鄂西宜昌黄陵背斜地区寒武纪早期小壳化石新材料*

湖北宜昌地区寒武系下部小壳化石的研究集中于黄陵背斜东翼和南翼, 对西翼地区尚未有详细的报道。 作者在黄陵背斜西翼高岚河剖面灯影组天柱山段下部发现寒武纪纽芬兰世的小壳化石, 既包括扬子板块小壳化石第一生物带标准化石Anabarites trisulcatus, 同时也有Eohalobia diandongensis与Oelandiella korobkovi等第二生物带标志化石, 以及可能为第三生物带或更晚期化石分子的Paragloborilus tenuis等。该化石组合为多生物带的化石混生, 其层位可能相当于峡东地区(黄陵背斜南翼)的岩家河组顶部。在黄陵背斜南翼的滚石坳剖面岩家河组下部发现小壳化石Anabarites ternarius Missarzhevsky in Rozanov et al., 1969、Kaiyangites novilis Qian and Yin, 1984、 海绵骨针和藻类化石, 属于小壳化石第一生物带Anabarites trisulcatus–Protohertzina anabarica组合带。化石组合与沉积记录表明, 高岚河剖面与东翼如泰山庙地区具有相似的潮坪相沉积, 多发沉积间断, 导致不同生物带化石混生; 南翼滚石坳地区水体较深, 早期沉积间断不显著, 可以识别小壳化石第一组合带。上述新化石材料的发现, 为黄陵背斜周缘寒武系下部地层对比与生物古地理分析提供了新的数据。     

鄂西宜昌黄陵背斜地区寒武纪早期小壳化石新材料*

湖北宜昌地区寒武系下部小壳化石的研究集中于黄陵背斜东翼和南翼, 对西翼地区尚未有详细的报道。 作者在黄陵背斜西翼高岚河剖面灯影组天柱山段下部发现寒武纪纽芬兰世的小壳化石, 既包括扬子板块小壳化石第一生物带标准化石Anabarites trisulcatus, 同时也有Eohalobia diandongensis与Oelandiella korobkovi等第二生物带标志化石, 以及可能为第三生物带或更晚期化石分子的Paragloborilus tenuis等。该化石组合为多生物带的化石混生, 其层位可能相当于峡东地区(黄陵背斜南翼)的岩家河组顶部。在黄陵背斜南翼的滚石坳剖面岩家河组下部发现小壳化石Anabarites ternarius Missarzhevsky in Rozanov et al., 1969、Kaiyangites novilis Qian and Yin, 1984、 海绵骨针和藻类化石, 属于小壳化石第一生物带Anabarites trisulcatus–Protohertzina anabarica组合带。化石组合与沉积记录表明, 高岚河剖面与东翼如泰山庙地区具有相似的潮坪相沉积, 多发沉积间断, 导致不同生物带化石混生; 南翼滚石坳地区水体较深, 早期沉积间断不显著, 可以识别小壳化石第一组合带。上述新化石材料的发现, 为黄陵背斜周缘寒武系下部地层对比与生物古地理分析提供了新的数据。     

贵州织金寒武系戈仲伍组钉形类骨片化石研究*

钉形类(nail-shaped)骨片化石是华南寒武纪早期地层中常见的一类具矿化骨骼的小壳化石。本文系统研究了贵州织金戈仲伍剖面寒武系戈仲伍组的钉形类骨片化石, 发现织金地区钉形类化石主要以织金钉类和疑似的寒武钉类为主, 共4属9种。相较于前人研究, 本文新发现了织金钉类: Zhijinites tumourifomis、Z. lubricus、Z. clavus, 和疑似的寒武钉类: ?Deiradoclavus sp.、?Cambroclavus sp.。排除埋藏学假象后, 分析了钉形类不同化石属种保存方式及形态结构, 发现Zhijinites的多数种都存在盘体顶面凹陷结构, 并且Zhijinites部分种的锥体内壁有收缩现象或具有十字交错纤维结构, 这些发现能较好地揭示出Zhijinites各形态种间的相似性和差异性。分析钉形化石时空分布特点发现, 目前钉形类骨片化石最早在织金地区有化石记录, 之后在扬子地台内部辐射扩散, 并几乎同时辐射扩散至邻近陆块。此外, 本文讨论的疑似寒武钉类化石时代可下延至寒武纪幸运期, 可能是目前该类化石在全球的最早记录, 为探索寒武钉类化石的系统演化和地层学意义提供了新信息。     

