Neoproterozoic to early Cambrian small shelly fossil assemblages and a revised biostratigraphic...

alaeoecology 254 (2007) 67–99www.elsevier.com/locate/palaeo

Palaeogeography, Palaeoclimatology, P

Neoproterozoic to early Cambrian small shelly fossil assemblagesand a revised biostratigraphic correlation of the

Yangtze Platform (China)

Michael Steiner a,⁎, Guoxiang Li b, Yi Qian b, Maoyan Zhu b, Bernd-Dietrich Erdtmann a

a TU Berlin, Sekr. ACK 14, Ackerstrasse 71-76, 13355 Berlin, Germanyb Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China

Accepted 5 March 2007

Abstract

Small shelly fossils (SSFs) occur widely on the Yangtze Platform and have great potential for biostratigraphic subdivision ofpre-trilobitic Early Cambrian strata. Based on the SSF record of the shallow water realm, five biozones can be recognized for theMeishucunian Stage. In ascending order the biozones are: Anabarites trisulcatus–Protohertzina anabarica Assemblage Zone;Paragloborilus subglobosus–Purella squamulosa Assemblage Zone; Watsonella crosbyi Assemblage Zone (formerly Heraulti-pegma yunnanensis Zone); poorly fossiliferous interzone; Sinosachites flabelliformis–Tannuolina zhangwentangi AssemblageZone. In addition one SSF biozone is recognized for the overlying Qiongzhusian Stage: Pelagiella subangulata Taxon-range Zone.The formerly used Siphogonuchites triangularis–Paragloborilus subglobosus Zone and Heraultipegma yunnanensis Zone arediscussed and redefined. Approximately 80 species of SSFs were screened for their spatial and temporal distribution on the YangtzePlatform. Variations in lithofacies and biofacies can be recognized throughout the Yangtze Platform, extending over an area of2000×900 km. In a deeper water shelf setting the first zone is represented by the Protohertzina anabarica–Kaiyangites novilisAssemblage Zone, while younger zones are not recognized in the southern region. At the northern platform margin theQiongzhusian is represented by the Ninella tarimensis–Cambroclavus fangxianensis Assemblage Zone and the Rhombocornicu-lum cancellatum Taxon-range Zone. The southeastern Shaanxi–western Hubei region followed a slightly different lithological andfaunal development than the rest of Yangtze Platform, indicating a stronger similarity with parts of East Gondwana.

Some taxa such as W. crosbyi, P. subangulata, R. cancellatum, Microdictyon effusum, A. trisulcatus, Protohertzinaunguliformis, and P. anabarica occur nearly worldwide and support an international correlation of Early Cambrian sequencesbetween the Yangtze Platform and smaller West Gondwanan blocks, Siberia, Newfoundland, and Australia. The six investigatedzones of the Yangtze Platform comprise an interval spanning the early Nemakit–Daldynian to the late Atdabanian/early BotomanStage on the Siberian Platform. Palaeobiogeographic analysis revealed a strong taxic similarity between the Yangtze Platform andthe Tarim Platform. A smaller number of species are shared with other West Gondwanan platform fragments such as India and Iran.Palaeobiogeographic results do not support the previously reported position of the South China Block between Australia andSiberia during the Early Cambrian.© 2007 Elsevier B.V. All rights reserved.

Keywords: Palaeontology; Yangtze Platform; South China; Lower Cambrian; Small shelly fossils; Biostratigraphy

⁎ Corresponding author. Tel.: +49 30 314 72876.E-mail address: [email protected] (M. Steiner).

0031-0182/$ - see front matter © 2007 Elsevier B.V. All rights reserved.doi:10.1016/j.palaeo.2007.03.046

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http://dx.doi.org/10.1016/j.palaeo.2007.03.046

68 M. Steiner et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 254 (2007) 67–99

1. Introduction

The aim of the present study is to define and discussthe SSF biozonation for the Yangtze Platform (SouthChina) and to discuss the regional and internationalcorrelation of earliest Cambrian strata. SSFs representan important biostratigraphic tool for the subdivisionand correlation of pre-trilobitic strata of the Cambrian.Despite strong attempts which are currently being madeto settle internationally accepted series and stagesubdivisions of the Cambrian system, the lower bound-ary problem and subdivision of pre-trilobitic LowerCambrian strata require continued attention. The newsubdivision of the Lower Cambrian of South China usingtwo series (Diandongian; Qiandongian) and four stages(Jinningian, Meishucunian, Nangaoan, Duyunian) asproposed by Geyer and Shergold (2000), Peng (2000),and Peng and Babcock (2001) did not find broad ap-proval and application, because it had not yet been fullydiscussed and approved by the national and internationalworking groups on Cambrian stratigraphy. To preventpremature judgement regarding the decisions of theinternational working group of stage subdivision weherein do not intend to apply the newly advocated seriesand stage subdivision for the Lower Cambrian of SouthChina. An application of the newly proposed stages forthe Lower Cambrian is also discredited by the fact thatthe intended zonal subdivision based on SSF genera anda “Hupediscus–Sinodiscus Zone” covering the entireQiongzhusian and the lower part of Canglangpuian(Geyer and Shergold, 2000; Peng, 2000; Peng andBabcock, 2001) is not acceptable (cf. Yang et al., 2003)and the proposed index fossils (first appearance datum(FAD) of Treptichnus/Trichophycus pedum, Paraglo-borilus subglobosus; FAD of trilobites) for defining thestages are problematic.

Mineralized remains of disarticulated endoskeletonsand exoskeletons of mainly unknown metazoans andshells of brachiopods and molluscs are widely distrib-uted in the Lower Cambrian ofmany platforms. The term“small shelly fossils” was first used by Matthews andMissarzhevsky (1975), accommodating mostly proble-matica, but also poriferans, molluscs, and hyoliths. Sub-sequently, the term found broad application for small-sized phosphatized problematica of pre-trilobitic strataof the traditional Lower Cambrian. Later, the term wasoften used as “small skeletal fossils”, because most re-mains are scaffoldings, stiffened walls, or shells. How-ever, neither Matthews and Missarzhevsky (1975) norany later authors have given a definition for the terms“small shelly fossils” or “small skeletal fossils” (SSFs),which resulted in diverging applications of the terms.

Some authors only considered problematic mineralizedmetazoan fossils of the Lower to Middle Cambrian andunrelated to younger Palaeozoic or modern faunas asSSFs, thus treating SSFs separately from brachiopod andmollusc shell material (Brock et al., 2000).

Sepkoski (1992) included data of “small shellyfossils” in his statistical investigation of patterns of di-versification and faunal changes in the early metazoanfossil record and proposed the term “Tommotian Fauna”for orthothecimorph hyoliths, monoplacophorans, sabel-liditids, and a variety of short-ranging problematica. Theterm remained weakly defined, because it was derivedfrom factor analysis of diversity data, which were sub-jectively influenced (limited knowledge of distributiondata; selection of data; uncertainties in taxonomy). Incontrast to the common usage of the term “small shellyfossils”, the “Tommotian Fauna” was neither strictlyconfined to mineralized remains (but possibly indirectlyinfluenced by taphonomic windows promoting specificpreservational modes in the fossil record and thus alsoinfluencing the data basis) nor to a stratigraphic dis-tribution within the Cambrian. Dzik (1994) also appliedthe term SSFs in a broader context to various phos-phatized skeletal remains of the Palaeozoic, such asmacheridians, gastropods, and bivalves. Porter (2004)later tried to test the influence of the phosphatizationtaphonomic window on the diversity pattern of SSFs.Although she recognized a taphonomic bias on thediversity pattern of SSFs, she concluded that the de-cline of SSFs in the Botoman, previously recognized bySepkoski (1992), was real. However, this analysisexcluded all fossils known from younger strata, such asbradoriids, trilobites, and brachiopods, but partly pre-served in a manner similar to most problematic SSFs,thus influencing the study by a preselection of inves-tigated skeletal fossils.

