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1.
The base of the Furongian Series in the Sino-Korean Block has not been clearly defined due to the lack of the index taxon, Glyptagnostus reticulatus. The Sesong Formation of the Taebaek Group, Taebaeksan Basin, Korea, has been known to range from the Guzhangian Stage of the Cambrian Series 3 to the middle Furongian Series, hence embracing the base of the Furongian Series. Silicified polymerid trilobites were recovered from the middle part of the Sesong Formation. Described are a total of 18 polymerid species of 13 genera: Neodrepanura sp. 1, Teinistion sp. 1, Huzhuia sp. 1, Huzhuia sp. 2, Liostracina simesi, Liostracina sp. 1, Parachangshania monkei, Parachangshania rectangularis nov. sp., Placosema bigranulosum, Fenghuangella laevis nov. sp., Baikadamaspis jikdongensis nov. sp., Baikadamaspis sp. 1, Prochuangia mansuyi, Maladioides coreanicus, Alataspis sesongensis nov. gen., nov. sp., Chuangia sp. 1, and ceratopygids genus and species indeterminate 1 and 2. The stratigraphic occurrence of these trilobites provides a basis for recognition of five zones across the base of the Furongian Series (in ascending order): the Neodrepanura, Liostracina simesi, Fenghuangella laevis, Prochuangia mansuyi, and Chuangia zones. The Neodrepanura and Chuangia zones are provisionally adopted from the previous biostratigraphic scheme, while the three other ones are newly proposed. The recommended base of the Furongian Series in the Taebaek Group of Korea coincides with the base of the Fenghuangella laevis Zone, which appears to represent an episode of profound trilobite faunal turnover.  相似文献   

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The Middle to Upper Cambrian Machari Formation in Korea is well known for abundant and diverse trilobites along with other invertebrate fossils. Based on recent reappraisal on the trilobites of the Machari Formation, eight trilobite zones have been proposed for the Upper Cambrian sequence: i.e., in ascending order the Glyptagnostus stolidotus, Glyptagnostus reticulatus, Proceratopyge tenuis, Hancrania brevilimbata, Eugonocare longifrons, Eochuangia hana, Agnostotes orientalis and Pseudoyuepingia asaphoides zones. Trilobites from the lower five zones and part of the Pseudoyuepingia asaphoides Zone have been already published elsewhere. In this paper, we describe the agnostoid trilobites of the upper three zones, Eochuangia hana, Agnostotes orientalis and Pseudoyuepingia asaphoides zones, of the Machari Formation. These comprise 24 species belonging to 13 genera, including one new genus (Yongwolagnostus) and ten new species (Homagnostus? sulcatus, Ivshinagnostus alatus, Ivshinagnostus quadratus, Yongwolagnostus stenorhachis, Yongwolagnostus dubius, Nahannagnostus pratti, Pseudagnostus? dividuus, Pseudagnostus medius, Pseudorhaptagnostus? urceus and Ammagnostus serus). These biozones correlate well with middle Upper Cambrian zones established in South China, Australia, Kazakhstan, Siberia, and Canadian Rocky Mountains.  相似文献   

4.
《Palaeoworld》2019,28(3):276-288
The Bowers Mountains in Northern Victoria Land contain the richest Cambrian Series 3 (Miaolingian, middle Cambrian) and Cambrian Series 4 (Furongian, late Cambrian) fossiliferous successions in Antarctica. Almost all the fossils are found within the Bowers Supergroup, which outcrops within the Bowers Terrane, a fault-bounded northwest-southeast oriented strip in Northern Victoria Land. The fossils provide the main age control on the history and evolution of the Bowers volcanic arc and back-arc basin. The great bulk of the fossils occur within the Spurs Formation. The fossil assemblages are dominated by agnostoids and polymerid trilobites with most ranging in age from Drumian to Paibian, although one fauna is of Jiangshanian age. Over 40 agnostoid taxa and over 100 polymerid trilobite taxa have been recorded from the rocks of the Bowers Supergroup. The youngest fauna occurs within the adjacent Robertson Bay Terrane, where a limited fauna of polymerid trilobites and conodonts from within a limestone olistolith have a very late Cambrian or early Ordovician age. Faunal affinities are mainly with Australia, New Zealand, North and South China and the Himalaya with lesser ties to Iran, Kazakhstan, Siberia and Laurentia.  相似文献   

