Vegetation changeover across the Permian–Triassic Boundary in Southwest China

    Vegetation changeover across the Permian-Triassic Boundary in Southwest China. Extinction, survival, recovery and palaeoclimate: A critical review Jianxin Yu, Jean Broutin, Zhong-Qiang Chen, Xiao Shi, Hui Li, Daoliang Chu, Qisheng Huang PII: DOI: Reference:

S0012-8252(15)00065-3 doi: 10.1016/j.earscirev.2015.04.005 EARTH 2106

To appear in:

Earth Science Reviews

Received date: Accepted date:

30 April 2014 8 April 2015

Please cite this article as: Yu, Jianxin, Broutin, Jean, Chen, Zhong-Qiang, Shi, Xiao, Li, Hui, Chu, Daoliang, Huang, Qisheng, Vegetation changeover across the Permian-Triassic Boundary in Southwest China. Extinction, survival, recovery and palaeoclimate: A critical review, Earth Science Reviews (2015), doi: 10.1016/j.earscirev.2015.04.005

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ACCEPTED MANUSCRIPT \ Vegetation changeover across the Permian-Triassic Boundary in Southwest

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China. Extinction, survival, recovery and palaeoclimate: a critical review

Jianxin Yua,
, Jean Broutinb, Zhong-Qiang Chena, Xiao Shia , Hui Li a, Daoliang, Chu a,

State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences,

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Qisheng Huangc

Wuhan, P.R. China

Sorbonne Universités, Centre de recherche sur la Paléobiodiversité et les Paléoenvironnements –

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Paleobotany and Paleoecology, University Pierre et Marie Curie – Paris 6, Paris, France Faculty of Earth Sciences, China University of Geosciences, Wuhan, 430074, P.R. China

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c

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* Corresponding authors. J. Yu: Tel: 86-18986112835; Fax: 86-27-67882345

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E-mail addresses: [email protected] (J Yu)

ABSTRACT

This paper reviews critically the Permian-Triassic (P-Tr) fossil plants and microflora recorded in three well-studied terrestrial Permian-Triassic boundary (PTB) sections, namely Chahe, Zhejue, and Jiucaichong, and two marine-terrestrial transitional PTB sections, namely Mide and Tucheng, in western Guizhou Province and eastern Yunnan Province (WGEY), Southwest China. Distinct floral composition, abundance and diversity across the PTB allow the establishment of two terrestrial macrofloral assemblages. The Lobatannularia multifoliaGigantoclea guiyangensis (L-G) assemblage was recognized from the upper Xuanwei Formation, while the Annalepis-Peltaspermum (A-P) assemblage from the lower Kayitou Formation. The former flora comprises 105 species in 39 genera and is late Changhsingian in age. The latter assemblage includes 18 species in 14 genera and is Induan in age. The

ACCEPTED MANUSCRIPT Changhsingian assemblage is characterized by the loss of many Wuchiapingian elements of the Gigantopteris flora and an increase of the gymnosperms. Most of the Permian-type plant

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taxa were wiped out in the PTB crisis on land with only few relicts persisting into the Early Triassic, which saw the flourishing of Annalepis and common presence of Peltaspermum and

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Permian relicts of the gigantopterids. During the Permian-Triassic transition some rare

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gigantopterids elements as well as some Peltaspermum representatives survived the biocrisis. Annalepis a pioneering lycopsid genus in the recovery of the Triassic land plants, and its

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proliferation marks the recovery of land plants after the PTB crisis on land in WGEY.

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Accordingly, vegetation changeover across the PTB is marked by a dramatic turnover of plants on land from the Permian Gigantopteris flora to the Triassic Annalepis-dominated assemblage. Palynofloras are characterized by a dramatic drop of palynomorphs in both

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abundance and diversity and show a stepwise extinction pattern. Moreover, macro- and microfloras of the WGEY region indicate that humid and warm climate regime prevailed

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through the P-Tr transition in Southwest China. The coal forming-swamps gradually migrated westward due to marine trangressions throughout the Late Permian. The “Gigantopteris flora” also migrated from east to west and a few species can survive into the earliest Triassic in the WGEY region, but disappeared soon after. Keywords: Vegetation changeover, extinction, survivor and recovery, terrestrial facies, Permian-Triassic boundary, Southwest China

Contents 1. Introduction 2. Key PTB sections and stratigraphy in the WGEY region, Southwest China 2.1. The Chahe section, Weining county, western Guizhou Province

ACCEPTED MANUSCRIPT 2.2. The Zhejue section, Weining county, western Guizhou Province 2.3. The Jiucaichong section, Weining county, western Guizhou Province

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2.4. The Mide section, Xuanwei City, eastern Yunnan Province 2.5. The Tucheng section, Panxian county, western Guizhou Province

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3. Palaeogeographic settings of the WGEY region

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4. Changhsingian floral assemblage 5. Earliest Triassic floral assemblage

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6. Key taxonomic proxies indicating floral survival and recovery after the PTB biocrisis

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6.1. Gigantopterids 6.2. Peltaspermum 6.3. Annalepis

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7. Palynofloral changeover across the PTB 7.1 Characteristic assemblage of spores and pollen

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7.2 Megaspore found in the Earliest Triassic of the Kayitou Formation 8. Vegetation changeover across the PTB: extinction, survival and recovery 9. Palaeoclimate changes over the P-Tr transition in WGEY 10. Conclusions

ACCEPTED MANUSCRIPT 1. Introduction

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The Latest Permian Mass Extinction (LPME) event, the most severe biocrisis of the Phanerozoic, marked the collapse of marine and terrestrial ecosystems on a world-wide scale

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(Erwin, 1994; Retallack, 1995; Looy et al., 2001; Chen and Benton, 2012). Locally, about

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95% of peat-forming plants became extinct and the number of families of higher land plants has drastically declined in this biocrisis (Retallack, 1995; Michaelsen, 2002).

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Recently developed botanical and palynological records from the Upper Permian to

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Lower Triassic have provided a better understanding of the mechanism and dynamic of floral turnover across the Permian-Triassic Boundary (PTB). Land vegetation, as one highly sensitive index to environmental change, is one of the most useful proxies for analyzing the

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patterns of biotic extinction, survival and recovery during this critical period of Earth life (Looy et al., 2001). Terrestrial floras over the Permian-Triassic (P-Tr) transition have been

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investigated in many terrestrial PTB sections from around the world. Nevertheless, the PTB in those terrestrial sections has not been precisely defined, and they do not correlate well with one another (Chen and Benton, 2012). South China records are not only the best exposed and most continuous marine PTB successions in the world (Chen and Benton, 2012), but also many well-exposed, continuous PTB successions of terrestrial-marine transition and terrestrial facies (Wang and Yin, 2001; Peng et al., 2005; Yu, 2008; Yu et al., 2007, 2010) (Fig. 1). The latter usually yield abundant fauna and flora, and are exposed mainly in the western Guizhou and eastern Yunnan (WGEY) region, Southwest China, which is tectonically located on the eastern margin of the wellknown Kangdian old Massif (Figs. 2 and 3). After a decade effort, both biostratigraphy, chemostratigraphy and geochronology of the non-marine P-Tr successions from the WGEY region have been much better studied (Wang and Yin, 2001; Peng et al., 2005; Zhang et al.,

ACCEPTED MANUSCRIPT 2006; Yin et al. 2007; Metcalfe and Nicoll, 2007; Yu et al., 2007, 2010; Shen et al., 2011; Chu et al., 2013). In particular, floras are considerably abundant and diverse across the PTB in

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those sections (Yu, 2008) and have been documented in numerous publications (Yu et al., 2007, 2010; Peng et al, 2005, 2006). The floral assemblages from southwestern China contain

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not only many widespread genera but also abundant endemic elements (Li, 1995) The

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southwestern Chinese floras therefore provide an excellent plant record revealing the extinction, survival and recovery patterns and evolutionary dynamics of floras across the PTB

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(Yu et al., 2007). Accordingly, this study aims to summarize the well-preserved palaeofloras

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from three best studied terrestrial PTB sections, namely Chahe, Zhejue and Jiucaichong, and two key terrestrial-marine transitional PTB sections, namely Mide and Tucheng (Fig. 1), based on recently published data and newly obtained materials from Southwest China, and

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then attempt to evaluate extinction, survival and recovery as well as evolutionary dynamic of those palaeofloras (including macro- and microfloras) over the P-Tr transition and discuss in a

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broad context on their implications on climatic changes during that times.

2. Key PTB sections and stratigraphy in the WGEY region

The WGEY region, geographically, covers the Anshun City of the western Guizhou Province in the east and Qujing City of eastern Yunnan Province in the west, Southwest China (Fig. 1). There are many continuous PTB sections from east to west in WGEY. These sections were deposited in a relatively deep shelf basin, shallow marine, nearshore littoral zone, terrestrial - marine transition, and terrestrial settings (Figs. 2). Are recorded in WGEY: the Xinmin section, Anshun City of shelf basin facies (Shen et al., 2013), the Zhongzhai section, Liupanshui City of shallow sea facies (Metcalfe et al., 2007), the Mide section, Xuanwei City and the Tucheng section, Liupanshui City of terrestrial-marine transitional facies, and the

ACCEPTED MANUSCRIPT Chahe, Zhejue and Jiucaichong sections, Weining County of terrestrial facies (Figs. 2). In particular, the last five PTB sections yield considerably abundant plant assemblages across the

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PTB, which form the basis of our review and are introduced below. As the stratigraphic units in the area were named, modified and even supplemented by

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different researchers, there is confusion surrounding the definition of stratigraphic units, with

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different names being used to describe the same stratigraphic unit (Table 1). Non marine Upper Permian to Lower Triassic successions of the WGEY region includes the Xuanwei and

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Kayitou Formations (Table 1). The former comprises yellowish green, greyish-green and

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brownish-yellow, fine-grained sandstone, siltstone, claystone, shale with coal-seams, and siderite in some parts, yielding rich gigantopterid flora elements of Late Permian age. The later formation is composed mainly of yellowish green, greyish-green and brownish-yellow

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conglomerate, siltstone, claystone, and shale at the lower part, and yellowish-green, grayishgreen and brownish-yellow siltstone, claystone and shale intercalated with purple-reddish

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sandstone and siltstone at the upper part. Both the reddish sandstone and siltstone increase up the section. The Kayitou Formation contains some latest Changhsingian surviving plants mixed with the Induan plant assemblage. The PTB in the WGEY region is marked by lithologic turnover from the latest Permian coal measures of the uppermost Xuanwei Formation to the terrestrial - marine transitional facies fine sediments of the basal Kayitou Formation.