It is obvious that the term “small shelly fossils”does not embrace a single biological group defined byautapomorphies, but rather represents a broad categoryof mineralized fossil remains of a specific taphonomicwindow in the latest Neoproterozoic to early Palaeozoic.The SSFs are not always shell or skeletal materials, norare they in all cases small (mostly ranging between 0.1and 1 mm, but sometimes reaching 1 cm or more). Herewe apply the term “small shelly fossils” (SSFs) in thebroadest sense, as small (mostly millimeter scale, butranging from tens of micrometers to centimeters scale)and primarily or secondarily mineralized (phosphatized,silicified, carbonatic, pyritic/limonitic) remains (skeletaland non-skeletal) of metazoans. Following this view,the term describes a preservational mode of metazoanfossils, not a specific taxonomic group. We propose to

69M. Steiner et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 254 (2007) 67–99

describe complete skeletal fossils, such as articulatedtrilobites, under the Linnean system. However, they maybe included within the concept of SSFs outlined herein,if they are small and mineralized.

Despite uncertainties with the definition, the term“small shelly fossils” has been widely accepted becausetheir biological affinities largely remain obscure owingto their fragmentary states of preservation, an early evo-lutionary state, and because they represent some dra-matic changes in body plans that occurred during thelatest Neoproterozoic and earliest Cambrian. Althoughmost reported SSFs are phosphatic, this may be due to acommon secondary mineralization or replacement.There exists mounting evidence that most SSFs wereprimarily calcareous, such as the anabaritids, or organic,such as embryos or cnidarian polyps. The usually appliedacid digestion approach in SSF studies also contributedto an observational bias toward phosphatic biostructuresin the Early Cambrian.

On theYangtze Platform, the commonEarly CambrianSSFs embrace many mineralized problematica, but alsoshells of brachiopods and molluscs, plates of lobopods,grasping spines of chaetognaths, sponge spicules, min-eralized carapaces of bivalved arthropods, occipitalspines of trilobites, and secondarily mineralized soft-bodied organisms, such as metazoan embryos, and cni-darian polyps. Despite the weaknesses of their uncertainaffinity, their fragmentary status of preservation, and theproblem of part-based taxonomy (Bengtson, 1985), SSFshave been empirically applied as a biostratigraphic tool,mainly in pre-trilobitic strata of the Lower Cambrianon old platforms (Rozanov and Missarzhevsky, 1966;Rozanov et al., 1969; Missarzhevsky and Mambetov,1981; Missarzhevsky, 1982; Brasier, 1989; Missarz-hevsky, 1989; Bengtson et al., 1990; Khomentovskyand Karlova, 1993; Landing et al., 1998).

Since the late 1970s, various attempts have beenmade to utilize SSFs for biozonation of the Lower Cam-brian on the Yangtze Platform (Qian, 1978; Jiang, 1980a;Luo et al., 1980, 1982; He andYang, 1982; Qian andYin,1984; Qian and Bengtson, 1989; Qian et al., 1996, 1999,2001). Subsequently severe doubts have been cast onthe utility of SSFs for biozonation and internationalcorrelation (Conway Morris, 1988; Qian and Bengtson,1989; Landing, 1994), mainly due to the facts that(a) some SSFs are long-ranging; (b) ecological variationand endemism occurred; (c) problems existed in thecomparability of taxa between different platforms, partlydue to the fact that diverging taxonomic concepts wereused by the different national working groups; (d) mor-phological variability in specific taxa is high, and multi-element scleritomes may occur; and (e) the affinities

of disarticulated sclerites to true biological speciesremained uncertain. In recent decades considerableprogress has been made to sort out species variability,taxonomic synonymies, and geographic and stratigraph-ic distribution.

In Siberia and South China, biozonations based onSSFs are available, however, the zonations still awaitdetailed definition of species-based zones, according tothe concept of the International Stratigraphic Guide(Salvador, 1994; Murphy and Salvador, 1999). Anappropriate definition of biozones, such as assemblagezones or interval zones, may diminish the problemsoccurring with long-ranging taxa. A firm taxonomicrevision of critical taxa, such as the micro-molluscs, is anecessary prerequisite to the definition of an interconti-nentally recognized zonation of SSFs.

2. Material and methods

Small shelly faunas from numerous outcrops of theYangtze Platform are described inmore than 130 articles.Biostratigraphic data on SSFs derived from the literaturehave been combined with data from our own investiga-tions covering most regions of the Yangtze Platform(Fig. 1). Together, this information is used to revise theEarly Cambrian biozonation of South China. A datamatrix of absence/presence data (0/1) of SSF taxa wascreated for the pre-trilobitic and basal trilobitic intervalsof the Yangtze, Tarim, and Siberian Platforms, and EarlyCambrian basins in Iran, India, Kazakhstan, Australia,and parts of West Avalonia. This data matrix containsdata for 217 species and 49 occurrences, of which most(84 species, 31 occurrences) are from the Yangtze Plat-form (see Supplementary data file #1). Taxonomicallyless well defined species, such as many tubular andhyolith-like taxa, have been omitted from the data set toavoid an overprinting of biologically derived diversifi-cation patterns by an artificial pseudo-taxonomy.Hierarchical cluster analysis has been carried out usingthe computer-program SPSS 12.0.

Fossil extraction from rock samples followed stan-dard techniques using 10% acetic acid. Fossils for SEMinvestigation were mounted on stubs using a double-sided adhesive carbon tape. Before viewing, the sampleswere coated twice at an angle of 45° with 15 nm of goldfrom two different directions. SEM investigations werecarried out on a HITACHI S520 or S2700.

3. Preservation of small shelly fossils

The occurrence of large numbers of phosphatic SSFsin the Early Cambrian has led to the assumption that

Fig. 1. Map of South China with the location of sections from where small shelly fossils (SSFs) were reported and correlation transects shown in Figs. 9 and 10.

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phosphate has been a common primary biomineralutilized in the formation of skeletons in a variety ofmetazoan clades at the beginning of the Phanerozoic(Lowenstam and Margulis, 1980; Jiang, 1984). Thisview was doubted early on (Qian and Bengtson, 1989;Zhu et al., 1996) and evidence is mounting that for mostanimal groups, except perhaps linguloid brachiopods,primary skeletons were calcitic/aragonitic (anabaritids:Conway Morris and Chen, 1989; Kouchinsky andBengtson, 2002; molluscs: Runnegar, 1985; Kou-chinsky, 2000), or organic (Butterfield and Nicholas,1996). It is now also obvious that not all SSFs wereorganic or mineralized skeletal remains, as is shown bythe preservation of originally soft-bodied embryos andhydrozoan polyps (Steiner et al., 2004). A few remainingSSF taxa are thought to have produced primaryphosphatic skeletal elements, such as the grasping spinesof Protohertzina and net-like plates of Microdictyon(Bengtson et al., 1990; Bengtson, 1994). However, theseelements can possibly be interpreted as early diageneticmineralization of hardened organic compounds, as in-ferred from a comparison of protoconodonts with thegrasping spines of modern chaetognaths and the de-formation of mostly limonitic Microdictyon plates inChengjiang-type occurrences (Chen et al., 1995).

Typical processes resulting in phosphatization oforiginal biominerals and organic tissues are phosphatepermineralization, replacement, infilling, and coating(Fig. 2M). The same processes can in principle alsooccur on abiotic clasts and crystals, as illustrated inphosphatic hardgrounds and apatitic coatings of dolo-mite crystals (Fig. 2F). Taphonomic investigations rep-resent an important prerequisite for the taxonomictreatment of phosphatic SSFs and a subsequent bio-stratigraphic application of species. Later diageneticphosphate coatings may suppress fine surface ornamen-tation, such as seen in some specimens of Arthrochitesfrom Maidiping, Sichuan Province (Conway Morris andChen, 1992), and inner and outer coating surfaces ofcarbonatic tubular fossils, such as Conotheca, may pro-duce different surface structures (Fig. 2I). If the influenceof diagenetic history is neglected (compare Zhu et al.,1996), pseudo-taxa may be introduced into the literature,and this would complicate the application of SSFs forbiostratigraphic purposes. Examples for preservationalvariants of SSFs are the pseudo-taxa “Bashanites” (Dinget al., 1992) and “Rhabdochites” (Yang et al., 1983).“Rhabdochites” represents bone-shaped steinkerns ofHyolithellus-type tubes with distended ends due to crys-tallisation pressure from early diagenetic silicates(Fig. 2D, E, G). SSFs reported as “Bashanites” can beinterpreted as hexactinellid sponge spicules that have

been replaced by phosphate that served as cores forcontinued phosphate precipitation forming tetragonal-pyramidal structures (Fig. 2A–C). Besides this, a largenumber of other taxonomic synonyms have so far partlydisguised the biostratigraphic application of true bios-pecies for the Meishucunian and Qiongzhusian of theYangtze Platform.

