Available online at www.sciencedirect.com

Palaeoworld 17 (2008) 166–171

Review

A review of recent advances in the study of earlyangiosperms from northeastern China

Ge Sun a,b,c,∗, David L. Dilcher c,d, Shao-Lin Zheng e

a Research Center of Paleontology, Jilin University, Changchun 130026, Chinab Paleontological Institute of Shenyang Normal University, Shenyang 110034, China

c Key-Lab for Evolution of Past Life and Environment in NE Asia, Ministry of Eduation, Chinad Florida Museum of Natural History, University of Florida, Gainesville, FL 32611-7800, USA

e Shenyang Institute of Geology and Mineral Resources, Shenyang 110031, China

Received 19 March 2008; received in revised form 27 September 2008; accepted 3 October 2008Available online 14 October 2008

Abstract

The last 10 years (1998–2007) were very productive and important in the study of early angiosperms in northeastern China. The new discoveriesof the earliest well-documented records of angiosperms such as Archaefructus, as well as Hyrcantha decussata (= Sinocarpus decussatus),provided fresh knowledge for better understanding the primitive characters of the ancient angiosperms and also their aquatic (or wet) habitatand their herbaceous nature. Some new approaches such as the combination of molecular and morphological characters joined together to placeArchaefructus in the angiosperm phylogenetic framework. These fossils demonstrate that we should expect more ancient angiosperms to be foundin the pre-Cretaceous which will continue to add important new understanding to the nature of the origin and evolution of the angiosperms.© 2008 Nanjing Institute of Geology and Palaeontology, CAS. Published by Elsevier Ltd. All rights reserved.

Keywords: Review; Advance; Study; Early angiosperms; Northeastern China

Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1662. Main achievements in the study of early angiosperms from northeastern China for 1998–2007 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167

2.1. Discovery of the earliest known angiosperm megafossil, Archaefructus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1672.2. Discovery of the early angiosperm Hyrcantha in China . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167

2.3. Considerations of a possible aquatic origin of angiosperms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1692.4. New approaches used in the study of ancient angiosperms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169

Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171. . . . . .

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References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1. Introduction

Angiosperms (flowering plants) represent the most diverseand widely distributed group in the plant kingdom today, consisting of over 300 000 species in the world with nearly 30 000

∗ Corresponding author at: Research Center of Paleontology, Jilin University,6, Xi-Minzhu Street, Changchun, 130026, China. Tel.: +86 431 88502487;fax: +86 431 88502487.

E-mail addresses: sunge@jlu.edu.cn, sunge@synu.edu.cn (G. Sun).

ecst

1871-174X/$ – see front matter © 2008 Nanjing Institute of Geology and Palaeontoldoi:10.1016/j.palwor.2008.10.002

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171

pecies belonging to 346 families recorded in China (Wu et al.,006). However, the origin of flowering plants and their earlyiversity have been a puzzle for paleobotanists for nearly 150ears, for which Charles Darwin (1879) named it as “an abom-nable mystery” (Darwin and Seward, 1903). The time, placend nature of the origin of the angiosperms have intrigued sci-

ntists and the lack of a complete resolution to these questionsauses them to continue to search for answers. The work pre-ented in this review demonstrates the efforts to begin to solvehis mystery that has existed for over a century.

ogy, CAS. Published by Elsevier Ltd. All rights reserved.

G. Sun et al. / Palaeoworld

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ig. 1. Geographic distribution of ancient angiosperms in northeastern China. I:eilongjiang; II: Jilin; III: Liaoning; IV: Inner Mongolia (after Sun et al., 2001).

