疑源类Tianzhushania在贵州瓮安震旦纪陡山沱组磷块岩中的发现

首次报道贵州瓮安地区震旦系陡山沱组磷块岩中的大型具刺凝源类Tianzhushania spinosa及其新种Tianzhushania tuberifera sp.nov.前者形态特征及内部结构与湖北峡尔地区震旦系陡山沱组隧石结核中发现的典型Tianzhushania spinosa 标本（硅化）完全相同,但多数未遭受重力挤压呈球形保存。新种特征明显,也呈球形保存,但内层表面具有明显瘤突,瘤突顶端向外延伸出单一或多条管状制,另外还探讨大型具刺疑源类Tianzhushania属的特征,已定种的地理分布,地层意义和亲缘关系。     

贵州瓮安新元古代陡山沱组磷酸盐化管柱状微体化石新材料

在用醋酸浸泡处理采自贵州瓮安新元古代陡山沱组磷酸质岩石样品时,获得大量微体动物骨骼化石。文中重点报道部分管柱状微体化石,即：Sinoquadraticus poratus gen.et sp.nov和Sinoquadraticus wenganensis gen. et sp.nov.。并对Sinocyclocylicus的部分特征进行补充。     

瓮安陡山沱组磷块岩中球状绿藻化石繁殖机制的发现

贵州瓮安陡山沱组上段含磷地层中产有大量球状微化石,其中一些被鉴定为绿藻类分子。肖书海等认为这些被鉴定为绿藻分子的单细胞和多细胞球状化石中的Megaspharea和Parapandorina两属是动物卵和胚胎发育早期的化石。这一解释引起国际古生物学界的关注。然而,动物胚胎早期几次分裂非常迅速,可能在24小时或更短的时间内即达到64细胞分裂阶段,这使“动物胚胎”的解释蒙上难以捉摸的阴云。近年来。我们在实体标本的电镜扫描和岩石薄片研究中,观察到配子的存在和动孢子的释放,这是绿藻类繁殖的明显证据。在电子显微镜下,一个8细胞球状化石（Parapandorina raphospissa）（直径约600μm）的一个细胞中有若干特别的小球体：外形陀螺状,直径和高均约为20μm,一端平而具螺旋状“脊”样装饰。我们认为这是被磷酸盐化而保存下来的配子。在岩石薄片中,见到表面光滑的球状化石的切面（直径约260μm）中有一个圆形开口（直径100μm）,原生质凝缩后被磷酸盐化,与壁分离产生的孔洞中有连续的葡萄状磷质膜围绕,残余孔洞为白云石充填。另一个类似的切面（直径240μm）显示具有较厚的细胞壁,也有一个直径100μm的开口,成岩白云石的“塞子”中保存着一个直径约20μm的磷酸盐化的小球,清晰地显示从开口处向外释放的状态。它们很象是一个合子和正在释放的动孢子。Megaclonophycus onustus的似冷冻孢子直径较大,其形状和特片象M.inornata的细胞.推测Megaclonophycus onustus和M.inornata是同一类生物在不同生活周期阶段中保存的化石(图1).而以动孢进行繁殖和以亲孢子繁殖的微生物不是一类,按Bold和Wynne的分类应分别置于绿球藻目和小球藻目。上述材料表明,Megasphaera inornata和Parapandorina raphospissa具有无性和有性繁殖机制,显然不是动物卵或胚胎早期发育阶段所应有的特征。现生Pandorina通常包含8-16个细胞,行无性繁殖时每个细胞进行一系列分裂而成为一个似亲群体,似亲群体被释放出来而发育成一个成熟个体;行有性繁殖时,雌雄异体的Pandorina的每一个细胞都能转变为一个配子囊,释放出的配子结合或合子,然后发育成新个体。     

氢氟酸浸解法研究华南陡山沱组燧石结核中硅化疑源类初探

华南埃迪卡拉系陡山沱组燧石结核中保存丰富的疑源类化石,对它们的研究一直以岩石切片为手段,这在很大程度上影响到对其三维形态的恢复、系统分类的讨论,以及不同埋藏相下化石组成的对比。本研究尝试用氢氟酸浸解燧石结核来获取立体保存的疑源类标本。本实验使用4%(体积分数)的稀氢氟酸配合20目和400目尼龙筛网,以每2-3小时一次的频率收集酸浸解残余,从来自宜昌地区晓峰河和五指山剖面的陡山沱组二段燧石结核中获得了一些硅质标本,包括立体保存的球状疑源类和疑似化石的片状标本。其中,球状疑源类保存了膜壳塑性变形、膜壳外板片状装饰、内部小球体等结构特征,与从燧石结核岩石薄片中获得的标本和从磷块岩中酸浸解获得的立体磷酸盐化标本完全可以对比;它们的保存状态显示多数标本为疑源类的硅质铸模。本研究表明,作为岩石薄片法的重要补充,氢氟酸浸解法在分离和研究埃迪卡拉系燧石中保存的硅化疑源类上有较大潜力。     

