Bryant University is currently one of only 18 schools worldwide that offers a SAS Joint Data Mining Certificate. With the availability of very large data sets, Data Mining has become an important quantitative skill to...Bryant University is currently one of only 18 schools worldwide that offers a SAS Joint Data Mining Certificate. With the availability of very large data sets, Data Mining has become an important quantitative skill to have in business and other fields. Bryant＇s program was successfully completed by 22 undergraduate students last year. This paper provides a description of Bryant＇s program along with the history of how the program was started and how it has grown. We discuss the curriculum, teaching materials, the SAS collaboration and some of the challenges which have been encountered.展开更多
The extant genus Paliurus Miller is divided into P. ramosissimus and P. spina-christi groups and is diagnostically characterized by distinctive orbicular-winged fruits with a trilocular （or often bilocular） ovary an...The extant genus Paliurus Miller is divided into P. ramosissimus and P. spina-christi groups and is diagnostically characterized by distinctive orbicular-winged fruits with a trilocular （or often bilocular） ovary and basally triveined leaves with a subentire to serrate margin. Here, structurally preserved winged fruits and associated compressed leaves of Paliurus （Paliureae, Rhamnaceae） are reported from the Middle-Upper Miocene Shengxian Formation of Tiantai, Zhejiang, eastern China. The fruits can be identified as Paliurus microcarpa Xiang-Chuan Lisp. nov., the diagnostic characters of external morphology and anatomy of which differ from those of both extant and fossil generic members; the leaves can be designated as Paliurus sp. The species based on winged fruits, P. microcarpa, might represent an ancient intermediate link exclusively known across the P. ramosissimus and P. spina-christi groups, showing a closer affinity to the P. ramosissimus group based on the resemblant smaller fruits with a narrower wing, and to the P. spina-christi group based on the similar wing structure and texture, respectively. Morphological analyses of the present and previous fossil fruit records around the world indicate that diversification of Paliurus had begun in northern transpacific regions by the Late Eocene. The macrofossil records, i.e., fruits and leaves of Paliurus globally when projected on paleoenvironmental maps in view of changing continental positions through time （from Eocene to Miocene） display that the past distribution of the genus was much wider than the present and belongs to a tropical and warm temperate realm of the Northern Hemisphere. Therefore, the modern restricted disjunction in tropical and warm temperate regions of East Asia and South Europe （even eastwards West Asia） might represent glacial refugia for some of the generic ancient lineages to survive severe cold at least since the terminal Pliocene.展开更多
Moving object database (MOD) engine is the foundation of Location-Based Service (LBS) information systems. Continuous queries are important in spatial-temporal reasoning of a MOD. The communication costs were the bott...Moving object database (MOD) engine is the foundation of Location-Based Service (LBS) information systems. Continuous queries are important in spatial-temporal reasoning of a MOD. The communication costs were the bottleneck for improving query efficiency until the rectangular safe region algorithm partly solved this problem. However, this algorithm can be further improved, as we demonstrate with the dynamic interval based continuous queries algorithm on moving objects. Two components, circular safe region and dynamic intervals were adopted by our algorithm. Theoretical proof and experimental results show that our algorithm substantially outperforms the traditional periodic monitoring and the rectangular safe region algorithm in terms of monitoring accuracy, reducing communication costs and server CPU time. Moreover, in our algorithm, the mobile terminals do not need to have any computational ability.展开更多