2.1. The Chahe section, Weining County, western Guizhou Province

The Chahe section (103.8°E; 26.7°N) is located bet ween the 31st and 32nd kilometer (km) milestones on the countryside motorway from Heishitou town to Haila, Weining County (Fig. 1). Lithologically, the Chahe section includes the upper Xuanwei

ACCEPTED MANUSCRIPT Formation (Beds 1-70) and Kayitou Formation (Beds 71-89). The upper part (Beds 167) of the Xuanwei Formation is dominated by mudstone and sandstone interbedded with coal

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measures, and yields abundant Permian fossil plants such as Lobatannularia, Gigantopteris, and Fascipteris. The uppermost Xuanwei Formation comprises a coal seam mixed with a

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volcanic ash layer (Bed 68), sandy mudstone (Bed 69) and siltstone (Bed 70) (Fig. 3a). Of

well-preserved

Permian

plants

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these, Bed 68 yields abundant plant roots (Stigmaria spp.). Bed 69 contains abundant and (Lobatannularia,

Gigantopteris,

Gigantoclea

and

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Compsopteris etc), conversely, Bed 70 has yielded a very few and broken Triassic fossil plant

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fragments (Lepidopteris sp.) and conchostracans (Euestheria gutta) (Fig. 3a). The lower Kayitou Formation also yields a few fossil plant fragments (Lepidopteris sp., Peltaspermum

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sp.) and conchostracans (Euestheria gutta, E. yanjingxiensis, Palaeolimnadia pusilla, P.

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xuanweiensis etc), which are characteristics of the Triassic flora and fauna elsewhere in the world (Kozur and Weems, 2010; Chu et al., 2013).

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Previously, the PTB was placed in the middle of Bed 67 based on palynological assemblages, eventostratigraphy, and radiometric age indicating the age’s incertainties (Yang et al., 2005; Peng et al., 2006; Yin et al., 2007; Yu et al., 2007). However, radiometric dating was measured using zircon SHRIMP technique, which usually has a low precision. Later, Shen et al. (2011) obtained a zircon

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Pb/238U date of 252.3 ± 0.07 Ma from Bed 68. These

authors have also dated both Beds 25 (252.28 ± 0.08 Ma) and Bed 28 (252.10 ± 0.06 Ma) of the Global Stratotype Section and Point of PTB in Meishan, South China and give an estimate age of 252.17 ± 0.06 Ma for the mid-Bed 27, at which the P-Tr boundary was placed (Yin et al., 2007). Bed 68 therefore can be correlated with Bed 25 of the Meishan section. The latter is also a volcanic ash layer, to which the LPME was calibrated. In addition, Bed 25 has also been usually used as the base of the P-Tr mixed fauna or survival fauna beds (Chen et al., 2005). As mentioned above, typical Permian plants are mixed with fossil plants (i.e.

ACCEPTED MANUSCRIPT Lepidopteris sp., Peltaspermum sp.), restricted to the Lowest Triassic Induan stage (Beds 6970). The floral and faunal mixture state in Chahe therefore is comparable with the same

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phenomenon indicated by the mixed faunas near the PTB in marine sections (i.e., Chen et al., 2005). As such, Beds 68-70, about 1.5 m thick, are termed the Permian-Triassic transitional

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beds (PTTB), a marker unit of the terrestrial PTB that is employed for the correlation of the

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PTB beds between the terrestrial settings (Fig. 3) and the Meishan Section (GSSP)(Fig. 4).

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2.2. The Zhejue section, Weining County, western Guizhou Province

This section is located between the 851st and 852nd km milestones on the national highway 326 from Xuanwei City to Weining County (Fig.1), in which the terrestrial P-Tr

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succession is comparable with that of the Chahe section (Fig. 3b). Rare sporopollens and abundant plants were obtained from both the Xuanwei and Kayitou Formations (Peng et al.,

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2006; Fig.4b). Of these, Beds 47-50 of the uppermost Xuanwei Formation correlate well with Beds 68-70 of Chahe in terms of lithology and floral compositions. Beds 47-50 therefore are regarded as the PTTB for the Zhejue section (Fig. 3b).

2.3. The Jiucaichong section, Weining County, western Guizhou Province

The section is located between the 832nd and 833rd km milestones on the national highway 326 from Xuanwei City to Weining County (Fig.1). Like Chahe and Zhejue, the Upper Permian and Lower Triassic successions are assignable to the Xuanwei (Beds 1-24) and Kayitou (Bed 25-31) Formations, respectively. Here, abundant fossil plants and conchostracans were found in the P-Tr succession. Of these, Bed 21 is a volcanic ash layer and correlates well with Bed 68 of Chahe. Both lithologic package and floral and faunal

ACCEPTED MANUSCRIPT compositions (Chu et al., 2013) suggest that Beds 21-24 can be employed as the PTTB (Fig.

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2.4. The Mide section, Xuanwei City, eastern Yunnan Province

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3c).

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This section crops out about 3 km east of Mide Village of Haidai town, Xuanwei City, Yunnan Province (Fig. 1). Here, the uppermost Permian to lowest Triassic succession is

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subdivided into the upper Xuanwei Formation (Beds 1-18) and lower Kayitou Formation

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(Beds 19-27), yielding abundant fossil plants, palynomorphs (Yu, 2008), ammonoids, bivalves, and brachiopods. Of these, the early Griesbachian (lowest Triassic) index ammonoid Ophiceras spp. was documented from Bed 25 (Tian et al., 2008). The First Appearance Datum

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(FAD) of the “pioneering lycopsid genus” Annalepis occurs in Bed 19, and some bivalves Pteria, Towapteria, Unionites and Eumorphotis, characteristic of the mixed fauna beds of

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marine PTB sections in South China (Chen et al., 2009, 2011), were also found in Beds 17-19. The latter therefore are considered as the PTTB for the Mide section (Fig. 3d).

2.5. The Tucheng section, Panxian County, western Guizhou Province

This section is exposed about 9 km south of Tucheng town (now named Baiguo town), Panxian County, Guizhou Province (Fig. 1). Like the Mide section, the Permian and Triassic successions are assignable to the upper Xuanwei Formation (Beds 1-16) and lower Kayitou Formation (Beds 17-24), respectively (Fig. 3e). Of these, Beds 17-21 contains Permian plants and Triassic floras, bivalves and brachiopods (Lingularia spp.). They therefore are referred to as the PTTB (Fig. 3e).

3. Palaeogeographic settings of the WGEY region

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The P-Tr floral data involved in this study are sourced mainly from the terrestrial-marine

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transitional facies in the Tucheng and Mide sections and terrestrial in the Chahe, Zhejue, and Jiucaichong sections. In fact, the WGEY region was part of the Yangtze Platform and thus

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was a shallow platform environment during the Late Devonian to Early Permian times (Wang

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and Yin, 2001). The Early Permian palaeogeographic configuration was drastically changed by the Dongwu rising movement (Yao et al., 1980) during the late Middle Permian due to the

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large eruption of the Emeishan Basalt in the bordering area of Sichuan-Guizhou-Yunnan,

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Southwest China at that time (He et al., 2005; Zhu et al., 2010). Since then, most parts of the WGEY area have uplifted, becoming the eastern margin of the “Kangdian old Massif”, having succeeded from its configuration since the Cambrian (Wang and Jin, 2000). The contact

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between the Middle and Upper Permian is usually disconformable in most areas of South China (Chen et al., 1998). The WGEY area was a narrow band, along the eastern margins of

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this old Massif during that time (Fig. 2). As a consequence of interplay of the Dongwu movement and global sea-level fall in the latest Guadalupian (Middle Permian) (Haq and Shutter, 2008; Chen et al., 2009), most areas of Southwest China became continental settings during the early Wuchiapingian (early Late Permian) (Chen et al., 1998). The WGEY region was partly flooded due to a regional westward transgression, originating in the Xinmin area and extending towards the Chahe area, during the late Wuchiapingian (Wang and Yin, 2001). Accordingly, a continental facies succession progressively overlain by the neritic deposits characterizes the Wuchiapingian sequence of many sections in WGEY (Fig. 2). The late Wuchiapingian palaeogeographic configuration was then inherited in early Changhsingian (Yin et al., 1995). The succeeding transgression resulted in the more and more nearshore zones surrounding the Kangdian Continent becoming shallow seas in that time. The

ACCEPTED MANUSCRIPT continental domain therefore further shrank westerly. Consequently, the Xuanwei and Weining areas changed from a fully continental setting to fluvial, lacustrine, swampy, and

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estuary environments (Yu, 2008; Fig. 2), in which sandstone, mudstone and coal seams/beds were deposited, and ostracods, concostracans, bivalves, and plants were abundant (Yao et al.,

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1980). The continent expanded easterly to some extent and the coast-line shifted a little bit

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eastward during the late Changhsingian, which saw a short time regression in the WGEY region. As a result, the uppermost Changhsingian successions in the Chahe, Zhejue and

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Jiucaichong sections are also characterized by swampy facies deposits, although the same area

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was a shallow sea setting in early-middle Changhsingian. A new transgression took place in the WGEY region during the Induan (Early Triassic). As a result, the coast-line moved westward again. The previously marine-terrestrial

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transitional zone (i.e., the Tucheng and Mide sections) was flooded by seawater and became nearshore marine environment in which the marine facies brachiopod Lingularia and bivalves

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Pteria and Towapteria proliferated (Peng et al., 2005; Yu et al., 2010; Tian et al., 2008). The previously terrestrial zone (i.e. Chahe, Jiucaichong and Zhejue) surrounding the Kangdian Continent remained as continental setting and composed by terrestrial sediments (Fig. 3). Therein, a succession of greyish-green and yellowish-green sandy mudstone interbedded with purple-reddish mudstones was deposited, and fossil plants are rather abundant, although coal measures are absent.

4. Changhsingian floral assemblage

Fossil plants extracted from the Changhsingian of those five PTB sections in the WGEY region are considerably abundant and diverse (Yu, 2008; Peng and Shi, 2009). A total of 105 species in 39 plant genera were found in the upper Xuanwei Formation of all studied sections

ACCEPTED MANUSCRIPT (see online supplementary data Figs. S1-4). Of these, a total of 68 known species in 39 genera were obtained from the terrestrial facies sections and 48 species in 31 genera from the

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terrestrial-marine transitional facies sections. Both lithofacies zones share 48 species and 31 genera, suggesting a very high similarity in floral compositions at either genus or species

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level. As consequence, the floras from both lithofacies zones can be assigned to the same

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floral assemblage.

