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寒 武 纪 两 侧 对 称 动 物 的 辐 射 : 演 化 起 源 与 古生 物 的 出 现 ; 地 球 历 史 改 变 与 生 物 因 素 = TheCambrian radiation of bilaterians: Evolutionaryorigins and palaeontological emergence; earthhistory change and biotic factors. ( 英 文 ). LiebermanB S. Palaeogeography PalaeoclimatologyPalaeoecology, 2008, 258(3): 180-188Evidence from a variety of research areas, includingphylogenetic palaeobiogeographic studiesof trilobites, indicates that there may be afuse to the Cambrian radiation, with a durationon the order of 20–70 myr. Evolution in trilobitesappears to have been powerfully influencedby the tectonic changes occurring at the end ofthe Neoproterozoic: especially the breakup ofPannotia. This continental fragmentation mayhave also elevated opportunities for vicarianceand speciation in trilobites, and other metazoans,given that speciation rates at this time periodwere high, though not phenomenally so. Thisprovides clear evidence that abiotic factorsplayed an important role in motivating evolutionduring this key episode in the history of life;biotic factors probably also played a role. Theevidence for the role of biotic factors is consideredin light of information from some problematicCambrian taxa. These may show affinitieswith modern problematic pseudocoelomatephyla, although Cambrian and modern exponentsdiffer dramatically in body size.2008040521漫 游 迹 (Planolites) 在 寒 武 纪 底 质 剧 变 中 的重 要 性 = The importance of Planolites in theCambrian substrate revolution. ( 英 文 ). MarencoK N; Bottjer D J. Palaeogeography PalaeoclimatologyPalaeoecology, 2008, 258(3): 189-199Early Cambrian subtidal shelf substrates werecharacterized by low water content and steepchemical gradients, conditions likely facilitatedby the presence of microbial mats as reflected byan abundance of microbially-mediated sedimentarystructures in Lower Cambrian strata. Suchsubstrate conditions would have been unfavourablefor burrowing by benthic metazoans. Acombination of environmental restrictions and alack of adaptations to vertical burrowing likelyprevented most benthic metazoans from burrowinginfaunally in Early Cambrian subtidal shelfsubstrates. The eventual acquisition of burrowingadaptations by benthic metazoans later in theCambrian promoted an increase in the depth andintensity of bioturbation and initiated a transitiontoward well-hydrated substrates in which extensiveinfaunal activity was possible.Siliciclastic units of the Lower Cambrian successionin the White–Inyo Mountains, easternCalifornia, contain abundant horizontal bioturbationon bedding planes, as documented by beddingplane bioturbation indices, but little verticalbioturbation, as shown by ichnofabric indicesand x-radiography. Planolites, a simple horizontaltrace fossil, represents the dominant type ofbioturbation in these units. Planolites is found ina range of diameters, indicating that more thanone species of tracemaker likely produced thistype of trace. Although these Planolites do nothave a vertical component, their abundance onbedding planes indicates that the activities ofPlanolites tracemakers had a significant impacton subtidal shelf substrates, represented byLower Cambrian units in the White–Inyo Mountains,early in the Cambrian substrate revolution.2008040522加 拿 大 安 大 略 Hungry Hollow 中 泥 盆 世 艾 菲尔 - 吉 维 特 阶 界 线 Kačák-otomari 事 件 稳 定 同位 素 记 录 = Stable isotope record of theEifelian-Givetian boundary Kačák-otomariEvent (Middle Devonian) from Hungry Hollow,Ontario, Canada. ( 英 文 ). Gröcke D R; vanHengstum P J. Canadian Journal of Earth Sciences,2008, 45(3): 353-366The Kačák Event in the Middle Devonian(Eifelian-Givetian (E-G) boundary) is a periodof apparent global anoxia coincident with widespreaddeposition of black shale in hemipelagic,pelagic, and some neritic facies. Conodont biostratigraphyin the North American AppalachianBasin has proven to be problematic in preciselydemarcating the E-G boundary. In this study, weshow that the E-G boundary may be definedmore accurately through isotope stratigraphy(δ 13 C) in conjunction with a conodont faunalchange across this boundary, identified as theKačák-otomari Event. The Canadian HamiltonGroup outcropping in Hungry Hollow, Ontario,is a 22m sedimentary succession spanning theMiddle Devonian. Conodont biostratigraphy forthis section makes it difficult to define the E-Gboundary, but the otomari Event can be detected.High-resolution isotopic analysis of bulk sedimentarycarbonate and organic matter for thissuccession records a significant negative δ 13 Cexcursion (δ 13 C carb = up to 2‰; δ 13 C org = ~3.0‰)that is synchronous with total organic carbon(TOC) values up to 12.5%. We identify thisnegative δ 13 C excursion as a result of marineanoxia associated with the Kačák-otomari Eventand suggest that the excursion is a global eventdriven by a source of isotopically light carbon,followed by a productivity event, similar toMesozoic oceanic anoxic events. Such similaritiesbetween Devonian and Mesozoic oceanicanoxic events may become more evident withincreased high-resolution isotopic and geochemicalinvestigations of Devonian successions.2008040523157