Quantitative Analysis of Flabellophyton from the Ediacaran Lantian Biota, South China: Application of Geometric Morphometrics in Precambrian Fossil Research

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 flabeilate fossils combining morphology, structure, population, and community-ecology study.

Rare earth elements and carbon isotope geochemistry of the Doushantuo Formation in South China:Implication for middle Ediacaran shallow marine redox conditions

The middle Ediacaran Shuram excursion, the largest negative δ 13 C carb excursion in Earth history, has been interpreted as indirect evidence for episodic oxidation and remineralization of deep ocean DOC (dissolved organic carbon). It has been hypothesized that such oxidation event may have occurred when anoxic DOC-laden deep water was brought to shallow shelves during oceanic upwelling, which is expected to cause localized anoxia in shallow environments. To test this prediction, we systematically analyzed rare earth elements (REE) and δ 13 C carb of the upper Doushantuo Formation carbonates in the Yangtze Gorges area of South China, which were deposited in an inner shelf environment and record a large negative δ 13 C carb excursion correlated to the Shuram event. The REE data show a significant positive shift in Ce/Ce* values, synchronous with a pronounced negative δ 13 C carb shift. This positive Ce/Ce* shift is interpreted to represent an oceanic anoxia event in shallow shelf environments, which may have been caused by the upwelling or impingement of oxygen-depleted and 12 C-enriched deep water onto shelves. This anoxia event coincides with a sharp decline in the abundance and diversity of Ediacaran acanthomorphic acritarchs, raising the possibility that these two geobiological events may be causally related.

Phosphatized biotas from the Neoproterozoic Doushantuo Formation on the Yangtze Platform

The Doushantuo Formation in South China was deposited after the Nantuo glaciation but before the evolution of complex Ediacaran metazoans. It contains multiple taphonomic windows, in its cherts, carbonaceous shales, and phosphorites, onto the late Neoproterozoic biosphere. The phosphatic window is unusually clear; Doushantuo phosphorites at Weng’an (Guizhou Province) are known to exquisitely preserve a multitude of single-celled eukaryotes, muiticellular algae, and microscopic animals. Our recent survey reveals that, in addition to the now famous Weng’an locality, Doushantuo phosphorites at Baokang (Hubei), Chadian (Shaanxi), and Shangrao (Jiangxi) also contain diverse eukaryotes preserved at the cellular level. All these phosphorites were deposited in shallow-water environments, typically above fair weather wave base and close to ancient islands. Along with Doushantuo cherts and shales, these phosphorites give us a clearer and more complete picture of late Neoproterozoic biological evolution: there

Paleoproterozoic glaciation: Evidence from carbon isotope record of the Hutuo Group, Wutai Mountain area of Shanxi Province, China

Palaeoproterozoic 全球冻结成冰(2.3 Ga ) 可以是地球历史上的第一个雪球地球事件。诺思中国暴露得好沉积存款这次有最小的 postdepositional 的时期改变。一个冻结成冰事件的沉积证据然而一直在缺乏。这里，我们在 Wutai 山区分析了 Paleoproterozoic Hutuo 组(2.52.2 Ga ) 的碳同位素作文，山西省，诺思中国。我们的数据表演，在里面一对更年轻的 chronostratigraphic 顺序更旧，(1 ) 积极 13Ccarb 在 Doucun 亚群的 Dashiling 形成珍视(3.2 ～ 1.0， VPDB ) ；(2 ) 在 13Ccarb 的减少从 Wenshan 形成珍视到中间的 Daguandong 形成(从 2.0 to1.2 ) ，在哪个时间期间 stromatolites 的出现衰退了；(3 ) 在上面的 Daguandong 形成的一次显著否定旅行，在 Daguandong 和 Huaiyincun 形成的边界(从 1.4 ～ 3.3 ) ，在 stromatolites 消失了的地方；并且(4 ) 13Ccarb 的渐渐的增加在 Beidaxing 和 Tianpengnao 形成珍视(从 1.2 ～ 1.4 ) ，在哪个期间时间 stromatolites 回来了。我们主张否定的碳同位素旅行从 Jianancun 形成记录了到 Hutuo 组的中间的 Daguandong 形成可以是对 Palaeoproterozoic 全球冻结成冰的诺思瓷器反应。

The Lantian biota:A new window onto the origin and early evolution of multicellular organisms