These Xuanwei Formation plants are dominated by species of both Gigantopteris and

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Gigantonoclea. These two genera contain 10 species and are characteristics of the Cathaysian

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floras during the Late Permian in China (Li, 1995). The predominant species include Gigantopteris dictyophylloides (Figs. 9D, 10B), Gigantonoclea guizhouensis (Fig. 8A), Lobatannularia multifolia (Fig. 6E), and Stigmaria ficoides (Fig. 6A). Of these, G.

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guizhouensis and L. multifolia, characteristic of the Changhsingian floras in South China (Li, 1985), are the commonest element in the Xuanwei floras in WGEY. Consequently, the

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Xuanwei Formation floras can be assigned to the Lobatannularia multifolia-Gigantonoclea guizhouensis (L-G) Assemblage, which overall is comparable with the coeval Gigantopteris flora elsewhere in South China (Li, 1995). Other elements such as Annularia shirakii (Fig. 5C), Lobatannularia cathaysiana (Figs. 6B, 6F), Paracalamites stenocostatus (Fig. 6D), Fascipteris stena (Fig. 9C), Pecopteris marginata (Fig. 9B), Compsopteris contracta (Fig. 7D), Rhipidopsis panii (Fig. 7E), and Lepidodendron acutangulum (Fig. 5A) are also commonly present. Taxonomically, the WGEY Changhsingian floral assemblage consists of 8 orders, namely the Lepidodendrales, Sphenophyllales, Equisetales, Filicales, Pteridospermopales, Noeggerathiales,

Glossopteridales,

Gigantopteridales

and

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classes:

Cycadopsida,

Ginkgopsida, Cordaitopsida. At species level, the Filicales and Pteridospermopales are the largest groups within the Changhsingian flora, respectively occupying 27.6% and17.1%

ACCEPTED MANUSCRIPT among all species, followed by the Sphenophyllales (14.3%), the Lepidodendrales (12.4%), and the Gigantopteridales (10.5%), the Glossopteridales is the smallest group and only 2

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remains (1.9%) possibly related to the Glossopteridales. Apart from the strong affinities to the coeval Gigantopteris flora reported elsewhere in

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China, the WGEY assemblage is also characterized by the following distinct compositions

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within various major groups. Unlike the coeval Gigantopteris flora in China, the Lycopsida contains very rare genera and species of the Lepidodendrales. The foliage morphogenera

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Annularia and Lobatannularia and their stem morphogenera (e.g. Calamites and

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Paracalamites) are numerically most abundant within the Sphenopsida. Within the Pteridopsida and Pteridospermopsida, both Pecopteris and Fascipteris are rather abundant and diverse, and the number of the Mesozoic-type ferns (i.e, Cladophlebis) in genus level

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increases clearly within the Xuanwei Formation up the section. Genus Cladophlebis increased from bottom to top of the Xuanwei Formation in species richness. The Noeggerathiales are

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characterized by the presence of rare fragments of Tingia cf. gerardii and T. crassinervis (Fig. 10A), which seem to be confined to the basal part of the upper Xuanwei Formation. Compsopteris of the Pteridospermopsida flourished and contains six species. In the Gigantopteridales, are dominated by two species of Gigantopteris and eight species of Gigantonoclea. Only one vegetative leaf was obtained from the uppermost Xuanwei Formation in the Tucheng section, and two small isolated fructifications similar to the glossopterid ones from the similar horizons in Chahe section. Within the Ginkgopsida, representatives of the genus Rhipidopsis are commonly present in the middle part of the upper Xuanwei Formation Clearly, the Changhsingian Gigantopteris flora of the WGEY area is different from the Wuchiapingian assemblages reported from China (Li, 1995). in generic and specific compositions. Species richness of the WGEY Gigantopteris flora decreased markedly in

ACCEPTED MANUSCRIPT Changhsingian when compared with the Wuchiapingian floras in China. In particular, the emblematic element Gigantopteris nicotianaefolia became very rare and was sporadically

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distributed in few horizons. Protoblechnum, characteristic of the Wuchiapingian floras in China, is absent in the WGEY assemblage, which contains more representatives of

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gymnosperms, namely the Cycadopsida, Ginkgopsida, and Cordaitopsida. As far as fossil

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conifers are concerned, they are absent in the non-marine succession of the upper Xuanwei Formation in the studied sections, but are present in coeval marine successions in Southwest

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China (Yu et al., work in progress).

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To sum up, the Changhsingian floral assemblage from WGEY is dominated by both the Filices (i.e., 11 Pecopteris species) and Pteridospermopsida. The Gigantopteris flora became gradually impoverished and declined. To the end of the Permian, the Cathaysian floras were

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extirpated, except that some relics persisted into the earliest Triassic in WGEY.

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5. Earliest Triassic floral assemblage

Previously, Yao et al. (1980) reported a considerably abundant and diverse plant flora from the lower Kayitou Formation of the WGEY region, including Paracalamites stenocostatus, Annularia shirakii, Lobatannularia multifolia, Pecopteris sp., Gigantopteris sp., Gigantoclea sp., and so on, but assigned them to the latest Permian in age. However, as correlated in Chapter 2 (Fig. 3), the lower Kayitou Formation in the WGEY region is assignable to the earliest Triassic in age in view of integration of biostratigraphic, chemostratigraphic and geochronologic correlations (Peng et al., 2006; Yu et al., 2010; Shen et al., 2011). More recently, Yu (2008) and Yu et al. (2010) re-sampled those PTB sections in the WGEY region and obtained even more abundant and diverse fossil plants. These authors have obtained not only all taxa reported by Yao et al. (1980), but also some additional taxa

ACCEPTED MANUSCRIPT such as Annalepis zeillerii, Annalepis latiloba, A. brevicystis, A. angusta, Annalepis furongqiaoensis, and Peltaspermum martinsii, which resembles foliage associated with

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Peltaspermum radially symmetrical peltate ovuliferous discs (Figs. 11-12) etc. The lower Kayitou Formation plant taxa include 18 species in 14 genera. Of these, 6

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species in 4 genera were obtained from the terrestrial facies sections, while 16 species in 12

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genera from the terrestrial-marine transitional facies sections. Clearly, the terrestrial-marine transitional facies flora is much more diverse than the terrestrial facies in the assemblage. A

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few dispersed and in situ megaspores of Annalepis were also extracted from the same strata.

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They include the Lycopsida Annalepis zeilleri (Fig. 11J, K), A. brevicystis (Fig. 11F,G, I), A. furongqiaoensis (Fig. 11H), and A. latiloba, the Sphenopsida Paracalamites stenocostatus, Pteridopsida ?Pecopteris sp. (Fig. 12J) and ?Sphenopteris sp., Pteridospermopsida

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Peltaspermum cf. martinsii (Fig. 12A-D), P. lobulatum (Fig. 12G), and Peltaspermum sp. (Fig. 12E-F), Ginkgopsida ?Sphenobaiera sp., Gigantopteridales Gigantonoclea sp. (Fig.12I) and

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Gigantopteris sp. (Fig. 12H), and a few undetermined fossil plant forms. The Early Triassic assemblage is overall dominated by both Annalepis and Peltaspermum, which occur in the lowest bed of the Kayitou Formation and persist onto two beds above the formation base. As such, the Kayitou Formation flora is assigned to the Annalepis-Peltaspermum (A-P) Assemblage.

Taxonomically, the WGEY Early Triassic floral assemblage consists of 4 orders, namely the Lepidodendrales, Isoetales, Sphenophyllales and Gigantopteridales, and 3 classes Pteridopsida, Pteridospermopsida, Ginkgopsida (Table 2). At species level, the Isoetales is the largest group within the Early Triassic flora, occupying 33.3% among all species. The Pteridospermopsida (22.2%) ranks the second largest group of the Early Triassic assemblage in species level, followed by the Sphenophyllales (11.1%), and the Gigantopteridales (11.1%), the Ginkgopsida being the smallest group and with only 1 species (5.6%) (Table 2). At genus

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6. Key taxonomic proxies indicating floral survival and recovery after the PTB biocrisis

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6.1. Gigantopterids

Gigantopterids are a plant group typical to the Permian Cathaysia floras, ranging from

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the Middle Permian to the latest Permian in South China (Li, 1995). This group includes 11

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species in two genera, which are mostly distributed in 16 horizons throughout the Late Permian Xuanwei Formation in WGEY. However, some incomplete and very minute plant’s fragments (possibly reworked from Permian) assignable to both Gigantopteris and

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Gigantoclea (Fig. 12H-I) were also found in at least 2-3 horizons at the lower Kayitou Formation in the terrestrial-marine transitional facies setting in the Chahe (i.e. Beds 70 and

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71), Mide (i.e. Beds 19 and 21) and Tucheng (i.e. Beds 22 and 23) sections, while megaremains are still present in bed 69 of the Chahe section (Fig.9D). Accordingly, the persistence of the Gigantopteris flora elements onto the lower Kayitou Formation indicates clearly that some plants of this paleophytic flora survived into the earliest Triassic. Some rare elements of Gigantopterids therefore survived after the PTB mass extinction.

6.2. Peltaspermum

This seed organ genus, ranging from the Permian to Triassic in age, is represented by over 10 morphogenera. Among them, three organ genera Lepidopteris (leaf), Antevsia (pollen organ), and Peltaspermum (seed organ) are widely preserved in WGEY. Many Late Palaeozoic and Mesozoic foliage types have been assigned to the Peltaspermales with varying

ACCEPTED MANUSCRIPT degrees of confidence, for example, the genera “Callipteris” (traditionally used morphogenus for the Late Palaeozoic foliage attributed to the peltasperms), Supaia (a putative peltasperm

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foliage type recorded in North China, Europe, and North America) (Wang, 1997; Gand et al., 1997; Galtier and Broutin, 2008; White, 1929; DiMichele et al., 2005), and Lepidopteris (the

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foliage organization of the Mesozoic peltasperms).

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Peltaspermum, established originally by Harris (1937) for typical female reproductive organs of the Peltaspermaceae, has been redefined by Poort and Kerp (1990) as a “natural”

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genus, including sterile foliage of Lepidopteris type, the pollen organ Antevsia zeilleri, and

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the seed-bearing organs for the species Peltaspermum rotula. Naugolnykh and Kerp (1996) re-categorized peltate discs reported by Gomankov and Meyen (1980) from the Kungurian of the Fore-Urals, together with sterile pinnae described by Zalessky (1939) as Callipteris

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retensoria, into Peltaspermum retensorium. In the northern hemisphere, this genus is mainly distributed in the late Early Permian in central Morocco (Kerp et al., 2001), the Late Permian

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in Ural region, Russia (Meyen, 1984), India (Srivastava et al., 2011), Northwest and North China (Huang and Ding, 1998), the Early Triassic in North and South China (Wang, 1997), the middle Late Triassic of the Tunguska Basin, Russia (Meyen, 1984), and North and South China (Wang, 1997), and the Late Triassic of Greenland (McElwain et al. 2007), Sweden, and Mid-Asia (Chen et al. 2011).