In South China, 155 valid metazoan genera and 159synonyms and problematic or invalid nomens have sofar been recognized for the Meishucunian (Li et al., 2007-this volume).Most of them can be assigned to small shellygenera. This early diversity contrasts with approximately80 genera of SSFs known from the Qiongzhusian. Therecorded species diversity of SSFs dramatically decreasedduring later stages of the Early Cambrian, although thismay be partly due to an observational bias, because only afew studies have focused on SSFs from those intervals.The reduced numbers of genera in the Canglangpuian andLongwanmiaoian may also be partly explained bytaphonomic effects (closing of the phosphatizationwindow) and evolutionary trends (Porter, 2004). For theCanglangpuian 31 genera are recorded, and for theLongwanmiaoian, only 9 genera –mostly tubular fossils,hyoliths, and bradoriids – are recorded.

4. Neoproterozoic “shelly” assemblages of SouthChina

Calcareous tubular fossils of cloudinids, such asCloudina and Namacalathus, are widely distributed onlate Neoproterozoic carbonate platforms, mainly inshallow water environments associated with microbialbuildups (Grotzinger et al., 2000; Hofmann andMountjoy, 2001; Amthor et al., 2003). They are oftenconsidered to represent biomineralized metazoans(Grant, 1990; Bengtson, 1994); however, the biologicalaffinities largely remain uncertain (Conway Morriset al., 1990). It is even unresolved whether the min-eralized tubes of Cloudina represent true biomineraliza-tions rather than the products of a biologically inducedmineralization (e.g., organic tubes that calcify through-out ontogeny). Folded structures of some individuals ofCloudina indicate that the tubes were primarily flexible,which supports the hypothesis of a weak mineralizationor organic composition in some stages (Conway Morriset al., 1990; Grant, 1990; Brain, 2001). Phosphatizedand siliceous examples of cloudinids (Chen et al., 1981;Bengtson and Yue, 1992; Brain, 2001) are consideredthe result of diagenetic replacement. Carbonate andsiliceous worm tubes were also reported from youngersediments, such as the Oligocene cold-seep carbonatesof western Washington (Goedert et al., 2000). Here the




original tube composition is also questionable. Howev-er, either a primary aragonitic composition or protein-mediated aragonite formation of an original chitin-pro-tein complex was considered as a possible scenario.

The tubular remains of Cloudina are often consideredas exoskeletons, a view that is supported by the occur-rence of predatorial borings (Bengtson and Yue, 1992;Hua et al., 2003). A recent consensus on the biological


affinity of Cloudina is to consider this genus as as-signable to a diploblastic grade of metazoans, such asstem- or crown-group cnidarians (Budd, 2003).

A number of mineralized tubular fossil taxa, mostlycloudinids and related forms, have been described fromthe late Neoproterozoic of the Yangtze Platform (12genera accommodating 34 species). Of this seeminglydiverse association, probably only a dozen or so specieswould stand up to critical revision considering the mor-phological variability and different taphonomic pathwaysof preservation. Species such as Chenella canaliculatadefinitely represent preservational variants of other spe-cies. In the case of C. canaliculata, a single compactedspecimen of a smooth mineralized tube existed. It ex-hibited a longitudinal furrow and dumbbell-shaped crosssection, both of which resulted from compaction. Thesefeatures were considered sufficient for the erection of anew species (Ding et al., 1992; Hua et al., 2000).

The most conspicuous taxa of cloudinids from thenorthern edge of the Yangtze Platform are Cloudinahartmannae (Fig. 2K), Sinotubulites cienegensis (Fig. 2J),Chenella laevis (Fig. 2H), and Conotubus hemiannulatus(Chen et al., 1981; Zhang, 1986; Hua et al., 2000; Chenand Sun, 2001; Ding et al., 1992; Bengtson and Yue,1992). Cloudinids have only been reported from thecarbonate-dominated Shibantan andGaojiashanmembersof the Dengying Formation (Ediacaran) of western Hubeiand southern Shaanxi provinces. Here we also reportfor the first time cloudinids (Fig. 2L) from the upper-most conglomerate bed of the Dengying Formation inXingshan County (NW Hubei).

Other non-mineralized band-like fossils with trans-verse annulations have been described as Shaanxilithesningqiangensis from the Gaojiashan Member of Dengy-ing Formation of southern Shaanxi. Previously thesewere considered trace fossils (Xing et al., 1984) orcompacted organic metazoan tubes (Bengtson and Yue,

Fig. 2. SEM micrographs (A–L) and thin-section photomicrograph with crosseand sedimentary structures. (A) Phosphatized pentactine, No. Xiw104-13b.phosphate precipitation; formerly described as “Bashanites yangjiagouensis”,external phosphate precipitation; formerly described as “Bashanites yangjiagoueNo. Sht100-43. (E) Hyolithellus sp. with preserved shell material, but beginnidiagenetic crystallisation pressure, No. Sht100-46. (F) Phosphate coating of a do(G) Bone-shaped steinkern of Hyolithellus sp. with strongly distended ends o“Rhabdochites exasperatus”, No. Sht100-55. (H) Chenella laevis, No. Lij41phosphate coating; shell dissolved during fossil extraction process, No. Hhartmannae, No. Lij41-5. (L) Cloudina cf. hartmannae, No. Shui 14. (M) Thiinner and outer phosphate coating (white arrow) and partly complete replacemenFormation, Xiaowan, Xixiang County, Shaanxi. (D, E, G) Top of Lower CamLower Cambrian Kuanchuanpu Formation, Yuanjiaping/Kuanchuanpu, NingqLijiagou/Kuanchuanpu,NingqiangCounty, Shaanxi. (I) LowerCambrianKuancNeoproterozoic Dengying Formation, Shuimoshan, Xingshan County, HuKuanchuanpu, Ningqiang County, Shaanxi. All specimens, TU Berlin collectio

1992). Besides cloudinids and Shaanxilithes from theDengying Formation there also occur phosphatized tu-bular remains in the slightly older Doushantuo For-mation (Ediacaran) of China. These tubes, includingSinocyclocyclicus and Quadratitubus (Xue et al.,1992), have recently been interpreted as cnidarians(Xiao et al., 2000; Chen et al., 2002). However, primarybiomineralization of these phosphatized remains hasbeen questioned. This arises from two facts. On the onehand the same beds contain exceptionally preservedphosphatized metazoan embryos and algae (Li et al.,1998; Chen et al., 2000; Xiao and Knoll, 2000; Xiaoet al., 1998), which were only secondarily phosphatized.On the other hand the uppermost Doushantuo Formationalso contains a fossil association having organic pre-servation that includes numerous tubular fossils, such asProtoconites, Sinospongia, Calyptrina (Xiao et al.,2002). These tubes resemble phosphatized tubular fos-sils of the terminal Neoproterozoic (e.g., Chenella, Si-notubulites). Here especially morphological similaritiesbetween Sinospongia and Sinotubulites are striking,although the species assigned to these genera are often indifferent size ranges. In general, the biomineralizednature of most forms here related to cloudinids remainsquestionable. Thus, it is doubtful if any true biominer-alized “shelly” organisms were present in the latestNeoproterozoic. The relatively rare vase-shaped fossilProtolagena also occurs as partly mineralized and or-ganic fossils in dolostones of the Dengying Formation(Ding et al., 1992). Although no detailed investigationson its composition are currently available, it can beassumed that it was preserved as secondarily phospha-tized remains of organic tests.

