A restudy of Oryctocephalus indicus (Reed, 1910)

Restudy on morphology of Oryctocephalus indicus (Reed, 1910), based on specimens from Guizhou, China and Nevada USA, suggests that the subspecies regarded previously as Oryctocephalus indicus indicus (Reed, 1910), O. indicus latus Zhao et Yuan 2002, and O. indicus kobayashi Saito, 1934, are synonymous, and Oryctocephalus americanus Sundberg et McCollum, 2003 is a similar form of O. indicus. Oryctocephalus indicus is rediagnosed as having a glabella that is subconical in outline and tapering forward slightly; a thorax that comprises 12 segments, and a small pygidium that bears 2?3 axial rings with a terminal piece and a postaxial ridge. Oryctocephalus indicus is widely distributed in eastern Guizhou and ranges through a great interval of Kaili Formation. Its first appearance is almost identical with these events of trilobite extinction-recovery occurring at the end of the Early Cambrian, the alternation of acritach assemblages, the change of trace elements (REE) and stable isotopes (carbon) at the Wuliu-Zengjiaya section. As one of the key forms for defining the traditional Lower - Middle Cambrian boundary (the base of Cambrian Series 3 and Stage 5 in the new Cambrian chronstratigraphic standard), O. indicus has received detailed study and has more advantages than other species such as Ovatoryctocara granulata Tchernysheva, 1962 or Arthricocephalus chauveaui Bergeron, 1899.     

A restudy of Oryctocephalus indicus (Reed,1910)

Since both Chinese[1]and American Palaeontolo-gists[2]proposed separately to mark the beginning ofthe Middle Cambrian based on the first appearancedatum (FAD) ofOryctocephalus indicus[3]in thesame year ,the suggestion has been considered seri-ously and adoptedfrequently[4—18].The InternationalSubcommission on Cambrian Stratigraphy (ISCS) hasorganized the Working Group,chaired by L.B. Mc-Collum,to select candidate sections that bear poten-tial to become a GSSPfor the traditional Lowe…     

A new section of Kaili Formation (Cambrian) and a biostratigraphic study of the boundary interval across the undefined Cambrian Series 2 and Series 3 at Jianshan, Jianhe County,China with a discussion of global correlation based on the first appearance datum of Oryctocephalus indicus(Reed,1910)

A trilobite biostratigraphic study of a new section of the Kaili Formation at Jianshan,Chuandong Village,Jianhe County,Guizhou is reported.Additional occurrences of key species associated with the Ovatoryctocara granulata-Bathynotus holopygus Zone and the overlying Oryctocephalus indicus Zone that were originally defined from the trilobite assemblages at the Wuliu-Zengjiayan section of the Kaili are reported from this new section.The first appearance datum (FAD) of Oryctocephalus indicus occurs at the 44.52 m above the base of the unit.Based on study of abundant specimens (n = 800) from the Kaili Formation,we argue that Oryctocephalus indicus is a widespread taxon with a global distribution.O.Reticulatus (Lermontova,1940) from the middle part of the Kounamkites Zone of the Amganian Stage in the Molodo River region of Siberia and O.Americanus (Sundberg and McCollum,2003) from Nevada,North America are similar to representatives of O.Indicus which occur in the O.Indicus Zone of the Kaili Formation.O.Reticulatus and O.Americanus are here synonymized with O.Indicus (Reed,1910).This study strengthens the Wuliu-Zengjiayan section of the Kaili Formation as a candidate section for a Global Stratotype for the base of the unnamed Cambrian Series 3.     