Our understanding of both the role and impact of Arctic environmental changes under the current global warming climate is rather limited despite efforts of improved monitoring and wider assessment through remote sensi...Our understanding of both the role and impact of Arctic environmental changes under the current global warming climate is rather limited despite efforts of improved monitoring and wider assessment through remote sensing technology. Changes of Arctic ecosystems under early Paleogene warming climate provide an analogue to evaluate long-term responses of Arctic environmental alteration to global warming. This study reviews Arctic terrestrial ecosystems and their transformation under marked change of hydrological conditions during the warmest period in early Cenozoic, the Paleocene and Eocene. We describe a new approach to quantitatively reconstruct high latitudinal paleohydrology using compound-specific hydrogen isotope analysis which applies empirically derived genus-specific hydrogen isotope fractionations to in situ biomolecules from fossil plants. We propose a moisture recycling model at the Arctic to explain the reconstructed hydrogen isotope signals of ancient high latitude precipitation during early Paleogene, which bears implications to the likely change of modern Arctic ecosystems under the projected accelerated global warming.展开更多
The hydrogen isotopic composition(δD) of leaf wax long-chain n-alkanes(C27, C29, and C31) from lacustrine sediments has been widely applied to reconstruct terrestrial paleoclimatic and paleohydrological changes. Howe...The hydrogen isotopic composition(δD) of leaf wax long-chain n-alkanes(C27, C29, and C31) from lacustrine sediments has been widely applied to reconstruct terrestrial paleoclimatic and paleohydrological changes. However, few studies have addressed whether the aquatic-derived n-alkanes can affect the δD values of lake sedimentary long-chain n-alkanes, which are usually regarded as a recorder of the terrestrial hydrological signals. Here we systematically investigated δD values of long-chain n-alkanes from modern aquatic plants, both near-shore and off-shore surface sediments, surrounding terrestrial plant litters, as well as river water and lake water in Lake Qinghai and its satellite lakes on the northeastern Qinghai-Tibet Plateau. Our data showed that(i) δD values of long-chain n-alkanes from aquatic plants varied from-184‰ to-132‰ for n-C27, from-183‰ to-138‰ for n-C29, and from-189‰ to-130‰ for n-C31, respectively, with no significant differences among the three n-alkanes homologues;(ii) δD values of long-chain n-alkanes from aquatic plants were generally more positive than those from surrounding terrestrial plants, possibly because that they recorded the D-enrichment of lake water in this semi-arid region;(iii) δD values of long-chain n-alkanes from surface sediments showed significant differences among the three n-alkanes homologues, due to the larger aquatic input of n-C27 to the sedimentary lipid pool than that of n-C31, and(iv) n-C27 δD values of near-shore aquatic plants and near-shore sediments are more negative than those from off-shore as a result of lower δD values of near-shore lake water. Our findings indicate that in this region(i) the offset between sedimentary n-C27 and n-C31 δD values(ΔδDC27-C31) could potentially be used to evaluate if sedimentary long-chain n-alkanes are derived from a single source;(ii) while δD values of n-C27 may be influenced by lake water hydrological changes, sedimentary n-C31 is derived predominantly from terrestrial plants and thus its δD can serve as a relatively reliable indicator for terrestrial paleoclimatic and paleohydrological reconstructions.展开更多
Reconstruction of ancient atmospheric conditions through the analysis of precipitation patterns is a novel endeavor in the study of paleoclimate. A new approach is now available for a quantitative reconstruction of Pa...Reconstruction of ancient atmospheric conditions through the analysis of precipitation patterns is a novel endeavor in the study of paleoclimate. A new approach is now available for a quantitative reconstruction of Paleogene atmospheric hydrological conditions in High Arctic. It is based on 1） the discovery of exceptionally-preserved Paleogene plant fossils from the Canadian Arctic which yielded in situ labile biomolecules 2） the development of compound-specific hydrogen isotope analysis which can be applied to small amount of plant material and 3） taxon-specific apparent hydrogen isotope fractionation factors obtained from empirical measurement. A new moisture recycling model is established to explain the reconstructed paleohydrologic pattern in the High Arctic during Paleogene.展开更多