Ancient angiosperms is a term suggested here to be used foremains of flowering plants that are early in the angiosperm lin-age and are known from the Lower Cretaceous (ca. 100 millionears or more) or perhaps even earlier. We might expect thatngiosperms of this age might possess more or less primitiveharacters (Retallack and Dilcher, 1981; Sun et al., 2001). Thearly angiosperms are widely distributed in western Liaoningnd its neighboring area of northeastern China (Fig. 1), withoristic characters which differ from extant flowering plants

n many aspects (Sun et al., 2001) and some might representntirely extinct lineages at the ordinal or familial levels andheir study was begun in the 1930s. Yabe and Endo (1935)rst reported some “monocot” fossils (Potomageton jeholen-is and Potomageton? sp.) from the Lycoptera-bed, a part ofhe lower Yixian Formation, in Lingyuan of western Liaoning,hich has been controversial in their classification. Miki (1964)

eported on his re-study of Yabe and Endo’s material and iden-ified Ranunculus jeholensis (= “Potamogeton jeholensis”) andonifer Podozamites gramineus Heer (= “Potamogeton? sp.”).owever, his identifications were also subject to revision (Sun

t al., 2001).Since the early 1990s, the Chinese paleobotanists have paid

ore and more attention to the study of early angiosperms.ao and Zhang (1990, 1992) described some Aptian-Albianngiosperms from the Dalazi Formation of Yanji, eastern Jilin,hich are similar to those of the Potomac flora from North Amer-

ca (Fontaine, 1889; Sun et al., 1995). Cao et al. (1998) and

uan (1998) reported some “angiosperms”, e.g., Liaoxia chenii,rogracites changii, and Chaoyangia liangii, from the Yixianormation in western Liaoning, which have been re-examinedy Guo and Wu (2000) and Rydin et al. (2006) who described

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17 (2008) 166–171 167

hem as gymnosperm Gnetalean plants. On the other hand, Pan1990, 1997) reported some “angiosperms”, e.g., Paliurus, Zizy-hyus and Pterocarya, from the Middle Jurassic, Haifanggouormation of Jinxi in western Liaoning, and his assignments toxtant angiosperm genera have been debated in East Asia (Hsü,987; Kimura et al., 1994; Zhou, 1995). Wang et al. (2007)eported a new taxon, Schmeissneria sinensis, as a “missing linko angiosperm”, from the same locality and same formation asan reported, which is also in controversy on his identification.

It would be worth mentioning that during the last 10 years,u (1999) reported some fossil “angiosperms” (e.g., Lilites,rchidites) from the lower Yixian Formation, which have noteen accepted by most paleobotanists so far, although the above-entioned work is significant for the further study of early

ngiosperms of western Liaoning (Sun et al., 2001).

. Main achievements in the study of early angiospermsrom northeastern China for 1998–2007

.1. Discovery of the earliest known angiospermegafossil, Archaefructus

During 1998–2002, the earliest known angiosperm megafos-ils, Archaefructus, including A. liaoningensis and A. sinensis,ere described from the lower Yixian Formation in the Huang-anjigou of Beipiao (Sun et al., 1998) (Figs. 2–4) and theawangzhangzi of Lingyuan (Sun et al., 2002) (Figs. 5–7), inestern Liaoning, respectively.Archaefructus has simple determinate axes bearing helical

onduplicate carpels enclosing several ovules in each. Thereppears to be an elongated adaxial region that may have beentigmatic; stamens often occur as paired stamens or there may behree or even four attached to the end of a short stock or “short-hoot”; the anthers appear to produce monosulcate pollen, andeaves with various petiolar lengths terminate in highly dissectedeaves. All of these characters set Archaefructus apart, as basalo all other basal angiosperms (Sun et al., 2002). On the otherand, their simple root system, delicate stems bearing highly dis-ected leaves and absence of perianth, imply that Archaefructuss aquatic and herbaceous in nature. Moreover, the phylogenetictudy with combined multiple genes and morphological charac-ers supports Archaefructus as one of the “basal angiosperms”nd a sister taxon to all extant flowering plants including theANITA” group (Amborella, Nymphaeales, Illicium, Tricolpatesnd Austrobaileya) (Sun et al., 2002).