Proposal and prospects for the global Lower-Middle Cambrian boundary

In recent years paleontologists have been working on the global stratotype section and standard point (GSSP) for the Lower-Middle Cambrian boundary in North America, China, Morocco, Spain and Russia. Continually, they suggest the potential first appearance datum (FAD) of the Middle Cambrian, such as Oryctocephalus indicus, Ovatoryctocara granulata, Acadoparadoxides mureroensis, Hupeolenus and Arthricocephalus chauveaui as being relevant to the potential stratotype section for the Lower-Middle Cambrian boundary. There are only a few trilobites distributed widely enough in the Early to Middle Cambrian connection, so virtually no trilobite(s) can act as the FAD for the global Middle Cambrian. The easily identified Oryctocephalus indicus is widely distributed in three realms of the global Cambrian. Its first appearance position is linked to the extinction of old species coevolution of new ones. It appears to be a comparatively good FAD of Middle Cambrian. The continuous and unbroken Wuliu section (Balang, Taijiang County, Guizhou Province, China) includes O. indicus and co-occurs with many benthic and nektonic trilobites. The evolution of acritarchs in the section, the changed characteristics of trace elements (REE and C isotopes) are generally consistent with the evolution of trilobites both above and below the boundary. Strata above the boundary yield the famous Kaili Biota. The Wuliu section is easily accessible from a main highway.     

A new section of Kaili Formation （Cambrian） and a biostratigraphic study of the boundary interval across the undefined Cambrian Series 2 and Series 3 at Jianshan,Jianhe County,China with a discussion of global correlation based on the first appearance datum of Oryctocephalus indicus （Reed, 1910）

A trilobite biostratigraphic study of a new section of the Kaili Formation at Jianshan, Chuandong Village, Jianhe County, Guizhou is reported. Additional occurrences of key species associated with the Ovatoryctocara granulata-Bathynotus holopygus Zone and the overlying Oryctocephalus indicus Zone that were originally defined from the trilobite assemblages at the WuliuZengjiayan section of the Kaili are reported from this new section. The first appearance datum （FAD） of Oryctocephalus indicus occurs at the 44.52 m above the base of the unit. Based on study of abundant specimens （n = 800） from the Kaili Formation, we argue that Oryctocephalus indicus is a widespread taxon with a global distribution. O. reticulatus （Lermontova, 1940） from the middle part of the Kounamkites Zone of the Amganian Stage in the Molodo River region of Siberia and O. americanus （Sundberg and McCollum, 2003） from Nevada, North America are similar to representatives of O. indicus which occur in the O. indicus Zone of the Kaili Formation. O. reticulatus and O. americanus are here synonymized with O. indicus （Reed, 1910）. This study strengthens the Wuliu-Zengjiayan section of the Kaili Formation as a candidate section for a Global Stratotype for the base of the unnamed Cambrian Series 3.     

Cambrian trilobite Ovatoryctocara granulata Tchernysheva, 1962 and its biostratigraphic significance

The genus Ovatoryctocara Tchernysheva, 1962 and its key species Ovatoryctocara granulata Tchernysheva, 1962 are revised. Ovatoryctocara granulata occurs near the base of the Ovatoryctocara Zone and ranges up into the lower portion of the Kounamkites Zone in the Siberian Platform. O. granulata also appears in southeastern Guizhou, South China, but, O. granulata in northern Greenland may represent an indefinite species. Specimens of Ovatoryctocara from Newfoundland cannot be identified to species level. Specimens including two cranidia and three pygidia from the lower part of the Aoxi Formation at Yaxi Village, Shizhu Town, eastern Tongren, northeastern Guizhou, were previously assigned to O. granulata , which is now reassigned as a new species O. yaxiensis sp. nov. It bears following main features: glabella club-shaped, slightly expanded medially, with 4 pairs of lateral furrows, of which S1-S3 triangular pits, S4 shallow , connecting with axial furrow; shorter palpebral lobe situated a little anterior to midway of facial suture across the fixigenae, longer posterolateral area (exsag.); semielliptical pygidium consisting of seven axial rings with a terminal piece and with eight pairs of marginal tips giving a sawtooth-like shape of the lateral margins in dorsal view. Although O. granulata is a widely distributed species, the FAD of O. granulata, for a global stage boundary has still some disadvantages. First, its distribution is not as wide as that of Oryctocephalus indicus (Reed, 1910). Second, specimens of O. granulata are only common in Siberia. Third, the stratigraphic range of the species has not been studied in detail in all continents. Fourth, O. granulata is relatively small and easily affected by post-burial distortion. Last but not least, there exists obviously a facies change between the Ovatoryctocara Zone ( lower Amgan Stage; deeper water facies) and underlying Anabaraspis splendens Zone (Toyonian Stage; shallow water facies) in Siberian Platform. Nevertheless, the stratigraphic correlation utility of O. granulata in South China and Siberia is discussed.     