Ancient DNA data have supported a sister relationship between woolly rhinoceros and extant Sumatran rhinoceros.This relationship has been used to explore the divergent times for the woolly rhinoceros from their relati...Ancient DNA data have supported a sister relationship between woolly rhinoceros and extant Sumatran rhinoceros.This relationship has been used to explore the divergent times for the woolly rhinoceros from their relatives.Complete and partial ancient DNA sequences of the mitochondrial cytochrome b(cyt b)gene were retrieved from bones of the late Pleistocene Coelodonta antiquitatis excavated from northern and northeastern China.The newly obtained sequences together with the European and northern Asian Coelodonta antiquitatis sequences from GenBank were used to estimate the evolutionary divergence time.Phylogenetic analyses showed the exchange of genetic information between the Chinese individuals and Coelodonta antiquitatis of north Asia,which also indicated a more recent evolutionary timescale(3.8–4.7 Ma)than previous molecular estimations(17.5–22.8 or 21–26 Ma)for woolly rhinoceros based on the fossil calibration of outgroups.This new timescale was more consistent with the fossil record of the earliest known genus Coelodonta.展开更多
The hydrogen isotopic composition(δD) of n-alkanes in lacustrine sediments is widely used in palaeoenvironmental studies, but the heterogeneous origins and relative contributions of these lipids provide challenges fo...The hydrogen isotopic composition(δD) of n-alkanes in lacustrine sediments is widely used in palaeoenvironmental studies, but the heterogeneous origins and relative contributions of these lipids provide challenges for the interpretation of the increasing dataset as an environment and climatic proxy. We systematically investigated n-alkane δD values from 51 submerged plants(39 Potamogeton, 1 Myriophyllum, and 11 Ruppia), 13 algae(5 Chara, 3 Cladophora, and 5 Spirogyra) and 20 terrestrial plants(10 grasses and 10 shrubs) in and around 15 lakes on the Tibetan Plateau. Our results demonstrate that δD values of C_(29) nalkane are correlated significantly with the lake water δD values both for algae(R^2=0.85, p<0.01, n=9) and submerged plants(R^2=0.90, p<0.01, n=25), indicating that δD values of these algae and submerged plants reflect the δD variation of lake water. We find that apparent hydrogen isotope fractionation factors between individual n-alkanes and water(εa/w) are not constant among different algae and submerged plants, as well as in a single genus under different liminological conditions, indicating that the biosynthesis or environmental conditions(e.g. salinity) may affect their δD values. The δD values of submerged plant Ruppia in the Xiligou Lake(a closed lake) are significant enriched in D than those of terrestrial grasses around the lake(one-way ANOVA,p<0.01), but the algae Chara in the Keluke Lake(an open lake) display similar δD values with grasses around the lake(one-way ANOVA, p=0.826>0.05), suggesting that the n-alkane δD values of the algae and submerged plants record the signal of D enrichment in lake water relative to precipitation only in closed lakes in arid and semi-arid area. For each algae and submerged plant sample, we find uniformed δD values of different chain length n-alkanes, implying that, in combination with other proxies such as Paq and Average Chain Length, the offset between the δD values of different chain length n-alkanes can help determine the source of sedimentary n-alkanes as well as inferring the hydrological characteristics of an ancient lake basin(open vs closed lake).展开更多
Mosses form a diverse land plant group in modern vegetation but have rarely showed up in the fossil record compared with vascular plants. Here, we report an extraordinarily-preserved early Miocene moss fossil from the...Mosses form a diverse land plant group in modern vegetation but have rarely showed up in the fossil record compared with vascular plants. Here, we report an extraordinarily-preserved early Miocene moss fossil from the lower Laoliangdi Formation in the Pingzhuang Coal Mine in Chifeng, Inner Mongolia Autonomous Region, northern China. Although lacking rhizoids and most reproductive organs, the well-preserved fossil allows us to assign it to Platydictya cf. jungermannioides (Amblystegiaceae) based upon its detailed gross and micro-morphology. The diagnostic characteristics include a small-sized body with slender stems bearing spirally arranged ovate-lanceolate leaves that lack costae. Leaf margins are mostly partly entire and partly dentate, a few dentate, and rarely completely entire. It represents the first fossil record of Platydictya in Asia. The specific living microenvironment of the extant P. jungermannioides enriched our understanding of the early Miocene environment that was previously based upon vascular plant fossils and sedimentary lithofacies in the area. Our early Miocene Platydictya cf. jungermannioides fossil lived in a warm and humid lush forest with a dense understory that received adequate water supplies.展开更多
