Remarkable preservation of microbial mats in Neoproterozoic siliciclastic settings: Implications for Ediacaran taphonomic models

It is beyond doubt that the appearance of infaunal bioturbation and metazoan biomineralization across the Ediacaran–Cambrian transition irreversibly affected the nature of marine sediment architecture and biogeochemistry. Here we review those changes in relation to their likely effect upon the processes of fossil preservation, especially within siliciclastic sediments. Processes of soft-tissue preservation in siliciclastic settings from the Ediacaran Period, including microbes and microbial mats as well as Ediacaran macrofossils, are here reviewed within this context. Highlighted examples include the exceptional preservation of microbes found in association with wrinkle structures and Ediacaran macrofossils in England and Newfoundland (replicated by silicate minerals) and in the White Sea region of Russia (replicated by iron sulphide). These occurrences show that soft-tissue preservation in siliciclastic settings went well beyond that typical for Ediacaran macrofossils alone and also extended to similar modes of preservation in associated microbes. Using these new observations it can be argued that several existing explanations for Ediacaran fossil preservation can be united within a biogeochemical model that involves evolution of the sediment mixed layer across this transition.     

Sedimentology,depositional environments and significance of an Ediacaran salt‐withdrawal minibasin,Billy Springs Formation,Flinders Ranges,South Australia

The late Ediacaran Billy Springs Formation is a little‐studied, mudstone‐dominated unit deposited in the Adelaide Rift Complex of South Australia. Sediments are exposed in an approximately 11 km × 15 km synclinal structure interpreted as a salt‐withdrawal minibasin. The stratigraphic succession is characterized by convolute‐laminated slump deposits, rhythmically laminated silty mudstones, rare diamictites and fining‐upward turbidite lithofacies. Lithofacies are the product of deposition in a deepwater slope or shelf setting, representing one of the few such examples preserved within the larger basin. Although exact correlations with other formations are unclear, the Billy Springs Formation probably represents the distal portion of a highstand systems tract, and is overlain by coarser sediments of the upper Pound Subgroup. Diamictite intervals are interpreted to be the product of mass flow processes originating from nearby emergent diapirs, in contrast to previous studies that suggest a glacial origin for extrabasinal clasts. Within the spectrum of outcropping minibasins around the world, the sediments described here are unique in their dominantly fine‐grained nature and overall lithological homogeneity. Exposures such as these provide an opportunity to better understand the sedimentological processes that operate in these environments, and provide an analogue for similar settings in the subsurface that act as hydrocarbon reservoir‐trap systems.     

Megascopic Symmetrical Metazoans from the Ediacaran Doushantuo Formation in the Northeastern Guizhou, South China

In South China, various megascopic symmetrical metazoan fossils were found in the upper Doushantuo (陡山沱)Formation of the Neoproterozoic Ediacaran.The worm-like fossil is characterized by modern taxological annelid, for many metameres, parapodia, one possible tentale, an alimentary canal, and a dorsal vessel. The triradiate discoidal fossil is belong to Trilobozoa, and the octaradiate discoidal fossil might be Ctenophora. All these fossils indicate that the megascopic metazoans have appeared in the Doushantuoian of Eidacaran and imply that the symmetrical metazoans must have originated at least 550 Ma ago.     

Vase-shaped microfossils from the Ediacaran Weng'an biota, Guizhou, South China

Vase-shaped microfossils (VSMs) are described from the Ediacaran Doushantuo phosphorites (ca. 599–584 Ma) of Guizhou Province, South China. They are morphologically attributed to two genera and three species, and thus expand our knowledge of the Neoproterozoic protozoans in the Weng'an biota. They resemble to the VSMs from the Lower Cambrian pre-trilobitic Kuanchuanpu Formation of southern Shaanxi Province in terms of the microstructures and chemical composition of the fossil walls. Microscopic observations indicate that the VSMs from both the Weng'an biota and the Kuanchuanpu Formation are preserved in either single-layered or multi-layered walls, and composed of calcium phosphate in chemical composition. The present fossils also share similarities, in size and general contour, to the VSMs previously described from the Gaojiashan Member, middle part of the Dengying Formation (ca. 551–542 Ma) in southern Shaanxi. The discovery of the VSMs from the Doushantuo phosphorite is an important contribution to the Weng'an biota, and may throw much light on the early evolution and diversification of protozoans during Precambrian–Cambrian interval.     