贵州剑河巴水崖、镇远朱砂凯里组研究--八郎潜在的国际中、下寒武统层型剖面的辅助剖面研究

贵州剑河县巴水崖和镇远县朱砂凯里组剖面中下部都有Oryctocephalus indicus的产出，说明Oryctocephalus indicus的分布具有普遍性。两个剖面中、下寒武统界线的划分和潜在的八郎鸟溜剖面中、下寒武统界线候选层型剖面的划分基本一致，可作为潜在的八郎鸟溜中、下寒武统层型剖面的辅助剖面。     

贵州寒武系棘皮动物研究新进展及其组合特征

贵州寒武系含有丰富的棘皮动物化石,其中凯里组及杷榔组中的始海百合数以千计.近期贵州下司淑里村杷榔组上部粉砂质泥岩中发现的新类型殷氏原始球状始海百合（新属、新种）Protogloboeocrinus yini （gen.et sp.nov.）,使贵州寒武系棘皮动物分异度加大,达8属、种及1科、属、种未定,分属3个亚门.演化趋势是：类群增多,始海百合个体变小,缝孔变圆,吸盘附着的化石类型增多,生态日趋复杂.凯里生物群也是棘皮动物大辐射的窗口.     

下寒武统宽背虫(Bathynotus)的灭绝过程——以贵州剑河八郎凯里组的Bathynotus kueichouensis为例

宽背虫(Bathynotus)这一传统早寒武世或寒武纪第2世晚期最重要的三叶虫属,广泛分布于全球寒武纪3个生物大区,为区域地层对比的标准化石.Bathynotus在贵州剑河八郎乌溜-曾家崖剖面凯里组下部极为丰富.该剖面已成为全球寒武系第2统和第3统界线层型候选剖面,表明凯里组是一个穿时的地层单元,其3个三叶虫带最下部一个带为Bathynotus holopygus-Ovatoryctocara granulata.经过逐层大量的化石标本采集统计证实,乌溜-曾家崖剖面宽背虫(Bathynotus)在距凯里组底部51.60 m处骤然绝灭,距寒武系第2统的顶界(距凯里组底52.80 m)只有1.20 m.本文就乌溜-曾家崖剖面凯里组下部宽背虫(Bathynotus)的数量分布变化认为其灭绝过程是逐步的.     

Discovery of Corallina fossil from the Middle Cambrian of Taijiang County, Guizhou Province, China

Abundant and well-preserved macroalgae fossils have been discovered in silty mudstones and shales from the Middle Cambrian of Taijiang County, Guizhou Province, China. CorallinaParaamphiroa siniansis gen. et sp. nov. in the Kaili Fm., is the earliest Corallina fossil, which usually coexists with other carbonaceous macroalgae fossils on the bedding planes of mudstone and shale and is different from the calcareous and phosphatized Precambrian-Cambrian thallus discovered in the Lower Cambrian of Siberia and the Doushantou phosphate rocks of Weng’an County, Guizhou Province, China. The discovery of calcified thallus in the Kaili Fm. bears great importance on the study of phylogeny and evolution of early calcareous macroalgae.     

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.     