The plant genus Metasequoia Miki,1941 and its sole living relict species Metasequoia glyptostroboides Hu et Cheng,1948 have been of special interest for both the public and scientists since 1941 when the genus was est...The plant genus Metasequoia Miki,1941 and its sole living relict species Metasequoia glyptostroboides Hu et Cheng,1948 have been of special interest for both the public and scientists since 1941 when the genus was established.Due to its unique discovery history（fossils discovered earlier than the living species） and incomparable scientific value in the research of plant evolution and its relationship with environmental and climatic changes, Metasequoia becomes arguably the most comprehensively studied higher plant in both fossil and living forms.This paper summarized recent advance in Metasequoia research by reviewing the research history of Metasequoia and the scientific value of this genus,while paid special attention to the application of new methods and techniques in the research field of Metasequoia in the recent decades.The application of biogeochemical（organic geochemistry and stable isotope） analysis as well as the new and innova ted methods of preparing large-sized cuticular membrane from leaves with originally thin and fragile cuticles further secure Metasequoia＇s super star status for the research of palaeoclimatic reconstruction.展开更多
文摘Bryant University is currently one of only 18 schools worldwide that offers a SAS Joint Data Mining Certificate. With the availability of very large data sets, Data Mining has become an important quantitative skill to have in business and other fields. Bryant＇s program was successfully completed by 22 undergraduate students last year. This paper provides a description of Bryant＇s program along with the history of how the program was started and how it has grown. We discuss the curriculum, teaching materials, the SAS collaboration and some of the challenges which have been encountered.
基金supported by the National Natural Science Foundation of China(Nos.41202008,41202009,41172022)the Natural Science Basic Research Plan in Shaanxi Province of China (No.2011JQ5012)+1 种基金the Special Fund for Basic Scientific Research of Central Colleges,Chang'an University(Nos. 2014G1271061,CHD2011JC122,CHD2011TD005, 20I4G3272013,2013G3274021 and 2013G1271101)the Foundation of the State Key Laboratory of Paleobiology and Stratigraphy,Nanjing Institute of Geology and Paleontology,Chinese Academy of Sciences (No.123112)
文摘The extant genus Paliurus Miller is divided into P. ramosissimus and P. spina-christi groups and is diagnostically characterized by distinctive orbicular-winged fruits with a trilocular （or often bilocular） ovary and basally triveined leaves with a subentire to serrate margin. Here, structurally preserved winged fruits and associated compressed leaves of Paliurus （Paliureae, Rhamnaceae） are reported from the Middle-Upper Miocene Shengxian Formation of Tiantai, Zhejiang, eastern China. The fruits can be identified as Paliurus microcarpa Xiang-Chuan Lisp. nov., the diagnostic characters of external morphology and anatomy of which differ from those of both extant and fossil generic members; the leaves can be designated as Paliurus sp. The species based on winged fruits, P. microcarpa, might represent an ancient intermediate link exclusively known across the P. ramosissimus and P. spina-christi groups, showing a closer affinity to the P. ramosissimus group based on the resemblant smaller fruits with a narrower wing, and to the P. spina-christi group based on the similar wing structure and texture, respectively. Morphological analyses of the present and previous fossil fruit records around the world indicate that diversification of Paliurus had begun in northern transpacific regions by the Late Eocene. The macrofossil records, i.e., fruits and leaves of Paliurus globally when projected on paleoenvironmental maps in view of changing continental positions through time （from Eocene to Miocene） display that the past distribution of the genus was much wider than the present and belongs to a tropical and warm temperate realm of the Northern Hemisphere. Therefore, the modern restricted disjunction in tropical and warm temperate regions of East Asia and South Europe （even eastwards West Asia） might represent glacial refugia for some of the generic ancient lineages to survive severe cold at least since the terminal Pliocene.