华南伊迪卡拉纪宏体生物群的古地理分布及意义*

伊迪卡拉纪（635—542Ma）是前寒武纪全球大规模末次冰期（Marinoan）结束后至寒武纪“生命大爆发”之前一段重要的地质时期,由于受到新元古代气候和环境剧变的影响,真核生物乃至多细胞生物迅速演化、分异,出现显著的适应辐射。中国华南的伊迪卡拉系——震旦系陡山沱组和灯影组及其相当地层代表着这一特殊地史时段的沉积,地层记录完整,岩相环境多样,化石产出丰富,是深入研究伊迪卡拉（震旦）纪（Ediacaran/Sinian）地层划分及全球对比、探讨早期多细胞生物起源和辐射的理想地区之一。其中,扬子台地边缘相地层中出露丰富的宏体化石材料,分异显著,具有较为独特的组合面貌。近年取得的研究成果表明华南宏体化石群中也含有澳洲伊迪卡拉生物群和俄罗斯白海生物群的典型分子。作者总结了前人关于华南伊迪卡拉纪岩相古地理的研究成果;重点展示了近年来开始研究的贵州江口“翁会生物群”、云南“江川生物群”的宏体化石;简要记述了华南伊迪卡拉系中以“庙河生物群”为代表的若干宏体生物群的古地理位置及其宏体化石组合特征,据此提出了华南伊迪卡拉纪丰富多样的宏体生物群基本发育在扬子台地边缘碎屑岩至碳酸盐岩相的过渡带和斜坡带;各生物群宏体化石的组合面貌受沉积微相的制约,存在一定的变化规律。宏体化石记录表明在这一时期,伴随着显著的气候和环境变化,不仅发生了一系列重要的生物演化事件,比如：多细胞藻类和后生动物普遍开始出现多样化发展,为寒武纪生命的演化辐射奠定了生态基础;而且在华南地区已经形成了一个全新的浅海生态系统,以浮游和底栖真核藻类为主的海洋初级生产者大量繁盛,尤其是丰富的多细胞藻类可能成为前寒武纪末期至寒武纪早期主要的生烃植物类群。     

Microbially induced sedimentary structures (MISS) from the Ediacaran Jodhpur Sandstone,Marwar Supergroup,western Rajasthan

Fourteen microbially induced sedimentary structures (MISS) have been described from the middle part of the Jodhpur Sandstone. They have been subdivided under three headings; (A) those microbially induced structures which could be compared with the structures also produced by the inorganic processes, (B) those structures which have unique morphologies and could not have produced by inorganic processes alone and (C) those structures which could not acquire specific morphologies and can be referred to as ‘textured morphological surfaces’ in the sense of Gehling and Droser (2009). These forms are described and their stratigraphic significance discussed. There are some morphologies like Arumberia banksi, Rameshia rampurensis and Jodhpuria circularis which have been restricted to latest Neoproterozoic sediments.     

Phosphogenesis of phosphorite from the Sinian Doushantuo Formation in Guizhou Province and its coupling relation with the Neoproterozoic Oxygenation Event

Phosphate deposits of the Ediacaran Doushantuo Formation accumulated in the central Guizhou Province are the typical phosphate-rich sediments during the Neoproterozoic Phosphogenic Episodes,which occurred after the “Snowball Earth”period and Neoproterozoic Oxygenation Event. However,the mechanisms of phosphate enrichment in seawater have always been hotly debated,and the research for correlations between phosphogenesis and transition of Ediacaran palaeo-ocean environments is still unsubstantial. This study focused on the sedimentological,petrological,mineralogical and geochemical analyses on the Doushantuo pristine phosphorite in Weng'an,Zunyi and Danzhai area. Documented by spherulitic phosphorites in the Lower Phosphorite beds from Weng'an area that contain abundant autogenetic Fe-bearing minerals such as pyrite and glauconite and show weak Ce negative anomaly,Fe-redox pumping in low-oxygen environments are the important phosphogenesis mechanism but only limited in coastal waters in the Early Doushantuo Period. Phosphorite in the Upper Phosphorite beds deposited within organic-rich beds and contain massive biological fossils suggests that phosphogenesis might have been triggered by degradation of organic matter and biological action in the Late Doushantuo Period,and distribution of phosphatic sediments extended to the deeper shelf to slope setting. Obvious Ce negative anomaly implies the increase of oxygen content in seawater. The transition of phosphogenesis mechanisms and the expansion of phosphorite deposits are the sedimentary response of ocean oxygenation,and the associated evolution of metazoans also changed the redox conditions of the deep seawater. These sedimentary and geochemistry data reflect the closed coupling relation between Doushantuo phosphorite in Guizhou Province and the Neoproterozoic Oxygenation Event.     