On emplacement ages of lamproites in Zhenyuan County, Guizhou Province, China

Emplacement ages of lamproites that comprise lamproite and olivine lamproite in Zhenyuan County, Guizhou Province, China, have been constrained by the whole-rock Sm-Nd and Rb-Sr isochron methods and the whole rock K-Ar method. Intrusive activities of lamproites in the Sinantang area of Zhenyuan County, Guizhou Province, took place during the Late Cambrian, as indicated by the Sm-Nd isochron ages ( t ) = (503 ± 17) (2σ) Ma and by the Rb-Sr isochron ages ( t ) = (501.2 ± 4.6) (2σ) Ma. Intrusive activities of olivine lamproites at the Maping with Ⅱ-type diamond and Xitou in Zhenyuan County, Guizhou Province, took place from the Late Cambrian to the Early Ordovician, as evidenced by the Sm-Nd isochron ages ( t ) = (502 ± 27) (2σ) Ma and by the Rb-Sr isochron age ( t ) = (502 ± 27) (2σ) Ma. This suggests that the upwelling hot materials derived from the deep mantle were emplaced from the Late Cambrian to the Early Ordovician (503-497 Ma), while the time terminal of cooling of the geothermal event of magmatism-tectonism probably was at 442.64-435.54 Ma, as dated by the whole rock K-Ar method.     

贵州黔东地区中-下寒武统凯里组发育特征

贵州黔东地区中－下寒武统凯里组主要由粉砂质泥岩，页岩及灰岩组成，富产三叶虫，其中台江八郎乌溜－曾家岩的凯时组含著名的中寒武世凯里生物群、早寒武世台江生物群，2001年成为国际中－下寒武统层型界线候选部，对其深入研究具有重大科学和实用意义。就我省黔东地区凯里组的岩石地层，生物地层，年代地层，沉积环境等进行研究及总结，亦确认黔东凯里组是一个十分重要的地层单位。     

贵州金沙寒武系牛蹄塘组古盘虫类三叶虫的地层意义

通过对贵州金沙岩孔剖面牛蹄塘组的逐层化石采集,发现了大量古盘虫类三叶虫,包括Tsunyidiscus armatus和Tsunyidiscus niutitangensis,同时确定了T.armatus的顶界,将T.armatus顶峰带修订为T.armatus延限带。T.armatus是贵州最早出现的三叶虫,其对于寒武系第3阶底界的确定具有重要意义,此次修订的T.armatus延限带体现了生物的演化阶段,为区域地层的精细划分与对比提供重要的基础资料。本文也对Tsunyidiscidae做了初步讨论,认为该科包括Tsunyidiscus,Hupeidiscus和Badiscus3个有效属。     

凯里动物群与我国早期后生动物演化的初步研究

作者所发现的中寒武世凯里动物群,属于带软躯体化石的布吉斯页岩型的动物群,是继云南澄江动物群之后我国发现的又一个早期后生动物群。它和新近发现的晚震旦世庙河生物群,分别填补了晚震旦世、中寒武世我国带软躯化石生(动)物群的空白,形成了我国多时期带软躯化石的生(动)物群体系。对于研究我国及世界早期后生动物演化并不断揭示其演化规律有重要意义。     

Yangtzedonta and the early evolution of shelled molluscs

The holotype of Yangtzedonta Yu, 1985 and its type species, Y. primitiva Yu, 1985, is an incomplete specimen of Xianfengella prima He et Yang, 1982. Therefore, based on the principle of priority, the names Yangtzedonta and Y. primitiva Yu (1985) should be abandoned. The fact that ventral valve of Xianfengella is bilaterally symmetrical indicates that they are not the left valve of a bivalved mollusc, as originally proposed by Yu. At present, the oldest certain bivalve is Xianfengoconcha elliptica Zhang, which occurs in the Early Cambrian Qiongzhusi Stage in China. The oldest known rostroconch is Heraultipegma yunnanensis He et Yang, which first occurs in the third small shelly fossil assemblage zone of the Early Cambrian Meishucunian Stage. The oldest known monoplacophoran, Maikhanella pristinis (Jiang), first occurs in the first small shelly fossil assemblage zone (Meishucunian Stage). Evidence derived from analyses of shell morphology, mode of growth, histology, and stratigraphic occurrence suggests that bivalves evolved from a branch of rostroconchs, and that rostroconchs in turn evolved from a branch of monoplacophorans. The hypothesis that these three groups originated simultaneously and independently at the beginning of the Cambrian and subsequently evolved in parallel, probably is incorrect.     