Due to the worldwide distribution of Cloudina and itstemporal restriction to the Ediacaran, this genus wassuggested as an index fossil for the Ediacaran period(Grant, 1990). However, there are indications that the

d nicols (M) of Neoproterozoic and Early Cambrian phosphatized fossils(B) Phosphatized pentactine serving as nucleus for continued externalNo. Xiw103-2b. (C) Abraded phosphatized pentactine with continuednsis”, No. Xiw103-1b. (D)Hyolithellus sp. with preserved shell material,ng distension at the openings of tube and development of cracks due tolomite crystal, dissolved by the fossil extraction process, No. KYuan-33.f tube due to diagenetic crystallisation pressure; formerly described as-13. (I) Conotheca subcurvata with smooth outer and annulated innere2-2-189. (J) Sinotubulites cienegensis, No. Lij41-14a. (K) Cloudinan section of Anabarites trisulcatus; note partly carbonatic shell with thint of shell by phosphate (black arrow). (A–C) Lower Cambrian Xihaopingbrian Kuanchuanpu Formation, Shatan, Nanjiang County, Sichuan. (F)iang County, Shaanxi. (H, J, K) Neoproterozoic Dengying Formation,huanpu Formation, Zhangjiagou/Hexi, XixiangCounty, Shaanxi. (L) Topbei. (M) Lower Cambrian Kuanchuanpu Formation, Shizhonggou/n. Thin scale bar equals 100 μm, thick scale bar 500 μm.


upper part of the stratigraphic range of Cloudina over-laps with those of Anabarites (Vidal et al., 1994). Herewe refrain from formally establishing a Neoproterozoicbiozone for the Yangtze Platform based on occurrencesof cloudinids. This is mainly due to the facts that theupper limit of the stratigraphic range of Cloudina is notwell constrained, that taxonomic revision of the groupfor Chinese material is presently not available, and thatthe occurrence of Cloudina in South China is limited tothe northern edge of carbonate platform.

5. Early Cambrian SSFs of South China

Mostly phosphatic SSFs occur in great numbers andhigh diversity in the Meishucunian and Qiongzhusianstrata of the Yangtze Platform. More than 200 validSSF form species have been reported from a varietyof localities (Fig. 1). The true biodiversity of thisstratigraphic interval is difficult to judge due to a com-mon part-based taxonomy. Of this diversity only partsof species are widely distributed and of potential bio-stratigraphic interest. Of the taxa occurring in SouthChina 84 have been selected for statistical treatmentwithin a data matrix of totally 214 species from severalworldwide Cambrian occurrences (49 horizons in 22localities, of which 17 are on the Yangtze Platform; seeSupplementary data file #1). Many hyolith-like andcap-shaped molluscan species have not been consid-ered in the data matrix to avoid the indication of anartificial diversity due to the lack of a modern tax-onomic revision for these groups and because speciesof these groups are often morphologically not wellconstrained. We have carried out a hierarchical clusteranalysis of the data matrix. Sample size effects (Koch,1987) must be taken into consideration when interpret-ing the dendrograms. However, the rarefication methodcannot be applied to the data set because of strongvariation in the taxic composition and habitats of shellyfaunas and the application of varying collection meth-ods by different primary investigators (Tipper, 1979).The existence of many long-ranging species may dis-guise the biostratigraphical interpretation of clusters ofspecific occurrences of SSFs.

The following major conclusions can be derivedfrom the hierarchical cluster analysis of 217 speciesfrom 49 regional occurrences on eight platforms/blocks(Fig. 3):

(1) Stratigraphic occurrences with extremely lowor high numbers of species are classified withintheir own clusters, regardless of the occurrence ofsingle index species within low diversity assem-

blages or even a complete set of index fossils inextremely high diversity assemblages.

(2) The biostratigraphically best constrained clus-ter is that of the lower Meishucunian Anabaritestrisulcatus–Protohertzina anabarica Zone.This also includes a distinct subcluster of theProtohertzina anabarica–Kaiyangites novilisZone and the Lower Nemakit–Daldynian strataof Siberia, although some occurrences withindex fossils of this zone from species-richregions in Yunnan, Sichuan, Shaanxi, andSiberia may form their own clusters or aregrouped within the less distinct clusters of theParagloborilus subglobosus–Purella squamu-losa Zone and the Watsonella crosbyi Zone.

(3) Less biostratigraphically constrained is a cluster,which mostly contains international occurrenceswith Rhombocorniculum cancellatum, includingthe upper Tommotian and Atdabanian strata ofSiberia and strata of West Avalonia and Tarim.The species-rich occurrence of Stansbury basin(Australia) with Rhombocorniculum forms itsown cluster. Other occurrences with R. cancella-tum in Shaanxi and Kazakhstan cluster withroughly time-equivalent strata of the Sinosa-chites flabelliformis–Tannuolina zhangwentangi,the Pelagiella subangulata, and the Ninellatarimensis–Cambroclavus fangxianensis zones.

(4) Less biostratigraphically constrained is a cluster,which mostly contains occurrences of the upperMeishucunian S. flabelliformis–T. zhangwentangiand the Qiongzhusian Ninella tarimensis–Cam-broclavus fangxiangensis zones, but also singleQiongzhusian occurrences of Yunnan and Shaanxiwith P. subangulata and R. cancellatum (due tothe distribution of several species of long-rangingchancelloriids).

(5) Weakly constrained is a cluster, which con-tains most middle Meishucunian occurrencesof the P. subglobosus–P. squamulosa and theW. crosbyi Zones. Both assemblages do not formdistinct subclusters, but are evenly scattered. Fewoccurrences of the A. trisulcatus–P. anabaricaZone are included into the cluster (due to thedistribution of long-ranging species, such assiphogonuchitids).

(6) Occurrences with P. subangulata are species-poor and thus do not form any distinct cluster.They are scattered within the cluster charac-terized by low species numbers and within thecluster of the S. flabelliformis–T. zhangwentangiand the N. tarimensis–C. fangxianensis Zones.

Fig. 3. Dendrogram of hierarchical cluster analysis using Ward method and squared Euclidean distance of a data matrix (see Supplementary data) ofthe distribution of 217 SSF species (84 from the Yangtze Platform) from 49 regional assemblages (Yangtze Platform, Tarim Platform, West Avalonia,Stansbury basin of South Australia, Siberian Platform, Kazakhstan, Iran, India); data set numbers correspond to the data in the supplementary datafile; regional Chinese assemblages are marked in bold (early Meishucunian), in Italics (middle Meishucunian), underlined (late Meishucunian toQiongzhusian) or in grey (reworked).



A reduction of species numbers included in the datamatrix (mainly rejection of long-ranging taxa; first re-duction from 217 to 165 species in total with 55 species

from South China; second reduction from 165 species to136 species in total with remaining 46 species fromSouth China) did not significantly improve the formation


of clusters with characteristic index fossils except foroccurrences of the lower Meishucunian A. trisulcatus–P. anabarica Zone. Here in both cluster analyses withreduced data matrices, one very distinct cluster includedall occurrences of the A. trisulcatus–P. anabarica Zone,part of those of the P. anabarica–K. novilis Zone, as wellas the upper and lower Nemakit–Daldynian strata ofSiberia. It is remarkable that within this cluster, stratafrom India are grouped with those from Shaanxi andSichuan, while in another subcluster, strata fromZhejiang, Hunan, Guizhou, and Yunnan are combinedwith those from Iran, Kazakhstan, and Siberia. Only twooccurrences of the P. anabarica–K. novilis Zone fromEast Guizhou and Tarim were then included into alargely increased group of occurrences with low speciesnumbers. The cluster analyses with reduced data ma-trix also showed that occurrences with other index fos-sils except those of the A. trisulcatus–P. anabarica andP. anabarica–K. novilis Zones form smaller clusters,which are more scattered. This is probably due to the factthat clustering based on low species numbers (low num-bers of presence characters, but high number of absencecharacters) does not produce robust results.

6. Biozonation of the Early Cambrian of South China

Biostratigraphic subdivisions of the pre-trilobiticstrata of South China have been developed since thelate 1970s with steady refinement. A historical over-view of this has been given by Qian et al. (2001).However, previous work failed to provide detaileddefinitions of the zones in accordance with the In-ternational Stratigraphic Guide (Salvador, 1994; Mur-phy and Salvador, 1999). The most complete SSFzonation is available from the shallow-shelf region ineastern Yunnan and partly from central Sichuan andsoutheastern Shaanxi. In the whole shallow-shelf re-

Fig. 4. SEM micrographs of SSFs of the lower Meishucunian Stage. (A) ProNo. He2-2-198a. (C, H) Paracanthodus variabilis, No. Mdp34-16. (D) AnabConotheca subcurvata and Anabarites cf. trisulcatus, note that the threeproximal part of tube, No. He2-2-194. (G) Mongolodus longispinus,(K) Kaiyangites novilis with a central and two lateral spines, No. Dap7-31. (spine, No. Kua10d-f-10a. (M) Kaiyangites novilis with a central and two latspine, No. T2L3-12a. (O) Slightly irregular, phosphatized megaster, No. Kucnidarian spicule, No. T2L3-04. (Q) Spindle-shaped spicule; possible phospspicule; possible phosphatic coat of a cnidarian spicule, No. Dap7-8. (A,Nanjiang County, Sichuan. (B, E, F, I) Lower Cambrian Kuanchuanpu ForCambrian Maidiping Formation, bed 34, Maidiping, Emei district, SichuaFormation, Shizhonggou/Kuanchuanpu, Ningqiang County, Shaanxi. (J) LoJiangshan County, Zhejiang. (K, R) Basal unit of Lower Cambrian NiuCambrian Kuanchuanpu Formation, Yuanjiaping/Kuanchuanpu, NingqiangHetang Formation, Changling Mine near Wujialing, Jiangshan County, Z100 μm, thick scale bar 500 μm.

