenoxylon phyllocladoides Gothan, by Holden, Ann. Bot. tal×vertical diameters, with a round to elliptical aperture about 27, p. 535, pl. 39, figs. 1–4. 6 μm in diameter; if biseriate, pits opposite; crassulae clearly 1919 Xenoxylon phyllocladoides Gothan, by Seward, Fossil developed between two adjacent pits (Fig. 3E, F). Late wood Plants, Vol. 4, p. 241, text-fig. 730, A. zones 1–5 cells wide, thick-walled; tracheids 31 μm in tan- 1936 Xenoxylon phyllocladoides Gothan, by Shimakura, Sci. gential diameter and 19 μm in radial diameter, bordered pits on Rep. Tohoku Imp. Univ., Ser. 2, 18, p. 276, pl. 13(2), figs. 8–9; radial walls uniseriate, round and separate; pits abundant on the pl. 14(3), figs. 1–6, text-fig. 3. tangential walls (Fig. 3D). 1995 Xenoxylon phyllocladoides Gothan, by Philippe, Palaeon- Wood rays — Prominent, uniseriate, 1–17 cells high (Fig. 3C); togr. B 236, p. 84, pl. 14, figs. 1–6. some cells full of resin (Fig. 3D); both horizontal and tangential 1999 Xenoxylon phyllocladoides Gothan, by Morgans, Palaeon- walls smooth; mostly 1, seldom 2 window-like pit(s) in each tology 42, p. 313, pl. 4, figs. 1–8. cross-field (Fig. 3B). 2005 Xenoxylon phyllocladoides Gothan, by Kim et al., IAWA Resin canals — Both horizontal and vertical resin canals absent. J. 26, p. 256, figs. 4–9. Wood parenchyma — Axial wood parenchyma absent. Description: Comparison: Tracheids — Growth rings distinct, 116 to 759 μm wide, The characteristics including vertically flattened and trans- transition from early to late wood gradual to abrupt (Fig. 3A); versely elongated pits on the radial walls of tracheids, unpitted early wood cells rectangular to hexagonal, seldom elliptical to walls of ray parenchyma cells, rectangular, simple, mostly one, round, 19–60 μm in tangential diameter, 33–57 μm in radial seldom two window-like pit(s) in each cross-field and the diameter; 1–10 rows (commonly 4 to 7) of regularly aligned absence of resin canals suggest that this specimen should be tracheids between the vascular rays; bordered pits on the radial referred to the genus Xenoxylon Gothan. walls of tracheids uniseriate to biseriate, usually vertically Twenty-five species were ascribed to the genus (Gothan flattened and transversely elongated, 23×18 μm in horizon- 1907, 1910; Chang, 1929; Kräusel, 1949; Vogellehner, 1965, H.-E. Jiang et al. / Review of Palaeobotany and Palynology 150 (2008) 37–47 43

1968; Medlyn and Tidwell, 1975; Yamazaki et al., 1980; 1996; Tidwell et al., 1998; Ding et al., 2000; Youssef, 2002). Yamazaki and Tsunada, 1981; Zheng and Zhang, 1982; Our specimen is more akin to X. phyllocladoides than that of Yamazaki et al., 1984; Nishida and Nishida, 1986; Müller- others. X. phyllocladoides was proposed by Gothan (1906) Stoll and Schultze-Motel, 1988; Nishida et al., 1993; Duan for wood from the Bathonian of Poland. Our specimen is et al., 1995; Philippe and Thévenard, 1996; Zhang and Shang, remarkably similar to the specimen of X. phyllocladoides

Fig. 4. Araucariopitys sp. A) Transverse section showing distinct growth rings. Scale bar=400 μm. B) Tangential section showing ray cells. Scale bar=100 μm. C) Radial section showing triseriate, opposite pits. Scale bar=50 μm. D) Radial section showing cupressoid cross-field pits. Scale bar=50 μm. E) Radial section showing nodular end walls of ray parenchyma cells. Scale bar=40 μm. F) Radial section showing bi- and triseriate alternate bordered pits. Scale bar=50 μm. G) Radial section showing biseriate opposite bordered pits and distinct craussulae. Scale bar= 50 μm. 44 H.-E. Jiang et al. / Review of Palaeobotany and Palynology 150 (2008) 37–47 described by Holden (1913). The only difference lies in the 2001; Harland et al., 2007). Our specimen is different from occurrence in our material of crassulae between the two A. bebenhusanum Khan, A. lindicianum Khan, A. nicri Khan, adjacent pits. Some scholars considered crassulae to be an A. liassicum Khan, A. tubingense Khan (Khan, 1961) by its lack important taxonomic character (Holden, 1910, 1913; Gerry, of simple cross-field pits which are present in these five species. 1910; Torrey, 1923; Chang, 1929), while others believed that it Our specimen is also different from Araucariopitys sp. (Harland might be obscured during preservation, or sometimes over- et al., 2007) and Araucariopitys sp. (Falcon-Lang and Cantrill, looked by the observers. The presence or absence of crassulae 2000) in that these do not have the pitted horizontal and terminal may also be governed by the density of the pitting, and have walls of the ray cells. However, the affinities of the present little value in wood identification (Seward, 1919; Bailey, 1919, specimen with A. americana Jeffrey (Jeffrey, 1907; Hollick and 1924, 1933; Read, 1932; Gothan and Sze, 1933; Shimakura, Jeffrey, 1909) and A. antarcticus Poole et Cantrill (Poole and 1936a; Sze, 1951; Arnold, 1953; Watari, 1960; Sze, 1963). In Cantrill, 2001) are not clear. The description