Eocrinoids from the Cambrian Mantou Formation of Dalian, Liaoning

Cambrian echinoderms,especially eocrinoids,have been reported recently from Guizhou and Yunnan provinces of China,such as the Kaili,Balang,and Guanshan faunas.The present paper reports abundant well-preserved eocrinoids from the Cambrian Mantou Formation of Dalian,Liaoning Province.This new discovery provides additional data on the early evolution of Echinodermata.It also gives us a clue as to where to seek the Cambrian soft-bodied fauna on the margin of the North China Platform.     

Paleoceangraphic significance of redox-sensitive metals of black shales in the basal Lower Cambrian Niutitang Formation in Guizhou Province, South China

TheLowerCambrianblackshalesequenceoccursinSouthChinaalonganarc parallellinearbeltex tendingmorethan 16 0 0km .Theseorganic richblackshalesformedinvariousmarineenvironmentsandtypicallycontainhigheramountsofmolybdenum ,nickel,vanadium ,andanumberofothereconomical lyimportantmetalsthandoanyothersedimentaryrocks[1,2 ] .Therefore ,thestudyoftheseblackshaleshasnotonlypaleoceangraphicimplicationbutalsoe conomicsignificance .Marinesedimentssuchasblackshalearecom plexmixturesofdetritalphasesandseawat…     

An armoured Cambrian lobopodian from China with arthropod-like appendages

Cambrian fossil Lagerst?tten preserving soft-bodied organisms have contributed much towards our understanding of metazoan origins. Lobopodians are a particularly interesting group that diversified and flourished in the Cambrian seas. Resembling 'worms with legs', they have long attracted much attention in that they may have given rise to both Onychophora (velvet worms) and Tardigrada (water bears), as well as to arthropods in general. Here we describe Diania cactiformis gen. et sp. nov. as an 'armoured' lobopodian from the Chengjiang fossil Lagerst?tte (Cambrian Stage 3), Yunnan, southwestern China. Although sharing features with other typical lobopodians, it is remarkable for possessing robust and probably sclerotized appendages, with what appear to be articulated elements. In terms of limb morphology it is therefore closer to the arthropod condition, to our knowledge, than any lobopodian recorded until now. Phylogenetic analysis recovers it in a derived position, close to Arthropoda; thus, it seems to belong to a grade of organization close to the point of becoming a true arthropod. Further, D. cactiformis could imply that arthropodization (sclerotization of the limbs) preceded arthrodization (sclerotization of the body). Comparing our fossils with other lobopodian appendage morphologies--see Kerygmachela, Jianshanopodia and Megadictyon--reinforces the hypothesis that the group as a whole is paraphyletic, with different taxa expressing different grades of arthropodization.     

Sponge spicules in phosphorites of the Early Cambrian Gezhongwu Formation, Zhijin, Guizhou

Phosphorites occurring at the bottom of the Cambrian system contain abundant small shelly fossils, which are the product of the first episode of life explosion in the Cambrian. It was previously reported that the small shelly fossils are dominated by hyolithids, olivooids, zhijinitids, conodontomorphs, yubelichitids, camenitids and algae, with minor amounts of sponge fossils. Large amounts of sponge spicules, diverse in form, have been found for the first time in the Gezhongwu Formation phosphorites at Shixing, Zhijin County, Guizhou Province, of which such spicules as diaxon-triactins, diaxon-tetractins, pentaxon-pentactins and hexon-hexactins account for 30%. These spicules constitute the sponge clastic phosphorites made up of sponge clastics. Meanwhile, it is also expected that the radiation and diversity of sponge animals started as early as in the earliest Early Cambrian. Habit and burying environment of sponge animal are discussed in the paper.