贵州瓮安上震旦统陡山沱组骨针状假化石

通过薄片观察,贵州瓮安上震旦统陡山沱组底部的岩石中保存许多不透明的海绵骨针状物体。扫描电子显微镜和能谱分析表明,它们不是化石而是毒砂矿物晶体。因此,薄片中见到的矿化的海绵骨针状化石,尤其是前寒武纪的骨针状化石,需应用多种手段的测试才能够可靠地确认。     

贵州黄花冲下奥陶统湄潭组疑源类

对贵州黄花冲奥陶系湄潭组Azygograptus suecicus带疑源类组合研究表明,该组合可以与扬子区陕南、川东南、黔北、黔南、湘西、鄂西等地同期组合对比,并根据特征分子产出判别该组合应划归环冈瓦纳疑源类生物地理区。鄂西宜昌大湾组疑源类组合与黄花冲湄潭组疑源类组合的差异系环境因素所致。     

Wengania globosa在陕西勉县茶店陡山沱组磷块岩中的发现

本文报道陕西勉县茶店陡山沱组磷块岩中的疑源多细胞生物化石,其中Ｗｅｎｇａｎｉａｇｌｏｂｏｓａ属于首次报道。勉县茶陡山组磷块岩中的化石组合与贵州瓮安陡山沱组与可以直接对比,进一步了此两地的磷块岩属同期沉积产物。这一发现表明新元古代磷块岩中可能保存了多细胞生物早期演化中最精采的章节,因而进一步深入研究陡山沱组磷块岩大有必要。本文还讨论了疑在Ｍｅｇｈｙｓｔｒｉｃｈｏｓｐｈａｅｒｉｄｉｕｍ ｃｈａｄｉａｎ     

宜昌峡东地区埃迪卡拉系陡山沱组疑源类化石新材料及其生物地层学意义

在湖北宜昌秭归青林口剖面埃迪卡拉系陡山沱组二段燧石结核中发现大量微体化石,其中包括大型带刺疑源类8属9种(含1个未定种):Appendisphaera?hemisphaerica,A.magnifica,Dicrospinasphaera zhangii,Eotylotopalla dactylos,Mengeosphaera chadianensis,Taedigerasphaera lappacea,Tanariumsp.,Tianzhushania spinosa,以及Variomargosphaeridium lithoschum。同时在宜昌秭归金瓜墩剖面陡山沱组二段发现一些新的具刺疑源类化石材料,结合过去的报道,总结该剖面陡山沱组二段的疑源类化石组成:共7属9种(含3个未定种和1个相似种),及1个不定种,包括Appendisphaera magnifica,Appendisphaera sp.,Dicrospinasphaera zhangii,Knollisphaeridiumsp.,Mengeosphaera chadianensis,Mengeosphaera sp.indet.,Tianzhushania spinosa,Variomargosphaeridium lithoschum,Weissiella cf.brevis,以及Weissiella sp.。在宜昌三斗坪九龙湾剖面陡山沱组二段发现具刺疑源类Variomargosphaeridium lithoschum。这些化石材料丰富了对峡东地区陡山沱组二段具刺疑源类化石组成的认识,表明峡东地区陡山沱组具刺疑源类下组合与上组合在化石组成上的差别或许小于过去的认识。     

