Doushantuo embryos preserved inside diapause egg cysts

Phosphatized microfossils in the Ediacaran (635-542 Myr ago) Doushantuo Formation, south China, have been interpreted as the embryos of early animals. Despite experimental demonstration that embryos can be preserved, microstructural evidence that the Doushantuo remains are embryonic and an unambiguous record of fossil embryos in Lower Cambrian rocks, questions about the phylogenetic relationships of these fossils remain. Most recently, some researchers have proposed that Doushantuo microfossils may be giant sulphur-oxidizing bacteria comparable to extant Thiomargarita sp. Here we report new observations that provide a test of the bacterial hypothesis. The discovery of embryo-like Doushantuo fossils inside large, highly ornamented organic vesicles (acritarchs) indicates that these organisms were eukaryotic, and most probably early cleavage stage embryos preserved within diapause egg cysts. Large acanthomorphic microfossils of the type observed to contain fossil embryos first appear in rocks just above a 632.5 +/- 0.5-Myr-old ash bed, suggesting that at least stem-group animals inhabited shallow seas in the immediate aftermath of global Neoproterozoic glaciation.     

Biodiversity of Early-Middle Ordovician acritarchs and sea level changes in South China

Acritarchs are organic-walled cysts of unicellular pro- tists that cannot be assigned to any known group of or- ganisms. Most acritarchs are probably the resting cysts of marine eukaryotic phytoplankton. Because of their small size, abundance and diversity, as well as widespread distri- bution, acritarchs are very useful in biostratigraphic cor- relation, as well as paleobiogeographic and paleoenviron- mental studies. Furthermore, they represent the fossil re- cord of the base of the marine fo…     

湘西花垣中寒武统具表面装饰的管状微体化石

对采自湘西花垣县排碧剖面中寒武统花桥组灰岩中具表面装饰的磷灰石质管状化石（Ornamented tubes）进行了研究,依据化石的壳面装饰特征,建立了3形态类型：Ornamented Tube Form Ⅰ,Ornamented Tube Form Ⅱ 和 Ornamented Tube Form Ⅲ。其中Ⅰ型壳体表面装饰有尖细的小刺,多数标本壳刺成行排列,行间存在宽约0.01～0.05 mm的间隔;Ⅱ 型管体表面具有零散稀疏而不规则分布的斑疹状壳饰,壳体微微向外弯曲的一侧具有一列粗壮的呈锯齿状排列的脊刺;Ⅲ型整个壳体表面布满圆形、卵圆形瘤状壳饰,壳饰中空,与壳体内腔相通,壳体微微向外弯曲的一侧具有一列粗壮的呈羽状排列的脊刺。从壳体形态、表面装饰特征分析,这类管状化石可能是节肢动物(如高肌虫类)生物体壳瓣上的前刺或背部的刺等管状硬体构造。     

Affinities and functional morphology of the Middle Cambrian ornamented tubules from West Hunan, China

Problematic phosphatic tubular microfossils with ornamented sculptures are documented to exist in limestones of the upper Middle Cambrian Huaqiao Formation at the Paibi section and the Wangcun section in West Hunan, China. Two morphological patterns, including Ornamented Tube Form I and Ornamented Tube Form II are described. Based on the analysis of the preservation, wall structure and composition of the fossils, it is deduced that these ornamented tubes may represent carapace spines of some Cambrian arthropods with phosphatic carapaces, such as bradoriid crustaceans. Analysis of functional morphology indicates that the sclerites may rather be considered of a defensive than grasping function on the original organism body.     