gion the SSF zonation, as revised herein, is in principlethe same:

QiongzhusianStage

tohertzina anabarites trisulcatulongitudinal suNo. NXC12-1

L) Two associateral spines, No.a10d-f-03. (P)hatic coat of a cG) Lower Cammation, Zhangjn. (D, L, O, Qwer Chert Memtitang FormatioCounty, Shaan

hejiang. All spe

(6) Pelagiella subangulata Taxon-range Zone

MeishucunianStage

(5) Sinosachites flabelliformis–Tannuolinazhangwentangi Assemblage Zone(4) Poorly fossiliferous interzone(3) Watsonella crosbyi Assemblage Zone (formerlyHeraultipegma yunnanensis Zone)(2) Paragloborilus subglobosus–Purellasquamulosa Assemblage Zone(1) Anabarites trisulcatus–Protohertzina anabaricaAssemblage Zone

Here the biozonation based on SSFs is redefined andthe spatial distribution of zones is discussed, with zonesarranged in ascending order.

6.1. Anabarites trisulcatus–Protohertzina anabaricaAssemblage Zone

The early Meishucunian zone was first introducedas the Circotheca–Tiksitheca–Anabarites–Protohert-zina Zone by Qian (1978), but then indicated asA. trisulcatus–P. anabarica Zone by Qian et al. (1996).

Here we redefine the assemblage zone by the co-oc-currence of the species A. trisulcatus, P. anabarica, andProtohertzina unguliformis (Fig. 4A, B, D). The lowerzone boundary is placed at the lowermost occurrence ofP. anabarica and P. unguliformis and the upper boundaryat the highest occurrence of A. trisulcatus. Other speciestypical for this zone that are only locally distributed areMongolodus platybasalis, Mongolodus longispinus(Fig. 4G), Paracanthodus variabilis (Fig. 4C, H), Puncta-tus emeiensis, Arthrochites emeishanensis, Carinachitesspinatus, and possibly Maikhanella multa. Locally com-mon are siphogonuchitids, such as Siphogonuchitestriangularis and Lopochites latazonalis, which also occur

arica, No. NXC8-3. (B) Protohertzina unguliformis,s, No. Kua125-43. (E, F, I) Form transitional betweenlci stop at about same height and are not present in2. (J) Fengzuella zhejiangensis, No. Dui21-12c.ed individuals of Kaiyangites novilis with one centralKYuan-13a. (N) Kaiyangites novilis with one centralSpindle-shaped spicule; possible phosphatic coat of anidarian spicule, No. K10d-f-02. (R) Spindle-shapedbrian Xinli Member of Dengying Formation, Xinli,iagou/Hexi, Xixiang County, Shaanxi. (C, H) Lower) Middle interval of Lower Cambrian Kuanchuanpuber of Lower Cambrian Hetang Formation, Duibian,n, Daping, Zhangjiajie County, Hunan. (M) Lowerxi. (N, P) Lower chert member of Lower Cambriancimens TU Berlin collection. Thin scale bar equals


in overlying zones. Many species recognized in this zoneare of enigmatic affinity. The zone is recognized over awide area covering eastern Yunnan, eastern Sichuan,southwestern Shaanxi, western Guizhou, and southwesternHubei. It is coeval with the P. anabarica–K. novilis Zoneof deeper shelf settings.

This zone has great potential for international cor-relation, because Protohertzina represents a pelagic ele-ment and occurs worldwide. The zone can also berecognized in Kazakhstan, Siberia, Mongolia, Iran, andIndia. However, in Siberia it would be more appropriateto define the SSF zones as interval zones due to aseemingly stronger overlap of species distribution. InMongolia and Siberia, A. trisulcatus ranges into theW. crosbyi Zone and also P. anabarica ranges into higherzones, at least into the Purella antiqua Zone respectivelythe Purella Zone (Brasier et al., 1996; Gubanov, 1998,2002). A similar trend is seen in Newfoundland (Landinget al., 1989; Landing, 1988); however, here the taxon-omic status of material described as P. anabarica andAnabarites korobovi is less secure. In South China theindex fossils of the A. trisulcatus–P. anabarica Assem-blage Zone do not range into higher zones. However, fewrecords of A. trisulcatus and P. anabarica have beenreported with index fossils of younger zones in ob-viously reworked shelly beds, such as the Huangshan-dong (Tianzhushan) Formation of western Hubei (Qianet al., 1979; Qian et al., 1999), the uppermost part of theYanjiahe Formation of southwestern Hubei (Chen,1984), and the uppermost part of the KuanchuanpuFormation of northern Sichuan (Steiner et al., 2004).

6.2. Protohertzina anabarica–Kaiyangites novilis As-semblage Zone

This early Meishucunian zone was first introduced asthe Protohertzina anabarica–Kaiyangites multispinatusZone by Ding and Qian (1988) in discussion of the lowerYangjiaping Formation of northwestern Hunan. How-ever, the zone was not defined in the original article norin later reviews on the SSFs of China (Ding and Qian,1988; Qian et al., 1999). Here we redefine theassemblage zone by the co-occurrence of the species P.anabarica, P. unguliformis, and K. novilis (Fig. 4K–N).The lower boundary is placed at the lowermost oc-currence of P. unguliformis and the upper boundary atthe highest occurrence of K. novilis. Other SSFs typicalof this zone, and which may range into younger zones,are Fengzuella zhejiangensis (Fig. 4J) and spindle-shaped spicules (Fig. 4P–R).

The distribution of K. novilis and A. trisulcatus isfacies-related. While Kaiyangites mostly occurs in sili-

ceous rocks or thin limestone beds of deeper shelf en-vironments, Anabarites is found in thick limestone ordolostone sequences of the shallower shelf (Fig. 5A).The protoconodonts P. anabarica and P. unguliformisare interpreted as the grasping spines of chaetognaths.Their wide distribution in shallow and deeper shelfsettings of the Yangtze Platform (Fig. 5A) indicates apelagic lifestyle. The distribution of Early Cambrianshallow water and deeper shelf deposits is controlled bythe architecture of the Ediacaran carbonate platform(Fig. 5B). Distribution patterns of the facies-dependentspecies K. novilis and A. trisulcatus in the Early Cam-brian in principle reflect the palaeogeographic config-uration of the underlying Ediacaran Dengying andLiuchapo formations (Fig. 5B). Kaiyangites only occursin the marginal carbonate platform settings where thethickness of the Dengying Formation is strongly re-duced, or in the basinal region where the predomi-nant deposition is of the siliceous Liuchapo Formation(Fig. 5B). Recognition of the P. anabarica–K. novilisZone in deeper shelf deposits is often difficult becausethe diversity and frequency in these assemblages is low.Thus, in central and eastern Guizhou Protohertzina hasnot yet been recovered. In Kuanchuanpu of southernShaanxi and in Zhejiang all index fossils of both theP. anabarica–K. novilis Zone and the A. trisulcatus–P. anabarica Zone can be found. Here the application ofone zonal concept is made according to the frequency ofthe specific index fossils. In Kuanchuanpu, Anabarites isa dominant species and Kaiyangites is rare, whereas theopposite situation occurs in Zhejiang, where few Ana-barites specimens are found butKaiyangites is common.The co-occurrence of critical index fossils in southernShaanxi and Zhejiang further demonstrates that theP. anabarica–K. novilis Zone is coeval with the A.trisulcatus–P. anabarica Zone of shallower shelf settings.

6.3. Paragloborilus subglobosus–Purella squamulosaAssemblage Zone

This middle Meishucunian zone is described herefor the first time in order to address problems with thedefinition of the former Siphogonuchites triangularis–Paragloborilus subglobosus Zone, which was firstintroduced as the Paragloborilus–SiphogonuchitesZone by Luo et al. (1980). The problems are derivedfrom the fact that all index fossils ranged into other zones,especially S. triangularis, which has a long range from theA. trisulcatus–P. anabarica Zone into the W. crosbyiZone.