.2. Discovery of the early angiosperm Hyrcantha in China

Another new discovery of the early angiosperms is Hyrcan-ha decussata (= Sinocarpus decussatus) from western Liaoningnd eastern Inner Mongolia (Leng and Friis, 2003; Dilcher etl., 2007) (Figs. 8–11). H. decussata is an aquatic and herba-eous angiosperm inflorescence, possessing slender axes with

umerous nodes, branching for three to four times and eachranch terminating a flower (fruit). The nodes are marked byhe presence of thin sheathes (ocrea) of leaf bases. The thin axeserminate in two to four carpels arranged oppositely and at right

168 G. Sun et al. / Palaeoworld 17 (2008) 166–171

Figs. 2–4. The topetype and type specimens of Archaefructus liaoningensis. Fig. 2. Topetype: the east hill of Huangbanjigou village of Beipiao, Liaoning; Fig. 3.Holotype (No. PB18938, housed in NIGPAS, Nanjing); Fig. 4. Paratype (No. B2000, housed in RCPS, JU, Changchun) (after Sun et al., 2001).

Figs. 5–7. The topetype and type-specimens of Archaefructus sinensis. Fig. 5. Topetype: west hill of Dawangzhangzi village of Lingyuan, Liaoning; Fig. 6. Holotype(No. J-0721, housed in CAGS, Beijing); Fig. 7. Reconstruction (after Sun et al., 2002).

Figs. 8–11. Hyrcantha decussata. Fig. 8. Holotype (No. NJU-DES-0001a, housed in CAGS, Beijing); Fig. 9. Seven fruiting terminal axes (No. CB31001, housed inRCPS, JU, Changchun); Fig. 10. Ocrea of stem (part of Fig. 8); Fig. 11. Reconstruction of the plant (after Dilcher et al., 2007).

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ngles, and the opposite carpels are syncarpous carpels, fusedentrally along middle-lower 1/3 to 1/2 of the carpels. All theseharacters are significant for the study of the early evolution ofngiosperms.

Beside the achievements in the study of these megafos-ils mentioned above, studies of the early angiospermousollen from the lower Yixian Formation in the western Liaon-ng are also in progress. Wang et al. (2000) reported threeypes of early angiospermous pollen, including inaperturate-,rotomonosulcate- and prototricolpate pollen grains.

.3. Considerations of a possible aquatic origin ofngiosperms

For over a century, most paleobotanists and botanists haveonsidered that angiosperms probably had a terrestrial originuch as shrubby, land-herbaceous, even tree-like woody plants.owever, the recent unexpected findings of Archaefructus andyrcantha from northeastern China suggest another possibility

or angiosperm origins, that is an aquatic origin (Sun et al., 2002;ilcher et al., 2007), although the terrestrial origin is still not

xcluded in these considerations.Archaefructus has no petals and sepals in its floral compo-

ition, which looks like some aquatic extant angiosperms, e.g.,ome taxa of Alismataceae, mainly as a result of their livingn water (Sun et al., 2003). On the other hand, Archaefructusas long and slender stems bearing highly dissected and thineaves and the reproductive axes are long and thin, terminatingn comparatively heavy follicles (carpels), which would most

robably require water supporting them just above the surfacef the water especially during flowering, pollination and seedsispersal. The characters may appear to be similar to some extantquatic angiosperms, e.g., Cabombaceae in the Nymphales (Sun

rpof

Figs. 12–14. Reconstructions of Archaefructus. Figs. 12 and 13. Archaefr

17 (2008) 166–171 169

t al., 2002). Also, the features of the slender and delicate stalksearing fruits known for H. decussata imply the aquatic nature.t is suggested that Archaefructus may have two aquatic habitats,ne in medium shallow water such as that of A. sinensis, as itsarger size suggests, and the other probably very near the lakeank in very shallow water as the smaller size of A. liaoningensisight suggest (Terada et al., 2005) (Figs. 12–14).