文摘Moving object database (MOD) engine is the foundation of Location-Based Service (LBS) information systems. Continuous queries are important in spatial-temporal reasoning of a MOD. The communication costs were the bottleneck for improving query efficiency until the rectangular safe region algorithm partly solved this problem. However, this algorithm can be further improved, as we demonstrate with the dynamic interval based continuous queries algorithm on moving objects. Two components, circular safe region and dynamic intervals were adopted by our algorithm. Theoretical proof and experimental results show that our algorithm substantially outperforms the traditional periodic monitoring and the rectangular safe region algorithm in terms of monitoring accuracy, reducing communication costs and server CPU time. Moreover, in our algorithm, the mobile terminals do not need to have any computational ability.
基金supported by CAS/SAFEA International Partnership Program for Creative Research Teams, the Pilot Project of Knowledge Innovation of CAS (Grant No. KZCX2-YW-105)the National Basic Research Program of China (Grant No. 2006CB806400)+2 种基金the National Natural Science Foun-dation of China (Grant Nos. 40402002, 40872011)the American Chemi-cal Society Petroleum Research Funds, NASA RI Space GrantBryant University Summer Research Funds.
文摘Our understanding of both the role and impact of Arctic environmental changes under the current global warming climate is rather limited despite efforts of improved monitoring and wider assessment through remote sensing technology. Changes of Arctic ecosystems under early Paleogene warming climate provide an analogue to evaluate long-term responses of Arctic environmental alteration to global warming. This study reviews Arctic terrestrial ecosystems and their transformation under marked change of hydrological conditions during the warmest period in early Cenozoic, the Paleocene and Eocene. We describe a new approach to quantitatively reconstruct high latitudinal paleohydrology using compound-specific hydrogen isotope analysis which applies empirically derived genus-specific hydrogen isotope fractionations to in situ biomolecules from fossil plants. We propose a moisture recycling model at the Arctic to explain the reconstructed hydrogen isotope signals of ancient high latitude precipitation during early Paleogene, which bears implications to the likely change of modern Arctic ecosystems under the projected accelerated global warming.
基金supported by the National Natural Science Foundation of China (Grant No. 41573005)the National Basic Research Program of China (Grant No. 2013CB955901)
文摘The hydrogen isotopic composition(δD) of leaf wax long-chain n-alkanes(C27, C29, and C31) from lacustrine sediments has been widely applied to reconstruct terrestrial paleoclimatic and paleohydrological changes. However, few studies have addressed whether the aquatic-derived n-alkanes can affect the δD values of lake sedimentary long-chain n-alkanes, which are usually regarded as a recorder of the terrestrial hydrological signals. Here we systematically investigated δD values of long-chain n-alkanes from modern aquatic plants, both near-shore and off-shore surface sediments, surrounding terrestrial plant litters, as well as river water and lake water in Lake Qinghai and its satellite lakes on the northeastern Qinghai-Tibet Plateau. Our data showed that(i) δD values of long-chain n-alkanes from aquatic plants varied from-184‰ to-132‰ for n-C27, from-183‰ to-138‰ for n-C29, and from-189‰ to-130‰ for n-C31, respectively, with no significant differences among the three n-alkanes homologues;(ii) δD values of long-chain n-alkanes from aquatic plants were generally more positive than those from surrounding terrestrial plants, possibly because that they recorded the D-enrichment of lake water in this semi-arid region;(iii) δD values of long-chain n-alkanes from surface sediments showed significant differences among the three n-alkanes homologues, due to the larger aquatic input of n-C27 to the sedimentary lipid pool than that of n-C31, and(iv) n-C27 δD values of near-shore aquatic plants and near-shore sediments are more negative than those from off-shore as a result of lower δD values of near-shore lake water. Our findings indicate that in this region(i) the offset between sedimentary n-C27 and n-C31 δD values(ΔδDC27-C31) could potentially be used to evaluate if sedimentary long-chain n-alkanes are derived from a single source;(ii) while δD values of n-C27 may be influenced by lake water hydrological changes, sedimentary n-C31 is derived predominantly from terrestrial plants and thus its δD can serve as a relatively reliable indicator for terrestrial paleoclimatic and paleohydrological reconstructions.