Numerous fragments of vegetative pinnae and female reproductive organs (Fig. 12E-G), likely related to Peltaspermales, were collected from 2-3 layers of the lower Kayitou Formation in terrestrial facies of the Chahe and Jiucaichong sections, and in terrestrial-marine alternation facies of the Mide and Tucheng sections in WGEY (Figs.1 and 4). It should be noted that we prefer to use Peltaspermum as the reproductive organ, and Lepidopteris as foliage sensu Harris (1937) in view of the discovered sterile pinnae and fertile organs occurring in the equivalent horizons in the studied sections.

ACCEPTED MANUSCRIPT It is also true that Pteridosperms were very widespread in the Carboniferous and Permian in South China (Li, 1995). Genus Peltaspermum from the Kayitou Formation in WGEY is

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also the first record in the Earliest Triassic strata (Fig. 13). The oldest species of Peltaspermum is present in the early Early Permian in Northwest China (Huang and Ding,

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1998). This genus has also been recorded in the late Late Permian Sunjiagou and Sunan

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Formations, North China (Huang, 1996). Peltaspermum occurred in WGEY has also been reported from the Early and Middle Triassic rocks in North China (Wang and Wang, 1990)

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(Fig. 13), but disappeared since the late Middle Triassic there.

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Accordingly, the presence of foliage and reproductive organs of Peltaspermum in the Kayitou Formation indicates that this genus survived the PTB mass extinction.

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6.3. Annalepis

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Annalepis was first established by Fliche (1910) from the Middle Triassic of Lorraine, France, and has been morphologically emended by later authors (Ye, 1979; Grauvogel-Stamm and Duringer, 1983; Retallack, 1997; Meng, 1994, 1998; Kustatscher et al., 2010). This plant genus has been considered as an important marker for the late Early Triassic and Middle Triassic successions worldwide (Retallack, 1975, 1997; Wang and Wang, 1990; Meng, 1994; Grauvogel-Stamm and Lugardon, 2001; Liu et al., 2004). In fact, Annalepis has also been reported from the Carnian (Late Triassic) strata in South China (Meng et al., 2000). As a result, the known record outside WGEY shows that Annalepis is a Triassic genus and confined to late Early Triassic to early Late Triassic in age. In WGEY, Annalepis was found in association with a diverse marine fauna from the basal Kayitou Formation. The associated fossil assemblage includes ammonoid Ophiceras sp., ostracod Langdaia suboblonga, and bivalves Myophoria (Neoschizodus) laevigata,

ACCEPTED MANUSCRIPT Myophoria (Leviconcha) orbicularis, Unionites fassaensis, and Unionites f. bittneri. Of these, Ophiceras is characteristic of the marine faunas immediately after the PTB biocrisis and the

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early Griesbachian (early Induan) faunas in South China (Chen et al., 2009). Other bivalves are also commonly present in the earliest Triassic successions in South China (Chen, 2004;

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Chen et al., 2009, 2011). Annalepis therefore is definitely early Induan in age in WGEY (Yu et

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al., 2010). The updated fossil record shows that Annalepis may have originated in WGEY soon after the PTB mass extinction, and then may have migrated to the north and spread over

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the Upper Yangtze region, South China and North China during the late Early Triassic to

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Middle Triassic times (Ye, 1979; Wang and Wang, 1990; Meng, 1994, 1996, 1998; Liu et al., 2004), and eventually migrated westerly to Europe (France and Italy) during the Middle Triassic (Grauvogel-Stamm and Duringer, 1983; Kustatscher et al., 2010). Meanwhile, this

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genus has also migrated to the south and spread over South-East Asia and Australia during the late Early Triassic and Middle Triassic times (Retallack, 1975, 1997; Liu et al., 2004). Finally,

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Annalepis seems to have disappeared in most of the above region by the end of the Middle Triassic, but still survived into the early Late Triassic in the WGEY region (Meng et al., 2000). Thus, Annalepis is a pioneering lycopsid genus in the recovery of the Triassic land plants, and its proliferation marks the recovery of land plants after the PTB crisis on land in WGEY.

7. Palynofloral changeover across the PTB in WGEY

7.1 Characteristic assemblage of spores and pollen

The Upper Permian to Lower Triassic strata in the terrestrial exposure sections of the WGEY region yields very few spores and pollen grains (Peng et al., 2006, Bercovici et al., 2015). In contrast, they are considerably abundant in three terrestrial-marine transition drilling

ACCEPTED MANUSCRIPT sections of WGEY (Ouyang, 1982; Fig. 1). Ouyang studied the spores and pollen content of 3 boreholes yielding Upper Permian to Lower Triassic rocks in the Fuyuan District (Fig.1).

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Based on rich and very well preserved palynomorphs, he defined three characteristic palynofloral assemblages: (1) The Torispora gigantea-Patellisporites meishanensis

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Assemblage for the lower Xuanwei Formation of Wuchiapingian age containing abundant

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pteridophyte and pteridosperm spores, and few gymnosperm pollen grains; (2) The Yunnanospora radiata - Gardenasporites Assemblage from the upper Xuanwei Formation, of

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Changhsigian age, is dominated by Permian pteridophytic spores, but “many Mesozoic

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elements make their appearance” such as Dictyophyllidites mortoni and Aratrisporites yunnanensis; (3) The Lundbladispora-Aratrisporites-Pteruchipollenites Assemblage from the lower Kayitou Formation of Induan age, is dominated by numerous Mesozoic pteridophyte

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and pteridosperm spores associated with some elements of “Paleozoic aspect” and a few gymnospermous pollen grains. This assemblage represents a true transitional or mixed

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microflora” (Ouyang, 1982, p.74). It should be noted that, as stated by Ouyang, most of the Palaeozoic-type microspores persisted into the lowest Triassic. Peng et al. (2006) have also established three distinct palynological assemblages across the PTB stratigraphic set (PTBST, term of Peng et al., 2006) in two terrestrial PTB sections of WGEY, namely Chahe and Zhejue (Fig. 3) (see online supplementary data Tables S1 and Figs. S5-7). Assemblage 1 of Peng et al. (2006), established from the upper Xuanwei Formation of Changhsingian age, is dominated by ferns and pteridosperms, with few gymnosperms. Most taxa are typical long-ranging Palaeozoic forms for this assemblage (Peng et al., 2006). Assemblage 2 was recognized from the PTBST and is marked by an abrupt decrease in palynomorph abundance and diversity, and thriving fungal/algal (?) spores. Although Assemblage 2 is still dominated by ferns and pteridosperms, with a few gymnosperms, it is characterized by a mixed palynoflora containing both Late Permian and Early Triassic

ACCEPTED MANUSCRIPT elements. Most taxa are typical Late Permian elements, which also occurred in Assemblage 1. However, some taxa of Early Triassic aspect such as Lundbladispora appeared for the first

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time in Assemblage 2. Assemblage 3, ranging from the uppermost Xuanwei Formation to lowest Kayitou Formation, saw a rapid increase in the proportion of gymnosperm pollen

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grains, exceeding that of ferns and pteridosperms. Nevertheless, abundance of palynomorphs

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still remains rather low. Typical Early Triassic taxa such as Lundbladispora and Aratrisporites are present in a greater abundance (Ouyang, 1982) and confirm an Early

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Triassic age for this assemblage.

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A few microspores have been obtained from four non-marine PTB sections (Mide, Chahe, Zhejue and Jiucaichong sections) by Bercovici et al. (2015). Compared with palynological assemblages established by Peng and Shi (2009), both common features are: an

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‘‘anomalously high abundance’’ of fungal spores and Reduviasporonites only occuring within a restricted stratigraphic interval at the very top of the Xuanwei Formation, corresponding to

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latest Permian deposits.

The above palynological studies also verified that some Paleozoic spores and pollen survived the main end-Permian mass extinction event as well. The palynoflora recovered by the palynological Assemblage 2 in the PTBST strongly shows transitional characteristics across the Paleozoic-Mesozoic transition. A few early Triassic elements, such as Aratrisporites yunnanensis, Lundbladispora communis, appeared in Assemblage 2, together with typical Paleozoic survivors (mainly spores). Similar transitional palynomorph assemblages are found all over the world, such as at the Kap Stosch and Jameson Land in East Greenland (Balme, 1980), Meishan section of Changxing, China (Ouyang & Utting, 1990).

7.2 Megaspore found in the Earliest Triassic of the Kayitou Formation

ACCEPTED MANUSCRIPT In addition, we have also found an abundant and diverse megaspore assemblage from the Early Triassic successions in WGEY (Li et al., 2014; Yu et al., 2010). In particular, the

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dispersed and in situ megaspores of Annalepis and Pleuromeia are very common in association with the Early Triassic fossil plants in WGEY. They include the Lycopsida pyramidalis,

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rotundus,

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parvus,

Triangulatisporites

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Maexisporites

sp.,

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Aneuletes

rotundus,

A.

sp.,

Otynisporites

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dalongkonensis, Trileites levis, T. vulgaris, Trileites sp., Horstisporites sulcatus, H. sp., eotriassicus,

Hughesisporites

simplex,

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Banksisporites pinguis, Zerndtisporites sp. (Fig. 14). Of these, the genus Trileites is most

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abundant and contains 8 species. The genus Maexisporites ranks the second most diverse group, including 3 species in Lycopsida.

The palynomorphs obtained from the different sedimentary facies sections of WGEY

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show an abrupt change of palynofloras across the PTB, marked by a distinct drop of palynomorphs in both abundance and diversity. However, it also indicate a stepwise

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extinction pattern as marine fauna did, for mixing palynofloral elements from both Late Permian and Early Triassic found in the PTBST following the end-Permian mass extinction, and most Late Permian survivors disappeared shortly thereafter in the Earliest Triassic.

