华南奥斯坦(Orsten)型保存化石的研究进展及展望

奥斯坦(Orsten)型保存化石是一类个体微小却三维保存软躯体的、表皮次生磷酸盐化的以节肢动物为主的化石。和澄江生物群化石不同的是,奥斯坦型保存化石无明显受垂向挤压变形,是一种特殊的保存方式。奥斯坦型保存化石呈现出精美的生物活体时的形态特征,对研究节肢动物的生长模式、系统分类及个体发育提供了重要的形态证据。二十多年来,中国的古生物学家锲而不舍地在寒武纪地层里找寻这类化石。中国的南方是世界奥斯坦型化石重要的产出地之一,其潜在的化石资源有待深入研究,研究前景具有挑战性。     

Cleiothyridina obmaxima McChesny的个体发育、生态特征及进化途径

本文通过对Cleiothyridina obmaxima在同一化石点产出的大量个体的统计研究,讨论了该种个体发育的阶段及其种群动力学特征,并做出了相应的解释。同时根据该种个体形态的特征及其在个体发育不同阶段的变化,结合其所赋存的群落及其围岩特征,讨论了其个体生态学及其环境意义,进而探讨了该种的演化途径。     

贵州晚二叠世—早三叠世介形虫动物群的演变

贵州有许多二叠系至三叠系的连续剖面，沉积类型多样，生物化石丰富，其中介形虫化石不但类型多，数量也很丰富，保存完好，发展阶段明显。即长兴阶介形虫类型多，数量也多，壳饰复杂，以具瘤刺的为多，早三叠世早期介形虫贫乏，数量及类型都不多，壳饰以光滑或具微细纹饰的为主。根据这些介形虫类型和数量的变化，以及壳饰特征的研究，表明二叠系与三叠系界线附近的介形虫动物群也同其它生物一样发生了重要变化。为二叠－三叠系界线     

河南西峡地区晚白垩世介形虫的发现及其地层意义

2005年在河南西峡含恐龙蛋层中首次发现介形虫化石,产自红山水库-丹水剖面上白垩统赵营组下段64层,是以Eucypris-Mongolocypris-Cypridea-Talicypridea为特征的介形虫化石组合,由12属20余种组成.其中Talicypridea是中国、蒙古和东亚晚白垩世最典型的化石,在非洲刚果及南美阿根廷的晚白垩世地层中也有分布,因此赵营组的时代无疑应归属为晚白垩世.赵营组介形虫化石的新发现,为地层的划分对比、沉积环境的演变和盆地的演化研究提供了重要的依据.     

松辽盆地上白垩统青山口组介形虫群集性死亡事件成因

松辽盆地上白垩统青山口组发育含大量介形虫化石的介形虫层,介形虫层的单层厚约5～200cm。介形虫层具有低伽马、高电阻、低声波等测井响应特征。以测井资料识别介形虫层为基础,研究了介形虫层在平面上不同相带及其在纵向高频层序格架下的分布规律,探讨了介形虫群集性死亡的原因。介形虫层平面上主要分布在大庆、龙虎泡—红岗阶地、黑帝庙等环坳带,盆地东部相对不太发育,滨浅湖是介形虫生存的有利环境;纵向上主要分布在青一段上部及青二段。高频层序旋回控制了介形虫的繁殖与死亡,介形虫群集性死亡事件主要发生在基准面下降期间。介形虫的群集性死亡与湖泊面积扩大无关,更与海侵事件无关。基准面下降造成水体变浅、矿化度增高以及砂岩进入滨浅湖可能是导致介形虫群集性死亡的直接原因。     