基金funded in part by the CAS/SAFEA International Partnership Program for Creatine Research Teams,the Pilot Project of Knowledge Innovation,CAS the Major Basis Research Projects(2006CB806400)+1 种基金the National Science Foundation of China(40402002)the American Chemical Society Petroleum Research Funds,and a NASA RI Space Grant
文摘Reconstruction of ancient atmospheric conditions through the analysis of precipitation patterns is a novel endeavor in the study of paleoclimate. A new approach is now available for a quantitative reconstruction of Paleogene atmospheric hydrological conditions in High Arctic. It is based on 1） the discovery of exceptionally-preserved Paleogene plant fossils from the Canadian Arctic which yielded in situ labile biomolecules 2） the development of compound-specific hydrogen isotope analysis which can be applied to small amount of plant material and 3） taxon-specific apparent hydrogen isotope fractionation factors obtained from empirical measurement. A new moisture recycling model is established to explain the reconstructed paleohydrologic pattern in the High Arctic during Paleogene.
基金Yang Hong was supported by a short term Guest Professor through the sponsorship of China University of Geosciences in Wuhansupported by National Basic Research Program of China(Grant No.2011CB808800)+1 种基金National Natural Science Foundation of China(Grant Nos.40672006,40902008)"111"Project of Chinese State Administration of Foreign Experts Affairs(Grant No.B08030)
文摘Ancient DNA data have supported a sister relationship between woolly rhinoceros and extant Sumatran rhinoceros.This relationship has been used to explore the divergent times for the woolly rhinoceros from their relatives.Complete and partial ancient DNA sequences of the mitochondrial cytochrome b(cyt b)gene were retrieved from bones of the late Pleistocene Coelodonta antiquitatis excavated from northern and northeastern China.The newly obtained sequences together with the European and northern Asian Coelodonta antiquitatis sequences from GenBank were used to estimate the evolutionary divergence time.Phylogenetic analyses showed the exchange of genetic information between the Chinese individuals and Coelodonta antiquitatis of north Asia,which also indicated a more recent evolutionary timescale(3.8–4.7 Ma)than previous molecular estimations(17.5–22.8 or 21–26 Ma)for woolly rhinoceros based on the fossil calibration of outgroups.This new timescale was more consistent with the fossil record of the earliest known genus Coelodonta.