The new zone is defined by the co-occurrence ofthe species P. subglobosus (Fig. 6L–O), P. squamulosa

Fig. 5. (A) Facies reconstruction of the Yangtze Platform for the early Meishucunian Stage with occurrences of SSFs and Anabarites trisulcatus–Protohertzina anabarica Zone respectively Protohertzina anabarica–Kaiyangites novilis Zone (occurrences of Kaiyangites novilis: 1 — Kaiyang,Guizhou; 2 — Wuhe, Guizhou; 3 — Daping, Hunan (new occurrence herein); 4 — Yangjiaping, Hunan; 5 — Jiangshan, Zhejiang; 6 — Miaohe,Hubei; 7 — Kuanchuanpu, Shaanxi (new occurrence herein)). (B) Isopach map of latest Neoproterozoic Dengying Formation of the carbonateplatform and of the basinal Liuchapo Formation (predominantly cherts).



(Fig. 6H), and Zhijinites longistriatus (Fig. 6I). Thelower boundary of the zone is placed at the lowermostoccurrence of P. subglobosus and Z. longistriatus,

whereas the upper boundary is drawn at the highestoccurrence of P. squamulosa. However, the zone isstill the most problematic of all SSF zones and can


presently be recognized only in northern Sichuan(Shatan section, where SSFs of the first and secondzones are mixed in a reworking horizon). In mostother shallow water regions only one or two indexfossils indicative of this zone are present. WhereasP. subglobosus is distributed in most shallow waterregions, Z. longistriatus has not yet been found in theKunming region of eastern Yunnan, where the zoneoccurs in the uppermost part of the Zhongyicun Mem-ber of the Zhujiaqing Formation. Distribution of thezone is mainly determined by the occurrence of the rarespecies P. squamulosa, which only occurs in easternYunnan and northern Sichuan. The zone may be dif-ficult to recognize, because P. squamulosa is rare, andmost records of P. subglobosus are of steinkerns. Alsothe type material of P. subglobosus from Maidiping(Sichuan Province), which is refigured here (Fig. 6L,M), is only based on steinkerns.

Confusion about recognition of this zone alsoresults from the fact that both P. subglobosus andZ. longistriatus are common in the Dahai Memberof Zhujiaqing Formation (Xiaotan section, northernYunnan; Li and Xiao, 2004) and the equivalent upperpart of the Maidiping Formation (Maidiping section,Sichuan; Qian et al., 1999), together with W. crosbyi(formerly Heraultipegma yunnanensis) and otherindex fossils of the overlying third SSF zone. Dueto this the second SSF zone shows stronger similar-ities with the third zone than with the underlying firstzone.

Another open question concerns the possible overlapof the A. trisulcatus–P. anabarica Assemblage Zonewith the P. subglobosus–P. squamulosa AssemblageZone and even theW. crosbyi Zone in eastern Yunnan. Itneeds to be further clarified whether the joint occurrenceof P. anabarica, P. subglobosus, and W. crosbyi in bed10 of the Xianfeng section, eastern Yunnan (Qian, 1989)is due to sediment reworking as is recognized here for

Fig. 6. SEM micrographs of SSFs and photographs of macroscopic fossilsWatsonella crosbyi Zone, and the poorly fossiliferous interzone of the middlmaterial, No. YXII 73.2-04. (B, C) Watsonella crosbyi in steinkern preserva(F)Oelandiella korobkovi, No. Mdp36-08a. (H) Purella squamulosa, No. Sht1No. Tao1. (K) Palaeacmaea sp., No. LesTao. (L) Syntype of ParagloborilusParagloborilus subglobosus, refigured from Qian (1977), No. 33772. (Nsubglobosus, No. Sht100-48. (P) Carbonaceous megaalga, No. LesZhu. (Q)No. Duo111. (A, D, E, G) Lower Cambrian Dahai Member of ZhujiaqingCambrian Maidiping Formation, bed 36, Maidiping, Emei district, Sichuan.Nanjiang County, Sichuan. (J, K) Basal Lower Cambrian Niutitang FormatiMaidiping Formation, Gaoqiao–Maidiping, Emei district, Sichuan. (P) BasGuizhou. (Q) Lower Cambrian Shiyantou Formation, Badaowan, Jinning CWengan County, Guizhou. All specimens TU Berlin collection, except paneNanjing. Thin scale bar equals 100 μm, thick scale bar 500 μm.

the upper Kuanchuanpu Formation of northern Sichuan,and the upper Yanjiahe Formation, and the Huangshan-dong Formation of western Hubei.

6.4. Watsonella crosbyi Assemblage Zone

This middle Meishucunian zone was first introducedas the Heraultipegma yunnanensis Zone by Qian et al.(1996), but not defined in detail. Here we considerH. yunnanensis as a junior synonym of W. crosbyiand redescribe the zone as the W. crosbyi AssemblageZone. The zone is defined by the co-occurrence ofW. crosbyi (formerly H. yunnanensis; Fig. 6A–D), Al-danella yanjiahensis (Fig. 6E, G), and Oelandiellakorobkovi (=Archaeospira ornata; see Gubanov andPeel, 2000) (Fig. 6F). The lower boundary is placedat the lowermost occurrence of W. crosbyi and the up-per boundary is drawn at the highest occurrenceof A. yanjiahensis and O. korobkovi. Except forW. crosbyi, other index fossils for the zone also havebeen reported from the underlying P. subglobosus–P. squamulosa Zone. Other important taxa of this zoneare Zhijinites longistriatus, Siphogonuchites triangularis,P. subglobosus, Bemella spp., and chancelloriids. Thezone is recognized in shallow shelf areas (eastern Yunnan,Sichuan, southern Shaanxi, western Hubei) and mainlycomprises the Dahai Member of the Zhujiaqing For-mation and the uppermost part of the Maidiping Forma-tion. The zone has great potential for internationalcorrelation, because of the worldwide occurrence of W.crosbyi.

6.5. Poorly fossiliferous interzone

The middle Meishucunian interval between theW. crosbyi Zone and the S. flabelliformis–T. zhang-wentangi Zone mostly comprises siliciclastic rocksequences (lower Shiyantou Formation in Yunnan,

from the Paragloborilus subglobosus–Purella squamulosa Zone, thee Meishucunian Stage. (A, D) Watsonella crosbyi with preserved shelltion, No. Mdp36-07. (E, G) Aldanella yanjiahensis, No. YXII102-02.00-23. (I) Zhijinites longistriatus, No. Sht100-15. (J) Palaeacmaea sp.,subglobosus, refigured from Qian (1977), No. 33771. (M) Syntype of) Paragloborilus subglobosus, No. Mdp36-10a. (O) ParagloborilusCarbonaceous megaalga, No. Ba8-12m. (R) Carbonaceous megaalga,Formation, Xiaotan, Yongshan County, Yunnan. (B, C, F, N) Lower(H, I, O) Top of Lower Cambrian Kuanchuanpu Formation, Shatan,on, Taozhicong, Qingzhen County, Guizhou. (L, M) Lower Cambrianal Lower Cambrian Niutitang Formation, Zhongnan, Zunyi County,ounty, Yunnan. (R) Lower Cambrian Niutitang Formation, Duoding,ls L, M, which are at Nanjing Institute of Geology and Palaeontology


lower Niutitang Formation in Guizhou) and is not richin fossils. It contains sponge spicules, typical largecarbonaceous algal remains (Fig. 6P–R), and fewhelcionellid shells. The helcionellids have been de-scribed as “Palaeacmaea sp.” (Jiang, 1980b; Luo et al.,1984). Later the name “Scenella kunyangensis” (Heand Yang, 1982) was introduced for specimens fromthe Shiyantou Formation of eastern Yunnan. Bothforms can be accommodated in the newly combinedspecies Helcionella kunyangensis (He and Yang). Aspecimen possibly belonging to this species has alsobeen recognized from the Chengjiang-type fauna of theYuanshan Formation (Zhang and Babcock, 2002), thusindicating a long stratigraphic range. However, Pa-laeacmaea sp. indeed occurs in the lower NiutitangFormation of central Guizhou (Fig. 6J, K).