贵州金沙长岩沟寒武系牛蹄塘组生物群组成特征

贵州金沙长岩沟牛蹄塘组生物群化石丰富,共计25属,以海绵动物为主,另有节肢动物及藻类两大门类化石代表.海绵动物以普通海绵为主,计8属,占整个海绵动物属的57％;六射海绵5属,占海绵的36％,另有纲、目及科未定1属.节肢动物8属中高肌虫占优势,计有5属;大型双壳节肢动物2属,三叶虫仅1属.藻类共计3属.与遵义牛蹄塘生物群相比,两地均以普通海绵为主,金沙长岩沟牛蹄塘生物群海绵更为丰富,与遵义黑沙坡的海绵组成有差异.金沙长岩沟节肢动物中三叶虫少,仅1属,但高肌虫丰富,达5属,而遵义黑沙坡只有2属高肌虫,三叶虫则达4属.遵义和金沙牛蹄塘组生物群分别有藻类属4个和3个,共有属2个.两地同一生物群组成的差异,说明同处扬子浅水区的金沙长岩沟及遵义黑沙坡沉积环境可能有所差异,因而组成面貌也有差异.两地牛蹄塘生物群均具有显著的澄江生物群色彩.     

罗平生物群的发现与研究进展——据云南1:5万罗平县等四幅区调和专题调查成果

成都地质调查中心云南区调项目组2007年在罗平县中三叠统关岭组二段中发现了罗平生物群。罗平生物群是三叠纪的化石宝库,化石包含了脊椎动物和无脊椎动物。脊椎动物以海生爬行类和鱼类为主。无脊椎动物以节肢动物为主,伴生有双壳类、腹足类、菊石、棘皮动物、腕足类、牙形石、有孔虫和植物类化石。牙形石研究显示罗平生物群处于Nicoraella kockeli牙形石带,时代上属于中三叠世安尼期Pelsonian亚期。罗平生物群保存在一个局限的台盆环境中。其化石的特异保存很可能与底层水缺氧和微生物席的密封作用有关。罗平生物群目前是研究三叠纪海洋生态系统复苏的最好的一扇窗口,也是三叠纪海生鱼类和节肢动物化石保存最好的产地之一,为研究二叠纪末大绝灭后海洋生态系统复苏以及中生代海洋生态系统的演化历史提供了新材料。     

大兴安岭中段晚二叠世林西组介形虫化石及环境意义

晚二叠世-中三叠世在中亚造山带东段构造演化过程中是承上启下的关键地质时期,所以晚二叠世林西组沉积环境对研究古亚洲洋闭合这一重大问题具有重要意义。大兴安岭地区晚二叠世林西组曾有双壳、叶肢介、植物及孢粉化石记录,但鲜有介形虫化石报道。在大兴安岭中段林西组研究中首次发现介形虫化石,经初步研究,主要分子有Kemeroviana,Volganella,Iniella,Qitaina,Darwinuloides,Palaeocypridopsis,Tomiella,Darwinula和Urumqiella等,暂划为Volganella-Kemeroviana组合,其时代为晚二叠世。与俄罗斯地台晚二叠世介形虫化石群关系较为密切,部分属种曾见于我国新疆准噶尔盆地和塔里木盆地。从介形虫化石组合特征和保存特点来看,其生存环境为淡水湖泊,故认为这一地区的林西组为陆相沉积。     

化石形态学中的对数螺线及其应用

许多化石都呈对数螺线形(ρ=Ae~(aθ))旋圈,其两条重要性质常用于数学模拟。数学模拟可以广泛应用于生物学及地层学研究:1、恢复残破及变形化石,从而避免了复形过程中的随意性;2、解释生物谱系的演化趋向(常表现为a值的递变)及其生理功能特征;3、依据同一谱系内各物种形态上的线性递变性,我们不仅可以确定地层的连续性及缺失数量,而且能将a值作为划分新物种的客观标准并预言新物种的存在;4、呈对数螺线形旋圈的化石在分析地层变形时具有其他形态的化石所不具的特殊优越性。     

