Coryphoid palms from the K-Pg boundary of central India and their biogeographical implications:Evidence from megafossil remains

Ten palm leaf impressions are documented from the latest Maastrichtian(late Cretaceous) to early Danian(earliest Paleocene) sediments(K-Pg,c.66-64 Ma) of the Mandla Lobe of the Deccan Intertrappean Beds,Madhya Pradesh,central India.The palmate leaf shape along with a definite wellpreserved costa support their placement in the subfamily Coryphoideae of the family Arecaceae.We place all recovered palm leaf specimens in the fossil genus Sabalites,report seven species of coryphoid palms and describe two new species namely,Sabalities umariaensis sp.nov.and Sabalites ghughuaensis sp.nov.The fossils indicate that coryphoid palms were highly diverse in central India by the latest Cretaceous.These and earlier reported coryphoid palm fossils from the same locality indicate that they experienced a warm and humid tropical environment during the time of deposition.These discoveries confirm the presence of a diversity of Coryphoideae in Gondwana prior to the India-Eurasia collision and provide information about coryphoid biogeographical history over geological time.Based on megafossil remains,we trace coryphoid palm migration pathways from India to mainland Southeast(SE) Asia and other parts of Asia after the docking of the Indian subcontinent with Eurasia early in the Paleogene.

Siwalik plant megafossil diversity in the Eastern Himalayas: A review

The Eastern Himalayas are renowned for their high plant diversity.To understand how this modern botanical richness formed,it is critical to investigate past plant biodiversity preserved as fossils throughout the eastern Himalayan Siwalik succession(middle Miocene-early Pleistocene).Here,we present a summary of plant diversity records that document Neogene floristic and climate changes.We do this by compiling published records of megafossil plant remains,because these offer better spatial and temporal resolution than do palynological records.Analyses of the Siwalik floral assemblages based on the distribution of the nearest living relative taxa suggest that a tropical wet evergreen forest was growing in a warm humid monsoonal climate at the deposition time.This qualitative interpretation is also corroborated by published CLAMP(Climate Leaf Analysis Multivariate Program) analyses.Here,we also reconstruct the climate by applying a new common proxy WorldClim2 calibration.This allows the detection of subtle climate differences between floral assemblages free of artefacts introduced by using different methodologies and climate calibrations.An analysis of the Siwalik floras indicates that there was a gradual change in floral composition.The lower Siwalik assemblages provide evidence of a predominance of evergreen elements.An increase in deciduous elements in the floral composition is noticed towards the close of the middle Siwalik and the beginning of the upper Siwalik formation.This change reflects a climatic difference between Miocene and Plio-Pleistocene times.This review helps us to understand under what paleoenvironmental conditions plant diversity occurred and evolved in the eastern Himalayas throughout the Cenozoic.

Cenozoic topography,monsoons and biodiversity conservation within the Tibetan Region:An evolving story