Discovery of Ordovician acritarchs in Buqingshan ophiolite complex, East Kunlun Mountains and its significance

This note reports the first discovery of Middle-Late Ordovician acritarchs from the Buqingshan ophiolite complex of the southern ophiolite zone of East Kunlun. The acritarch assemblage is dominated with acanthomorphids (approx. 32%) and sphaeromorphds (approx. 63%) and contains more characteristic forms, such as Lophosphaeridium edenense, L. varum, Nothooidium sp.,? Buedingiisphaaeridium sp., Visbysphaera sp., Strophomorpha sp., etc. In addition, some tube-like fragments and tetrads, which are recognized as affinity to terrestrial plants and usual occurrence in Late Ordovician-Early Silurian strata, are preserved together with acritarchs. All the known fossil evidence indicates that the strata should be Middle-Late Ordovician in age. It not only provides paleontological proof for the existence of Ordovician ophiolite, but also challenges the usual ideas on strata composition of the studied area and the southern ophiolite zone of East Kunlun, and the models on tectonic framework and evolution of this area and the northern part of the Qinghai-Tibetan Plateau.     

贵州新元古代瓮安生物群中动物胚胎化石研究进展

 瓮安生物群指产出于贵州瓮安磷矿地区新元古代埃迪卡拉纪陡山沱组（635~551Ma）上磷矿段的一个特殊磷酸盐化微体化石组合,主要由多细胞藻类、大型带刺疑源类和处于不同发育阶段的多种后生动物胚胎组成,并包括少量可能的后生动物幼虫和成体化石。瓮安生物群作为迄今为止世界上最古老的前寒武纪后生动物化石群,为探索后生动物的起源和早期演化历程提供了独一无二的实证记录。10余年来,瓮安生物群中动物胚胎化石的研究取得多项突破性进展,已确认至少5种不同卵裂方式的动物胚胎化石,胚胎化石分类从单纯的形态学分类向生物学分类转变,为揭示瓮安生物群中动物多样性提供了更多线索。同时,相关研究更新了繁盛于埃迪卡拉纪大型带刺疑源类生物属性的传统认识,并将之与有表面装饰的动物休眠卵（滞育胚胎）化石相联系。同步辐射X射线显微CT技术的应用成功解决了胚胎化石三维无损成像难题,为古胚胎学的发展带来了新的机遇。     

New data regarding acritarch biostratigraphy from the Early-Middle Cambrian Kaili Formation in Chuandong, Guizhou Province, China

Previous studies have evaluated acritarchs from the Balang and Pingzhai sections of the Early-Middle Cambrian Kaili Formation in east Guizhou, China. The results of these studies suggest that the acritarchs in these sections have potential biostratigraphic significance. More recently, 34 samples collected from 83m lower part of the Lower-Middle cambrian Kaili Formation in the Jianshan section of Chuandong, Guizhou Province were prepared for palynological analysis. Analysis of these samples revealed a distinct change in the acritarch assemblages at the bed, which was approximately 46m above the bottom of the Kaili Formation. These findings suggest a boundary represented by an important alteration of the ecological environment. In addition, the position of the acritarch biostratigraphic change is somewhat higher than the boundary between Cambrian Series 2 and Series 3 based on trilobites found in the same section. This indicates that the distinct change in acritarch assemblages is similar to the change in trilobite assemblages that occurs around the boundary between Cambrian Series 2 and Series 3. Therefore, acritarch biostratigraphy can provide data that can be used to define the base of Cambrian Series 3 in this region, and possibly worldwide.     

The palaeoenvironmental implication of Early-Middle Ordovician acritarch communities from South China

As primary producers,acritarchs that represented the base of the food chain in the Early Paleozoic marine ecosystem formed the marine phytoplankton communities whose distributions might affect those of other faunas.Ten acritarch ecological assemblages with their distributions controlled by the environmental factors were recognized in the Meitan Formation of the Honghuayuan section,Tongzi,Guizhou Province,the Dawan Formation of the Huanghuachang and Daping section,Yichang,Hubei Province,and the Dacao Formati...     