8. Vegetation changeover across the PTB: extinction, survival and recovery

Stratigraphic distribution shows that both the macro- and microfloras from the WGEY region have suffered a dramatic change in composition, abundance and diversity across the PTB (Fig. 15). The Wuchiapingian flora is characterized by abundant gigantopterids, which were abundant and diverse and commonly present in most of the Upper Permian successions in South China (Fig. 16). The coeval palynoflora was dominated by spores of the Pteridophyta and Pteridospermae. Most genera are characteristics of the Permian Cathaysian elements (i.e.,

ACCEPTED MANUSCRIPT Nixispora and Patellisporites). During the Changhsingian stage, the Gigantopteris flora markedly decreased in species richness and localities (Figs.15 and 16). In contrast, increasing

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representatives of gymnosperms occurred in the Changhsingian palaeoflora. It should be noted that the WGEY flora contains not only many taxa typical of the Late Permian

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Gigantopteris flora (such as Lobatannularia, Fascipteris, Gigantoclea, and Gigantopteris),

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but also rare Triassic-type elements (i.e. Lepidopteris) in the PTTB, and thus, appears a mixture nature of the Permian-type and some Triassic-type floral elements, like the well-

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known mixed faunas near the PTB in marine regime in South China (Chen et al., 2005).

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Most of the Permian-type plant taxa wiped out in the PTB crisis on land with only few relicts persisting into the Early Triassic. Those relict taxa, however, are usually represented by few fragmented specimens from the basal Kayitou Formation, suggesting being transported in

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a long distance or being reworked. In contrast, abundant and well preserved Annalepis representatives characterize the Early Triassic floral assemblage. Those Annalepis elements

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were mainly founded as isolated sporophylls with dispersed and in situ megaspores, and in association with strobile-like forms, indicating a transport on a short distance (Fig. 11C). Accordingly, the vegetation changeover across the PTB is marked by a dramatic turnover of plants on land from the Permian Gigantopteris flora to the Triassic Annalepis-dominated assemblage.

Palaeogeographically, The Wuchianpingian Gigantopteris flora was widespread over the entire South China block and also extended to Tibet. In contrast, the Changhsingian floral distribution became restricted to the WGEY region and the southern Sichuan of the Yangtze Platform, occurring sporadically in the adjacent Jiangnan Block during that time (Fig. 16). After the PTB biocrisis on land, the earliest Triassic flora only was discovered in the WGEY, Southwest China, which may have acted as a refuge for plants to survive the PTB extinction. Therefore, some rare Gigantopterid elements survived from the PTB mass extinction. The

ACCEPTED MANUSCRIPT presence of foliage and reproductive organs of Peltaspermum in the Kayitou Formation indicates that this genus survived the PTB mass extinction. The first appearance of Annalepis,

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a pioneering lycopsid genus, and its proliferation marks a first step of the recovery of land plants after the PTB crisis on land in WGEY.

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In addition, the palynomorphs recorded from the different sedimentary facies sections of

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WGEY show an abrupt change of palynofloras across the PTB, marked by a distinct drop of palynomorphs in both abundance and diversity. However, it also indicates a stepwise

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extinction pattern as observed in the marine faunas temporal distribution. There are also

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evidences for mixing of palynofloral elements from both Late Permian and Early Triassic found in the PTTB following the end-Permian mass extinction. Most Late Permian survivors

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disappeared shortly thereafter in the Earliest Triassic.

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9. Palaeoclimate changes over the P-Tr transition in WGEY

The updated palaeogeographic reconstructions (Ziegler et al., 2003; Yin et al., 2013) show that the South China block was located nearby the equatorial zone during the PermianTriassic transition, whereas the North China block and Europe were close to the northern tropic latitude characterized by arid climates. Therein, the South China block had a warm and humid climate condition favorable to the development of coal-forming swamps (Golonka et al., 1994; Yin et al., 1999; Fluteau et al., 2001). Nevertheless, the periods of significant coal accumulations, linked with terrestrial environment, varied in different areas depending on various episodes of marine transgression-regression throughout the Permian times. In Zhejiang, Fujian and northeastern Guangdong Provinces, eastern part of South China, coal measures deposited only during the Capitanian (late Middle Permian) to Wuchiapingian (early Late Permian) (Fig. 17), whereas the Changhsingian deposits were fully marine facies

ACCEPTED MANUSCRIPT due to the late Wuchiapingian transgression prevailing in those areas (Chen et al., 1998). In Hunan, Jiangxi, northern Guangdong, and eastern Guangxi Provinces, central part of South

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China, coal measures were deposited only during the Wuchiapingian when terrestrial-marine transitional deposits overlaid the marine Middle Permian rocks (Figs. 16-17). In contrast, the

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coverage of the Changhsingian coal measures retrogrades to the southern part of the Upper

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Yangtze Platform (Li and Yao, 1980; Yu et al., 2007) due to the succeeding transgression that generated massive carbonate platforms and reef settings across the entire South China block

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in that time (Chen et al., 1998). In contrast, the coal measures were continuously deposited

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through the early Late Permian until the latest Permian in WGEY (e.g. the Tucheng section, in which the last Permian bed deposited at the top of the Xuanwei Formation, covered by the first Triassic marine bed i.e. just below the PTB, is a coal seam being likely the youngest

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Permian coal deposit in South China, Fig. 3e). These coal measures originated from accumulations of tropical Gigantopteris floral elements in swampy areas (Yao, 1978). A

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general picture of temporal distributions of coal measures shows that the Permian coalbearing strata tended to migrate from east to west throughout the Permian across the entire South China due to the westward migration of coal forming-swamp habitats (Fig.17). Conversely in North China, far from the sea during the Late Permian, the coal-forming environments decreased strongly due to a severe warming giving rise to a hot and arid climatic condition. At the same time Euramerican plants, especially meso-xerophytic woody scrubs (Dimichele, 2014), dominated by Ullmannia-like conifers, migrated to this region. The uppermost Xuanwei Formation palaeofloral assemblage of latest Permian age contains abundant coal-forming plant taxa: Lepidodendron, Paracalamites, gigantopterids, and other forms. Thus, the latest Permian climatic condition of the WGEY region was humid and warm. Although the coal measures disappeared in the Kayitou Formation, the Induan floral assemblage contains some surviving swampy plant such as Paracalamites that co-

ACCEPTED MANUSCRIPT existed with Annalepis in the basal deposits of the Kayitou Formation, as some fragments of gigantopterids and Peltaspermales in the higher horizons of the formation (Fig.4d-e). Those

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climatically sensitive plant taxa reflected that the humid and warm climate still prevailed in the WGEY region during the Early Triassic, just like the latest Permian climatic condition in

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the same region.

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The plant-based inference of the P-Tr climates is reinforced by palynofloral assemblages across the PTB in WGEY. Palynological data published by Ouyang (1982) and Peng et al.

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(2006) showed that some Palaeozoic plants that inhabited in humid and warm climate

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persisted into the earliest Triassic time in WGEY. Accordingly, both macro- and microfloral assemblages indicate that the latest Permian humid and warm climate was inherited to the Early Triassic in the WGEY region. However, it should be noted that climatic conditions in

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many Late Permian continents, for instance, the Karoo Basin of South Africa (Ward et al., 2000), the Urals of Russia (Benton et al., 2004), the Junggar basin of Xinjiang, northwest

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China (Yang et al., 2010) have begun to undergo a change to a dry and hot climate from the latest Permian to the Early Triassic. In contrast, the warm, humid climatic condition prevailed over the P-Tr transition in WGEY, which may have provided suitable climatic condition for some Permian plant relicts to survive the PTB biocrisis and the rise of some Mesozoic pioneers in Early Triassic in WGEY.

10. Conclusions

(1) The Late Permian Changhsingian Xuanwei Formation yields abundant fossil plants, 105 species in 39 genera, which are assigned to the L-G Assemblage. The Gigantopteris flora gradually declined during the Changhsingian and suffered a dramatic decline in biodiversity in the LPME with a few relics persisting into the earliest Triassic in the WGEY region. The

ACCEPTED MANUSCRIPT earliest Triassic Kayitou Formation yields 18 plant species in 14 genera, which are assigned the A-P Assemblage. A great number of dispersed sporophylls, and in situ megaspores of the

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Annalepis, occurred immediately after the LPME. Sterile pinna, fertile organs of the Peltaspermaceae and gigantopterids were also mixed in the earliest Triassic floral assemblage,

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dominated by the Annalepis remains and associated with the earliest Triassic marine faunas of

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ammonoids Ophiceras, bivalves Pteria and Towapteria, and brachiopod Lingularia in the marine beds of the marine-terrestrial transitional sections in WGEY.

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(2) During the P-Tr transition some rare gigantopterids representatives survived the

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LPME, but preserved only as tiny fragments (possibly reworked?). The presence of foliage and reproductive organs of Peltaspermum in the Kayitou Formation indicates that this genus truly survived the LPME. Annalepis acted as a pioneering lycopsid genus initiating the

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recovery of land plants at the beginning of the Triassic. After the PTB biocrisis on land, the earliest Triassic flora in the WGEY region, Southwest China may have served as a refuge for

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plants to survive the LPME. Vegetation changeover across the PTB is then marked by a dramatic turnover of plants on land from the Permian Gigantopteris flora to the Triassic Annalepis-dominated assemblage. Palynofloras are characterized by a dramatic drop of palynomorphs in both abundance and diversity and show a stepwise extinction pattern. (3) Temporal and spatial distributions of the Late Permian Gigantopteris flora show that the coal forming-swamps gradually migrated from east to west across the entire South China. Both macro- and microfloras indicate that humid and warm climatic regimes prevailed over the P-Tr transition. The persistence of suitable climate conditions may have been crucial for plants to survive and recover from the LPME in WGEY.

Acknowledgments This work was supported by the NSFC (project no. 40972002, 41272024 and 41272372),

ACCEPTED MANUSCRIPT and the State Key Laboratory of Biogeology and Environmental Geology, China University

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of Geosciences, Wuhan (program: GBL11302).

References

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Balme B.E., 1970. Palynology of Permian-Tiassic strata in the Salt Range and Surghar, West

SC

Pakistan. In B. Kummel & C. Teichert (Eds.), Stratigraphic Boundary Problems: Permian and Triassic of West Pakistan. University of Kansas, Special Publication 4, pp.306-453.

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Benton, M.J., Tverdokhlebov, V.P., & Surkov, M.V., 2004. Ecosystem remodeling among

MA

vertebrates at the Permian-Triassic boundary in Russia. Nature 432, 97-100. Bercovici, A., Ying, C., Forel, M-B., Yu, J., Vajda, V., 2015. Terrestrial palaeoenvironment

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Earth Sciences 98, 225-246.