.4. New approaches used in the study of ancientngiosperms

The application of combined use of the molecular charac-ers of living angiosperms and the morphological characters ofncient angiosperms in order to construct and integrate fossilaxa into the molecular cladistic schemes of relationships is aew application. These data, when combined, make a muchore important statement than when the fossils are excluded.his is a big event in this research area and such combina-

ions of these data promise to change our understanding ofngiosperm systematics. Combining multiple gene and mor-hologic analyses, the phylogenetic study of Archaefructusupports the concept that this plant should be placed as basalo all angiosperms. That means that Archaefructus is a sisteraxon to extant flowering plants including the “ANITA” groupAmborella, Nymphaeales, Illicium, Tricolpates and Austrobai-eya) (Sun et al., 2002) (Fig. 15). Raven et al. (2005) presentedhis phylogenetic view in his textbook of Introductory Botany.

Another achievement in the study of early angiospermsas made by a synthesis of the phytogeography of the fossil

ecord of the ancient angiosperms. For nearly a century, manyaleobotanists have considered the low latitude tropical areasf the world as the place of origin or the center of dispersalor ancient angiosperms. This is based on the fact that some

uctus sinensis; Fig. 14. A. liaoningensis (after Terada et al., 2005).

170 G. Sun et al. / Palaeoworld 17 (2008) 166–171

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xtant “basal” flowering plant families live in tropical regions;.g., Magnoliaceae possess more or less primitive charactersf angiosperms (Axelrod, 1959; Takhtajan, 1969; Burger,990). However, since the earliest known angiosperms, e.g.rchaefructus, with very primitive floristic characters ofncient angiosperms, are found in western Liaoning and itseighboring areas in the East Asia at northern middle latitudes,ogically then the place of origin (or one of the places) with thearliest diversification of ancient angiosperms should includeestern Liaoning in East Asia. Sun (1998) and Sun et al.

2002) proposed the hypothesis of “Eastern Asian origin of

ngiosperms”, suggesting that the ancient angiosperms mightrst occur at the middle latitudes of East Asia, covering the

erritory of western Liaoning, mid-eastern Monglolia, Russianaikalia and Far-East. This region probably contained some

ticd

Fig. 16. Sketch of a suggested center of origin of ang

g taxa of seed plants, plus the fossil Archaefructus (after Sun et al., 2002).

ifficult paleoenvironmental challenges under which plantsight live, such as volcanic activity, arid or semiarid climates,

ften isolating plant populations during pre-Cretaceous timeSun et al., 1998, 2002). The data mentioned above provideew perspectives for the study of angiosperm origins (Fig. 16).

It is important to mention that during recent years the syn-hetic studies of early angiosperms in NE China include researchn the co-evolution of early angiosperms with insects and othernimals concerned. Dilcher (2000), Dilcher and Sun (2007) andu et al. (2008) have emphasized the importance of this method

nd pointed out that effective pollen transfer became impor-

ant for the ancient angiosperms and these pollen acted as anmportant food source for the insects. The clustering of thearpels and associated stamens in Archaefructus and Hyrcanthaemonstrates early stages in this co-evolution. The co-evolution

iosperms in the world (after Sun et al., 2001).

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as influenced the closure of the carpels and the positioningf the floral organs. The flowers, fruits and the diversificationf the ancient angiosperms are products of this co-evolutionetween insects and the earliest angiosperms (Dilcher and Sun,007). In addition, paleoentomologists have made their contri-utions to the study of the co-evolution for the angiosperm originLabandeira et al., 1994; Ren, 1998, 2003) with findings of someurassic flower-visiting insect fossils from northeastern China,hich puts the study of ancient angiosperm origins, in this area,

nto a new era.

cknowledgements

The authors would like to thank Yang Q. and Wang Y.D.NIGPAS, China) for their encouragement of this paper. Manyhanks are also due to M. Akhmetiev (GIRAS, Russia) and Zhou.K. (KIBCAS, China) for their reviews and suggestions to thisanuscript. Thanks are extended to the Project 111 of China

No. B6008) of the Ministry of Education, China and the Bureauf Foreign Experts of China for the support.

eferences

xelrod, D.I., 1959. Poleward migration of early angiosperm floras. Science130, 203–207.