The correlation between macroscopic algae and metazoans in the Ediacaran: a case study on the Wenghui biota in northeastern Guizhou,South China

After the Marinoan glaciation, macroscopic organisms thrived in the Yangtze Sea, South China, during the Ediacaran period. The Wenghui biota, which is found from the upper Doushantuo Formation black shales (>551 Ma) in northeastern Guizhou, South China, includes macroscopic algae, metazoans and ichnofossils. Most macroalgae in the Wenghui biota bear a holdfast to secure them onto seafloor and have a thallus of various lengths extending into the water column. This biota can be divided into Globusphyton, Sectoralga–Longifuniculum, Cucullus, Beltanelliformis and Baculiphyca–Gesinella assemblages. A fossil-barren interval containing a thin layer of feldspathic sandstone separates the macroscopic organisms into two distinct parts. From the Globusphyton assemblage through the Sectoralga–Longifuniculum assemblage to the Cucullus assemblage, metazoans show a positive correlation with the abundance and diversity of branching macroalgae at both metre and millimetre scales. Nevertheless, both Beltanelliformis and Baculiphyca–Gesinella assemblages, in which the number and diversity of macroscopic algae and metazoans, especially the shorter branching macroalgae, are obviously decreasing or even lacking, might be related to a special environment and a fragile ecosystem. In addition, the ratios of Ni/Co, U/Th and V/(V + Ni) display zigzagged profiles at millimetre scales indicating frequent redox fluctuations. Variations in macrofossils and trace elements at both millimetre and metre scales indicate that the oxygen content in the northeast Guizhou Sea fluctuated frequently during the middle–late Ediacaran period and the Wenghui biota possibly lived in the redox buffering zone. Moreover, the abundance and diversity of macroalgae, especially the branching macroalgae, could have significantly influenced the redox conditions in water column. The increase in oxygen may have improved the environment for the growth and reproduction of macroalgae and metazoans.     

Acritarchs of Las Ventanas Formation (Ediacaran, Uruguay): Implications for the timing of coeval rifting and glacial events in western Gondwana

Acritarchs and other organic-walled microfossils occurring in siltstones of the Las Ventanas Formation (Quebrada de Viera and El Perdido members) are systematically described and illustrated. The assemblage includes the following species: Leiosphaeridia tenuissima, Leiosphaeridia minutissima, Lophosphaeridium sp., Soldadophycus bossii, Soldadophycus major, Soldadophycus sp. and Vendotaenia antiqua. The microflora is characterized by low diversity (six species), dominance of L. tenuissima, absence of acanthomorphic acritarchs, and relatively large size of sphaeromorphs, reaching 400 μm in diameter. A number of species are shared with acritarch assemblages preserved in the overlying Arroyo del Soldado Group. Differences between assemblages include the occurrence of abundant Bavlinella faveolata and small size of spheroids in the Arroyo del Soldado Group. The assemblage occurring in Las Ventanas Formation is assigned to the Ediacaran Leiosphere Palynoflora, which spans the interval between the base of the Ediacaran (end of the Marinoan Glaciation, 635 Ma) and the termination of the Gaskiers Glaciation (582 Ma). An early Ediacaran age between 615 and 579 Ma is also supported by available radiometric ages. An extensional setting for Las Ventanas basin is suggested on the basis of the bimodal, synsedimentary volcanism, strong palaeorelief, great thickness of alluvial fan conglomerates and the evolution from continental to open marine environments. Diamictites occurring in the Quebrada de Viera Member are described for the first time, including associated dropstones which suggest a glacial origin. If confirmed, this would be one more example of the association between rifting and glaciation in the Neoproterozoic, coeval with a low-diversity, high-abundance acritarch microflora. A causal relationship between these tectonic, climatic and biologic events is discussed.     