贵州寒武系第二统杷榔组有壳变形虫的新发现*

有壳变形虫(testate amoebae)的演化历史最早可追溯至新元古代早期, 以该时期北美、华北、挪威以及澳洲等多个地区浅海相碳酸盐岩、页岩中发现的瓶状微体化石(vase-shaped microfossils)为标志。此前认为, 显生宙的有壳变形虫最早出现在早泥盆世。长期以来, 早古生代的地层中未发现这类原生生物的明确化石证据。本研究通过对岩石样品进行常规孢粉酸泡分析处理和切磨岩石薄片, 获取原位保存的化石标本的技术方法, 从贵州东部剑河县交榜剖面出露的寒武系杷榔组(第2统第4阶)中获得数枚有壳变形虫(testate amoebae)化石标本。基于标本的显微形态特征, 并结合激光拉曼光谱等研究, 对原先记述为疑源类的Plagasphaera balangensis和P. sp. A两形态种进行重新认识和描述。由于它们在结构和形态上与一些现生的鳞壳虫目(Euglyphida)有壳变形虫极为相似, 因此将先前定为疑源类的Plagasphaera balangensis和P. sp. A两形态属、种名, 分别修订为Palaeoassulina balangensis gen. et sp. nov.和?Palaeoassulina sp. A。该发现不仅将显生宙有壳变形虫的原有化石记录从晚古生代泥盆纪向前延伸至寒武纪早期, 还为调查研究有壳变形虫的系统演化提供关键的生物化石证据。     

贵州寒武纪海绵动物化石组合特征

贵州寒武纪海绵化石丰富。分布广泛,主要产于早寒武世梅树村期的戈仲伍组或牛蹄塘组底部、筇竹寺期的牛蹄塘组和早、中寒武世凯里组。梅树村期的海绵属种单调,主要为六射海绵类麦粒海绵（Triticispongia sp．）及一些海绵骨针,代表寒武纪海绵首次爆发或辐射的前奏和先驱。牛蹄塘组海绵多达13个属,是寒武纪海绵辐射的重要窗口,以普通海绵略占优势,Leptomitus为优势属。凯里组的海绵共计7属,以普通海绵为主。贵州寒武纪海绵动物群的发展具有明显的阶段性和组成的差异性,其演变过程受到环境的制约。贵州早期海绵动物的发现和研究不仅改变了寒武纪生物多样性的认识,而且还为探讨海绵动物本身的起源、辐射提供了重要材料。     

广西中部下泥盆统无颌类和鱼类微体化石——兼论桂中与滇东下泥盆统的对比*

记述了广西横县六景那高岭组、郁江组,武宣二塘二塘组和象州大乐四排组(大乐组)的无颌类和鱼类微体化石。经过形态学和古组织学的研究,这些化石被归于13属(其中包括1新属、2未定属)11种(其中包括3新种4未定种和1比较种)。结合以往在莲花山组和那高岭组下部已报道的脊椎动物大化石资料讨论了广西中部下泥盆统的脊椎动物组合序列:莲花山组以Yunnanolepis-Qujinolepis组合,那高岭组以Asiaspis expansa-Machaeracanthus? bohemicus组合,郁江组以Turinia sp.-Cheiracanthoides comptus-Ohiolepis newberryi组合,二塘组以Nostolepis guangxinensis-Wuxuanichthys wangi-Ligulalepis cf. toombsi组合为代表。另外,据已报道的脊椎动物微体化石和大化石资料,对广西中部和云南东部下泥盆统进行了对比。     

