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排序方式: 共有130条查询结果,搜索用时 15 毫秒
41.
在中国贵州江口地区陡山沱组新发现的化石材料表明,伊迪卡拉/震旦纪(Ediacaran/Sinian)的宏体化石——八臂仙母虫Eoandromeda octobrachiata的原始生活状态可能为一个较高的圆锥形生命体,具有沿着侧面锥状螺旋排列的八条旋臂.旋臂表面保存有与栉水母动物的栉板可能同源的横向有机质条带,规则排列... 相似文献
42.
Macroscopic organisms lived in the Yangtze Sea of South China during the Late Doushantuo period of the Ediacaran. The results of the specimen collections and statistics within each meter show that the macroscopic biota from the Ediacaran Doushantuo Formation in northeast Guizhou, South China, can be subdivided into Globusphyton, Cucullus, Sectoralga–Longifuniculum, Beltanelliformis, and Baculiphyca–Gesinella paleo-communities. The paleo-community evolution indicates the relationship not only between biota and environment, but also between metaphytes and metazoans. From the Globusphyton paleo-community, through to the Sectoralga–Longifuniculum paleo-community, to the Cucullus paleo-community, the increase in the abundance and diversity of metaphytes (especially the branching macroalgae) and metazoans implies that the oxygen content in the seawater increased gradually. Both the Beltanelliformis and Baculiphyca–Gesinella paleo-communities could be related to a deteriorated environment and fragile ecosystem. The emergence, abundance, and diversity of macroscopic metaphytes, which were closely connected with the environmental microchanges, accelerated the process, improving the environment and increasing oxygen, and established an important platform for the development of macroscopic metazoans. 相似文献
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Metazoan fossils in the Gaojiashan Biota are famous for being well preserved and may provide new insights into the early evolution and skeletonization of Metazoans. We are studying the isotopic compositions of organic and carbonate carbon from a sequence of sedimentary rocks at the Gaojiashan section, northern Yangtze Platform, Shaanxi Province of China. Organic carbon isotope values display a range between –30.8‰ and –24.7‰ with clear stratigraphic variations. Carbonate carbon isotope data vary between 0.1‰ and +6‰. Positive δ13C values from sediments with Gaojiashan biota reflect temporal variations in carbon turnover, i.e. an increasing in photosynthetic carbon fixation followed by an increasing subsequent fractional organic carbon burial, and that related to bio-radiation such as increasing algae, bacteria, and original creatures productivity in biomass. These secular variations are interpreted to reflect perturbations of the regional carbon cycle, specifically changes in the fractional burial of organic carbon, and discuss the relationship between Gaojiashan biota and paleoenvrionmental variation. 相似文献
45.
WAN Bin YUAN Xunlai CHEN Zhe GUAN Chengguo PANG Ke TANG Qing and RAO Xin 《《地质学报》英文版》2013,87(4):905-915
As a more efficient quantitative method for morphological analysis, geometric morphometrics is applied to the flabellate fossils Flabellophyton including Flabellophyton lantianensis and Flabellophyton strigata from Neoproterozoic Ediacaran Lantian biota, South China. Both traditional morphometric analysis (including diverging angle, length, and width distribution) and geometric morphometric analysis [including superposition of normalized area analysis, non-metric multidimensional scaling (n-MDS), Bray-Curtis similarity cluster analysis (CLUSTER) and analysis of similarities (ANOSIM)] were performed. The results indicate there are great interspecific morphological differences between F. lantianensis and F. strigata, in addition to some intraspecific variations within each species. Here we preliminarily suggest that the previously defined Flabellophyton should be subdivided into 2 genera at least: one marked by the dark transverse striated structure, and the other without. This recharacterization and reclassification work still needs further careful observation and comprehensive analysis with large number of flabellate fossils combining morphology, structure, population, and community-ecology study. 相似文献
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关岭生物群产出地层的岩石微相和环境意义 总被引:3,自引:0,他引:3
关岭生物群产于中国贵州关岭县新铺乡,在贵州省会贵阳以西约188km的晚三叠世早期地层小凹组底部。化石群主要门类有海生爬行类(鱼龙、海龙、鳍龙、盾齿龙等)、海百合、菊石、双壳、腕足、牙形刺、鱼类和植物。以保存完整精美、数量巨大的海生爬行类和棘皮动物海百合为标志。化石产出地层岩石为(微含泥质)含生物屑泥晶灰岩,其上下地层的岩石还有(含泥质)含粉砂质不等晶灰岩和含生物屑泥晶灰岩。根据岩石组成、结构、构造、微相特征提出关岭生物群生活环境离岸较近、沉积作用以悬浮方式为主,少牵引流影响、水体总体比较安静。 相似文献
48.
First biogeographic maps are proposed for the late Eocene-Oligocene of the North Pacific. The maps are compiled based on distribution of 120 molluscan species studied in 30 reference sections of the region. The analyzed Machigar (Sakhalin), Rategin, Amanina-Gakh (western Kamchatka), Asagai-Momidziyama (Japan) type assemblages and their age analogues are well known and described long ago. Over 50 schematic biogeographic maps illustrate distribution areas of different taxa in the late Eocene, early Oligocene, and late Oligocene epochs. Some of them characterize distribution areas of individual species, while the others depict habitat areas of typical (Machigar and Rategin) assemblages or certain genera different in terms of their thermotropism. Analysis of the maps resulted in recognition of the Japan-Kamchatka and Kamchatka-North American paleoprovinces, and indications of general gradual seawater temperature decrease during the Oligocene are defined. The attention is paid to the commenced diversification of North Pacific biota that leads to formation of boreal communities and also to different-rank the amphipacific dusjunctions. 相似文献
49.
V. V. Baranov 《Stratigraphy and Geological Correlation》2009,17(4):382-395
It is established that the Pridolian-Eifelian megacycle in Northeast Asia is represented by five macrocyclites. The analysis of fossils in Upper Silurian-Lower Devonian sections of the region reveals ten levels marked by large-scale reorganizations in the composition and structure of the biota in this basin. These levels are united in pairs by five maximums, which are characterized by the highest values of the taxonomic renewal coefficient, coincide with the boundaries of macrocyclites, and are traceable through the entire sedimentation basin. 相似文献
50.