基于岩石薄片分析的介形类化石赋存状态及地质意义——以济阳坳陷始新统泥页岩为例

首次利用岩石薄片观察和统计介形类化石的赋存状态,对济阳坳陷页岩的沉积环境及层序进行了研究。根据介形类化石在层面上的分布特征,将化石分布形式分为均匀分布、零星分布、条带状分布三种,按其保存状况分为双瓣、单瓣、破碎及压扁变形四种类型,化石丰度分为丰富(100瓣/4cm2)、中等(30~100瓣/4cm2)和稀少(30瓣/4cm2)三种。介形类化石的赋存状态与古盐度、岩相、层序及页岩中碳酸盐含量密切相关。研究表明:1济阳坳陷古近系沙河街组四段纯下亚段(Es4cx)——古近系沙河街组三段下亚段(Es3x)沉积期水体环境经历了由咸变淡的过程,盐度变化与化石丰度变化一致;2碳酸盐含量处于50%~60%范围内,最有利于介形类化石的保存;3纹层状灰质泥岩相和纹层状泥质灰岩相化石丰度高,但纹层状构造形成时期沉积速率慢,沉积基底较坚实,不利于介形虫死亡后的埋藏和保存,因此化石多以破碎为主。4介形类化石的盛衰与地层层序关系密切,一个层序内化石丰度呈现为出现-繁盛-衰退三个阶段,分别对应于低位体系域、湖扩展体系域和高位体系域。该方法解决了常规分析中难以观察到的化石原始保存和分布状态的问题,实现化石信息获取的最大化。     

Ostracods: The ultimate survivors

Ostracods are tiny crustacean arthropods just a few millimetres long, with a bivalved carapace made of calcium carbonate that covers the whole body, and into which the animal can retreat from the world outside. Because of their diminutive size they are largely overlooked as fossils, but they have a fascinating history. Silent witnesses to life in the seas since the time of trilobites, they have a fossil record extending back to the Early Ordovician, and possibly the Cambrian. Ostracods have survived nearly 500 million years of Earth history including the ‘big five’ mass extinctions of the Phanerozoic Eon; they are true survivors. They are almost perfectly adapted for the aquatic environments in which they live, and can be found from the ocean abyssal plains to damp leaf litter. The ostracod carapace is a triumph of biological engineering that has been re‐configured into myriad different morphologies according to environment. Streamlined and agile species plough through the ocean water column, sometimes reaching a ‘giant’ size of a centimetre in length, whilst their tinier sea bottom cousins make elaborately ornamented carapaces to withstand the pressures of living at the seabed, or shape their carapaces into forms that facilitate burrowing into sediment. Ostracods are key components of aquatic ecosystems. As primary consumers they are food for larger animals both in seabed and planktonic habitats, and they recycle much of the organic detritus produced by larger animals and plants. Delve into the history of ostracods and it is possible to find pioneers who triumphed in the plankton, early colonisers of terrestrial aquatic ecosystems, and ostracods that literally conquered the land. And in more recent times, ostracods have even hitched rides on rockets into space.     

Dimorphism of Bivalved Arthropod Branchiocaris? Yunnanensis from the Early Cambrian Chengjiang Biota, South China

The bivalved arthropod Branchiocaris? yunnanensis Hou, 1987 is redescribed on the basis of new fossil material from the early Cambrian Chengjiang biota, South China. In total, 81 specimens have been examined. The carapace comprises two identical valves, each valve are sub-circular in outline, ranging from 24 mm to 58 mm in length, and from 15 mm to 46 mm in height. The dorsal margin is straight and bears two short cardinal spines. The valve surface is either smooth or ornamented with polygonal reticular structures, which may result from different preservation conditions. Two morphotypes have been recognized based on the presence or absence of a subdorsal swelling of the valve, which is convex dorsolaterally and extends beyond the dorsal margin when it appears. Statistic and ontogenetic analyses show both morphotypes grow isometrically and have the same growth trajectory. Therefore, the two morphotypes are interpreted as dimorphism within the same species. Our results are helpful for investigating the taxonomy and ontogeny of arthropod fossils and suggest that dimorphism might be fairly common in these early arthropods.     