贵州晚新元古代陡山沱磷块岩中疑似磷酸盐化原生动物化石

发现于贵州省瓮安和福泉县晚新元古代陡山沱期磷块岩中的一组可疑的磷酸盐化原生动物化石,暂定为1新属——侧孔虫(Luxapertus gen．nov．)。单房室壳体,卵形、球形及椭球形,磷酸盐化外壁1—2层,房室内分布磷酸盐化微粒和原生质(?)残留物分布不均匀形成各种不规则斑纹。壳体前方一侧发育内口管的管状或乳头状口孔,管状口孔有清晰的丝状伪足伸出,其前端或壳体后方附有一团原生质(?)残留物。上述特征表明这一类化石与有孔虫(Foraminifera)似有明显的亲缘关系。根据标本的形态特征和口孔性质,本文初步记述了这批材料中的瓮安侧孔虫(Luxapertus wenganensis gen．et sp．nov．)、球形侧孔虫(Luxapertus sphaeroidolis gen．et sp．nov．)和乳头侧孔虫(Luxapertus papillaformis gen．et sp．nov．)等三种侧孔虫新种,疑为地球早期原生动物的代表。这一发现丰富了瓮安生物群的内容,证明瓮安生物群中确有可疑的原生动物化石存在。一般认为有孔虫在寒武纪开始出现。瓮安生物群中可疑的有孔虫类的发现,使有孔虫首次出现的记录大大提前。     

峡东地区埃迪卡拉系陡山沱组疑源类生物地层序列

峡东地区埃迪卡拉系陡山沱组自下而上可分4个岩性段:第1段为1.5-5m具帐篷和板裂构造的"盖帽白云岩";第2段是90-120m白云质灰岩夹黑色页岩,富含燧石结核;第3段为40-70m的白云岩夹燧石层和燧石结核;第4段10-20m为黑色碳质页岩夹碳酸盐岩透镜体.根据对该区九龙湾、王丰岗、田家园子、九曲脑、晓峰河、樟村坪等多条陡山沱组剖面的重新调查,确认第2和第3段分别含有不同的疑源类组合,二者被之间出现的δ13C负漂移(EN2)所分隔.下组合以Tianzhushania和高分异的具刺疑源类出现为特征.上组合与下组合的区别是:(1)Tianzhushania绝迹;(2)出现大量表面光滑,介于90-150μm的球状膜壳;(3)高分异的具刺疑源类既包括下伏上延的种类,又含有首次出现的新类型;(4)还出现可能为单细胞原生动物的微化石;(5)管状化石震旦圆圆茎(Sinocyclocylicus guizhouensis)首现.     

Macroalgal holdfasts and their interaction with environments from the Neoproterozoic Doushantuo Formation in Guizhou,South China

Numerous macro-organisms of the Doushantuo macrobiota, which were found in the black carbonaceous mudstone of the upper Neoproterozoic Ediacraan Doushan-tuo Formation in Jiangkou County, Guizhou Province, China, are considered to live on sea floor by their holdfasts. The appearance and preserved forms of the macroalgal holdfasts may provide some data to the study of the living and buried environments ofmacrobiota. They lived in the lower energy and clear environment, and fixed on a soupground with rich water (about 79% water). Currents, possibly ocean currents, could pull out the macroalgal holdfasts from the soupground and break off the macroalgal foliations. After such events, the corpses of macro-organisms would be covered in a reduced environment by the deposits. Afterwards, a new community, including regenerating and undying macro-organisms, lived continuously on a new deposit.     

Macroalgal holdfasts and their interaction with environments from the Neoproterozoic Doushantuo Formation in Guizhou, South China

Numerous macro-organisms of the Doushantuo macrobiota, which were found in the black carbonaceous mudstone of the upper Neoproterozoic Ediacraan Doushantuo Formation in Jiangkou County, Guizhou Province, China, are considered to live on sea floor by their holdfasts. The appearance and preserved forms of the macroalgal holdfasts may provide some data to the study of the living and buried environments of macrobiota. They lived in the lower energy and clear environment, and fixed on a soupground with rich water (about 79 water). Currents, possibly ocean currents, could pull out the macroalgal holdfasts from the soupground and break off the macroalgal foliations. After such events, the corpses of macro-organisms would be covered in a reduced environment by the deposits. Afterwards, a new community, including regenerating and undying macro-organisms, lived continuously on a new deposit. __________ Translated from Acta Micropalaeontologica Sinica, 2005, 23(2): 154-C164 [译自: 微体古生物学报]     

Three-Dimensional Phosphatic Preservation Of Giant Acritarchs From The Terminal Proterozoic Doushantuo Formation In Guizhou And Hubei Provinces, South China