urger, D., 1990. Early Cretaceous angiosperm from Queesland, Australia.Review of Palaeobotany and Palynology 65, 153–163.

ao, Z.Y., Wu, S.Q., Zhang, P.A., Li, J.R., 1998. Discovery of fossil mono-cotyledons from the Yixian Formation, western Liaoning. Chinese ScienceBulletin 43 (3), 230–232.

arwin, F., Seward, A.C., 1903. More Letters of Charles Darwin. John Myrray,London, pp. 20–21.

ilcher, D.L., 2000. Toward a new synthesis: major evolutionary trends in theangiosperm fossil record. Proceedings of the National Academy of Sciencesof the United States of America 97 (13), 7030–7036.

ilcher, D.L., Sun, G., 2007. Fossils from Liaoning and their importance in theco-evolution of Life. In: Sun, G. (Ed.), Proceedings of International Sympo-sium on Paleontology and Stratigraphy in Benxi of China. Jilin UniversityPress, Changchun, pp. 14–15.

ilcher, D.L., Sun, G., Ji, Q., Li, H.Q., 2007. An early angiosperm Hyrcanthadecussata (com. nov.) from northeastern China. Proceedings of the NationalAcademy of Sciences of the United States of America 104, 9370–9374.

uan, S.Y., 1998. The oldest angiosperm — a tricarpous female reproductivefossil from Western Liaoning Province, NE China. Science in China SeriesD 41 (1), 14–20.

ontaine, W.M., 1889. The Potomac or Younger Mesozoic flora. Monograph ofUS Geological Survey 15, 1–337.

uo, S.X., Wu, X.W., 2000. Ephedrites from latest Jurassic Yixian Formationin Western Liaoning, Northeast China. Acta Palaeontologica Sinica 39 (1),89–91.

sü, J., 1987. Do fossil angiosperms really occur in Jurassic beds of the Yanshan-Liaoning area, China? Chinese Science Bulletin 32 (24), 1712–1714.

u, S., Dilcher, D.L., Jarzen, D.M., Taylor, D.W., 2008. Early steps ofangiosperm-pollinator coevolutrion. Proceedings of the National Academyof Sciences of the United States of America 105, 240–245.

imura, T., Ohana, T., Zhao, L.M., Geng, B.Y., 1994. Pankuangia haifang-gouensis gen. et sp. nov., a fossil plant with unknown affinity from theMiddle Jurassic Haifanggou Formation, western Liaoning, Northeast China.

Bulletin of Kitakyushu Museum of Natural History 1, 255–261.

abandeira, C.C., Dilcher, D.L., Davis, D.R., Wagner, D.L., 1994. Ninety-sevenmillion years of angiosperm-insect association: Paleobiological insights intothe meaning of coevolution. Proceedings of the National Academy of Sci-ences of the United States of America 91, 12278–12282.

Z

17 (2008) 166–171 171

eng, Q., Friis, E.M., 2003. Sinocarpus decussatus gen et sp. nov., a newangiosperm with basally symcarpous fruits from the Yixian Formation ofNortheast China. Plant Systematics and Evolution 241, 77–88.

iki, S., 1964. Mesozoic flora of Lycoptera beds in South Manchuria. Bulletinof Mukogawa Woman’s University 12, S13–S22.

an, K., 1990. Rhamnaceous plants from Middle Jurassic of Yanliao region,North China. Geology of Liaoning (2), 1–8.

an, K., 1997. Juglandaceous plant (Pterocarya) from Middle Jurassic of Yanliaoregion, North China. Acta Scientiarum Naturalium Universitatis Sunyatseni36 (3), 82–86.

aven, P.H., Johnson, G.B., Losos, J.B., Singer, S.R., 2005. Biology, 7th edition.McGraw Hill Higher Education, pp. 594–595.

en, D., 1998. Flower-associated Brachycera flies as fossil evidence for Jurassicangiosperm origins. Science 280, 85–88.

