贵州剑河交榜剖面杷榔组顶底完整,三叶虫序列完整,产出掘头虫类三叶虫5属7种。其中Arthricocephalus chauveaui Bergeron,1899,Changaspis elongata Lee in Chien,1961,Arthricocephalites jishouensis(Zhou in Zhou et al.),1977,3个种也出现在北美格陵兰的Henson Glatsche组,提供了三叶虫全球对比的重要信息。其中A.chauveaui在交榜剖面杷榔组底部4 m首现,延伸至近顶部278 m。交榜剖面杷榔组岩石地层、生物地层和年代地层研究信息表明该剖面更适合作杷榔组岩石地层标准剖面,该剖面应是A.chauveaui首现点位定义的都匀阶界线层型剖面。可能是全球寒武系第4阶具有竟争潜力的界线层型剖面。
The Cambrian explosion was coined to describe the geologically sudden appearance of numerous bilaterian body plans(Phyla)around the Ediacaran-Cambrian transition,around 565-520million years ago.Many explanations and conjectures have been postulated in order to explain the pattern and duration of this explosive radiation of many different phyla of early metazoans.Here,we focus on the evolution of a phylum of marine suspension-feeding animals—the brachiopods,as exemplified by the exceptionally preserved taxa from the celebrated Chengjiang Konservat Lagerst(a|¨)tte(Yunnan,China).The abundant soft-bodied preservation at these fossil quarries gives us the only firm insights into what brachiopods looked like and how they functioned and lived when they first appeared on the Earth.Studies of Chengjiang brachiopods demonstrate that the early animals developed a remarkably varied organization of tissues and organs shortly after the onset of Cambrian explosion.In the marine suspension-feeding brachiopods,most importantly the tentaculate feeding structure of early brachiopods is already differentiated into two shapes of lophophore,anteriorly coiled(spiralled)and posteriorly arching tentacle crowns and the unique latter type was previously not documented from fossil and living brachiopods.Also unlike any known Recent brachiopod,all the known Cambrian brachiopods from Chengjiang have an open digestive tract that was disposed either as a Ushaped gut in linguliform and stem group brachiopods,or straight gut with a posterior anus in some calcareous-shelled stocks.Moreover,in contrast toliving lingulids,all the Cambrian brachiopods have an epibenthic lifestyle either cemented by a ventral valve or attached by variable pedicles to establish complex ecological community encompassing primary tierers and variable secondary tierers.It is therefore assumed that brachiopods were the first benthic metazoan that achieved their success in ecological stratification and tiering complexity by late Atdabanian.The setae are also important for
近期在贵州剑河八郎地区寒武系甲劳组发现了具软躯体的多门类化石,其中三叶虫最为丰富,计有6属7种,包括Fuchouia(Parafuchouia)transversa Lu et Qian in Zhang et al.,1980,Fuchouia(Parafuchouia)limbata Zhou in Lu et al.,1974a,Oryctocephalus sp.,Kooteniasp.及Jialaopsis latus Chien et Zhou in Lu et al.,1974a,Solenopleurinacf.xingrenensis Zhou(Chow)in Lu et al.,1974b和Probowmania(?)sp.,分属耸棒头虫目和褶颊虫目,以耸棒头虫目Fuchouia(Parafuchouia)为主。Oryctocephalus和Probowmania在寒武系甲劳组尚属首次报道,Probowmania在剑河八郎甲劳组中的报道是目前该属在贵州地区的最高层位。同时也确认了黔东南地区甲劳组的Fuchouia(Parafuchouia)三叶虫带为该地区寒武系最高三叶虫带,为国内外寒武系三叶虫同期地层划分及对比提供了材料。研究不仅丰富了丹寨-剑河寒武系甲劳组三叶虫组合,而且为研究Probowmania和Oryctocephalus的演化起到重要作用。
Calcified biofilms are preserved as thin micritic coatings in the Cambrian oolitic limestone of two sections in North and South China. Standard petrographic examination revealed that the biofilms were developed during the early diagenetic stage immediately after the freshly deposited ooids, proceeding in the continuous sequence of depositional processes. The biofilm outlines are highly irregular, with steep sides, tower-like structures and overhanging projections; the internal fabric of the biofilms is composed of roughly laminated micrite aggregates with channel-like structures. Biofilms exhibit a strong fluorescent reaction. Detailed SEM examination suggests that the biofilms are biotically dominated by cyanobacteria. Our study demonstrates that microbial colonies, such as biofilms, can develop on ooid cortices and influence the formation and microstructures of those ooids.