During the last two decades, a diverse assemblage of multicellular algae, spherical microfossils, bacteria and cyanobacteria (the Weng'an Biota) has been reported from the Terminal Proterozoic Doushantuo phosphorite in south China, which provides an important window for evolutionary studies of multicellular life just before the Ediacaran animal radiation. In this paper we report on three-dimensionally preserved acritarchs from the Doushantuo phosphorites at Weng'an in Guizhou Province and, for the first time, from Baokang in Hubei Province. Our assemblage contains species of the genus Meghystrichosphaeridium Zhang, Yin, Xiao and Knoll, 1998 non Chen and Liu, 1986 including M. chadianensis (Chen and Liu) Zhang, Yin, Xiao and Knoll, emend. 1998, and M. reticulatum Xiao and Knoll, 1999; the genus Echinosphaeridium Knoll, 1992 including the species E. maximum (Yin) Knoll, 1992; the new genus Bacatisphaera including the new species B. baokangensis and the new genus Castaneasphaera including the new species C. speciosa . The latter shows a marked resemblance to similarly preserved phosphatized Palaeozoic acritarchs called 'mazuelloids', consistent with a phytoplanktonic mode of life for the global Doushantuo/Pertatataka microflora (DPM).     

Diverse small spinose acritarchs from the Ediacaran Doushantuo Formation, South China

The Ediacaran Doushantuo Formation in South China is underlain by the Cryogenian Nantuo Formation (glacial rocks) and overlain by the late Ediacaran Dengying Formation. It is characterized by well-preserved, large (normally >100 μm in size) spinose acritarchs (LSAs), which have been shown to be probably the only useful biostratigraphic tool for the global correlation of the early- and middle-Ediacaran. Acritarchs are organic microfossils normally known as single-celled eukaryotic organisms (protists). Although recent research suggests that some large spinose acritarchs may represent diapause egg cysts of metazoans, the biological affinities of the Ediacaran spinose acritarchs, especially for those displaying remarkable size ranges, are still debatable.Recently, smaller specimens of the Ediacaran spinose acritarchs have been found in cherts and phosphorites of the Doushantuo Formation in South China. Many described Ediacaran spinose acritarch taxa display large size variation (from tens to hundreds of microns in vesicle diameter), but some taxa only have smaller (<70 μm) specimens. The morphological comparison with Paleozoic counterparts indicates that some Ediacaran spinose acritarchs may have phylogenetic affinity to eukaryotic algae. More evidence, including wall ultra-structure, geochemical analysis and comparison with modern analogs, is needed to understand the biological affinity of the Ediacaran spinose acritarchs. The remarkable radiation of planktonic protists, characterized by abundant, diverse spinose acritarchs, occurred as early as in the late Neoproterozoic, i.e., 40–60 million years earlier than previously thought.     

Fossil preservation in the Neoproterozoic Doushantuo phosphorite Lagerstätte, South China

Phosphorites of the late Neoproterozoic Doushantuo Formation exposed in the vicinity of Weng'an, Guizhou Province, and Chadian, Shaanxi Province, South China, contain exceptionally well-preserved algal thalli, acritarchs, and globular microfossils interpreted as animal embryos. Combined optical microscopic and SEM observations provide insights into the taphonomy of phosphatized fossils. Algal cells and tissues are variably resistant to decay, and within preserved populations permineralization began at varying stages of degradation. In consequence, there is a spectrum of quality in cellular preservation. Algal cell walls, acritarch vesicles, and embryo envelopes are commonly encrusted by an isopachous rim of apatite, with cell interiors filled by collophane and later diagenetic dolomite. In contrast, blastomere surfaces of animal embryos are encrusted primarily by minute phosphatic spherules and filaments, possibly reflecting an immediately postmortem infestation of bacteria that provided nucleation sites for phosphate crystal growth. Thus, the same processes that gave rise to Phanerozoic phosphatized Lagerstätten - phosphatic encrustation, and impregnation, probably mediated by microbial activity - effected soft-tissue preservation in the Doushantuo Lagerstätte. It remains unclear how phosphatic ions and organic macro-molecules interact at the molecular level and to what extent specific microbial metabolisms or microenvironmental conditions control the phosphatization of soft tissues. New observations of phosphatized Doushantuo fossils include: a second locality (Chadian) for Wengania globosa , interpreted as an algal thallus and previously known only from Weng'an; microtunnels in Weng'an phosphorites interpreted as pyrite trails; and new taxa described from Weng'an: Meghystrichosphaeridium reticulatum (acritarch), Sarcinophycus radiatus (algal thallus), and one unnamed problematic form.     