5.
A core drilling (Andrarum‐3), from the classical locality at Andrarum, Scania, southernmost Sweden, penetrated a 28.90‐m‐thick Cambrian succession. The core comprises dark grey to black, finely laminated mudstones and shales with early concretionary carbonate lenses (stinkstones or orsten) and a few primary carbonate beds. The middle Cambrian (provisional Series 3) part of the core comprises 17.35 m, whereas the Furongian Series (upper Cambrian) part covers the remaining 11.55 m. Nineteen trilobite and two phosphatocopine genera are present in the middle Cambrian, whereas the less diverse Furongian interval yielded four trilobite and three phosphatocopine genera. Other, less frequent, faunal elements include conodonts (s. l.), brachiopods, sponge spicules, bradoriids, and coprolites. Trilobites and phosphatocopines were used to subdivide the core into seven biozones ranging from the Ptychagnostus atavus Zone to the Parabolina spinulosa Zone (P. spinulosa Subzone). Carbon isotopic analyses (δ13Corg) through the core show two important excursions, the negative DrumIan Carbon isotope Excursion (DICE) in the Pt. atavus Zone, and the Steptoean Positive Carbon Isotope Excursion (SPICE) beginning near the first appearance of Glyptagnostus reticulatus and extending upward into the Olenus and Agnostus (Homagnostus) obesus Zone. The DICE displays a peak value, in the samples at hand, of –30.45‰δ13Corg in the lower part of the P. atavus Zone. The δ13Corg values increase through the overlying L. laevigata and A. pisiformis zones and display peak values of c. –28.00‰δ13Corg in the lowermost Furongian Olenus wahlenbergi and O. attenuatus subzones. Thereafter the values decrease significantly through the O. scanicus Subzone. Both isotopic excursions have been documented from several palaeocontinents, but never before from Baltica. Moreover, for the first time these excursions are recorded from organic matter in an alum shale setting. The recorded shift of +1.50–2.00‰δ13Corg is approximately half the magnitude of the SPICE documented from other regions. This discrepancy may be related to temporal variations in the type, origin, or diagenesis of the organic fraction analysed.  相似文献   

6.
    
《Palaeoworld》2021,30(3):398-421
The lower Cambrian succession in the Jiaobang section, Jianhe County, eastern Guizhou, China, includes, in ascending order, the Bianmachong, Balang, and Tsinghsutung formations, with a total thickness of about 645 m. Twenty-six morphological genera (including one new genus) are identified from the Balang and the underlying Bianmachong formations, many of which are common and widely distributed. Six acritarch assemblages are discerned in the Balang Formation. They are, in ascending order, the Adara alea‒Skiagia ornata, the Acrum radiale‒Pterospermella velata, the Comasphaeridium molliculum‒Solisphaeridium baltoscandium, the Corrugasphaera perfecta n. sp.‒Pterospermella vinctusa n. sp., the Acrum novum‒Heliosphaeridium oligum, and the Acrum membranosum‒Adarve diafanum acritarch assemblages. An obvious change of organic-walled microfossil assemblages occurred in the interval between 84 m and 98 m from the bottom of the Balang Formation which roughly corresponds to the boundary between the Oryctacarella duyunensis trilobite Zone and the overlying Arthricocephalus chauveaui trilobite Zone. In addition, organic-walled microfossils are scarce in about 24 m thick from the bottom of the Balang Formation. One new genus and five new species including Plagasphaera balangensis n. gen. n. sp., Asteridium tubulus n. sp., Cymatiosphaera spina n. sp., Corrugasphaera perfecta n. sp., and Pterospermella vinctusa n. sp. are described.  相似文献   

7.
  总被引:1,自引:0,他引:1  
A latest Early Cambrian and earliest Mid Cambrian polymeroid trilobite fauna, consisting of 16 genera and 25 species, is reported from the peritidal deposits of the Mule Spring Limestone and outer-shelf deposits of the Emigrant and Monola formations of Nevada and California. The Mid Cambrian fauna includes a new genus, Tonopahella , and four new species, T. goldfieldensis , Oryctocephalus americanus , Onchocephalites claytonensis , and Syspacephalus variosus . The peri-Gondwana species Oryctocephalus orientalis , Oryctocephalites runcinatus , and Paraantagmus latus are recorded in Laurentia for the first time.  相似文献   

8.
    