6.6. Sinosachites flabelliformis–Tannuolina zhangwen-tangi Assemblage Zone

This late Meishucunian zone was first described asthe Sinosachites–Tannuolina Zone by Qian and Yin(1984) and later modified by Jiang et al. (1988), Qianand Bengtson (1989), and Qian et al. (2001). Until nowthis zone lacked detailed definition.

Here we define the zone by the co-occurrence of S.flabelliformis (Fig. 7A), T. zhangwentangi (Fig. 7B),and Lapworthella rete (Fig. 7D). The lower boundaryof zone is drawn at the lowermost occurrence ofT. zhangwentangi and the upper boundary is placed atthe highest occurrence of S. flabelliformis and L. rete.Lapworthella is rare and thus its distribution limitsrecognition of the zone. Chancelloriids (Fig. 7C) andhalkieriids (Fig. 7H) are common in this zone. An-other typical but rare species is Coleoloides typicalis(Fig. 7E). The zone is typically recognized in the shal-low water platform realm of eastern Yunnan (Meishu-cun, Xiaotan) and central Sichuan (Maidiping). Itpossibly occurs in southwestern Shaanxi; however,here only T. zhangwentangi could be recovered (Steineret al., 2004). The zone occurs in the upper ShiyantouFormation, the basal Yuanshan Formation, and themiddle Jiulaodong Formation. In the Meishucun andChengjiang region of Yunnan, the zone is only rep-resented by a thin phosphatic conglomerate bed. Aminor overlap with the overlying P. subangulata Zone ispossible, especially because the latter zone is defined asa taxon-range zone. P. subangulata (Fig. 7F, G) andT. zhangwentangi co-occur in a thin phosphatic con-glomerate bed in the lower Yuanshan Formation inChengjiang (but Lapworthella and Sinosachites are ab-sent). This problem might be resolved in the future if the

P. subangulata Zone can be based on the occurrence ofmore index fossils.

6.7. Pelagiella subangulata Taxon-range Zone

This Qiongzhusian zone was first mentioned byQian et al. (1999) for the Maidiping area of SichuanProvince as the Pelagiella emeishanensis Range Zone,without giving a closer description. It is defined here bythe occurrence of P. subangulata (Fig. 7I, J), and itsdistribution is extended to eastern Yunnan and centralSichuan. The lower and upper boundaries are repre-sented by the first and last occurrences, respectively,of P. subangulata. The zone embraces most of theYuanshan Formation (phosphatic conglomerate unit toupper siltstone unit) and the upper Jiulaodong Forma-tion. There have been few SSFs described from thiszone due to the mostly siliciclastic lithology of thestrata. Therefore the zone can only be defined as ataxon-range zone. Future SSF work should aim at thedescription of more complete fossil assemblages andredefinition of the zone as an assemblage zone or in-terval zone.

Other important taxa from this zone include Micro-dictyon effusum (Fig. 7K), Bemella sp., hyoliths, andbradoriids. The soft-bodied Chengjiang-type fauna ofeastern Yunnan occurs within the P. subangulata Zoneand contains articulated lobopods (Microdictyon sini-cum: possible junior synonym of M. effusum; compareChen et al., 1995).

6.8. Ninella tarimensis–Cambroclavus fangxianensisAssemblage Zone

This Qiongzhusian zone was first recognized bySteiner et al. (2004). It replaced the formerly usedRhombocorniculum insolutum Acme Zone of Qian et al.(1999). The zone is defined by the co-occurrence ofN. tarimensis (Fig. 8B, C), C. fangxianensis (Fig. 8A),and Cambrothyra truncata (Fig. 8D). The lower bound-ary of the zone is placed at the lowermost occurrence ofC. fangxianensis and the upper boundary is drawn at thehighest occurrence of N. tarimensis and C. truncata.The occurrence of this zone is limited to the XihaopingMember of the Dengying Formation in southeasternShaanxi and northwestern Hubei. Additional taxadetected in this zone are Yochelcionella cf. chinensisand numerous chancelloriids. Former records ofRhombocorniculum (Xie, 1990) from the XihaopingMember could not be confirmed by later studies(Li et al., 2004). The fossil assemblage of this zone isquite different from that of the rest of the Yangtze

Fig. 7. SEMmicrographs and photographs of SSFs from the late Meishucunian Sinosachites flabelliformis–Tannuolina zhangwentangi Zone and theQiongzhusian Pelagiella subangulata Zone. (A) Sinosachites flabelliformis, No. 99-3-05. (B) Tannuolina zhangwentangi, No. MeiYu-22.(C) Archiasterella pentactina, No. HK9-JJ. (D) Lapworthella rete, No. YX-T-001. (E) Coleoloides typicalis, No. MeiYu-1. (F, G) Pelagiellasubangulata, No. HK9-AA. (H) Halkieria sthenobasis, No. MeiYu-8. (I, J) Pelagiella subangulata, No. HK-2-45m-09-2/3. (K) Microdictyon sp.,No. Wud-01. (A, B, E, H) Phosphatic conglomerate unit of Lower Cambrian Yuanshan Formation, Badaowan, Jinning County, Yunnan. (C, F, G)Phosphatic conglomerate unit of Lower Cambrian Yuanshan Formation, Haikou, Chengjiang County, Yunnan. (D) Upper part of Lower CambrianShiyantou Formation, Xiaotan, Yongshan County, Yunnan. (I, J) Upper siltstone unit of Lower Cambrian Yuanshan Formation, Haikou, ChengjiangCounty, Yunnan. (K) Middle interval of Lower Cambrian Yuanshan Formation, Sapushan, Wuding County, Yunnan. All specimens TU Berlincollection, except panel D, which is at Nanjing Institute of Geology and Palaeontology. Thin scale bar equals 100 μm, thick scale bar 500 μm.


Platform. It shows stronger biogeographic affinities withAustralia, Kazakhstan, and Tarim.

6.9. Rhombocorniculum cancellatum Taxon-rangeZone

This Qiongzhusian zone was first used as theR. cancellatum Acme Zone for the Xixiang–Zhenbaregion and as the R. cancellatum–Microcornus parvulusAssemblage Zone for northwestern Hubei by Qian et al.(1999). A detailed description and definition was

not provided. However, here the zone is defined as theR. cancellatum Taxon-range Zone based on the oc-currence of R. cancellatum (Fig. 8E) and due to thescarcity of SSFs in the region. The lower and upperboundaries of the zone are defined by the first and lastoccurrences, respectively, of R. cancellatum. The zoneis only recognized in the lower Shuijingtuo Formation atthe northern edge of the Yangtze Platform in southeast-ern Shaanxi and northwestern Hubei.

Other characteristic skeletal fossils of the zone areMicrodictyon effusum (Fig. 8F), chancelloriids,

Fig. 8. SEM micrographs of SSFs from the Qiongzhusian Rhombocorniculum cancellatum Zone and Ninella tarimensis–Cambroclavusfangxianensis Zone. (A) Cambroclavus fangxianensis, No. Xiw104-07. (B, C) Ninella tarimensis, No. Xiw104-01. (D) Cambrothyra truncata,No. Xiw103-06. (E) Rhombocorniculum cancellatum, No. ZX-P-035. (F) Microdictyon effusum, No. ZX-M-003. (G) Eohadrotreta zhenbaensis,No. Slp3-8. (H) Eohadrotreta zhenbaensis, No. Slp3-13. (A–D) Lower Cambrian Xihaoping Member of Dengying Formation, Xiaowan, XixiangCounty, Shaanxi. (E, F) Lower Cambrian Shuijingtuo Formation, Xiaoyangba, Zhenba County, Shaanxi. (G, H) Lower part of Lower CambrianXiannudong Formation, Sanlangpu, Xixiang County, Shaanxi. All specimens TU Berlin collection, except panels E, F, which are at Nanjing Instituteof Geology and Palaeontology. Thin scale bar equals 100 μm.


trilobites (Hupeidiscus), and brachiopods (Eohadrotretazhenbaensis, E. zhujiahensis, Lingulellotreta malongen-sis; Fig. 8G, H). The protoconodont Gapparodusbisulcatus, which has rarely been described from theR. cancellatum Zone (Xie, 1990) may have its regionalFAD within the zone. However, it ranges through theMiddle Cambrian into the Furongian (Dong andBergström, 2001). It may have potential for biostrati-graphic use. However, its rare recognition so farprecludes its utilization as an index fossil for theLower Cambrian.