江西玉山Etagraptus approximatus笔石带疑源类化石的发现及其意义

首次报道发现于江西玉山Etagraptus approximatus笔石带的疑源类化石，计12属23种，其中包括3个未定种，含量最高的3属是Stelliferidium、Polygonium、Micrhystridium，占总含量的77．4％，此外，Multiplicisphaeridium、Caldariola、Baltispharidium、Pteinosphaeridium也较常见，一定程度上反映了阿伦尼格期早期疑源类组合面貌。     

The microfossils in phosphate deposit in Doushantuo stage, Sinian System, Weng’ an, Guizhou Province

The aim of this study is to discuss the microfossils in phosphate deposit in the Doushantuo stage, Sinian System, Weng’an, Guizhou Province. Based on the detailed observation in morphology and microstructures, it is considered that those acritarchs with interior spicules probably belong to sponge animals. However, some explanations for a part of soft-tissue are still controversial. The reliable conclusion still needs more evidence to study. The scientific significance of this study and the key questions for further studies are suggested here.     

Female swallow preference for symmetrical male sexual ornaments.

Many secondary sexual characters are supposed to have evolved as a response to female choice of the most extravagantly ornamented males, a hypothesis supported by studies demonstrating female preferences for the most ornamented males. Comparative studies of elaborate feather ornaments in birds have shown that (1) ornaments have larger degrees of fluctuating asymmetry (small, random deviations from bilateral symmetry caused by an inability of individuals to cope with environmental and genetic stress during development of a character) than other morphological traits, and (2) the degree of fluctuating asymmetry is often negatively related to the size of the ornament. The negative relationship between ornament asymmetry and size suggests that ornament size reliably reflects male quality because the largest secondary sex traits demonstrate the least degree of fluctuating asymmetry. I manipulated tail length and tail asymmetry independently in male swallows (Hirundo rustica) to determine whether ornament size or asymmetry were used as cues in mate choice. Male swallows with elongated, symmetric tails mated earlier, and enjoyed larger annual reproductive success than did males with shortened tails and increased asymmetry. Females therefore prefer large as well as symmetric ornaments, which suggests that females in their mate choice use ornament asymmetry and size as reliable indicators of male quality.     

The oldest known dinoflagellates： Morphological and molecular evidence from Mesoproterozoic rocks at Yongji, Shanxi Province

Abundant and well-preserved organic-walled microfossils including acanthomorphic acritarchs have been found in Mesoproterozoic Beidajian Formation in the Yongji area of Shanxi Province, North China. The morphological and ultrastructural features of these acanthomorphic acritarchs resemble living dinofiagellates (e.g. double-walled and polygonal structures), which leads to the interpretation of these fossils as probably the oldest dinofiagellates. The detection of dinosterane, a dinofiagellate biomarker, from pyrolytic product of these fossils further supports the morphological inference. This finding is consistent with molecular clock estimate that dinofiagellates may have diverged 700 to 900 million years (Ma) before previously known fossil record.     

Coprophagy: an unusual source of essential carotenoids

The rare Egyptian vulture (Neophron percnopterus) stands out among the Old World vultures (Family Accipitridae) because of its brightly ornamented head, which is coloured yellow by carotenoid pigments, and its practice of feeding on faeces. Here we show that Egyptian vultures obtain these pigments from the excrement of ungulates. To our knowledge, this is the first demonstration that faeces can be used as a source of carotenoids by a vertebrate.     

井栏边草（pteris multifida Poir.）配子体的培养与观察

本文对井栏边草配子体的发育进行了研究,其孢子为淡褐色、三裂缝,赤道面观呈椭圆形,极面观呈钝三角形有瘤状纹饰,孢子培养7～9d开始萌发,孢子萌发为通常切线型,幼时丝状体阶段为3细胞长。培养80～100d后原叶体成熟,其精子器呈球形,颈卵器为高等蕨类植物典型类型。     

Exceptional preservation of fossils in an Upper Proterozoic shale

Late Proterozoic organisms must have been diverse and widely distributed, but in general their fossil record is both taxonomically and environmentally limited. Exceptional preservation of Proterozoic fossils is not unknown, but it is usually associated with silicified carbonates from restricted peritidal or playa lake environments. We report here an exceptionally well preserved and distinctive assemblage of Late Proterozoic fossils from subtidal marine shales. In addition to the sphaeromorphic acritarchs and cyanobacterial sheaths routinely preserved in Proterozoic rocks, this assemblage includes multicellular algae ('seaweeds'), a diverse assortment of morphologically complex protistan vesicles, and probable heterotrophic bacteria. Thus, it provides one of the clearest and most taxonomically varied views of Proterozoic life yet reported.     