of A. americana is this case, their presence is not sufficient to distinguish our not very informative as the number and type of cross-field pitting material from Holden's specimen. Accordingly, we identified were not given (Jeffrey, 1907; Seward, 1919). Similarly, it is not the specimen as X. phyllocladoides. clear if the terminal and horizontal walls of the ray cells were pitted or not in A. antarcticus. In this case, we temporarily assign Family: Araucariaceae Henkel and Hochstetter our specimen to Araucariopitys sp., pending further studies of Genus: Araucariopitys Jeffrey the genus. Species: Araucariopitys sp. Fig. 4A–G 4. Discussion Material: FWLX033, collected as part of a trunk, 18.6 cm in diameter, and 25.2 cm in length. The discovery of three additional species of wood in the Description: present study, brings the total number of taxa reported from Tracheids — Growth rings distinct, transition from early to late the Lanqi Formation to 92. The Lanqi flora is dominated by wood abrupt (Fig. 4A), width of annual rings varies from 0.6 to Cycadopsida (43.5%), belonging to 15 genera and 40 species. 1.9 mm; early wood always crushed, and tracheids rectangular, Such Cycadopsida are typical of subtropical to tropical regions elliptical to round in transverse view, tracheids 21–82 μmin (Fu et al., 1978). In particular, the occurrence of Zamites, tangential diameter, 14–56 μm in radial diameter; bordered pits on Zamiophyllum, Ptilophyllum, and Lixylon liaoningense with the radial walls of tracheids uniseriate to biseriate, seldom triseriate; stems of the manoxylic type suggests that they were living in a if uniseriate, round and separate, sometimes vertically flattened and warm to hot climate (Vakhrameev, 1991). continuous; if biseriate, opposite or sub-opposite, rarely alternate Ten genera and fourteen species of conifers (15.2% of the (Fig. 4G); when in contact, pits usually vertically flattened (Fig. 4F); total assemblage) were found in the Lanqi Formation. Among triseriate radial pits rarely found (only 2 rows) (Fig. 4C, F); pits them, Pinoxylon was considered to have a close affinity to consist of two types, some alternate and hexagonal in outline Keteleeria (Shimakura, 1937; Medlyn and Tidwell, 1979; Du, (Fig. 4F), while the others are circular to elliptical, opposite and in 1982). Keteleeria is largely restricted to subtropical to north one row (Fig. 4C); diameter of bordered pits on the radial walls tropical hill regions of southern China and eastern Indochina varies from 12 to 23 μm with an average diameter 19 μm; crassulae (Wang Y.F. et al., 2006), where the climate is warm and hu- clearly visible between the two adjacent rows of pits (Fig. 4G). Late mid. This would suggest that Pinoxylon lived in a warm and wood zone of 3–12 cells with thick cell walls; average diameter of humid environment like its nearest living relative. Moreover, tracheids 53 μm in tangential direction and 27 μm in radial direction; Hausmannia shebudaiensis (Dipteridaceae) also suggests a bordered pits uniseriate to biseriate, round and separate. very hot climate. The presence of 13 genera and 25 species of Wood rays — Prominent, usually uniseriate, very seldom hygrophilous plants (27.2% of the total assemblage), includ- biseriate in the middle part, 1–37 cells high (Fig. 4B), average ing 10 genera and 20 species of Filicopsida, one genus with a height 4–13 cells; horizontal walls heavily pitted, tangential single species of Hepaticae (Hepaticites shebudaiensis), two walls nodular (Fig. 4E), pits in cross-fields cupressoid; mostly genera and four species of Sphenopsida, indicate a fairy hu- 2–3, seldom 1 or 4 in each cross-field (Fig. 4D). mid environment. The abundance of fern rhizomes assignable Resin canals — Absent. to Millerocaulis and Ashicaulis (Osmundaceae) suggests moist Wood parenchyma — Axial wood parenchyma absent. conditions (Wang Y.D. et al., 2006b). On the other hand, Comparison: the clear annual rings of the wood of Pinoxylon dacotense, Araucariopitys was established by Jeffrey (1907). Its main X. phyllocladoides and Araucariopitys sp. indicate a seasonal characters are the mixed pits (araucarian and/or abietinean) on environment. The floral composition as a whole points to humid the radial walls of the tracheids and the abietineous type of pits subtropical and seasonally alternating climate. This scenario on the terminal and horizontal walls of the ray cells (Bamford agrees well with the Mesozoic geochemical characteristics of and Philippe, 2001; Philippe and Bamford, 2008). Our speci- basin sediments in the Lanqi Formation (Yan et al., 2003). men has the above characteristics, and thus can be considered to The wood of X. phyllocladoides is of particular interest, as it is belong to the genus Araucariopitys. considered to represent a wet and/or cool environment (Philippe Nine species were ascribed to the genus (Jeffrey, 1907; and Thévenard, 1996). However, according to Harris (1926),both Khan, 1961; Falcon-Lang and Cantrill, 2000; Poole and Cantrill, the “Xenoxylon type of wood” and Dictyophyllum, a tropical H.