峡东水井沱组顶部微体骨骼化石初探北大核心

报道湖北宜昌地区寒武纪早期水井沱组顶部灰岩中赋含的壳体动物群及一些骨骼化石,主要包括软舌螺、腕足动物、开腔骨类骨针、海绵骨针、原始赫兹刺、阿纳巴管、管状微体化石、单板类、古杯类等。初步研究认为软舌螺可归属为2纲3目8科9属,2种、2相似种和6未定种;腕足动物主要以乳孔贝和古圆货贝为主;单板纲归属为1科3属,1相似种、2未定种;分类位置不明的Coleoloides cf.prindlei Lochman,1956和Coleolussp.,归属1科2属,1相似种,1未定种。这些骨骼化石中,古杯类Archaeocyaths和9个其他微体骨骼化石种:如软舌螺四边螺类Quadrotheca sp.,中槽螺类Altaicornus sp.,线带螺类Linevitus sp.,似软舌螺类Hyolithellus cf. micans Bil-lings,1871和Coleoloides cf. prindleiLochman,1956,单板动物太阳女神螺类Securiconus sp.和Igorella cf. minuta,以及腕足动物乳孔贝类Eohadrotreta zhenbaensis Li and Hol mer,在峡东地区水井沱组尚属首次报道。该层位微体骨骼化石丰度大,分异度较高,海绵骨针粗壮,骨骼化石保存分散。     

西沙群岛琛科二井中新世和更新世的珊瑚一些化石*

Sphenothallus Hall, 1847是刺胞动物中以细长锥管状为特征, 底栖固着的一个属, 始现于寒武纪延伸至二叠纪。之前该属在贵州寒武纪的牛蹄塘生物群、剑河生物群和凯里生物群中均有报道。位于寒武纪第4阶的杷榔生物群也发现该属的化石, 杷榔生物群的Sphenothallus由S. kozaki和S. kozaki? 2个种组成。杷榔生物群的时代位于牛蹄塘生物群和剑河生物群之间, S. kozaki之前仅出现在捷克Jince组和中国湖北石牌组。杷榔生物群Sphenothallus的发现增加了该属在寒武纪第4期刺胞动物的多样性古生态、古地理分布及演化信息, 丰富了杷榔生物群底栖固着类群的组合面貌。     

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。     

贵州台江凯里组的双瓣壳节肢动物Tuzoia*

记述贵州台江凯里组中部青灰色泥岩内的无腹双瓣壳节肢动物Tuzoia两新种 :T .bispinosa sp .nov .,T .magna sp .nov .。扼要地讨论了Tuzoia的起源、演化趋向和分类位置。Tuzoia浮游的生活方式和其它营浮游生活的三叶虫一样 ,具有广泛的地理分布 ,不仅能在印度太平洋古动物地理区出现 ,也能在大西洋古动物地理区出现 ,不仅能在地台区出现 ,而且能在斜坡区出现。     

Giving the early fossil record of sponges a squeeze

Twenty candidate fossils with claim to be the oldest representative of the Phylum Porifera have been re‐analysed. Three criteria are used to assess each candidate: (i) the diagnostic criteria needed to categorize sponges in the fossil record; (ii) the presence, or absence, of such diagnostic features in the putative poriferan fossils; and (iii) the age constraints for the candidate fossils. All three criteria are critical to the correct interpretation of any fossil and its placement within an evolutionary context. Our analysis shows that no Precambrian fossil candidate yet satisfies all three of these criteria to be a reliable sponge fossil. The oldest widely accepted candidate, Mongolian silica hexacts from c. 545 million years ago (Ma), are here shown to be cruciform arsenopyrite crystals. The oldest reliable sponge remains are siliceous spicules from the basal Cambrian (Protohertzina anabarica Zone) Soltanieh Formation, Iran, which are described and analysed here in detail for the first time. Extensive archaeocyathan sponge reefs emerge and radiate as late as the middle of the Fortunian Stage of the Cambrian and demonstrate a gradual assembly of their skeletal structure through this time coincident with the evolution of other metazoan groups. Since the Porifera are basal in the Metazoa, their presence within the late Proterozoic has been widely anticipated. Molecular clock calibration for the earliest Porifera and Metazoa should now be based on the Iranian hexactinellid material dated to c. 535 Ma. The earliest convincing fossil sponge remains appeared at around the time of the Precambrian‐Cambrian boundary, associated with the great radiation events of that interval.     