早寒武世疑源类的古生物地理学意义

根据早寒武世疑源类在全球的古地理分布，并参考古地磁和动物化石等方面的资料，进行了早寒武世疑源类的古地理分区。结果表明：早寒武世在全球范围内可分为2个疑源类古地理大区，即波罗的海－北美－亚、澳大区和地中海大区；我国西南地区早寒武区筇竹寺期，可根据疑源类分为两个生态区，即扬子区和江南区。这一研究结果为今后各区生态结构分析，提供了重要基础资料。     

New observations on spiculelike structures from Doushantuo phosphorites at Weng’an, Guizhou Province

Doushantuo phosphorites at Weng’an, Guizhou Province, provide a unique opportunity for the study of early evolution of multicellular organisms, including metazoans. Our light microscope and SEM observations, however, do not substantiate a sponge spicule interpretation of spicular structures. No convincing axial canals have been seen in the observed spicule population. Instead, the coexistence of some monaxonal spicules with clearly diagenetic crystal fascicles and dumbbells suggest that these monaxons may also be diagenetic in origin. Our preliminary EDS analyses detect no significant silicon in spicule-containing intraclasts (including abiotic clasts and fragments of sphaeromorphic acritarchs and algal thalli), that contain abundant monaxonal spicular structures. We, therefore, believe that the evidence for a sponge spicule interpretation of the Doushantuo spicular structures are at best ambiguous at present; these alleged sponge spicules are indistinguishable from coexistent diagenetic crystals.     

Ediacaran oxidation and biotic evolution

The link between the radiation of various lineages of eukaryotes in the latest Proterozoic and massive environmental changes--oxygenation, global ice ages and bolide impact--is the focus of much research interest. Fike et al. use carbon and sulphur isotope-chemostratigraphic data from Oman to propose three stages of oxidation in the Ediacaran oceans, and link the second and third stages to eukaryote diversification. The second stage, signalled by strongly 13C-depleted sedimentary carbonates (the 'Shuram excursion'), is believed to result from oxidation of a large, deep-ocean reservoir of organic carbon. Fike et al. use our data to assert that a correlative carbon isotope excursion in Australia coincided with the initial diversification of acanthomorphic acritarchs. Peak diversity is claimed to have coincided with subsequent deposition of 13C-enriched carbonate and the third oxidation stage. However, the authors seem to have misinterpreted our data, which instead indicate that diversification significantly preceded the Shuram excursion; this weakens their argument for a link between the inferred oxidation events and eukaryote evolution.     

Precambrian phosphatized embryos and larvae from the Doushantuo Formation and their affinities, Guizhou （SW China）

Weng＇an phosphates of the Precambrian Doushantuo Formation, Guizhou （southwestern China） preserve a large number of exquisite biological structures, which are mostly micro-spherical and represent seaweeds, acritarchs and developing eggs related to various groups of metazoans. Here is a report of a variety of developing eggs and larvae, which are most probably of Cnidarian affinity. The eggs examined in the study are composed of early cleavage embryos and two-layered gastrulae. The early cleavage embryos are radial and total cleavage with equal-size blastomeres. The gastrulae mostly bear a large archenteron, which is filled with yolk-degrading organic matter. Ovoid to fusiform planula-like larvae identified in thin sections under light microscope are mostly mouthless and their gastrovascular cavity is filled with possible yolk-degrading organic matter. They are likely representatives of non-feeding larva. The uncommon planula-like structures are hollow, with each having a mouth-like structure on its narrow end. We interpret them as feeding larva. Study of these embryos with possible Cnidarian affinities shed new insight on the origin of metazoans.     

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.