内蒙古宁城县道虎沟叶肢介化石群的时代

内蒙古赤峰宁城县道虎沟含丰富的叶肢介壳瓣及许多珍罕的软体化石 ,计有 1属 4种 :Euestheria ziliu-jingensis Chen,Euestheria haifanggouensis Chen,Euestheria jingyuanensis Chen,Euestheria luanpingensis Shen etNiu。这些分子都是我国中侏罗世早期自流井真叶肢介 (Euestheria ziliujingensis)动物群的重要成员 ,以个体较小、壳瓣圆或椭圆形、生长带具小网状装饰、种类单调、密集群生为特点 ,主要出现于中侏罗世早中期 (Bajocian- MiddleBothonia)。特别是 Euestheria luanpingensis Shen et Niu及其软体化石在道虎沟的发现 ,证明其层位应与冀北滦平九龙山组相当。道虎沟叶肢介群与中侏罗世晚期的假线叶肢介 (Pseudograpta)动物群的面貌相差甚远 ,与比其层位更高的大北沟组的尼斯脱叶肢介 (N estoria)动物群及义县组的东方叶肢介 (Eosestheria)动物群迥然不同 .     

Sex in the footprint bed

Many animals show sexual dimorphism, one sex being consistently larger and heavier than the other. No doubt, examples of the same phenomenon also occur in the fossil record, but they may be difficult to spot and even more difficult to prove. The problems are greater still when considering trace fossils such as footprints. Even so, there seems reason to believe that some types of footprint do show sexual dimorphism.     

生物化石钙质结构的分类与演化(连载)

绝大部份无脊椎动物和藻类化石由碳酸钙组成。研究生物化石钙质结构是为了对化石进行正确鉴定和合理分类,探索古生物间相互的演化关系。沉积岩,特别是碳酸岩中含有大量的生物组份,研究其结构是确定岩石薄片内生物化石及其碎片类型的必要手段,在研究岩石、岩相和古生态时必需广泛采用。     

Revision of the conchostracan genus Estherites from the Upper Cretaceous Nenjiang Formation of the Songliao Basin and its biogeographic significance in China

The diagnosis of Estherites corrugatus from the basal part of the Coniacian Second Member of the Nenjiang Formation in Nenjiang County, north-east China is revised following the application of a new preparation technique to some of the carapaces and an examination of specimens under a scanning electron microscope, both of which revealed morphological features on the carapace that had not been recognized previously. Restudy of the type species of the two subgenera Estherites (Euestherites) and Estherites (Parestherites) also revealed details of carapace features not seen hitherto. These indicate that they should be separated from Estherites. As a result, Euestherites is upgraded to genus level and Parestherites is placed in synonymy. The importance of Estherites and Euestherites is considered in the context of Late Cretaceous assemblages of these crustaceans and the three conchostracan provinces (South-West, South-East and North China) that are recognized to have been present in China during the Turonian–Santonian period.     

Diminutive trace fossils in the Chengjiang Lagerstätte

Diminutive trace fossils described here have been well preserved in connection with certain pliable carapaces or skeletons of the Chengjiang animals. Taphonomic evidence suggests that these traces were formed in situ. The peculiar preservation indicates that some bilaterians of uncertain affinities seem to have been active at the burial site, constituting an important group of the hidden majority of Cambrian marine community. This may be an essential feature closely associated with the palaeoecology and exceptional preservation of the Cambrian fossil Lagerstätten. The rare preservation of such millimetre‐sized trace fossils raises further doubts about the timing of the initial benthic bilaterians by applying trace fossil evidence.     

生物礁的群落相

本文提出了生物瞧群落相的概念。群落相是指保存在生物礁中一组能够反映适应它们生长和繁衍环境条件的古生物群团的特征和面貌。群落相是研究生物礁的发展演化规律、空间分布规律及与油气储集分布规律的关系的一个重要途径。