First Report: Trace Fossil Assemblage Ptychoplasma (P. excelsum,P. vagans), Dendroidichnites (D. irregulare), Ctenopholeus (?C. kutcheri) and Bergaueria (B. hemispherica) in the Cretaceous Rocks of Bagh Formation,Mainland Gujarat,India

Abstract

This report documents the discovery of repichnia trace fossils Ptychoplasma (P. excelsum and P. vagans) and Dendroidichnites (D. irregulare); the fodichnia traces ?Ctenopholeus (?C. kutcheri) and cubichnia traces Bergaueria (B. hemishperica) from silty limestones of the Cretaceous Bagh Formation. These trace fossils have significant implications for the depositional facies and the paleo-environmental interpretations of the Bagh Formation, which have long been debated. Previously identified traces of Protovirgularia were also found in association with the newly discovered trace fossils, indicating the coexistence of both wedge and cleft-foot bivalves. The western area of the mainland Gujarat is known for its abundance and diversity of trace fossils. The trace fossil bearing Cretaceous rocks in the region occur as thin irregular detached patches and linear outcrops. Previous studies documenting trace fossil assemblages from the Bagh Formation characterised them as a combination of dwelling, feeding and locomotion forms, with the stratigraphic unit becoming less fossiliferous westward. Trace fossils in this formation have been studied and described by many workers in the surrounding areas; however, ichnofossils described in this study are new to the Bagh Formation in this area. These trace fossils were observed on recently exposed outcrops along road cuts associated with new road construction from Khasra to Mogra village around Kadipani in Mainland Gujarat.     

Small carbonaceous fossils (SCFs) from the Terreneuvian (lower Cambrian) of Baltica

We describe a new assemblage of small carbonaceous fossils (SCFs) from diagenetically minimally altered clays and siltstones of Terreneuvian age from the Lontova and Voosi formations of Estonia, Lithuania and Russia. This is the first detailed account of an SCF assemblage from the Terreneuvian and includes a number of previously undocumented Cambrian organisms. Recognizably bilaterian‐derived SCFs include abundant protoconodonts (total‐group Chaetognatha), and distinctive cuticular spines of scalidophoran worms. Alongside these metazoan remains are a range of protistan‐grade fossils, including Retiranus balticus gen. et sp. nov., a distinctive funnel‐shaped or sheet‐like problematicum characterized by terminal or marginal vesicles, and Lontohystrichosphaera grandis gen. et sp. nov., a large (100–550 μm) ornamented vesicular microfossil. Together these data offer a fundamentally enriched view of Terreneuvian life in the epicratonic seas of Baltica, from an episode where records of non‐biomineralized life are currently sparse. Even so, the recovered assemblages contain a lower diversity of metazoans than SCF biotas from younger (Stage 4) Baltic successions that represent broadly equivalent environments, echoing the diversification signal recorded in the coeval shelly and trace‐fossil records. Close comparison to the biostratigraphical signal from Fortunian small shelly fossils supports a late Fortunian age for most of the Lontova/Voosi succession, rather than a younger (wholly Stage 2) range.     

