澄江生物群中的卵形川滇虫

近年来在云南昆明附近的海口镇和大板桥地区发现大量的节肢动物卵形川滇虫化石,这些化石隶属于澄江生物群,其所处的地层是下寒武统玉案山组。卵形川滇虫化石的不断发掘使得对该属种化石的研究和认识能在很大程度上取得新的进展。文章基于相当数量化石的信息统计,首先对化石保存的多种方式进行总结并分析其埋藏时的环境条件,其次分析卵形川滇虫一些有趣的生活习性并初步划分卵形川滇虫生长中历经3次蜕皮的发育阶段;对雌雄性个体特征(包括外部形态和内部器官的解剖)进行对照性描述。文中揭示卵形川滇虫的生活环境及运动方式,并将卵形川滇虫与中寒武世瓦普塔虾进行较为详尽的比较,列举两者不可归为一属的可靠证据。     

四川盆地井研—犍为地区寒武系第二统九老洞组古生物化石及其地层划分对比

井研—犍为地区麦地坪组—九老洞组是四川盆地寒武系页岩气重要的勘探目的层,但至今区内缺乏比较可靠的古生物化石资料,严重制约着勘探区地层的精确划分与对比。通过对该地区相关资料的收集和金石1井和金页1井岩心样品的采集分析,在本区九老洞组建立了尖头遵义盘虫(Tsunyidiscus acutus)-阎家寨遵义盘虫(Tsun-yidiscus yanjiazhaiensis)和始莱得利基虫(Eoredlichia)-武定虫属(Wutingaspis)两个三叶虫组合,以及梁山虫(Liangshanella)-小遵义虫(Tsunyiella),朵氏昆明虫(Kunmingella douvillei)-卵形川滇虫(Chuandianella ovata(Lee))-简单虫(Mononotella)和峨眉虫(Emeiella)-粗脊昆明虫(Kunmingella(Validocostatella)fusulus)等三个高肌虫组合,为研究区建立了较为详细的化石对比标准;通过典型化石的分析,对比金石1井和金页1井的地层层位,认为金页1井(3 403 m以下)和金石1井(3 503 m以下)属于深水陆棚相沉积,金页1井(3 403m以上)和金石1井(3 503 m以上)为海水较浅的陆棚沉积带,推测研究区在寒武纪幸运世早期存在局部断陷,造成了沉积环境的重大变化,反映海平面快速下降及随后原断陷盆地的快速充填。     

寒武纪早期宽川铺生物群中圆管螺化石显微结构及显微谱学分析

陕南寒武系底部宽川铺组不仅保存了大量的小壳化石,还以磷酸盐化的方式立体保存了多种软躯体动物的胚胎和成体化石,为研究早期动物矿化模式、个体发育方式以及动物躯体构型的早期辐射过程提供了非常关键的信息。然而宽川铺生物群的研究大多聚焦于化石系统分类及亲缘关系探索,对生物群的沉积背景、埋藏过程和保存模式的分析甚少。本文以宽川铺生物群的核心产出层位——陕西省西乡县大河镇宽川铺组下部磷质碎屑灰岩为研究对象,对其中的一类管状化石圆管螺及其围岩进行了显微结构学和显微谱学综合分析,获得了化石显微结构和关键结构对应的元素、矿物成分等信息,讨论了管状化石圆管螺的埋藏过程和保存模式,并在此基础上对其生物学特征进行了初步探讨。该研究对理解宽川铺生物群的埋藏机制提供了新的线索。     

寒武纪早期锥管状化石Anabarites trisulcatus群居行为的计算流体力学分析

Anabarites trisulcatus是寒武纪早期一类三辐射对称的管栖生物,推测营群居的方式生活在浅海。本文对来自陕南宁强石钟沟剖面寒武系底部宽川铺组的Anabarites trisulcatus进行了计算机流体力学分析。根据化石形态构建3D模型,依据推测的生活环境设计流域参数,进行了单体与群居两种不同生活方式下的流体动力学模拟,结果表明:(1)水动力条件对于底栖Anabarites trisulcatus而言是重要的影响因素;(2)Anabarites trisulcatus以群居的方式生活阻力系数更小,更有利于生存。本文使用计算流体力学的方法对长期存在的功能和生态假说进行定量检验,是微体化石研究新思路的一次有益尝试。     

我国寒武系底部几种磷酸盐化保存的蓝菌类化石

本文系统描述了产于我国寒武系底部磷矿层中的微型蓝菌类化石4属4种,其中Girvanella sp.和Spirellus columnaris产于新疆阿克苏、乌什玉尔吐斯组和云南会泽、安宁朱家箐组中谊村段,Endoconchia lata产于四川峨眉灯影组麦地坪段,Cambricodium capilloides和一块属种名未定的化石产于陕西宁强灯影组宽川铺段,从而丰富了我国寒武系底部磷块岩层中的蓝菌类化石。本文还讨论了上述微型蓝菌类化石有直接磷酸盐化保存和钻孔磷酸盐铸模保存的两种保存方式。     