The use of carbon isotope excursion in Cambrian stratigraphical correlation is a standard practice at both the intercontinental and intracontinental scales. The Steptoean positive carbon isotope excursion (SPICE) is one of the prime examples in this regard in correlating the base of the Paibian Stage and Furongian Series. A lack of definite SPICE evidence in the North China craton has been a challenge in precision correlation between North China and other palaeo‐continents. This study provides new carbonates carbon isotope data from the type locality of the Changshan Formation in Hebei Province, North China. Our new δ13Ccarb data provide new objective evidence for the presence of the SPICE in North China. The sampling section is relatively condensed, and the interval of the SPICE curve is less than one and half‐metres after analysing 64 samples (the sampling interval within the SPICE is less than 10 cm). The onset of the SPICE curve in Tangshan, Hebei, occurs in the barren interval between the Neodrepanura and Chuangia trilobite zones. Based on this study and previous work, this could imply the middle part of the Prochuangia‐Paracoosia trilobite Zone in North China and can be correlated with the base of the Paibian Stage and Furongian Series.  相似文献   

9.
雒昆利 《古生物学报》2001,40(3):371-387
陕西韩城寒武系出露良好,化石丰富,从下寒武统上部至奥陶系为连续沉积,底部平行不整合覆盖厚约20m的霍山组石英砂岩之上。本区寒武 系主要以紫色和黄色泥页岩、泥灰岩、灰岩和白云质灰岩为主,张夏组主要以鲕状灰岩为主,夹生物碎屑灰岩,三叶虫主要有Changqingia chalcon,Changqingia luia sp.nov.,Manchuriella macar,Lianglangshania hueir ensis,Crepicephalia convexus,Eilura quadrata,Eilura(?)hanchengensis sp.nov.,Anmocarella chinensis,Dorypyge pergranosa,Dorypyge richthofeni,Liopeishania lubrica,Liopeishania marginata和Damesella paronai等。三山子组以白云质灰岩和灰质白云岩为主,在底部的白云质灰岩中产三叶虫Blackwelderia sp.,Damesops convexus和Cyclolorenzella acalle等,其中、上部未采到化石。  相似文献   

10.
张文堂 《古生物学报》2003,42(3):305-316
二十世纪中叶以后,中、美寒武纪地层研究都有重大进展。三叶虫是寒武纪的重要化石,中、晚寒武世牙形石有显著的生物地层意义。二十世纪中叶国内研究寒武系的学者,认为北美寒武系与西欧及北欧的相似,与中国的差异较大。目前看来,北美东部斜坡相区的寒武系与西欧、北欧相似外,北美西部广大地区(包括阿拉斯加、加拿大及美国境内的落基山等地区),分别与西伯利亚,蒙古西北部一些地区,及我国华北、东北南部及华南等地区的寒武系关系较近。北美西部Nevada及Utah等地也显示地台区及斜坡相区的不同。文内对两个地区早、中、晚寒武世地层内相同的属或种,分别进行对比。两地区属种相同的数目,由老到新逐渐增多。岩石方面,也有相似之处,如Pioche页岩和馒头组的岩性,Notch Peak灰岩与凤山组藻类灰岩及Hales灰岩与华北晚寒武世的竹叶状灰岩等,都有相似之处。  相似文献   

11.
    
Logical connections exist between evolutionary modularity and heterochrony, two unifying and structuring themes in the expanding field of evolutionary developmental biology. The former sees complex phenotypes as being made up of semi-independent units of evolutionary transformation; the latter requires such a modular organization of phenotypes to occur in a localized or mosaic fashion. This conceptual relationship is illustrated here by analyzing the evolutionary changes in the cranidial ontogeny of two related species of Cambrian trilobites. With arguments from comparative developmental genetics and functional morphology, we delineate putative evolutionary modules within the cranidium and examine patterns of evolutionary changes in ontogeny at both global and local scales. Results support a case of mosaic heterochrony, that is, a combination of local heterochronies affecting the different parts individuated in the cranidium, leading to the complex pattern of allometric repatterning observed at the global scale. Through this example, we show that recasting morphological analyses of complex phenotypes with a priori knowledge or hypotheses about their organizational and variational properties can significantly improve our interpretation and understanding of evolutionary changes among related taxa, fossil and extant. Such considerations open avenues to investigate the large-scale dynamics of modularity and its role in phenotypic evolution.  相似文献   

12.
    