The biodiversity of the Himalaya,Hengduan Mountains and Tibet,here collectively termed the Tibetan Region,is exceptional in a global context.To contextualize and understand the origins of this biotic richness,and its conservation value,we examine recent fossil finds and review progress in understanding the orogeny of the Tibetan Region.We examine the deep-time origins of monsoons affecting Asia,climate variation over different timescales,and the establishment of environmental niche heterogeneity linked to topographic development.The origins of the modern biodiversity were established in the Eocene,concurrent with the formation of pronounced topographic relief across the Tibetan Region.High(>4 km)mountains to the north and south of what is now the Tibetan Plateau bounded a Paleogene central lowland(<2.5 km)hosting moist subtropical vegetation influenced by an intensifying monsoon.In mid Miocene times,before the Himalaya reached their current elevation,sediment infilling and compressional tectonics raised the floor of the central valley to above 3000 m,but central Tibet was still moist enough,and low enough,to host a warm temperate angiosperm-dominated woodland.After 15 Ma,global cooling,the further rise of central Tibet,and the rain shadow cast by the growing Himalaya,progressively led to more open,herb-rich vegetation as the modern high plateau formed with its cool,dry climate.In the moist monsoonal Hengduan Mountains,high and spatially extensive since the Eocene but subsequently deeply dissected by river incision,Neogene cooling depressed the tree line,compressed altitudinal zonation,and created strong environmental heterogeneity.This served as a cradle for the then newly-evolving alpine biota and favoured diversity within more thermophilic vegetation at lower elevations.This diversity has survived through a combination of minimal Quaternary glaciation,and complex relief-related environmental niche heterogeneity.The great antiquity and diversity of the Tibetan Region biota argues for its conservation,and the importance of that biota is demonstrated through our insights into its long temporal gestation provided by fossil archives and information written in surviving genomes.These data sources are worthy of conservation in their own right,but for the living biotic inventory we need to ask what it is we want to conserve.Is it 1)individual taxa for their intrinsic properties,2)their services in functioning ecosystems,or 3)their capacity to generate future new biodiversity?If 2 or 3 are our goal then landscape conservation at scale is required,and not just seed banks or botanical/zoological gardens.

Environmental adaptations and constraints on latest Cretaceous Arctic dinosaurs

The Arct ic hosts an extraordinary wealth of terrestrial fossil biotas of Late Cretaceous age representing a diverse and highly productive near-polar ecosystem that has no modern analogue. Compared to the rest of the Late Cretaceous Maastrichtian plant diversity was at its lowest and the temperature regime the coolest, yet the semi-open forests supported a rich dinosaur fauna made up of a wide range of body sizes and feeding strategies. The combination of mild winter temperatures and continuous darkness lasting several months imposed severe constraints on primary productivity. Plant survival strategies involved almost universal winter loss of foliage, which in turn limited food supply for non-migratory overwintering herbivorous animals. A combination of leaf form and tree ring studies has been used to quantify year round variations in temperature and determine the tim-ing of spring bud-break and autumnal leaf fall. While Maastrichtian winter temperatures were cold enough （down to - 10°C for brief intervals） for frequent frosts and snowfall, summer temperatures were cool but highly variable and at -830N along the north Alaskan coast frequently fel l below ＋ 10°C . Theropod egg shell frag-ments at - 76° N in the Maastrichtian of Northeastern Russia may indicate that dinosaur reproduction took place in the Arctic ecosystem, as distinct from taking place at lower latitude breeding grounds reached by migration. This raises the question of nest management and specifically the maintenance of incubation temperatures, and the duration of incubation. Of critical importance to year-round residency is the timing of hatching and juvenile care before winter darkness set in, temperatures fell to near freezing and food resources became limited.

Earliest megafossils of scandent calamoid palms from the Deccan Intertrappean Beds of Central India and their paleobiogeographic implications

Two well-preserved petrified palm stems from the latest Maastrichtian(Late Cretaceous) to earliest Danian(Early Paleocene) sediments of the Deccan Intertrappean Beds of Madhya Pradesh, Central India are described. Their significant anatomical characteristics include a Calamus-type general stem pattern,the presence of well-preserved fibrovascular bundles(fvbs) with two wide metaxylem vessel elements(230 μm-250 μm) and one phloem strand, uniform density of fvbs, lack of continuity between protoxylem and metaxylem vessel elements, and an absence of centrifugal differentiation of sclerenchymatous fibrous parts.These features reveal a close resemblance to those of extant genera of scandent Calamoideae. The permineralized stems are described as a new species namely, Palmoxylon calamoides Kumar, Roy et Khan sp. nov.The fossils represent the oldest reliable fossil records of this family, supporting their Gondwanan origin, their importance in tracing their migration pathways from India to Europe and other continents after the docking of the Indian subcontinent with Eurasia during the Paleocene, and an “Out-of-India” dispersal hypothesis. Today the subfamily Calamoideae is disjunctly occurred in Africa, Asia, Australia, Europe, and South America, but the poor deep-time fossil record of this subfamily with a small number of Cenozoic fossils makes hypotheses concerning its origin and dispersal difficult to evaluate. The present study has significant implications for the origin and migration of this subfamily and the paleoclimate.

