Xingxueanthus: An Enigmatic Jurassic Seed Plant and Its Implications for the Origin of Angiospermy   总被引：1，自引：1，他引：0  

WANG Xin  and WANG Shijun 《《地质学报》英文版》2010,84(1):47-55

Abstract: The origin of angiosperms has been tantalizing botanists for centuries. Despite the efforts of palaeobotanists, most of the pre-Cretaceous angiosperms are regarded either non-convincing or misdated. The applications of SEM and LM (light microscope) enable us to recognize a coalified fossil plant, Xingxueanthus sinensis gen. et sp. nov., from the Haifanggou Formation (Middle Jurassic, >160 Ma) in western Liaoning, China. Xingxueanthus is an “inflorescence” with more than 20 female units spirally arranged. Each female unit is situated in the axil of a bract. The female unit is composed of an ovule-container and a style-like projection at the top. There is a vertical column bearing several ovules in the ovule-container. The general morphology and the internal structure of Xingxueanthus distinguish itself from any known fossil and extant gymnosperms, and its structures are more comparable to those of angiosperms. Xingxueanthus, if taken as a gymnosperm, would represent a new class, demonstrate an evolutionarily advanced status of ovule-protection in gymnosperms never seen before, and provide new insights into the origin of angiospermy. Alternatively, if taken as an angiosperm, together with Schmeissneria, it would increase the diversity of Jurassic angiosperms, which has been underestimated for a long time, and suggest a much earlier origin of angiospermy than currently accepted.  相似文献   

Magnetic field fossilization and tail reconfiguration in Titan's plasma environment during a magnetopause passage: 3D adaptive hybrid code simulations     

Joachim Müller  Sven Simon  Karl-Heinz Glassmeier  Joachim Saur  Gavin J. Pringle 《Planetary and Space Science》2010,58(12):1526-1546

We present a hybrid simulation study (kinetic ions, fluid electrons) of Titan's plasma interaction during an excursion of this moon from Saturn's magnetosphere into its magnetosheath, as observed for the first time during Cassini's T32 flyby on 13 June 2007. In contrast to earlier simulations of Titan's plasma environment under non-stationary upstream conditions, our model considers a difference in the flow directions of magnetospheric and magnetosheath plasma. Two complementary scenarios are investigated, with the flow directions of the impinging magnetospheric/magnetosheath plasmas being (A) antiparallel and (B) parallel. In both cases, our simulations show that due to the drastically reduced convection speed in the slow and dense heavy ion plasma near Titan, the satellite carries a bundle of “fossilized” magnetic field lines from the magnetosphere in the magnetosheath. Furthermore, the passage through Saturn's magnetopause goes along with a disruption of Titan's pick-up tail. Although the tail is not detached from the satellite, large clouds of heavy ion plasma are stripped of its outer flank, featuring a wave-like pattern. Whereas in case (B) under parallel flow conditions there is only a small retardation of about 5 min between the passage of Titan through the magnetopause and the reconfiguration of the pick-up tail, the tail reconfiguration in the case (A) scenario is completed not until 25 min after the magnetopause passage. The lifetime of fossil fields in the moon's ionosphere is approximately 25 min, regardless of whether parallel or antiparallel flow conditions are applied.  相似文献   

Eocene fauna of Messel Pit Fossil Site, Germany     

Stephan Schaal 《东北亚地学研究》2005,(Z1)

The paper reports sunthetically the Cocene fauna of the Messel Pit Fossil site of Germany, in detail, including its rich taxanomic compositions, geological and paleogeographic backgroud, and the studying and applying history.  相似文献   

三种裸子植物化石木的研究     

杨家驹  齐国凡  徐瑞瑚  杨礼茂 《国土资源》1996,(4)

本文研究了我国长江北岸湖北省武汉市新洲县阳逻镇北部晚第三纪的三种裸子植物化石木。它们是水松ＧｌｙｐｔｏｓｔｒｏｂｕｓｐｅｎｓｉｌｉｓＫ．Ｋｏｃｈ，武汉柏本ＣｕｐｒｅｓｓｕｓｗｕｈａｎｅｎｓｉｓＪ．ＪＹａｎｇｓｐ．ｎｏｖ．和武汉刺柏ＪｕｎｉｐｅｒｕｓｗｕｈａｎｅｎｓｉｓＪ．Ｊ．Ｙａｎｇｓｐ．ｎｏｖ，这些化石本的发现，给研究我国裸子植物提供了良好的依据．此外，对１９９０年发表于《林业科学》（２６卷４期）上的湖北柏木和河南松化石木也给了拉丁种名，它们分别是ＣｕｐｒｅｓｓｕｓｈｕｂｅｉｓｎｓｉｓＪ．Ｊ．Ｙａｎｇｓｐｎｏｖ．和ｐｉｎｕｓｈｅｎａｎｅｎｓｉｓＪ．Ｊ．Ｙａｎｇｓｐ．ｎｏｖ．  相似文献   

乔治王岛菲尔德斯半岛早第三纪植物群及其环境意义          下载免费PDF全文

刘清泗 《极地研究》1990,2(3):39-45

南极乔治王岛菲尔德斯半岛化石山植物群的发现是研究该地区新生代地质历史的一件大事。通过层位对比、化石特征、植物群组合面貌的研究,认为该植物层的时代为始新世末期至渐新世早、中期,当时为温暖偏干的温带或亚热带疏林环境。  相似文献   