基金supported by the National Natural Science Foundation of China(Grant No.41573005)National Basic Research Programme of China(Grant No.2013CB955901)Key Program of the Chinese Academy of Sciences(Grant No.QYZDY-SSWDQC001)
文摘The hydrogen isotopic composition(δD) of n-alkanes in lacustrine sediments is widely used in palaeoenvironmental studies, but the heterogeneous origins and relative contributions of these lipids provide challenges for the interpretation of the increasing dataset as an environment and climatic proxy. We systematically investigated n-alkane δD values from 51 submerged plants(39 Potamogeton, 1 Myriophyllum, and 11 Ruppia), 13 algae(5 Chara, 3 Cladophora, and 5 Spirogyra) and 20 terrestrial plants(10 grasses and 10 shrubs) in and around 15 lakes on the Tibetan Plateau. Our results demonstrate that δD values of C_(29) nalkane are correlated significantly with the lake water δD values both for algae(R^2=0.85, p<0.01, n=9) and submerged plants(R^2=0.90, p<0.01, n=25), indicating that δD values of these algae and submerged plants reflect the δD variation of lake water. We find that apparent hydrogen isotope fractionation factors between individual n-alkanes and water(εa/w) are not constant among different algae and submerged plants, as well as in a single genus under different liminological conditions, indicating that the biosynthesis or environmental conditions(e.g. salinity) may affect their δD values. The δD values of submerged plant Ruppia in the Xiligou Lake(a closed lake) are significant enriched in D than those of terrestrial grasses around the lake(one-way ANOVA,p<0.01), but the algae Chara in the Keluke Lake(an open lake) display similar δD values with grasses around the lake(one-way ANOVA, p=0.826>0.05), suggesting that the n-alkane δD values of the algae and submerged plants record the signal of D enrichment in lake water relative to precipitation only in closed lakes in arid and semi-arid area. For each algae and submerged plant sample, we find uniformed δD values of different chain length n-alkanes, implying that, in combination with other proxies such as Paq and Average Chain Length, the offset between the δD values of different chain length n-alkanes can help determine the source of sedimentary n-alkanes as well as inferring the hydrological characteristics of an ancient lake basin(open vs closed lake).
基金This research was supported by the National Natural Science Foundation of China(Grant Nos.41872017 and 42072015)the Fundamental Research Funds for the Central Universities,CHD(Nos.300102272206,300102272901,300102271402,and 300102262903)+2 种基金the Foundation of State Key Laboratory of Palaeobiology and Stratigraphy(Nanjing Institute of Geology and Palaeontology,CAS)(Nos.183125 and 20172106)the Natural Science Basic Research Program in Shaanxi Province of China(No.2023-JC-YB-223)Chang᾽an University Students᾽innovation and entrepreneurship training program(No.G202210710054).
文摘Mosses form a diverse land plant group in modern vegetation but have rarely showed up in the fossil record compared with vascular plants. Here, we report an extraordinarily-preserved early Miocene moss fossil from the lower Laoliangdi Formation in the Pingzhuang Coal Mine in Chifeng, Inner Mongolia Autonomous Region, northern China. Although lacking rhizoids and most reproductive organs, the well-preserved fossil allows us to assign it to Platydictya cf. jungermannioides (Amblystegiaceae) based upon its detailed gross and micro-morphology. The diagnostic characteristics include a small-sized body with slender stems bearing spirally arranged ovate-lanceolate leaves that lack costae. Leaf margins are mostly partly entire and partly dentate, a few dentate, and rarely completely entire. It represents the first fossil record of Platydictya in Asia. The specific living microenvironment of the extant P. jungermannioides enriched our understanding of the early Miocene environment that was previously based upon vascular plant fossils and sedimentary lithofacies in the area. Our early Miocene Platydictya cf. jungermannioides fossil lived in a warm and humid lush forest with a dense understory that received adequate water supplies.
文摘The plant genus Metasequoia Miki,1941 and its sole living relict species Metasequoia glyptostroboides Hu et Cheng,1948 have been of special interest for both the public and scientists since 1941 when the genus was established.Due to its unique discovery history（fossils discovered earlier than the living species） and incomparable scientific value in the research of plant evolution and its relationship with environmental and climatic changes, Metasequoia becomes arguably the most comprehensively studied higher plant in both fossil and living forms.This paper summarized recent advance in Metasequoia research by reviewing the research history of Metasequoia and the scientific value of this genus,while paid special attention to the application of new methods and techniques in the research field of Metasequoia in the recent decades.The application of biogeochemical（organic geochemistry and stable isotope） analysis as well as the new and innova ted methods of preparing large-sized cuticular membrane from leaves with originally thin and fragile cuticles further secure Metasequoia＇s super star status for the research of palaeoclimatic reconstruction.