西藏新生代植物近十年来的重要发现、认识及其意义

植物化石在青藏高原形成过程、植物系统演化和高原生物多样性格局演变的研究中,发挥着不可替代的作用.近十年来,青藏高原新生代植物学研究取得重要进展,主要包括:(1)大量新类群被发现.在西藏新生代植物记录中,一共发表了63个新种,其中45个是2010年以后发表的,占全部新种的70%以上.这些新种不少是其所在科、属在亚洲乃至全球最早的化石记录,因此青藏高原是亚洲植物区系的重要源头.(2)古近纪青藏高原是全球植物区系交流的十字路口,是植物区系交汇的一个港湾.目前的古植物地理学研究表明,该地区植物区系成分的传播和交流,有进入青藏、走出青藏、走出印度和进出非洲4种模式.(3)植物化石见证了青藏高原差异隆升的历史.古高程重建发现古近纪青藏高原中部存在东西向的亚热带中央谷地.对西藏芒康不同层位植物组合的古高程研究表明,这一地区在始新世-渐新世之交快速抬升了将近1000m,达到现今高程;结合其他古高程重建工作,推断青藏高原东南缘(即横断山地区)在早渐新世就已经达到现代的高程,而此时青藏高原中部仍存在着一个东西向的中央谷地.(4)植被与地球环境协同演化.青藏高原地区经历了热带、亚热带、温带、高寒区等不同气候类型的演替,植被和植物多样性也随之改变,体现了植被对青藏高原地形地貌演变的响应.(5)先进方法和新思路逐渐应用于古植物学研究和古环境分析.荧光显微技术、古气候模型等在古植物学研究中得到应用,多学科交叉融合正在成为青藏高原新生代植物学研究的新趋势.尽管青藏高原新生代植物学研究取得了长足进步,但是该地区的化石记录仍旧缺乏,今后需要继续开展古植物学的研究,利用多学科手段深入解析青藏高原植物多样性演变历史与古环境变化过程.

Cenozoic plants from Tibet:An extraordinary decade of discovery,understanding and implications

Plant fossils play an important role in understanding landscape evolution across the Tibetan Region,as well as plant diversity across wider eastern Asia.Within the last decade or so,paleobotanical investigations within the Tibet Region have led to a paradigm shift in our understanding of how the present plateau formed and how this affected the regional climate and biota.This is because:(1)Numerous new taxa have been reported.Of all the Cenozoic records of new plant fossil species reported from the Tibet(Xizang)Autonomous Region 45 out of 63(70%)were documented after 2010.Among these,many represent the earliest records from Asia,or in some cases worldwide,at the genus or family level.(2)These fossils show that during the Paleogene,the region now occupied by the Tibetan Plateau was a globally significant floristic exchange hub.Based on paleobiogeographic studies,grounded by fossil evidence,there are four models of regional floristic migration and exchange,i.e.,into Tibet,out of Tibet,out of India and into/out of Africa.(3)Plant fossils evidence the asynchronous formation histories for different parts of the Tibetan Plateau.During most of the Paleogene,there was a wide east-west trending valley with a subtropical climate in central Tibet bounded by high(>4 km)mountain systems,but that by the early Oligocene the modern high plateau had begun to form by the rise of the valley floor.Paleoelevation reconstructions using radiometrically-dated plant fossil assemblages in southeastern Tibet show that by the earliest Oligocene southeastern Tibet(including the Hengduan Mountains)had reached its present elevation.(4)The coevolution between vegetation,landform and paleoenvironment is evidenced by fossil records from what is now the central Tibetan Plateau.From the Paleocene to Pliocene,plant diversity transformed from that of tropical,to subtropical forests,through warm to cool temperate woodland and eventually to deciduous shrubland in response to landscape evolution from a seasonally humid lowland valley,to a high and dry plateau.(5)Advanced multidisciplinary technologies and novel ideas applied to paleobotanical material and paleoenvironmental reconstructions,e.g.,fluorescence microscopy and paleoclimatic models,have been essential for interpreting Cenozoic floras on the Tibetan Region.However,despite significant progress investigating Cenozoic floras of the Tibetan Region,fossil records across this large region remain sparse,and for a better understanding of regional ecosystem dynamics and management more paleobotanical discoveries and multidisciplinary studies are required.