D

characterization across the Permian-Triassic boundary in South China. Journal of Asian

Chen, Z.Q., Benton, M.J., 2012. The timing and pattern of biotic recovery following the end-

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Permian mass extinction. Nature Geoscience 5, 375-383. Chen, Z.Q., Jin, Y.G., Shi, G.R., 1998. Permian transgression-regression sequences and sealevel changes of South China. Proceeding of the Royal Society of Victoria 110, 345-368. Chen, Z.Q., Kaiho, K., George, A.D., 2005. Survival strategies of brachiopod faunas from the end-Permian mass extinction. Palaeogeography, Palaeoclimatology, Palaeoecology 224, 232-269. Chen, Z.Q., George, A.D., Yang, W.R., 2009. Effects of Middle–Late Permian sea-level changes and mass extinction on the formation of the Tieqiao skeletal mound in the Laibin area, South China. Australian Journal of Earth Sciences 56, 745-763. Chen, Z.Q., Chen J., Tong, J.N., Fraiser, M.L. 2011. Marine ecosystem changes from the latest Permian to Middle Triassic in Qingyan area, Guizhou, Southwest China. Journal of Earth Science 21, 125-129.

ACCEPTED MANUSCRIPT Chu, D.L., Tong, J.N., Yu, J.X., Song, H.J., Tian, L., 2013. The conchostracan fauna from the Kayitou Foramtion of western Guizhou, China. Acta palaeontologica Sinica 52, 265-276.

PT

( in Chinese with English abstract)

tropics. Journal of Plants Sciences, 175, 123-164.

RI

DiMichele, W.A., 2014. Wetland-dryland vegetational dynamics in the Pennsylvanian ice age

SC

DiMichele, W.A., Kerp, H., Krings, M., Chaney, D.S., 2005. The Permian peltasperm radiation: Evidence from the southwestern United States. New Mexico Museum of

NU

Natural History and Science Bulletin 30, 67-79.

MA

Erwin, D.H., 1994. The Permo-Triassic extinction. Nature 367, 231-236. Fliche, P., 1910. Flore fossile du Trias en Lorraine et Franche-Comté (avec des considérations finales par M. R. Zeiller). Bulletin de la Société des Sciences de Nancy III, XI 1, 222-286.

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D

Fluteau, F., Besse, J., Broutin, J. & Ramstein, G., 2001. The Late Permian climate: what can be inferred from climate modelling concerning Pangea scenarios and Hercynian range

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altitude? Palaeogeography, Palaeoclimatology, Palaeoecology 167, 39-71. Galtier, J., Broutin, J., 2008. Floras from red beds of the Permian Basin of Lodève (Southern France). Journal of Iberian Geology 34, 57-72. Gand, G., Kerp, H., Parsons, C., Martinez-Garcia, E., 1997. Palaeoenvironmental and stratigraphic aspects of animal traces and plant remains in Spanish Permian red beds (Pena Sagra, Cantabrian Mountains, Spain). Geobios 30, 295-318. Golonka, J., Ross, J. I., Scotese, C. R., 1994. Phanerozoic paleogeographic and paleoclimatic modeling maps. In: Embry, A. F., et al. (Eds), Pangea: global environments and resources. Canadian Society of Petroleum Geologists Memoir, 17, pp.1-47. Gomankov, A.V., Meyen, S.V., 1980. On representatives of the family Peltaspermaceae from the Permian of the Russian platform. Palaeontological Journal 13, 240-254. Grauvogel-Stamm, L., Duringer, P., 1983. Annalepis zeilleri Fliche 1910 emend., un organe

ACCEPTED MANUSCRIPT reproducteur de Lycophyte de la Lettenkohle de l’Est de la France. Morphologie, spores in situ et paléoécologie. Geologische Rundschau 72, 23-51.

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Grauvogel-Stamm L., Lugardon, B., 2001. The Triassic Lycopsids Pleuromeia and Annalepis: relationship, evolution and origin. American Fern Journal 91, 115-149.

RI

Haq, B.U., Shutter, S.R., 2008, A chronology of Paleozoic sea-level changes. Science 322, 64-

SC

68.

Harris, T.M., 1937. The fossil flora of Scoresby Sound, East Greenland. Part 5: Stratigraphic

NU

relations of the plant beds. Meddelelser om Grønland 112, 1-114.

MA

He, B., Xu, Y.G., Wang, Y.M., Xiao, L., 2005. Nature of the Dongwu Movment and its temporal and spatial evolution. Earth Science – Journal of China University of

D

Geosciences 30, 89-96.

TE

Huang, B.H., 1996. The Angara flora from North China. Palaeobotanist 45, 309-314.

AC CE P

Huang, B., Ding, Q., 1998. The Angara flora from North China. Acta Geoscientia Sinica, Geologica Sciences 19, 97-104. Kerp, H., Broutin J., Lausberg S., Aassoumi H., 2001. Discovery of latest CarboniferousEarly Permian radially symmetrical peltaspermaceous megasporophylls from Europe and North Africa. Comptes Rendus de l’Académie des Sciences, Sciences de la Terre 332, 513-519. Kozur, H.W., Weems, R.E., 2010. The biostratigraphic importance of conchostracans in the continental Triassic of the northern hemisphere. In: Lucas, S. G. (ed.), The Triassic Timescale. Geological Society, London, Special Publications, 334, 315– 417. Kustatscher, K., Wachtler, M., Van Konijnenburg–Van Cittert, J.H.A., 2010. Lycophytes from the Middle Triassic (Anisian) locality Kühweiesenkopf (Monte Prà della Vacca) in the Dolomites (Northern Italy). Palaeontology 53, 595-626. Li H., Yu J.X., Huang, Q.S., Shi, X., Huang, C., 2014. Geological significances of the

ACCEPTED MANUSCRIPT lycopods megaspores from the early Triassic Kayitou formation of the Western Guizhou and Eastern Yunnan Region. Journal of Lanzhou University (Natural Sciences) 50 (2), 1-

PT

11.

Guangdong Science and technology Press, 1-695.

RI

Li X.X., (ed.), 1995. Fossil floras of China through the geological ages. Guangzhou:

SC

Li, X.X., Yao, Z.Q., 1980. Permian coal-bearing formations in South China. Journal of

NU

Stratigraphy 4, 241-255 (In Chinese).

Liu, X., Gituru, W.R., Wang, Q.F., 2004. Distribution of basic diploid and polyploid species of

MA

Isoetes in East Asia. Journal of Biogeography 31, 1239-1250. Looy C.V., Twitchett R.J., Dilcher D.L., Van Konijnenburg-Van Cittert J.H., Visscher H., 2001.

TE

USA 98, 7879-7883.

D

Life in the end-Permian dead zone. Proceedings of the National Academy of Sciences,

AC CE P

Mangerud, G., 1994. Palynostratigraphy of the Permian and lowermost Triassic succession, Finnmark Platform, Barents Sea. Review of Paleobotany and Palynology 82, 317-349. McElwain, J.C., Popa, S.P., Hesselbo, S.P., Haworth, M and Surlyk, F., 2007. Macroecological responses of terrestrial vegetation to climatic and atmospheric change across the Triassic/Jurassic boundary in East Greenland. Paleobiology 33, 543-573 Meng, F.S., 1994. Discovery of Pleuromeia - Annalepis flora in South China and its significance. Chinese Science Bulletin 39, 130-134. Meng, F.S., 1996. Middle Triassic Lycopsid flora and its palaeoecological significance in South China. Palaeobotanist 45, 334-343. Meng, F.S., 1998. Studies on Annalepis from Middle Triassic along the Yangtze River and its bearing on the origin of Isoetes. Acta Botanica Sinica 40, 768-774 (in Chinese with English abstract).

ACCEPTED MANUSCRIPT Meng, F.S., Zhang, Z.L., Niu, Z.J., Chen D.Y., 2000. Primitive lycopsid flora in the Yangtze Valley of China and systematics and evolution of Isoetales. Hunan Science and

PT

Technology Press, Hunan (in Chinese with English abstract). Metcalfe, I., Nicoll, R.S., 2007. Conodont biostratigraphic control on transitional marine to Permian-Triassic

boundary

sequences

in

Yunnan-Guizhou,

RI

non-marine

China.

SC

Palaeogeography, Palaeoclimatology, Palaeoecology 252, 56-65.

NU

Meyen, S.V., 1984. Basic features of gymnosperm systematics and phylogeny as evidenced by the fossil record. The Botanical Review 50, 1-112.

MA

Michaelsen, P., 2002. Mass extinction of peat-forming plant and the effect on fluvial styles across the Permian-Triassic boundary, northern Bowen basin, Australia. Palaeogeography,

D

Palaeoclimatology, Palaeoecology 179, 173-188.

TE

Naugolnykh, S.V., Kerp, J.H.F., 1996. Aspects of Permian palaeobotany and palynology. XV.

AC CE P

On the oldest known peltasperms with radially symmetrical ovuliferous discs from the Kungurian (uppermost Lower Permian) of the fore-Urals (Russia). Review of Palaeobotany and Palynology 91, 35-62. Ouyang, S., 1982. Upper Permian and Lower Triassic palynomophs from eastern Yunnan. Canadian Journal of Earth Sciences 19, 68-80. Ouyang S., 1986. Palynology of Upper Permian and Lower Triassic strata of Fuyuan district, eastern Yunnan. Science Press, Beijing. 122 pp. (in Chinese with English Summary). Ouyang S. and Utting J., 1990. Palynology of Upper Permian and Lower Triassic rocks, Meishan, Changxing County, Zhejiang province, China. Review of Palaeobotany and Palynology 66, 65-103. Ouyang, S., and Norris, G., 1999. Earliest Triassic (Induan) spores and pollen from the Junggar Basin, Xinjiang, northwestern China. Review of Palaeobotany and Palynology 106, 1-56.

ACCEPTED MANUSCRIPT Peng, Y.Q., Zhang, S.X., Yu, J.X., Yang, F.Q., Gao, Y.Q., Shi, G.R., 2005. High-resolution terrestrial Permian-Triassic eventostratigraphic boundary in western Guizhou and eastern

PT

Yunnan, southwestern China. Palaeogeography, Palaeoclimatology, Palaeoecology 215, 285-295.

RI

Peng Y.Q., Yu J.X., Gao Y.Q., Yang F.Q., 2006. Palynological assemblages of non-marine

SC

rocks at the Permian-Triassic boundary, western Guizhou and eastern Yunnan, South

NU

China. Journal of Asian Earth Sciences 28, 291-305.