Evidence for spicule homology in calcareous and siliceous sponges: biminerallic spicules in Lenica sp. from the Early Cambrian of South China

Botting, J.P., Muir, L.A., Xiao, S., Li, X. & Lin, J.‐P. 2012: Evidence for spicule homology in calcareous and siliceous sponges: biminerallic spicules in Lenica sp. from the Early Cambrian of South China. Lethaia, Vol. 45, pp. 463–475. The relationships of the extant sponge classes, and the nature of the last common ancestor of all sponges, are currently unclear. Early sponges preserved in the fossil record differ greatly from extant taxa, and therefore information from the fossil record is critical for testing hypotheses of sponge phylogenetic relationships that are based on modern taxa. New specimens of the enigmatic sponge Lenica sp., from the Early Cambrian Hetang Biota of South China, exhibit an unusual spicule structure. Each spicule consists of a siliceous core with an axial canal, an organic outer layer and a middle layer interpreted to have been originally calcium carbonate. This finding confirms previous work suggesting the existence of biminerallic spicules in early sponges. Combined with data from other early sponges, the new findings imply that the two fundamental spicule structures of modern sponges were derived from a compound, biminerallic precursor. Spicules are therefore homologous structures in Calcarea and Silicea, and if sponges are paraphyletic with respect to Eumetazoa, then spicules may also have been a primitive feature of Metazoa. □Calcarea, Early Cambrian, Hetang Biota, phylogeny, Silicea, taphonomy.     

华南贵州宾夕法尼亚亚纪牙形类Neognathodus动物群:演化及地层对比意义

以华南斜坡相的罗甸纳庆剖面为代表,我国石炭纪宾夕法尼亚亚纪早–中期地层建立起了基于多个属种的牙形类分带,并可与全球其他地区同期地层进行广泛对比。Neognathodus属是这一时期一类常见的浅水相牙形类分子,在北美、东欧等地的浅水相地层中被广泛用作地层划分对比标志。该属分子在我国北方地区浅水相地层中是重要的带化石分子,而在华南斜坡相剖面中占比非常低。结合现有的生物地层框架,本文厘清了华南贵州罗甸附近3条斜坡相剖面中Neognathodus属分子的延限,尝试利用牙形类P1分子齿台的对称特征将其演化过程归纳为五个阶段,并提出阶段4中对称分子(如:N. bothrops, N. colombiensis, N. nataliae等)的再次出现可作为全球莫斯科阶底界的辅助对比标志。     

Hydraulic sorting of microbiota in calciturbidites— A dinantian case study from the rheinische schiefergebirge,Germany

Summary A calciturbidite bed from the lower part of the Kieselkalk Formation (late cd II) at Wallau, eastern Rheinisches Schiefergebirge, displays ideal grading of reworked calcareous shallow-water microbiota, ranging from plurimillimetric agglutinated foraminifers and fragments of calcareous algae (Koninckopora sp.) to plurimicronic calcispheres, radiolarians and sponge spicules. Microbiota derived from all levels of the platform. Correspondingly, several carbonate microfacies types could be discerned. The early diagenetic micrite base of the turbidite preserved the anoxic basinal facies. The turbidite bed belongs to Foraminiferal Zone 15 (V3bα), theAlbaillella cartalla Zone (radiolarian chronology), and is the Lower and part of the Uppertexanus Zone (standard conodont zonation). From the few published data on foraminifers, the Kieselkalk is thought to range from Mid Viséan V2b to Late Viséan V3b gamma.     

A Late Devonian plant assemblage from the Avon Gorge, west England: taxonomic, phylogenetic and stratigraphic implications

Plant fossils from the Avon Gorge originally identified as Rhacophyton sp. have been subjected to a detailed morphological study incorporating examination of both previously known material and new specimens. A single taxon, Chlidanophylon dublinensis, dominates the assemblage accounting for over 90% of the fossils encountered. Other plant organs identified include dispersed acupulate preovules and five less frequently occurring organs of which four are of unknown affinities; the leaf genus Platyphyllum, Alicomopleris sp., two kinds of novel and frequendy dichotomizing branching structures and the spermatophyte synangium Telangiopsis. Possible whole plant relationships between the components of the fossil assemblage are discussed and the stratigraphic, systematic and evolutionary position of the component taxa are considered.