The first megafossil of Cibotium within its modern distribution

The‘man fern’(Cibotium,Cibotiaceae),a typical tree fern of tropical and subtropical climates,is today mainly distributed in the Hawaiian Islands,Mesoamerica,and tropical and subtropical regions of East and Southeast Asia.Reliable fossil records of this genus are rare.Only two cases of stem fossils have been reported from the Upper Cretaceous of Iwate-Ken,Japan and the upper Eocene of Oregon,USA.In this paper,ultimate fertile pinna fossils of Cibotium are described from the Miocene Erzitang Formation of Guiping Basin,Guangxi Zhuang Autonomous Region,South China,which also preserve in situ spores and cuticles.As the first global discovery of Cibotium pinna fossils preserving both in situ spores and cuticles,this find enriches the organ types of Cibotium fossils.This is also the first discovery of Cibotium fossils within its modern distribution range,indicating that Cibotium had migrated southwards into its modern distribution by at least the Miocene.Based on the modern habitat of Cibotium,we infer that the Guiping Basin was under a warm and humid tropical/subtropical climate in the Miocene.

A distinctive Eocene Asian monsoon and modern biodiversity resulted from the rise of eastern Tibet

The uplift of eastern Tibet,Asian monsoon development and the evolution of globally significant Asian biodiversity are all linked,but in obscure ways.Sedimentology,geochronology,clumped isotope thermometry,and fossil leaf-derived numerical climate data from the Relu Basin,eastern Tibet,show at~50–45 Ma the basin was a hot(mean annual air temperature,MAAT,~27℃)dry desert at a low-elevation of 0.6±0.6 km.Rapid basin rise to 2.0±0.9 km at 45–42 Ma and to 2.9±0.9 km at 42–40 Ma,with MAATs of~20 and~16℃,respectively,accompanied seasonally varying increased annual precipitation to>1500 mm.From~39 to 34 Ma,the basin attained 3.5±1.0 km,near its present-day elevation(~3.7 km),and MAAT cooled to~6℃.Numerically-modelled Asian monsoon strength increased significantly when this Eocene uplift of eastern Tibet was incorporated.The simulation/proxy congruence points to a distinctive Eocene Asian monsoon,quite unlike that seen today,in that it featured bimodal precipitation and a winter-wet regime,and this enhanced biodiversity modernisation across eastern Asia.The Paleogene biodiversity of Asia evolved under a continually modifying monsoon influence,with the modern Asian monsoon system being unique to the present and a product of a long gradual development in the context of an ever-changing Earth system.

中中新世气候适宜期环境变化:来自中国西南部湖泊沉积地球化学的证据

中中新世气候适宜期（ca.15~17Ma）是新生代气候变冷背景下的一次短期气候温暖事件.由于缺乏陆相记录,目前对于该事件的研究多来自于海洋钻孔.本文对云南东南部的文山盆地湖相地层开展了高分辨率的古地磁定年（剖面厚约270 m）和地球化学研究（剖面厚约400 m）.古地磁结果显示文山剖面上段约145 m为负极性,下段约125 m为正极性.参考邻近区域中新世湖相地层的沉积速率特征,