安徽潜山盆地早第三纪叶肢介化石

笔者于1981年6月与安徽省地质局327地质队李继超工程师前往江苏六合冶山,观察寒武系剖面时,在冶山东部下寒武统深灰色薄层灰岩中,找到金臂虫、三叶虫(Redlichia,Pa-raprotolenella 等)(图版Ⅰ)、无铰纲腕足类以及软舌螺类等化石。金臂虫化石系在本区寒武系第一次发现,也是江苏省境内首次发现。该标本经笔者研究为一新属——Yeshanella。这不仅丰富了金臂虫类化石资料,而且为研究我国东部金臂虫类化石提供重要线索。     

广东省海南岛崖县中寒武世的高肌虫及其地质意义

本文描述的全部高肌虫化石系笔者与西北大学地质系79级同学郭健、冯望云于1982年采自海南岛崖县大茅,共计4科9属19种,其中包括1新科2新属1新亚属13新种和4未定种。依据这些高肌虫的新资料,本文论述了崖县中寒武世高肌虫动物群的特征及其在地质学上的意义,并初步探讨了崖县与澳大利亚Queensland中寒武统底界附近生物地层的划分和对比。一、剖面介绍崖县大茅剖面位于大茅磷矿矿区,仅为中寒武统大茅组部分地层,相当于葛梅钰等(1983)所划分的大茅组1段上部至3段中部。其层序如下:     

川蔓藻属系统分类和演化评述

川蔓藻属Ruppia为沉水单子叶植物,世界广布,主要为咸水和盐水生境,具有重要的生态价值、环境指示作用以及植物系统学研究意义.长期以来,川蔓藻属内种的数目以及属的系统位置一直存在争议.根据已有研究资料,目前川蔓藻属共有5个种--R.maritima、R cirrhosa、R. tuberosa、R, megacarpa和R.tuberosa、R.megacarpa和R.palycarpa得到多数学者的认可.关于其系统位置,主要有隶属于眼子菜科Potamogetonaceae和独立成川蔓藻科Ruppiaceae两种观点.尽管目前许多被子植物分类系统都承认了川蔓藻科.近年来分子系统学研究显示川蔓藻属与丝粉藻科cymodoceaceae和波喜荡科Posidoniaceae有近的亲缘关系,但对川蔓藻属和眼子菜属Potamogeton区别特征的比较结果倾向于支持将其放在眼子菜科.本文还结合川蔓藻属及相关类群的化石记录和果实特征对其演化进行了初步探讨,化石属Limnocarpus和Midravalva被认为是川蔓藻属较早的祖先类群,并认为该属植物应该是由淡水祖先逐渐演变成现在的咸水生长植物.最后,提出了在川蔓藻属未来研究中有待进一步解决的问题.     

湖南西部中寒武世早期蠕虫化石

本文所报道的蠕虫材料,部分是1978年湖南省地矿局405队在湘西花垣县渔塘中寒武统高台组底部(属扬子区)采集的;部分是笔者于1983年在湘西慈利县丛木坪中寒武统敖溪组(属过渡区)采集的。蠕虫是一种软体动物,因而在地层中多数是呈虫管、虫迹保存,成为痕迹化石的一种类型,而其驱体,一般很难保存成化石。迄今为止,我国仅在震旦系内发现有蠕虫虫体化石。如湖南沅陵凉水井升天坪震旦系灯影组的中华燐沙蚕(唐天福等,1978)。另外,汪贵翔也报道在安徽的震旦系亦产有蠕虫化石(汪贵翔,1982)。至于寒武系,在国内尚未见有报道。     

贵州中寒武世凯里生物群双刺吐卓虫(Tuzoia bispinosa)个体发育的研究

大型双瓣壳节肢动物是凯里生物群中重要组成部分,其中吐卓虫属（Tuzoia）最为常见,化石标本达200多件。吐卓虫常见于全球早、中寒武世地层,地理分布广泛,在地层对比和古环境研究中具有重要意义。文章运用数理统计和对比研究的方法,详细检测130多块双刺吐卓虫（Tuzoia bispinosa Yuan and Zhao,1999）化石标本,发现明显可分为幼年期、青年期和成年期3个不同的生长发育阶段。文中探讨双刺吐卓虫的个体发育,确认先前建立的凯里生物群中Tuzoia的2个种：Tuzoia bispinosa和T．magna,应为Tuzoia bispinosa一种。     