New observations on Cucullus Steiner from the Neoproterozoic Doushantuo Formation of Guizhou,South China

Wang, Y & Wang, X. 2011: New observations on Cucullus Steiner from the Neoproterozoic Doushantuo Formation of Guizhou, South China. Lethaia, Vol. 44, pp. 275–286. The Neoproterozoic genus Cucullus is the most abundant and largest organism in the Miaohe biota in China, but has remained poorly understood both in morphology and classification. New material recently obtained from the upper Doushantuo Formation (Ediacaran) of northeastern Guizhou, South China, indicates that Cucullus bears thin organic walls composed of complex spongin fibres forming vertical filaments, which may have given rise to transverse filaments. Filaments, non‐mineralized spongin fibres, which may have served to support body, regularly interweave with each other in a body, and form openings on body sides that may have served as incurrent canals. The top pores may have served as excurrent canals. The overall features, including the organic wall, the complex spongin fibre networks, and the possible canal system of Cucullus, suggest a primitive element of the Demospongea. This benthic organism lived in a low‐energy, calm environment near or below the storm wave‐base with influence of episodic storms. Cucullus’ base nestled into the muddy substrate and its sacciform body floated in seawater. □ Cucullus, Doushantuo Formation, Neoproterozoic, Porifera, South China.     

Wall ultrastructure of an Ediacaran acritarch from the Officer Basin, Australia

Well-preserved organic-walled microfossils referred to as acritarchs occur abundantly in Ediacaran deposits in the Officer Basin in Australia. The assemblages are taxonomically diverse, change over short stratigraphical intervals and are largely facies independent across marine basins. Affinities of this informal group of fossils to modern biota are poorly recognized or unknown, with the exception of only a few taxa. Morphological studies by use of transmitted light microscopy, geochemical analyses and other lines of evidence, suggest that some Precambrian acritarchs are related to algae (including prasinophytes, chlorophytes, and perhaps also dinoflagellates). Limitations in magnification and resolution using transmitted light microscopy may be relevant when assessing relationships to modern taxa. Scanning electron microscopy reveals details of morphology, microstructure and wall surface microelements, whereas transmission electron microscopy provides high-resolution images of the cell wall ultrastructure. In the light of previous ultrastructural studies it can be concluded that the division of acritarchs into leiospheres (unornamented) and acanthomorphs (ornamented) is entirely artificial and has no phylogenetic meaning. Examination of Gyalosphaeridium pulchrum using transmission electron microscopy reveals a vesicle wall with four distinct layers. This multilayered wall ultrastructure is broadly shared by a range of morphologically diverse acritarchs as well as some extant microalgae. The chemically resistant biopolymers forming the comparatively thick cell, together with the overall morphology support the interpretation of the microfossil as being in the resting stage in the life cycle. The set of features, morphological and ultrastructural, suggests closer relationship to green algae than dinoflagellates.     

贵州寒武纪杷榔组古蠕虫类埋藏特征及意义*

贵州剑河寒武纪杷榔组辣子寨剖面含有丰度较高的古蠕虫类化石。化石鉴定为Wronascolex geyiensis, 主要保存在三个层位。在对三个层位的岩石、沉积特征、化石成因及埋藏特征探讨分析后, 证实W. geyiensis化石保存于快速的沉积事件导致的浊流沉积层内, 而化石埋藏的完美程度受到成岩过程中埋藏位置、沉积物中矿物结晶和充填方式的影响, 这些后期的成岩、成矿作用对先期形成的化石精细结构产生了直接和间接的破坏作用。本文通过对W. geyiensis化石体上黏土矿物、草莓状黄铁矿、自形–半自形黄铁矿的成因分析后, 获得最适合保存软躯体化石的环境应该为缺氧且生物体与孔隙水中的硫酸盐无接触的原地和近原地埋藏条件。     

Unusual compound zooecia in the trepostome bryozoan Eostenopora from the Devonian of Guizhou,China

Enlarged, ‘compound zooecia’ are described for the first time in a trepostome bryozoan. Several of these zooecia are visible in tangential sections of Eostenopora guizhouensis (Hu) from the Devonian (Eifelian) Houershan Formation of Houershan, Dushan, southern Guizhou, China. They are broad and occupy the space of two or occasionally three or four normal autozooecia. Some have bridging walls extending partway across the enlarged zooecial chamber. Without serial sectioning, the origin of compound zooecia in E. guizhouensis is debatable. However, the existence of irregular gaps in some zooecial walls leads to the hypothesis that compound zooecia originated from the loss by resorption of the skeletal walls between two normal autozooecia. The bridging walls are interpreted as a response by the bryozoan to restore the integrity of the constituent zooecia. By analogy with the ‘Doppelgänger’ zooids of some modern cheilostome bryozoans, compound zooecia of E. guizhouensis may have housed the lophophores of more than one zooid.