Response of a warm temperate peatland to Holocene climate change in northeastern Pennsylvania   总被引：1，自引：0，他引：1  

Shanshan Cai  Zicheng Yu   《Quaternary Research》2011,75(3):531-540

Studying boreal-type peatlands near the edge of their southern limit can provide insight into responses of boreal and sub-arctic peatlands to warmer climates. In this study, we investigated peatland history using multi-proxy records of sediment composition, plant macrofossil, pollen, and diatom analysis from a ¹⁴C-dated sediment core at Tannersville Bog in northeastern Pennsylvania, USA. Our results indicate that peat accumulation began with lake infilling of a glacial lake at ~ 9 ka as a rich fen dominated by brown mosses. It changed to a poor fen dominated by Cyperaceae (sedges) and Sphagnum (peat mosses) at ~ 1.4 ka and to a Sphagnum-dominated poor fen at ~ 200 cal yr BP (~ AD 1750). Apparent carbon accumulation rates increased from 13.4 to 101.2 g C m^? 2 yr^? 1 during the last 8000 yr, with a time-averaged mean of 27.3 g C m^? 2 yr^? 1. This relatively high accumulation rate, compared to many northern peatlands, was likely caused by high primary production associated with a warmer and wetter temperate climate. This study implies that some northern peatlands can continue to serve as carbon sinks under a warmer and wetter climate, providing a negative feedback to climate warming.  相似文献   

Four thousand years of environmental change and human activity in the Cochabamba Basin, Bolivia     

Joseph J. Williams  William D. Gosling  Stephen J. Brooks 《Quaternary Research》2011,76(1):58-126

The Cochabamba Basin (Bolivia) is on the ancient road network connecting Andean and lowland areas. Little is known about the longevity of this trade route or how people responded to past environmental changes. The eastern end of the Cochabamba valley system constricts at the Vacas Lake District, constraining the road network and providing an ideal location in which to examine past human-environmental interactions. Multi-proxy analysis of sediment from Lake Challacaba has allowed a c. 4000 year environmental history to be reconstructed. Fluctuations in drought tolerant pollen taxa and calcium carbonate indicate two periods of reduced moisture availability (c. 4000-3370 and c. 2190-1020 cal yr BP) compared to adjacent wetter episodes (c. 3370-2190 and c. 1020 cal yr BP-present). The moisture fluctuations broadly correlate to El Niño/Southern Oscillation variations reported elsewhere. High charcoal abundance from c. 4000 to 2000 yr ago indicates continuous use of the ancient road network. A decline in charcoal and an increase in dung fungus (Sporormiella) c. 1340-1210 cal yr BP, suggests that cultural changes were a major factor in shaping the modern landscape. Despite undisputable impacts of human populations on the Polylepis woodlands today, we see no evidence of woodland clearance in the Challacaba record.  相似文献   

Knoblochia cretacea,Late Cretaceous insect eggs from Central Europe     

《Cretaceous Research》2013

The genus Knoblochia is established for fossil insect eggs. The fossils are small, longitudinally ridged, ovoid to round with projections on both ends. Their thin perforated wall is covered by minute papillae, inner surface of the wall is smooth or covered by rectangular files of cells. Fossils assigned here to Knoblochia cretacea were earlier assigned to the genus Spirellea, which encompass a heterogenous complex of small fossils being or resembling angiosperm seeds from the Late Cretaceous. The majority of species of the genus Spirellea clearly represents remains of angiosperms. However, fossils described by Knobloch and Mai (1986) as Spirellea kvacekii are distinct, particularly in having external walls perforated, neither apex nor basal projection showing any absition scar or micropyle in the botanical sense. Attribution of these fossils to insects led us to designate the new name Knoblochia cretacea with a new holotype for fossils of this kind. Comparison of Knoblochia with insect eggs of species of Phasmatodea and Lepidoptera, and seeds of Stemonaceae showed clear affinity to insects. Due to the high amount of extinction among insects since the Cretaceous, the systematic affinity of Knoblochia remains open.  相似文献   

Disi Water Use for Irrigation – a False Decision and Its Consequences          下载免费PDF全文

Elias Salameh  Marwan Alraggad  Arwa Tarawneh 《洁净——土壤、空气、水》2014,42(12):1681-1686

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AMS dating of insect chitin – A discussion of new dates,problems and potential     

《Quaternary Geochronology》2015

Results from AMS dating applied to insect chitin from a variety of contexts and different preservation conditions and retrieval methods are presented. Secure contexts, which include other dated organic material from different geographic locations ranging from Egypt to Greenland and different chronological periods, from Lateglacial to Medieval, have been used. In addition, insect species with different dietary requirements have been selected for dating purposes in order to provide an understanding as to whether diet plays a role in the chitin dating results. Dates from each context/site are discussed separately in the context of their stratigraphy and/or archaeology. Our research concentrates on the results from pre-treatment methods which require small quantities of chitin as these could be applied in a variety of Quaternary and archaeological contexts. The dates from carbonised and desiccated remains where no chemicals had been involved in storage fell within the range of dates from other organics or the archaeology. Although some of the dates from waterlogged contexts were successful, problems were encountered and these have been linked with long term storage in various alcohols of uncertain provenance. Whilst short term immersion in paraffin (kerosene) and alcohols during processing probably has no impact, it is recommended that chitinous material for dating be stored in acidified distilled water. Our results demonstrate the potential of chitin as a dating medium and provide a basis for its wider application.  相似文献