贵州震旦系陡山沱组磷块岩成磷作用及与新元古代末期氧化事件(NOE)的耦合*

新元古代末期历经“雪球地球”和大气、海洋增氧事件后,发生了全球性成磷事件,贵州省震旦系陡山沱组大规模磷矿床沉积是本次成磷事件的典型代表。然而现阶段对贵州陡山沱组磷块岩成磷作用机制研究存在诸多争议,成磷事件与同期古海洋环境转变之间的关联研究也较为薄弱。作者以贵州省瓮安、遵义和丹寨地区陡山沱组原生磷块岩为研究对象开展的沉积学、岩石学、矿物学和地球化学特征研究表明: 陡山沱早期成磷作用被限制在浅水海岸,瓮安地区A矿层球粒磷块岩中大量的含铁自生矿物黄铁矿、海绿石以及无Ce负异常指示的贫氧沉积水体环境均表明,Fe-氧化还原泵成磷模式在富磷过程中发挥了重要作用;陡山沱晚期磷块岩分布扩散至较深水陆棚—斜坡沉积相区,磷块岩与富有机质岩层共生,矿物晶体形态特征与矿石内富含的大量生物化石均表明,有机质沉降聚磷作用和生物成磷作用促使磷块岩大量沉积,较明显的Ce负异常值也指示了海水氧气含量的提升。成磷作用模式的转变和磷块岩分布的扩展是对海洋增氧事件的沉积响应,同时造成的多细胞动物演化也影响了深部水体的氧化还原状态,进而反映了贵州省陡山沱组磷块岩大规模沉积与新元古代末期氧化事件(NOE)密切的耦合关系。     

Sedimentological interpretation of an Ediacaran delta: Bonney Sandstone,South Australia

The type section of the late Ediacaran (ca 565 Ma) Bonney Sandstone in South Australia provides an opportunity to interpret a succession of Precambrian clastic sediments using physical sedimentary structures, lithologies and stacking patterns. Facies models, sequence stratigraphic analysis, and process-based architectural classification of depositional elements were used to interpret depositional environments for a series of disconformity-bounded intervals. This study is the first detailed published work on the Bonney Sandstone, and provides additional context for other Wilpena Group sediments, including the overlying Rawnsley Quartzite and its early metazoan fossils. Results show that the ～300 m-thick section studied here shows a progressive change from shallow marine to fluvially dominated sediments, having been deposited in storm-dominated shelf and lower shoreface environments, lower in the section, and consisting primarily of stacked channel sands, in a proximal deltaic environment near the top. Based on the degree of influence of wave, tidal or fluvial depositional processes, shallow marine sediments can be classified into beach, mouth bar, delta lobe and channel depositional elements, which can be used to assist in predicting sandbody geometries when only limited information is available. Sediments are contained within a hierarchical series of regressive, coarsening-upward sequences, which are in turn part of a larger basin-scale sequence that likely reflects normal regression and filling of accommodation throughout a highstand systems tract. Paleogeographic reconstructions suggest the area was part of a fluvially dominated clastic shoreline; this is consistent with previous reconstructions that indicate the area was on the western edge of the basin adjacent to the landward Gawler Craton. This research fills in a knowledge gap in the depositional history of a prominent unit in the Adelaide Rift Complex and is a case study in the interpretation of ancient deposits that are limited in extent or lacking diagnostic features.     

新元古代末期高家山生物群的生态多样性

新元古代末期是生命演化的关键转折期,也是以微生物占主导的生态系统向显生宙以后生动物占主导的生态系统的转变期,埃迪卡拉纪大型软躯体生物以固着、底栖、食悬浮为特色,普遍缺乏运动能力。作为这一时期特殊代表的高家山生物群,是目前新元古代唯一一个以黄铁矿化三维保存的管状和锥管状化石为主导,兼有骨骼生物、原生动物、钙化蓝细菌类及遗迹化石的多门类生物组合,是研究埃迪卡拉纪末期生命演化和生态系统演变十分重要的载体。本文通过对高家山生物群古生态学的初步研究,揭示出在前寒武纪—寒武纪之交,生态系统已显示一定的多样性。为适应平底面上(level-bottom)微生物席的发育,高家山生物群的许多生物采取了适应性的生存策略,通过黏附或插入微生物席中,营底栖固着食悬浮(如Cloudina、Conotubus)或化学共生(可能的Shaanxilithes)或平躺(如Gaojiashania和Sinotubulites)食碎屑生活。底内遗迹化石表明存在可能的表栖和半内栖、可自由运动、食碎屑的造迹生物。Conotubus中常见的“回春”或“复苏”现象,Gaojiashania和Sinotubulites的身体扭转或生活姿态调整则是对频繁风暴事件的被动适应。     