A New Bivalved Arthropod from the Early Cambrian Sirius Passet Fauna, North Greenland

A new bivalved arthropod is described from the Lower Cambrian (?Upper Atdabanian) Buen Formation of North Greenland. Pauloterminus spinodorsalis gen. et sp. nov. possesses a bivalved carapace that covers the head, which has a single pair of antennae, and anteriormost thorax. No mouthparts are visible. The five‐segmented abdomen was limbless and terminated in a telson plus a pair of large, lobate uropods. A suite of at least six biramous thoracic limbs are present: the short endopods are made up of small, serial podomeres, while the exopods are lobate and may have functioned as gills as well as in swimming. Partially infilled guts are occasionally visible, suggesting that this animal may have been a sediment feeder. It is compared to other Cambrian bivalved arthropods, especially the waptiids Chuandianella ovata from the Lower Cambrian Chengjiang fauna (China) and Waptia fieldensis from the Middle Cambrian Burgess Shale (British Columbia). Of these three animals, the Greenland and Chinese taxa appear to be the most closely related. P. spinodorsalis possesses many typical arthropod features, but it also demonstrates more primitive characters that are more reminiscent of the lobopodians.     

贵州早、中寒武世斗篷海绵科(Choiidae)的发现

本文描述了贵州遵义下寒武统牛蹄塘组生物群和台江中寒武世凯里生物群中保存完整的斗篷海绵科(Choiidae)中斗篷海绵(Choia)和小斗篷海绵(Choiaella)化石标本,共计2属2种2未定种：Choia zunyiensis sp.nov.,Choia sp.,Choiaella avata sp.nov.和Choiaella sp.。Choia分布很广．在我国下寒武统澄江生物群及北美中寒武统的四大生物群中均有产出。Choiaella原仅产于我国澄江生物群,凯里生物群中Choiaella的发现使其时代上延至中寒武世。贵州早、中寒武世斗篷海绵科的发现及研究为海绵动物的早期演化及古地理学等方面的研究提供了重要的新材料。     

A first report of Sphenothallus Hall, 1847 in the Cambrian of Variscan Europe

Ten specimens of two phosphatic fossils have been recently discovered in lower and middle portions of Middle Cambrian Jince Formation in the Czech Republic. They are attributed to the genus Sphenothallus Hall, 1847 and described as two separate species; comparatively small conchs are described as S. kozaki sp. nov., the much larger specimens characterized by its smooth and partly flexible organo-phosphatic walls of shell are determined as ?S. kordulei sp. nov. Sphenothallus is known to range from Cambrian to Permian and accommodates numerous species. However, its Cambrian distribution is considerably restricted. Generally rare specimens have been described from Lower to Middle Cambrian of Laurentia and from the Lower Cambrian of Gondwana and peri-Gondwana. The new record of Sphenothallus from the Jince Biota represents a notable extension of their geographic range.     

Trace fossils of Cambrian aglaspidid arthropods

A new trace fossil, Raaschichnus gundersoni , from the Upper Cambrian St. Lawrence Formation of Wisconsin, was produced by an aglaspidid arthropod. The rusophyciform trace, which occurs singly and in series, is distinctive in showing marks left by the tail-spine. Other trace fossils previously considered to have been made by aglaspidids were probably excavated by animals lacking a tail-spine and with appendage morphologies very different from the aglaspidids of Wisconsin.     

Trans-continental visible morph-frequency variation at homologous loci in two species of spider, Enoplognatha ovata s.s. & E. latimana

The spiders Enoplognatha ovata s.s. and E. latimana are sibling species which share a number of visible genetic polymorphisms. Data on colour and black-spotting morph frequencies in these species have been collected from 67 sites in western Europe. Sixty nine percent of the collections contained both species. In all adequately-sized samples, both species were polymorphic for colour and, in general, exhibited the same rank order of morphs lineata and redimita. (The top dominant morph, ovata, has not been found in E. latimana). Colour-morph frequencies are not correlated between species in sympatric populations from mainland Europe and from a previously studied area in Pembrokeshire, South Wales. Although associations with certain climatic variables are evident in E. ovata they are not consistent between transects, making their biological significance unclear. For black spotting, E. ovata s.s. is nearly fixed for spotting throughout mainland Europe but is highly variable in the Pembrokeshire populations. E. latimana is polymorphic in both areas. In Europe, spotting frequencies in E. latimana show significant associations with climatic factors but, again, their biological significance is not obvious. In E. ovata s.s. the variance in both colour and spotting frequencies among populations in Pembrokeshire is significantly greater than that in the whole of mainland Europe. The implications of these and previous results are considered in the context of the persistence of visible polymorphisms across species and the forces which determine morph frequencies in local populations.     