Asymmetry in fossils can arise through a variety of biological and geological mechanisms. If geological sources of asymmetry can be minimized or factored out, it might be possible to assess biological sources of asymmetry. Fluctuating asymmetry (FA), a general measure of developmental precision, is documented for nine species of lower Paleozoic trilobites. Taphonomic analyses suggest that the populations studied for each taxon span relatively short time intervals that are approximately equal in duration. Tectonic deformation may have affected the specimens studied, since deviations from normal distributions are common. Several measures of FA were applied to 3–5 homologous measures in each taxon. Measurement error was assessed by the analysis of variance (ANOVA) for repeated measurements of individual specimens and by analysis of the statistical moments of the distributions of asymmetry measures. Measurement error was significantly smaller than the difference between measures taken on each side of a specimen. However, the distribution of differences between sides often deviated from a mean of zero, or was skewed or kurtosic. Regression of levels of FA against geologic age revealed no statistically significant changes in levels of asymmetry through time. Geological and taphonomic effects make it difficult to identify asymmetry due to biological factors. Although fluctuating asymmetry is a function of both intrinsic and extrinsic factors, the results suggest that early Cambrian trilobites possessed genetic or developmental mechanisms used to maintain developmental stability comparable to those of younger trilobites. Although the measures are biased by time averaging and deviations from the normal distribution, these data do not lend strong support to 'genomic' hypotheses that have been suggested to control the tempo of the Cambrian radiation.  相似文献   

13.
太阳女神螺类(helcionellids)是寒武纪常见的一类软体动物,广布全球,多见于碳酸盐岩沉积地层中,而布尔吉斯页岩型生物群中却少有报道。贵州剑河凯里生物群是典型的特异埋藏化石库,产有700余件太阳女神螺类标本,这在世界各地同时期的布尔吉斯页岩型生物群中是很少见的。本文对贵州剑河八郎寒武系凯里组太阳女神螺类化石标本进行了系统研究,采用几何形态测量学的典型变量分析进行量化分析。几何形态测量学(Geometric morphometrics)是用界标点或轮廓线等来描绘生物的形态或者标记特征部位及器官,将生物形态特征归纳为数据变化的定量学方法,其中的典型变量分析(Canonical Variate Analysis)是多变量分析中进行判别分析的一个重要方法,可以用于多组数据之间的判别。CVA判别结果显示:利用壳体侧视轮廓线判别Dorispira属中三个种的正确率为92%,验证了Dorispira accordinonata、D.taijiangensis和D.cf.pearylandica化石种分类合理性。本文研究表明即使壳体形态较为相似的类群,也可以较为准确地使用CVA量化其中的差别,...  相似文献   

14.
The Montagne Noire (southern France) possesses one of the most complete Cambrian successions in the western peri-Gondwana margin and might provide a good stratigraphic reference for both regional charts and international correlations. However, to date, the lower Cambrian succession of the northern Montagne Noire has been supposed to be devoid of biostratigraphically significant fossils. The complex tectonostratigraphic framework of the area (a range divided into Axial Zone, northern and southern Montagne Noire) exacerbated problems related to regional correlations and palaeogeographic reconstructions. As a result, the chronostratigraphic context of the lower Cambrian of northern Montagne Noire is still uncertain and stratigraphic reports have broadly relied on putative lithostratigraphic correlations with the southern Montagne Noire. The purpose of this study is to characterise, for the first time, the fossil record of carbonate beds and lenses of the northern Montagne Noire occurring at the top of the siliciclastic-dominated Marcory Formation, in order to provide regional bio- and chronostratigraphic constraints on lower Cambrian strata. Moreover, this study is aimed at improving international chronostratigraphic correlation. Carbonate beds and lenses cropping out along the Orque Cliff, in the Mélagues thrust slice, were investigated. They yielded a faunal assemblage constituted of molluscs (Igorella cf. ungulata and Igorella moncereti n. sp.), hyoliths (Conotheca brevica), chancelloriids (Archiasterella cf. pentactina and Allonnia sp.) and tommotiids (Lapworthella rete). L. rete is recorded in upper Meishucunian (Cambrian Stage 3) strata of the Yangtze Platform (South China) where it is used as index fossil of the Cambrian Stage 3 Sinosachites flabelliformisTannuolina zhangwentangi Assemblage Zone. Therefore, the presence of this tommotiid provides evidence that the studied carbonate beds and lenses are Cambrian Age 3 (Atdabanian according to the Siberian chart). The upper part of the Marcory Formation in the Mélagues slice, dated as Cambrian Stage 3, might represent a lateral equivalent of the mixed (carbonate-siliciclastic) Pardailhan Formation defined in the southern Montagne Noire.  相似文献   