Ediacaran ice-rafting and coeval asteroid impact,South Australia: insights into the terminal Proterozoic environment

Isolated quartzose pebbles, clusters of quartz granules, orthogonal aggregates of poorly sorted quartzose coarse sand, and ovoid pellets (≤2 mm long) of quartz silt occur in hemipelagic marine mudstone of the mid-Ediacaran Bunyeroo Formation exposed in the Adelaide Geosyncline (Adelaide Rift Complex), and ovoid pellets of quartz silt in cores of the correlative marine Dey Dey Mudstone from deep drillholes in the Officer Basin, South Australia. This detritus is interpreted respectively as dropstones, dumps, and frozen aggregates dispersed by sea ice possibly of seasonal origin, and till pellets transported by glacial ice. The ice-rafted material in the Bunyeroo Formation only has been found <10 m stratigraphically below and above a horizon of dacitic ejecta related to the 90 km diameter Acraman impact structure in the Mesoproterozoic Gawler Range Volcanics 300 km to the west. Furthermore, till pellets have been identified 4.4 to 68 m below distal Acraman ejecta in the Dey Dey Mudstone >500 km northwest of the impact site. The Acraman impact took place at a low paleolatitude (～12.5°) and would have adversely affected the global environment. The stratigraphic observations imply, however, that the impact occurred during, but did not trigger, a cold interval marked by sea ice and glacial ice, although the temporal relationship with Ediacaran glaciations elsewhere in Australia and on other continents is unclear. Release from the combined environmental stresses of a frigid, glacial climate near sea-level and a major impact in low latitudes may have been a factor influencing subsequent Ediacaran biotic evolution.     

On the reliability of stable carbon isotopes for Neoproterozoic chemostratigraphic correlation

The reliability of δ¹³C trends in Neoproterozoic carbonate-dominated successions for regional and global chemostratigraphic correlation is discussed. In the light of recent findings of a predominantly non-marine rare earth element and yttrium signature in most Neoproterozoic carbonates and a comparatively short oceanic residence time of carbon, trends towards enrichment in ¹³C seen in many of these carbonates are considered to reflect facies variations rather than temporal signals of ocean chemistry. Positive δ¹³C_Carb excursions are explained by elevated bioproductivity and/or increased evaporation in shallow marine, near-coastal, temporarily restricted depositional environments. Examples are provided that illustrate that C isotope trends can be highly ambiguous temporal markers and are in the absence of other chemostratigraphic data, such as Sr isotope ratios, and radiometric age control of only limited use for stratigraphic correlation. The overall enrichment in ¹³C recorded by most Neoproterozoic carbonates, except for those in close stratigraphic proximity to glacial deposits, is suggested to reflect a dominance of microbially mediated carbonate formation in the Neoproterozoic. This might explain why C isotope chemostratigraphy in Neoproterozoic successions is less reliable than in Phanerozoic successions in which carbonates are, with only few exceptions, biogenic products of shelly fossils.     

Molecular composition and indigenity of organic matter in Late Neoproterozoic sedimentary rocks from the Yangtze region, South China

1 Introduction As a linkage between the biosphere and the geosphere, organic geochemistry, especially molecular markers, has become a powerful tool for investigating important geological events and the evolutionary history of ancient life on Earth (Kvenvo…     

Duration and synchroneity of the largest negative carbon isotope excursion on Earth: The Shuram/Wonoka anomaly