Physiological responses to stoichiometric constraints: nutrient limitation and compensatory feeding in a freshwater snail

Nitrogen (N) and phosphorus (P) are considered to be essential nutrients that control secondary production in various ecosystems; insufficient availability of N and P can limit herbivore growth. Here, data are presented from field samplings and from a laboratory experiment on the potential of primary producers low in P, N, or P and N to constrain growth of the freshwater gastropod Radix ovata . The filamentous green alga Ulothrix fimbriata was cultured under different nutrient regimes, resulting in algae with different C:N:P ratios. The pure algae were fed in high and low quantities to juvenile R. ovata . Low availability of N and especially P in the algae strongly constrained the biomass accrual of the herbivore. In accordance with theoretical predictions, these food quality differences were highly dependent on the food quantity. The snails' growth rate was significantly related to their body C:P ratio, thereby supporting the growth rate hypothesis. R. ovata displayed a pronounced compensatory feeding response to low-nutrient food that could partly dampen but not fully compensate the food quality effects on snail growth. Increased feeding of gastropods at low P and/or N availability leads to depletion of periphyton biomass; hence compensatory feeding would shift the benthic herbivore community from a P or N limitation to a C limitation and thus have whole-ecosystem effects.     

Fuxianospira gyrata和Morania fragmenta(宏观藻类)在华北寒武系馒头组的发现

本文描述了山东省临朐县龙岗村寒武系苗岭统乌溜阶馒头组上页岩段的宏观藻类化石,计2属2种:环圈螺旋抚仙藻Fuxianospira gyrata Chen et Zhou, 1997和碎片玛拉利亚藻Morania fragmenta Walcott, 1919。这两种藻类在大小和形态上可与布尔吉斯页岩和澄江生物群中的宏观藻类相比较。本研究通过探讨藻体的长宽比,认为M.fragmenta的碎片状形态可能是藻体本身生长而成的形态,而不是其命名者所认为的碎裂而成的形态。这两个属种首次在馒头组的发现,拓展了其时空分布,为华北地区寒武纪宏观藻类研究提供了较有价值的资料。     

Controls on gut phosphatisation: the trilobites from the Weeks Formation Lagerstätte (Cambrian; Utah)

Despite being internal organs, digestive structures are frequently preserved in Cambrian Lagerstätten. However, the reasons for their fossilisation and their biological implications remain to be thoroughly explored. This is particularly true with arthropods – typically the most diverse fossilised organisms in Cambrian ecosystems – where digestive structures represent an as-yet underexploited alternative to appendage morphology for inferences on their biology. Here we describe the phosphatised digestive structures of three trilobite species from the Cambrian Weeks Formation Lagerstätte (Utah). Their exquisite, three-dimensional preservation reveals unique details on trilobite internal anatomy, such as the position of the mouth and the absence of a differentiated crop. In addition, the presence of paired pygidial organs of an unknown function is reported for the first time. This exceptional material enables exploration of the relationships between gut phosphatisation and the biology of organisms. Indeed, soft-tissue preservation is unusual in these fossils as it is restricted to the digestive structures, which indicates that the gut played a central role in its own phosphatisation. We hypothesize that the gut provided a microenvironment where special conditions could develop and harboured a source of phosphorus. The fact that gut phosphatization has almost exclusively been observed in arthropods could be explained by their uncommon ability to store ions (including phosphorous) in their digestive tissues. However, in some specimens from the Weeks Formation, the phosphatisation extends to the entire digestive system, suggesting that trilobites might have had some biological particularities not observed in modern arthropods. We speculate that one of them might have been an increased capacity for ion storage in the gut tissues, related to the moulting of their heavily-mineralised carapace.     

The morphology and affinity of anabaritids revealed by their internal molds from the Cambrian Fortunian,southern Shaanxi,China

Anabaritids are a group of tubular skeletal fossils known from the lower Cambrian worldwide. Many previously collected specimens of anabaritids lack both the apical and apertural regions, and thus their complete morphology and growth patterns are not fully understood. Here we describe a number of internal molds of Anabarites from the lower Cambrian (Fortunian Stage) Zhangjiagou Lagerstätte, southern Shaanxi Province. Our new specimens preserved the apex, the aperture with three lobes, and three longitudinal grooves initiating apically rather than adapically as previously reported. This work enriches the morphology of anabaritids, casting doubt on the previous proposition that anabaritids originated from a cylindrical tubular ancestor. It is proposed here that a triradial symmetry may have been established in very early ontogenetic stages of some anabaritids; furthermore, the aperture with three lobes resembles those of olivooids and thus supports a possible close relationship between anabaritids and olivooid scyphozoans.