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Several hundred specimens of a tiny olenid trilobite, Ctenopyge ceciliae sp. nov., have been found in stinkstone nodules in the upper Cambrian Peltura scarabaeoides Zone in southern Sweden. This exceptionally spinose form is known only from disarticulated specimens, but is quite well preserved, and all growth stages are represented. The early ontogenetic stages are exceptionally small, the protaspis being only half the size of that of the associated Peltura species. There may have been no more than three thoracic segments. Thus the whole ontogeny was compressed, and this together with the very small size of the adult indicates a true miniaturisation. Whereas the likely control of the origin of the tiny C. ceciliae was basically progenesis, the extreme spinosity had a different origin; allometric growth or possibly peramorphosis. C. ceciliae is small enough for the spines to have appreciably retarded sinking through frictional effects, and this small trilobite is interpreted as a free-swimming or floating form.  相似文献   

18.
    
Abstract:  Ontogenies are described for the first time for three species of Early Cambrian oryctocephalid trilobites: the oryctocephaline Changaspis elongata Lee, in Chien and the oryctocarines Duyunaspis duyunensis Chang and Chien, in Zhou et al . and Balangia balangensis Chien from the Balang Formation in eastern Ghuizhou Province, south-west China. The complete protaspid to holaspid ontogeny for Duyunaspis duyunensis and incomplete meraspid to holaspid ontogenies for Changaspis elongata and Balangia balangensis are described. The relative degree of ontogenetic variation within the lineage Duyunaspis duyunensis – Balangia balangensis is analysed and indicates that Balangia may have evolved from Duyunaspis by paedomorphosis. Decrease in thoracic segment number and concomitant increase in pygidial segment number in the later genus mirrors the pattern seen in the evolution of another oryctocephalid genus, Arthricocephalus . In both cases, selection was probably targeting an increase in cephalic convexity. This resulted in the evolution of a larger pygidium due to increased elevation of the axis above the substrate. The ontogenetic development of Changaspis provides evidence supporting the view that the Oryctocarinae may be considered as paedomorphic descendants of the Oryctocephalinae.  相似文献   

19.
记述内蒙古清水河刘家窑上寒武统崮山组中下部灰色中一薄层含鲕粒灰岩.泥质条带灰岩夹竹叶状灰岩中的三叶虫化石10种,其中3新种(包括1新亚种),分属于7属4科。  相似文献   

20.
A phylogeny of the Cambrian solenopleuropsine trilobites is constructed to evaluate the importance of differential speciation, extinction and developmental constraints in the evolutionary history of the clade. The transformation of the Pardailhania–Solenopleuropsis ( Manublesia )– Solenopleuropsis ( Solenopleuropsis ) lineages occurred during the mid Caesaraugustian–early Languedocian interval, with all measured morphological variables exhibiting continuous and gradual changes. Several evolutionary trends show tendencies towards an increase in tuberculation and its complexity on the anterior part of the cephalon. A mid Caesaraugustian anagenetic tendency is related to the influence of constant environmental conditions, whereas a late Caesaraugustian–early Languedocian cladogenetic tendency seems to have been an adaptative response to unstable environments. The Solenopleuropsinae clade has a well-preserved continuous fossil record over its full biogeographical range in the Mediterranean region. The sympatric evolution in centrally located populations (Mediterranean area) follows the model of phyletic gradualism, whilst a peripheral population in Avalonia gave rise (by allopatric speciation) to a distinct species, characterized by a variation in the relative size of the palpebral lobes, which may be evidence of a parallel evolution in the trends of ornamentation.  相似文献   

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