Peng, Y.Q., Shi, G.R. 2009. Life crises on land across the Permian–Triassic boundary in South

MA

China. Global and Planetary Change 65 (3-4), 155-165. Poort, R.J., Kerp, J. H. F., 1990. Aspects of Permian palaeobotany and palynology. XI. On the

D

recognition of true peltasperms in the Upper Permian of Western and Central Europe and

TE

a reclassification of species formerly included in Peltaspermum Harris. Review of

AC CE P

Palaeobotany and Palynology 63, 197-225. Retallack, G.J., 1975. The life and times of a Triassic lycopod. Alcheringa 1, 3-29. Retallack, G.J., 1995. Permian-Triassic life crisis on land. Science 267, 77-80. Retallack, G.J., 1997. Earliest Triassic origin of Isoetes and quillwort evolutionary radiation. Journal of Paleontology 71, 500-521. Shen, J., Lei, Y., Thomas J.A., Feng, Q.L., Thomas S., Yu, J.X., Zhou L., 2013. Volcanic effects on microplankton during the Permian-Triassic transition (Shangsi and Xinmin, South China). Palaios 28, 552–567. Shen, S.Z., Crowiley, J.L., Wang, Y., Bowring, S.A., Erwin, D.H., Sadler, P.M., Cao, C.Q., Rothman, D.H., Henderson, C.M., Ramezani, J., Zhang, H., Shen, Y.A., WANG, X.D., Wang, W., Mu, L., LI, W.Z., Tang, Y.G., LIU, X.L., Liu, L.J., Zeng, Y., Jiang, Y.F., and Jin, Y.G., 2011. Calibrating the end-Permian mass extinction: Science 334, 1367-1372.

ACCEPTED MANUSCRIPT Srivastava, A.K., Krassilov, V.A., Agnihotri, D., 2011. Peltasperms in the Permian of India and their bearing on Gondwanaland reconstruction and climatic interpretation.

PT

Palaeogeography, Palaeoclimatology, Palaeoecology 310, 393-399. Tian, Y.T., Yu, J.X., Feng, Q.L., 2008. The Discovery of Ophiceras in the Kayitou Formation

RI

in Eastern Yunnan Province and Its signification. Journal of Stratigraphy 32, 153-158.

SC

Utting, J., 1989. Preliminary palynological zonation of surface and subsurface sections of

NU

Carboniferous, Permian and Lowest Triassic rocks, Sverdrup Basin, Canadian Arctic Archipelago. Geological Survey of Canada, Paper 89-1G, 233-240.

MA

Visscher H., 1971. The Permian and Triassic of the Kingscount Outlier, Ireland. Geological Survey of Ireland, special Paper, No. 1.

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Wang, Y., Jin, Y.G., 2000. Permian palaeogeographic evolution of the Jiangnan Basin, South

TE

China. Palaeogeography, Palaeoclimatology, Palaeoecology, 160: 35-44. Wang, Z.Q., 1997. Permian Supaia fronds and an associated Autunia fructification from

AC CE P

Shanxi, China. Palaeontology 40, 245-277. Wang, Z.Q., Wang, L.X., 1990. Late Early Triassic fossil plants from upper part of the Shiqianfeng Group in North China. Shanxi Geology 5, 97-154. (in Chinese with English abstract)

Wang, S.Y., Yin, H.F., 2001. Study on terrestrial Permian–Triassic boundary in eastern Yunnan and western Guizhou. China University of Geosciences Press, Wuhan. 88 pp. (in Chinese with English abstract). Ward, P.D., Montgomery, D.R., Smith, R.M.H., 2000. Altered river morphology in South Africa related to the Permian-Triassic extinction. Science 289, 1740-1743. White, D., 1929. Flora of the Hermit Shale, Grand Canyon, Arizona. Bulletin of the Carnegie Institution of Washington 405, 1-221. Yang F.Q., Yin H.F., Yu J.X., Zhang S.X., Huang J.H., Peng Y.Q., Huang Q.S., Zhao Q.M.,

ACCEPTED MANUSCRIPT 2005. Study of the terrestrial Permian-Triassic boundary in Chahe, Weining, Guizhou Province. Science in China (Series D) 35, 519-529 (in Chinese).

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Yang, W., Feng, Q., Liu, Y.Q., Tabor, N., Miggins, D., Crowley, J., Lin, J.Y., Thomas, S., 2010. Depositional Environments and Cyclo- and Chronostratigraphy of Uppermost

RI

Carboniferous-Lower Triassic Fluvial-Lacustrine Deposits, Southern Bogda Mountains,

SC

NW China – A Terrestrial Paleoclimatic Record of Mid-Latitude NE Pangea. Global and Planetary Change 73, 15–113.

NU

Yao, Z.Q., 1978. On the age of “Gigantopteris coal series” and Gigantopteris-flora in South

MA

China. Acta Palaeontologica Sinica 17, 81-89 (in Chinese with English abstract). Yao, Z.Q., Xu, J.T., Zhen, Z.G., Zhao, X.G., Mo, Z.G., 1980. Late Permian biostratigraphy and

D

the Permian-Triassic boundary in western Guizhou and eastern Yunnan. In: Nanjing

TE

Institute of Geology and Palaeontology (Eds.), Stratigraphy and Palaeontology of Late Permian coal-bearing formations in western Guizhou and eastern Yunnan. Science Press,

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Beijing, pp. 1-69 (in Chinese).

Ye, M.N., 1979. On some Middle Triassic plants from Hupeh and Szechuan. Acta Palaeontologica Sinica 18, 73-82 (in Chinese with English abstract). Yin H.F., Ding M.H., Zhang K.X., Tong J.N., Yang F.Q., Lai X.L., 1995. DongwuanIndosinian (Late Permian-Middle Triassic) ecostratigraphy of the Yangtze region and its margins. Science Press, Beijing, 1-338. Yin, H.F., Wu, S.B., Du, Y.S., Peng, Y.Q., 1999. South China defined as part of Tethyan archipelagic ocean system. Earth Science-Journal of China University of Geosciences 24, 1-12 ( in Chinese with English abstract). Yin H.F., Zhang, K.X., Tong, J.N., Yang, Z.Y., Wu, S.B., 2001. The Global Stratotype Section and Point (GSSP) of the Permian-Triassic Boundary. Episodes 24, 102-114.

ACCEPTED MANUSCRIPT Yin H.F., Yang F.Q., Yu J.X., Peng Y.Q., Zhang S.X., Wang S.Y., 2007. An accurately delineated terrestrial Permian-Triassic Boundary and its implication. Science in China (D)

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50, 1281-1292. Yin, H.F., Jiang, H.S., Xia, W.C., Feng, Q.L., Zhang, N., Shen, J., 2013. The end-Permian

RI

regression in South China and its implication on mass extinction: Earth-Science Reviews,

SC

doi: 10.1016/j.earscirev.2013.06.003.

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Yu, J.X., 2008. Floras (macro- and microfloras) and evolutionary dynamics across the Permian-Triassic boundary along Guizhou and Yunnan border, South China, PhD Thesis,

(unpublished,

web

access:

http://cdmd.cnki.com.cn/article/CDMD-104-10491-

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200809651.htm)

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University Geosciences China Wuhan – University Pierre et Marie Curie, Paris 6, 220 p.

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Yu, J.X., Peng, Y.Q., Zhang, S.X., Yang, F.Q., Zhao, Q.M., Huang, Q.S., 2007. Terrestrial events across the Permian–Triassic boundary along the Yunnan–Guizhou border, SW

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China. Global and Planetary Change 55, 193-208. Yu, J.X., Broutin, J., Huang, Q.S., Grauvogel-Stamm, L., 2010. Annalepis, a pioneering lycopsid genus in the recovery of the Triassic land flora in South China. Comptes Rendus Palevol 9, 479-486.

Zalessky, M.D., 1939. Permian vegetation in the Ural Basin. In: Problems of Palaeontology, Moscow University Publish, Moscow 5, 329-374. Zhang, S.X., Peng, Y.Q., Yu, J.X., Lei, X.R., Gao, R.Q., 2006. Characteristics of claystones across the terrestrial Permian-Triassic boundary: Evidence from the Chahe section, western Guizhou, South China. Journal of Asian Earth Science, 27, 358-370. Zhu, C.Q., Tian,Y.T., Xu,M., Rao, S., Yuan, Y.S., Zhao, Y.Q., Hu, S.B., 2010. The effect of Emeishan supper mantle plume on the thermal evolution of hydrocarbon source rocks in

ACCEPTED MANUSCRIPT the Sichuang Basin. Chinese Journal of Geophysics 53, 83-91. Ziegler, A.M., Eshel, G., Rees, P.M., Rothfus, T.A., Rowley, D., Sunderlin, D., 2003. Tracing

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the tropics across land and sea: Permian to present. Lethaia 36, 227-254.

ACCEPTED MANUSCRIPT Figure captions Figure 1 Location of the studied marine and non-marine PTB sections in western Guizhou and

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eastern Yunnan, southwestern China

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Figure 2 Sketch map of the Permian Changhsingian and Triassic Induan lithofacies and paleogeography in western Guizhou and eastern Yunnan, southwestern China (after Yao et al.,

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Figure 3 Correlation of the lithostratigraphic columns and biostratigraphic zones of the PTB sequence from marine to terrestrial facies in western Guizhou and eastern Yunnan,

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Figure 4 Correlation of PTBST between terrestrial Chahe Section and the GSSP of Meishan Av. Aviculopecten; C. Clarkina; I. Isarcicella; Or. Orthotetina; ls. limestone; cb., claybed

Figure 5 All specimens here described are housed in China University of Geosciences (Wuhan) and University Pierre et Marie Curie-Paris 6. Scale bar: 1cm unless other stated. A. Lepidodendron acutangulum (Halle) Stockman et Mathieu Locality: Mide section, Xuanwei City, Yunnan Province Sample Number: YXM -0-1 B. Sphenophyllum sp. Locality: Chahe section, Xuanwei City, Yunnan Province Sample Number: GWC-4-8 C. Annularia shirakii Kawasaki

ACCEPTED MANUSCRIPT Locality: Mide section, Xuanwei City, Yunnan Province Sample Number: YXM-0-1

Locality: Mide section, Xuanwei City, Yunnan Province

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Sample Number: YXM-12-16

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D. Annularia pingloensis (Sze) Gu et Zhi

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E. Lobatannularia heianensis (Kod.) Kawasaki

Sample Number: GWC-21-1

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F. Schizoneura manchuriensis Kon’no

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Locality: Chahe section, Weining County, Guizhou

Locality: Chahe section, Weining County, Guizhou

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Sample Number: GWC-18-19

Figure 6 All specimens here described are housed in China University of Geosciences (Wuhan)

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and University Pierre et Marie Curie-Paris 6. The scale bar of this figure stands for 1cm unless other stated.