The Lantian biota at the Lantian Town of Xiuning County,Anhui Province,is preserved in black shales of the Ediacaran Lantian Formation.It yields some of the oldest known complex macroorganisms,including fan-shaped seaweeds and possible animal fossils with tentacles and intestinal-like structures reminiscent of modern coelenterates and bilaterians.The Lantian Lagerst tte sheds new light on the origin and early evolution of multicellular organisms in relatively quiet and deep environments soon after the Neoproterozoic Marinoan glaciation.The morphological complexity and diversity of early multicellular organisms may be closely related to sexual reproduction and alternation of generations.The fluctuation of oceanic redox conditions during this period may have played a role in the ecology and preservation of the Lantian biota.

Anatomy and plant affinity of Chuaria

Chuaria is one of the few globally distributed macrofossil pioneers documented in the Precambrian. It is perhaps the most controversial fossil in term of its affinity despite more than one hundred years of study. Many mutually exclusive affinities have been suggested for this frequently encountered fossil. Although often treated as a multicellular alga, this interpretation remains inconclusive because the lacking unambiguous demonstration of cellular structures. In this paper the cellular details of Chuaria are clearly revealed for the first time. The cell walls in Chuaria suggest that it is a multicellular eukaryotic alga, in agreement with the latest biogeochemical analyses. Different thicknesses of cell walls suggest primary cellular differentiation in this organism. Membrane-like structures within the cells (the first to be reported in Precambrian fossils) imply a eukaryotic nature. This study partially resolves the century-long controversy over the affinity of Chuaria, and makes Chuaria one of the few recognized multicellular eukaryotes before the Neoproterozoic glaciation.

Cell wall ultrastructures of the Proterozoic acritarch Leiosphaeridia asperata and their implications for biological affinity

Abundant sphaeroidal acritarch Leiosphaeridia asperata,with vesicle size ranging from 13 to 360 μm,occurred in the Proterozoic Liulaobei Formation shales in Huainan,Anhui Province.TEM/SEM studies of these sphaeroidal acritarchs have revealed complex ultrastructures,including ridges,bands,and possible trilaminar structures(TLS).Ridges,spaced ~1 μm apart,are distributed regularly on the vesicle internal surface of one specimen.Some specimens have alternating electron-dense and electron-tenuous bands that are perpendicular to vesicle walls.Some specimens have trilaminar structures(TLS),while a few others have both bands and TLS.These wall ultrastructures provide evidence that the Liulaobei leiosphaerids are of green microalgae.The variation in wall ultrastructures may represent various stages in a life cycle or developmental phases in the cyst formation analogous to some modern chlorophyceaen microalgae.

The earliest Foraminifera from southern Shaanxi,China

Vase-shaped microfossils(VSMs) described herein mainly occur as isolated individuals in thin bedded siltstone and silty carbonate of the Gaojiashan Member of the upper Ediacaran Dengying Formation(ca.551-541 Ma).Although these fossils are abundant,chained tests or other types of colonial aggregates have not been observed.Specimens in the siltstones can easily be isolated from the host rocks by ultrasonic vibrators.Compared with the co-occurring fossils Gaojiashania and Conotubus,VSMs are rarely pyritized,yet they are always three-dimensionally persevered with little deformation,suggesting that their tests were sturdy and possibly mineralized.Petrological observation and elemental mapping reveal two types of tests that are respectively calcareous and siliceous in composition.Calcareous tests typically consist of two to three crypto-crystal laminae,somewhat resembling bilamellar walls of foraminifers.Siliceous tests consist of fine-grained particles agglutinated with siliceous cement,similar to agglutinated walls of foraminifers.The Gaojiashan VSMs are broadly similar,at least in gross morphology,to the testate amoebae-like VSMs,but their relative large sizes(600-2400 μm) and possibly mineralized(rather than organic) tests argue against this comparison.They also show some similarities to other protozoans,especially tintinnids.However,tintinnids have robust pesudochitinous loricae consisting of both secreted and agglutinated materials.Moreover,tintinnid loricae differ in shape from the Gaojiashan VSM tests in having a constricted aboral end(sometimes with a caudal appendix) and a flaring oral opening.If the Gaojiashan VSMs are indeed related to foraminifers,they indicate that foraminifers were important players in late Ediacaran communities.