-E. Jiang et al. / Review of Palaeobotany and Palynology 150 (2008) 37–47 45 element, were found in the same horizon. Wood of X. latiporosum and occurs in a region with a seasonal, temperate to subtropical and leaves of Zamites, a thermophilic element belonging to climate, the abundance of fossil Ginkgopsida would tend to cycads, were also found together (Duan, 1986). Wood of X. indicate a warm climate. Moreover, thermophilic elements such phyllocladoides, together with the other thermophilic megafos- as Elatides cf. ovalis, Elatocladus sp., and the scale-like leaves sils, was identified in the Upper Triassic Jogyeri Formation in of Brachyphyllum obesum indicate that the climate became South Korea (Kim et al., 2005). In the Lanqi flora, we have the drier and hotter. Considering all the above evidence, the climate same phenomenon, i.e. the co-occurrence of X. phyllocladoides during the deposition of the Shenmengou Formation would and Cycadopsida such as Zamites, Zamiophyllum, Ptilophyllum. appear to have been drier and more temperate than during the We suggest that the thermophilic elements such as Dictyophyllum deposition of the Lanqi and Longmen formations. and Zamites once were living in the hot and wet lowland areas, The climate of the Mesozoic was more equable than that while X. phyllocladoides and Pinoxylon dacotense prospered in of today (Hallam, 1985; Vakhrameev, 1991). During the Ju- the cool to warm and wet upland areas. Together with ferns of rassic, Eurasia was divided into the Euro-Sinian and Siberian Millerocaulis sinica, Millerocaulis preosmunda and Ashicaulis regions based on the differences in phytogeography. Shebudai- liaoningensis, trees with Xenoxylon and Pinoxylon wood were gou (Lanqi Formation), Dameigou (Shimengou Formation) and important constituents of the montane forests. Western Hills (Longmen Formation) belonged to the Siberian The Longmen Formation in the Western Hills of Beijing region. The climate during the deposition of the Shimengou is late Middle Jurassic in age, and yielded 27 taxa of plants Formation was warm temperate and dry. On the other hand, it (see Table 1)(Chen et al., 1984). Unlike the Lanqi flora that was subtropical and humid during the deposition of the Lanqi mainly consists of Cycadopsida (43.5%), the Longmen flora and Longmen formations, with the former being warmer but was dominated by Filicopsida, belonging to 5 genera and 12 less humid than the latter. The humid climate in Shebudaigou species (44.4%), whereas Cycadopsida were represented by and Western Hills could be influenced by the ancient Pacific only 4 genera and 6 species (22%). Together with the lycopsid Ocean, as these two localities were closer to the ocean than (Lycopodites falcatus) and the horsetail (Equisetum), the 15 Dameigou. hygrophilous plants (55.6%) suggest an environment, Globally, the climates from the Early to Middle Jurassic were which was more humid than during the deposition of the humid and warm, but became increasingly hot and dry in the Lanqi Formation. The typical thermophilic element, Clathrop- Late Jurassic. This is supported by the distribution of distinc- teris pekingensis (Dipteridaceae), also suggests a warm-hot tive sediments, fossils, and oxygen isotope data (Hallam, 1975, climate (Chen et al., 1984). 1984, 1985; Vakhrameev, 1991). We present a climatic map of The Shimengou Formation in the Dameigou District of humid and arid belts during the Late Jurassic based on figure 7 Qinghai Province is also late Middle Jurassic in age, and yielded of Hallam (1985) with the positions of the three localities, 39 taxa of plants (see Table 1)(Li et al., 1988). In contrast to i.e. Shebudaigou (Lanqi Formation) and Western Hills (Long- the above two floras, the Shimengou flora was dominated by men Formation) being located in humid areas, and Dameigou Ginkgopsida, belonging to 8 genera and 17 species (43.6% of (Shimengou Formation) in an arid area (Fig. 5). Although all the total assemblage). The ferns (Cladophlebis, Coniopteris) three formations are late Middle Jurassic in age, the climatic and the horsetails (Equisetum, Neocalamites) are assumed to be signature resembles that of the Late Jurassic rather than the typical for moist habitats (Vakhrameev, 1991). Cycadopsida are Early to Middle Jurassic. This phenomenon could indicate that represented by only two genera and three species (7.7% of the the Late Jurassic climatic pattern may have been initiated as total assemblage). Since the extant Ginkgo biloba is deciduous early as the late Middle Jurassic.

Fig. 5. Map showing continental humid and arid belts in the Late Jurassic, and the geological setting of Shebudaigou (1), Western Hills (2), and Dameigou (3) (Based on Hallam, 1985). 46 H.-E. Jiang et al. / Review of Palaeobotany and Palynology 150 (2008) 37–47

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