en, D., 2003. Nonmarine Jurassic strata and Neuropteran assemblages fromNE China. Mahasarakham University Journal 22 (Spec.), 253–255.

etallack, G., Dilcher, D.L., 1981. Early angiosperm reproduction: Priscareynoldsii gen. et sp. nov. from Mid-Cretaceous coastal deposits in Kansas,USA. Palaeontographica B 179, 103–137.

ydin, C., Wu, S.Q., Friis, E.M., 2006. Liaoxia Cao et S.Q. Wu (Gnetales):ephedroids from the Early Cretaceous Yixian Formation in Liaoning, north-eastern China. Plant Systematics and Evolution 262, 239–265.

un, G., 1998. Eastern Asian centre of angiosperm origin. Proceedings of 1stInternational Symposium on Geoenvironmental Changes and Biodiversityin NE Asia, Seoul, pp. 245–253.

un, G., Cao, Z.Y., Li, H.M., Wang, X.F., 1995. Cretaceous floras ofChina. In: Li, X.X. (Ed.), Fossil Floras of China through the GeologicalAges. Guangdong Science and Technology Press, Guangzhou, pp. 411–452.

un, G., Dilcher, D.L., Zheng, S.L., Zhou, Z.K., 1998. In search of the firstflower: a Jurassic angiosperm, Archaefructus, from Northeast China. Science282, 1692–1695.

un, G., Zheng, S.L., Dilcher, D.L., Wang, Y.D., Mei, S.W., 2001. EarlyAngiosperms and Their Associated Plants from Western Liaoning, China.Shanghai Scientific and Technological. Education Publishing House, Shang-hai, 227 pp.

un, G., Ji, Q., Dilcher, D.L., Zheng, S.L., Nixon, K., Wang, X.F., 2002. Archae-fructaceae, a new basal angiosperm family. Science 296, 899–904.

un, G., Zheng, S.L., Sun, C.L., Sun, Y.W., Mei, S.W., 2003. Advance in study ofArchaefructus with discussion of its ages. Journal of Jilin University (EarthEdition) 33 (4), 393–398.

akhtajan, A., 1969. Flowering Plants. Origin and Dispersal. Oliver & Boyd,Edingburgh, 135 pp.

ao, J.R., Zhang, C.B., 1990. Early Cretaceous angiosperms of the Yanji Basin,Jilin Province. Acta Botanica Sinica 32 (3), 220–229.

ao, J.R., Zhang, C.B., 1992. Two angiosperm reproductive organs from theEarly Cretaceous of China. Acta Phytotaxonomica Sinica 30 (5), 423–426.

erada, K., Nishida, H., Sun, G., 2005. 3D models of two species of Archaefruc-tus, one of the earliest angiosperms, reconstructed taking account of theirecological strategies. Memoir of the Fukui Prefectural Dinosaur Museum 4,35–44.

ang, X.Z., Ren, D., Wang, Y.F., 2000. First discovery of angiosperm pollenfrom Yixian Formation of western Liaoning. Acta Geologica Sinica 74 (3),265–272.

ang, X., Duan, S.Y., Geng, B.Y., Cui, J.Z., Yang, Y., 2007. Schmeissneria: Amissing link to angiosperms? BMC Evolutionary Biology 7 (14), 1–13.

u, S.Q., 1999. A preliminary study of the Jehol Flora from western Liaoning.Palaeoward 11, 7–57.

u, Z.Y., Zhou, Z.K., Sun, H., Li, D.Z., Peng, H., 2006. The Areal-type Seed-Plants and Their Origin and Distribution. Yunnan Science and TechnologyPress, Kunming, 566 pp.

abe, H., Endo, S., 1935. Potamogeton remains from the Lower Cretaceous?

Lycoptera bed of Jehol. Proceedings of the Japanese Academy 11 (7),274–276.

hou, Z.Y., 1995. Jurassic flora. In: Li, X.X. (Ed.), Fossil Floras of Chinathrough the Geological Ages. Guangdong Science and Technology Press,Guangzhou, pp. 343–410.