Carbonate δ¹³C values provide a useful monitor of changes in the global carbon cycle because they can record the burial ratio of organic to carbonate carbon. The most pronounced isotope excursions in the geologic record occur during the Neoproterozoic and have assumed a central role in the interpretation of biogeochemical events preceding the Ediacaran and Cambrian radiations. The most profound negative carbon isotope excursion is best recorded in the Ediacaran-aged Shuram Formation of Oman and has potential equivalents worldwide including the Wonoka Formation of South Australia and other sections in China, India, Siberia, Canada, Scandinavia and Brazil. All these excursions are less well understood than those in the Phanerozoic because of their unusual magnitude, long duration (> 1 Ma) and the difficulty in correlating Neoproterozoic basins to confirm independently that they do indeed record global change in the mixed ocean reservoir. Alternatively, these δ¹³C anomalies could reflect diachronous diagenetic processes. Currently none of these excursion are firmly time constrained and critical to their interpretation is a coherent reproducibility and synchroneity at the global ocean scale. Here we use available strontium isotope record as an independent chronometer to test the timing and synchroneity of the Shuram δ¹³C and its potential equivalents. The use of the ⁸⁶Sr/⁸⁷Sr ratio allows the reconstruction of a coherent, global δ¹³C record calibrated independently against time. The calibrated δ¹³C curve indicates that the Shuram negative anomaly spans several tens of millions of years and reaches values below −10‰. This carbon isotopic anomaly therefore represents a meaningful oceanographic event that fundamentally challenges our understanding of the carbon cycle as defined in the Phanerozoic.     

Octoradiate Spiral Organisms in the Ediacaran of South China

Shales of the Ediacaran Doushantuo Formation of South China contain a new disc-shaped macrofossil, Eoandromeda octobrachiata, characterized by eight spiral arms that were probably housed within an outer membrane. Although the presence of eight radiating structures entails a resemblance to cnidarian octocorals as well as to ctenophores, direct homologies with these extant groups are unlikely. Instead we bring attention to the helicospiral morphology of newly reported embryos from the Doushantuo Formation, suggesting that the long-sought adults of the Ediacaran embryonic metazoans have finally been found.     

Neoproterozoic trace fossils vs. microbial mat structures: Examples from the Tandilia Belt of Argentina

The Tandilia Belt in northeast Argentina includes a Neoproterozoic sequence of sediments (Sierras Bayas Group), in which the Cerro Largo Formation, ca. 750 Ma in age, forms a siliciclastic, shallowing upward succession of subtidal nearshore to tidal flat deposits. Trace fossils Palaeophycus isp. and Didymaulichnus isp. have been described from the upper part of this succession. Specific sedimentary structures consisting of round-crested bulges, arranged in a reticulate pattern, and networks of curved cracks are associated with the trace fossils. These structures are considered to be related to epibenthic microbial mats that once colonized the sediment surface. They reflect stages of mat growth and mat destruction, if compared to analogous structures in modern cyanobacterial mats of peritidal, siliciclastic depositional systems. Also the trace fossils are interpreted as mat-related structures, partly forming components of networks of shrinkage cracks, partly representing the upturned and involute margins of shrinkage cracks or circular openings in desiccating and shrinking, thin microbial mats.

The definition of Didymaulichnus miettensis Young as a Terminal Proterozoic trace fossil is questioned, and it may be considered to interpret the ‘bilobate’ structure as the upturned, opposite margins of microbial shrinkage cracks which have been brought back into contact by compaction after burial.     

Discoveries of new Longfengshaniaceae from the uppermost Ediacaran in eastern Yunnan, South China and the significance

A morphologically more diverse assemblage of Longfengshaniaceae has been found in the uppermost Ediacaran (Sinian) Jiucheng Member, Yuhucun Formation at Jinning and Jiangchuan, eastern Yunnan, South China. A majority of them are different from the Longfengshania found in the Neoproterozoic Changlongshan Formation, Yanshan Mountain area, North China and the Little Dal Group, North America. They are mainly characterized by a more varied, often thallus-like appearance with no branches, such as oval, pyriform, spindle, shovel, heart, ribbon and balloon shapes, and more sturdy stalk-like projection (stipe) with a smooth connection on the basal part of the thallus. In addition, they appear to have a remarkable attaching organ of lanceolate, shuttle-like or short stem-like structure at the base of the stipe. Six distinct morphological taxa are recognized, including one new genus, two new species and three conformis species. The characteristics of the family and the genus Longfengshania are further discussed in this paper. The new discoveries of these carbonaceous macrofossils identified as Longfengshaniaceae algae on the basis of the diagnostic forms and anastomosis patterns of their thalli and stipes demonstrate that an important evolutionary radiation of metaphytes took place in the last Ediacaran stage. The flourishing of the benthonic thallophytes attached to the substrate from eastern Yunnan and considered to be photosynthetic alga probably provided continuous nutritional habitats for the explosion and diversification of the Early Cambrian “Chengjiang biota”. Translated from Acta Geologica Sinica, 2006, 80(11): 1643–1649 [译自: 地质学报]