A. Stigmaria ficoides (Sternb.) Brongniart Locality: Zhejue section, Weining County, Guizhou Province Sample Number: GWZ-47-2aff. B, F. Lobatannularia cathaysiana Yao Locality: 1. Chahe section, Weining County, Guizhou 2. Tucheng section, Panxian County, Guizhou Sample Number: GPT-10-1, GWC-21-4 C. Annularia pingloensis (Sze) Gu et Zhi Locality: Chahe section, Weining County, Guizhou Province Sample Number: GWC-18-97

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Sample Number: YXM-0-3 E. Lobatannularia multifolia Kon’no et Asama

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Locality: Tucheng section, Panxian County, Guizhou Province

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Sample Number: GPT-10-2 G. Compsopteris punctinervis Mo

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Locality: Chahe section, Weining County, Guizhou Province

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Sample Number: GWC-28-1

Figure 7 All specimens here described are housed in China University of Geosciences (Wuhan)

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A, H Pecopteris orientalis (Schenk) Potonié Locality: Chahe section, Weining County, Guizhou Province Sample Number: GWC-28-1, GWC-69-7 B. Pecopteris lativenosa Halle

Locality: Chahe section, Weining County, Guizhou Province Sample Number: GWC-58-20 C. Compsopteris imparis Gu et Zhi Locality: Chahe section, Weining County, Guizhou Province Sample Number: GWC-3-7a D. Compsopteris contracta Gu et Zhi Locality: Chahe section, Weining County, Guizhou Province Sample Number: GWC-58-4

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F. Rhabdocarpus sp.

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Locality: Xinmin section, Anshun City, Guizhou Province

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Sample Number: GWC-18-27

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Sample Number: XM-2-6-46 G. Cordaites principalis (Germar) Geinitz

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Locality: Chahe section, Weining County, Guizhou Province

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Sample Number: GWC-53-3

Figure 8 All specimens here described are housed in China University of Geosciences (Wuhan)

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A, Aa Gigantonoclea guizhouensis Gu et Zhi Locality: Mide section, Xuanwei City, Yunnan Province Sample Number: YXM-1-4 B. Gigantonoclea lagrelii (Halle) Koidzumi Locality: Chahe section, Weining County, Guizhou Province Sample Number: GWC-3-8a C. Gigantopteris nicotianaefolia Schenk Locality: Chahe section, Weining County, Guizhou Province Sample Number: GWC-48-1 D. Gigantonoclea plumosa Mo Locality: Tucheng section, Panxian County, Guizhou Province Sample Number: GPT-5-2a

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Figure 9 All specimens here described are housed in China University of Geosciences

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A. Rajahia guizhouensis Zhang

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B. Pecopteris marginata Gu et Zhi

Sample Number: GWC-4-6 C. Fascipteris stena Gu et Zhi

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Locality: Chahe section, Weining County, Guizhou Province Sample Number: GWC-58-14

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D. Gigantopteris dictyophylloides Gu et Zhi Locality: Chahe section, Weining County, Guizhou Province Sample Number: GWC-69-13

Figure 10 All specimens here described are housed in China University of Geosciences (Wuhan) and University Pierre et Marie Curie-Paris 6. The scale bar of this figure stands for 1cm unless other stated. A. Tingia cf. gerardii Stockmans et Mathieu Locality: Chahe section, Weining County, Guizhou Province Sample Number: GWC-3-1 B, Ba. Gigantopteris dictyophylloides Gu et Zhi Locality: Tucheng section, Panxian County, Guizhou Province

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Locality: Chahe section, Weining County, Guizhou Province

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Sample Number: GWC-29-1

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Figure 11 All specimens here described are housed in China University of Geosciences (Wuhan) and University Pierre et Marie Curie-Paris 6. The scale bar of this figure stands for

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A. Fragment of Stigmaria sp.

Locality: Tucheng section, Panxian County, Guizhou Province Sample Number: GPT-17-2

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B, D. Reworked? isolated leaf cushions of Lepidodendron or Sigillaria Locality: Tucheng section, Panxian County, Guizhou Province

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Sample Number: GPT-17-1, GPT-18-1 C, E. Possible Annalepis strobile with megaspores in situ Locality: Tucheng section, Panxian County, Guizhou Province Sample Number: YXM-25-2 F, G, I. Annalepis brevicystis Meng Locality: Mide section, Xuanwei City, Yunnan Province Sample Number: YXM-21-63, YXM-19-21, YXM-19-22 H. Annalepis furongqiaoensis Meng Locality: Mide section, Xuanwei City, Yunnan Province Sample Number: YXM-19-24 J, K. Annalepis zeilleri Fliche Locality: Mide section, Xuanwei City, Yunnan Province

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Figure 12 All specimens here described are housed in China University of Geosciences (Wuhan) and University Pierre et Marie Curie-Paris 6. The scale bar of this figure stands for

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A, B, C, D. Peltaspermum cf. martinsii (Harris) Poort et Kerp

1-Peltaspermum was found in the same layer with Euestheria gutta Lyutkevich

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Locality: 1, 2, 4-Jiucaichong section, Weining County, Guizhou Province

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3- Tucheng section, Panxian County, Guizhou Province Sample Number: GWJ-25-002, GWJ-25-004, GPT-23- 43, GWJ25-007 E, F. Peltaspermum sp.

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Locality: Tucheng section, Panxian County, Guizhou Province Sample Number: GPT-23-4, GPT-22-6

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G. Peltaspermum lobutalum Wang et Wang Locality: Tucheng section, Panxian County, Guizhou Province Sample Number: GPT-22-1

H. Fragment of Gigantopteris sp. Locality: Tucheng section, Panxian County, Guizhou Province Sample Number: GPT-22-9 I. Fragment of Gigantonoclea sp. Locality: Tucheng section, Panxian County, Guizhou Province Sample Number: GPT-23-6 J. ? Pecopteris sp. Locality: Tucheng section, Panxian County, Guizhou Province Sample Number: GPT-22-8

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Sample Number: YXM-25- 4

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Figure 13 Space and time distribution pattern of the genus Peltaspermum in China

Figure 14 Megaspores of the Induan Kayitou Formation at Mide Section, Yunnan Province.

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A Zerndtisporites sp.

Specimen’s number: YXM-B-M-005;

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B Maexisporites pyramidalis Fuglewicz, 1973 Specimen’s number: YXM-B-M-060; C Trileites vulgaris Fuglewicz, 1973 Specimen’s number: YXM-B-M-010; D Trileites levis Fuglewicz, 1973 Specimen’s number: YXM-B-M-237; E Otynisporites eotriassicus Fuglewicz, 1973 Specimen’s number: YXM-B-M-232; F Hughesisporites simplex Fuglewicz, 1977 Specimen’s number: YXM-B-M-105; G Banksisporites pinguis (Harris) Dettmann, 1961 Specimen’s number: YXM-B-M-091;

ACCEPTED MANUSCRIPT H Maexisporites parvus Fuglewicz, 1973 Specimen’s number: YXM-B-M-168;

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I Triangulatisporites dalongkonensis Yang & Sun, 1986

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Specimen’s number: YXM-B-M-045

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Figure 15 Changes in fossil floras of non-marine facies deposits across the Permian-Triassic boundary within the Southwestern China, showing abrupt decline of the coal-forming

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Gigantopteris flora and replacement by a low-diversity lycopod flora

Figure 16 Distribution of the Late Permian Gigantopteris flora localities related with marine

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transgressions in South China

Figure 17 Showing temporal appearance of the Late Permian coal measures in South China

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(after Li and Yao, 1980)

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Figure S2 Stratigraphic distributions of fossil plants across the P-Tr boundary in the Zhejue

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Figure S3 Stratigraphic distributions of fossil plants across the P-Tr boundary in the Mide

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Figure S4 Stratigraphic distributions of fossil plants across the P-Tr boundary in the Tucheng

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Figure S5 Percentage of selected genera and suprageneric groups near Permian-Triassic

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Boundary from the Chahe Section

Figure S6 Percentage of selected genera and suprageneric groups near Permian-Triassic

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Boundary from the Zhejue Section Figure S7 Percentage of selected genera and suprageneric groups near Permian-Triassic Boundary from the Mide Section

ACCEPTED MANUSCRIPT Captions of Supplementary Table Table S1 Palynological categories and content statistic of Latest Permian and

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RI

PT

ACCEPTED MANUSCRIPT

FIgure 12

AC CE P

TE

D

MA

NU

SC

RI

PT

ACCEPTED MANUSCRIPT

Figure 13

Figure 14

AC CE P

TE

D

MA

NU

SC

RI

PT

ACCEPTED MANUSCRIPT

AC CE P

Figure 15

TE

D

MA

NU

SC

RI

PT

ACCEPTED MANUSCRIPT

AC CE P

TE

D

MA

NU

SC

RI

PT

ACCEPTED MANUSCRIPT

Figure 16

AC CE P

TE

D

MA

NU

SC

RI

PT

ACCEPTED MANUSCRIPT

Figure 17

ACCEPTED MANUSCRIPT Table 1 Stratigraphic classification near the terrestrial and marine Permian-Triassic transition

Daye Formation

Yelang Formation

Dalung Formation

Lungtan Formation

Induan

P3

Changhsingian Wuchiapingian

Nearshore facies

RI

Neritic clastic facies

NU

T1

Shallow marine Carbonate facies

Terrestrial facies

Dongchuan Formation

Dongchuan Formation

Kayitou Formation

Kayitou Formation

SC

Stage

PT

in western Guizhou-eastern Yunnan, Southwestern China

Xuanwei Formation

Xuanwei Formation

Emeishan basalt

Emeishan basalt

Maokou Formation

Maokou Formation

P2

MA

Don gwu Movem ent Capitanian

Maokou Formation

Maokou Formation

TE

D

Wordian

AC CE P

Stratigraphic period studied in this paper

Table 2 Genus and species numbers of the paleofloras during the Permian-Triassic transition in western Guizhou and eastern Yunnan Type

Genus

Percentage of species（ species（%）

Species

Changhsingian Induan Changhsingian Induan Changhsingian Induan

Lepidodendrales and Equisetales

4

3

13

6

12.4

33.3

Sphenophyllales

6

2

15

2

14.3

11.1

Filicales Noeggerathiales

7

1

29

1

27.6

5.6

Pteridospermopales

7

3

18

4

17.1

Cycadopsida

2

Ginkgopsida

2

Cordaitopsida

1

3

2.9

Gymnospermum seeds

1

1

1.0

Gigantopteridales Glossopteridales

2

Plantae incertae sedis

3

1

3

2.9

3 1

2

3

4

11

2.9 1

2

2 2

4

22.2

3.8

10.5

5.6

11.1

1.9 2

3.8

11.1

ACCEPTED MANUSCRIPT 2

Total

39

2 14

105

1.9 18

AC CE P

TE

D

MA

NU

SC

RI

PT

Other forms

100.0

100.0