7. Revised intra-platform correlation for SouthChina

The temporal and spatial distribution of SSFs on theYangtze Platform is controlled by lithofacies and meta-zoan evolution. Correlation of pre-trilobitic strata withinthe same facies belts, and especially within carbonatesediments of shallow-shelf deposits, is now relatively

well constrained (Fig. 9). However, problems still existwith the correlation of strata between shallow-shelf anddeeper shelf settings (Fig. 10) because fossils are sparsein deeper water sediments.

Problems also exist with the definition of the Pre-cambrian–Cambrian boundary on the Yangtze Platform.According to the decision by the International Subcom-mission on Cambrian Stratigraphy and the InternationalCommission on Stratigraphy, the Precambrian–Cambri-an boundary is based on the first occurrence of the tracefossil Treptichnus (formerly Phycodes) pedum (also re-ported as Trichophycus pedum) (Landing, 1994). How-ever, the distribution of this trace fossil is limited due toits occurrence in a specific lithofacies (coarse-grainedsediments, such as quartz sandstone and granular phos-phorite). The trace maker of Treptichnus pedum is alsospeculative and thus its linkage to a true biological spe-cies of metazoan is less secure than with mostbody fossils. Although indeed new behaviour pattern

Fig. 9. Correlation table of Lower Cambrian strata along transect A (see Fig. 1) with biozonation based on SSFs (stippled line indicates Precambrian–Cambrian boundary according to the FADof Protohertzina anabarica).

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Fig. 10. Correlation table of Lower Cambrian strata along transect B (see Fig. 1) with biozonation based on SSFs (stippled line indicates Precambrian–Cambrian boundary according to the FADof Protohertzina anabarica).

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developed during metazoan evolution in the EarlyCambrian, it appears that these are not confined to astrict first appearance datum (FAD). The appearance of avariety of metazoans capable of producing similar tracepatterns and a stepwise adaption of metazoan speciesbehaviour to the changing environments rather suggeststhe existence of transitional forms between Neoproter-ozoic horizontal burrows (e.g., Planolites, Palaeophy-cus) and typical Treptichnus pedum-type traces (Jensen,1997). Indeed, a gradational onset of treptichnid tracesacross the Precambrian–Cambrian boundary and anoccurrence of Treptichnus pedum below the GlobalStandard Stratotype-section and Point (GSSP) for thebase of Cambrian has been documented by Gehling et al.(2001). Additional data document that Treptichnuspedum and forms closely allied with this ichnospecieshave a long stratigraphic range covering an interval fromthe Ediacaran to the Ordovician (Geyer and Uchman,1995; Jensen et al., 2000; Seilacher et al., 2005). Thus,the decision to choose a FAD of a trace fossil for de-fining a system boundary can only be considered as acompromise.

In South China Treptichnus pedum has only beenreported from the Meishucun section of eastern Yunnan(Zhu, 1997; Zhu et al., 2005), where it first occurswithin the A. trisulcatus–P. anabarica Zone (Zhu et al.,2001). Thus, part of the first SSF zone should beconsidered as Neoproterozoic if this approach isadopted. In contrast to this, in the Chinese literaturethe lower stage boundary for the Meishucunian and thusthe Precambrian–Cambrian boundary, has mostly beenplaced at the FAD of A. trisulcatus (Qian et al., 2001;Zhu et al., 2001). However, it may be more useful toredefine the Precambrian–Cambrian boundary at theFAD of P. anabarica or P. unguliformis, because theseSSFs occur as pelagic elements in both shallow anddeeper shelf sediments (see discussion above; Fig. 5A).In most regions of South China there exists a hiatus atthe Precambrian–Cambrian boundary (Figs. 9 and 10).Most continuous Neoproterozoic–Cambrian sequencesoccur in northeastern Yunnan, eastern Guizhou, andcentral Hunan. Unfortunately, these sequences of deepershelf settings are poor in fossils.

In northeastern Yunnan the Zhongyicun Member ofthe Zhujiaqing Formation, which is rich in SSFs of theA. trisulcatus–P. anabarica and P. subglobosus–P. squamulosaZones, is underlain by the DaibuMember,mainly consisting of cherts and dolomicrites withphosphatic clasts (Zhu et al., 2001). Lithologically theDaibuMember represents a sedimentary cycle typical forthe Early Cambrian. The equivalent basal KuanchuanpuFormation (southern Shaanxi, Fig. 9) also contained

a few unidentifiable phosphobioclasts, which may bederived from SSFs.

The most complete SSF record is available fromthe shallow shelf region of eastern Yunnan and partlyfrom central Sichuan and southeastern Shaanxi (Fig. 9).Parts of some zones have not yet been fully con-firmed for Sichuan or southeastern Shaanxi, such as theP. subglobosus–P. squamulosa Zone and the W. crosbyiZone (Fig. 9). From the Yuanjiaping section ofsouthwestern Shaanxi only Aldanella sp., cf. Watso-nella sp. (as ? Heraultipegma sp.), and a questionableOelandiella korobkovi (wrongly assigned to Latou-chella cf. costata) were reported (Xing and Yue, 1984).Therefore, recognition of the W. crosbyi Zone insoutheastern Shaanxi requires further confirmation.The P. subglobosus–P. squamulosa Zone only occursin a reworked horizon at the top of the KuanchuanpuFormation at Shatan (Fig. 6H, I, O). Reworked SSFsfrom the underlying Zone occur in this bed (Steineret al., 2004).

The early to middle Meishucunian Zhujiaqing For-mation of eastern Yunnan can be correlated with theMaidiping Formation of central Sichuan and the Kuan-chuanpu Formation of northern Sichuan/southwesternShaanxi, while the siliciclastic upper MeishucunianShiyantou Formation and Qiongzhusian Yuanshan For-mation are correlative with the Jiulaodong Formation ofSichuan and the Guojiaba Formation of southern Shaanxi(Fig. 9).

The southeastern Shaanxi–northwestern Hubei re-gion, at the northern edge of the Yangtze Platform, hada unique lithologic and tectonic history and a uniquefaunal composition and biozonation during the EarlyCambrian. Sections such as Sanlangpu, Xiaowan (bothXixiang County), and Xiaoyang (Zhenba County) arelocated in the Sishang–Jixinling Fold and Fault BundleZone of the marginal platform. This zone is separatedfrom Palaeozoic strata in southwestern Shaanxi by theSishang–Zhenba–Yudu Fault Zone, and it appearspossible that the region has been brought into closerproximity to southwestern Shaanxi, due to collision ofthe platform in the Permo-Triassic or earlier. A largestratigraphic hiatus, comprising the whole Meishucu-nian, is found in southeastern Shaanxi–northwesternHubei (Fig. 5A). This remarkable hiatus, and the widedistribution of breccia beds in the shallow platformregion (Fig. 5A, stars), indicates strong tectonic activityon the Yangtze Platform during the Meishucunian.

Correlation of strata between southeastern Shaanxi–northwestern Hubei and the rest of the Yangtze Plat-form remains problematic due to significantly differentSSF assemblages (N. tarimensis–C. fangxianensis and


R. cancellatum Zones in SE Shaanxi; Fig. 9). Cor-relation mainly relies on the presence of Hupeidiscusorientalis Microdictyon effusum, and Eohadrotreta sp.,all of which are common in the upper Qiongzhusian ofthe shallow shelf region.

Correlation of strata from the shallow shelf (easternYunnan) toward the deeper shelf (Guizhou, Hunan,Zhejiang) is made possible mostly by the presence of theP. anabarica–K. novilis Zone in northern Hunan andZhejiang (Figs. 5A and 10). This zone is time equivalentto the A. trisulcatus–P. anabarica Zone. Deeper waterfaunas are characterized by the dominance of chaeto-gnath grasping spines (P. unguliformis and P. anabar-ica), and the enigmatic cap-shaped skeletal remains ofK. novilis. Only few specimens of the otherwise commontubular fossil A. trisulcatus have been recovered fromthe deeper water realm. The platform-wide distribu-tion and common occurrence of P. unguliformis andP. anabarica both in shallow and deeper shelf settingssupports a pelagic lifestyle for Protohertzina.

Deeper shelf settings are characterized by a strongercondensation of the Meishucunian strata and a pre-dominance of siliciclastic and siliceous sediments. Darkphosphorites and cherts with minor intercalations of thinlenticular carbonate beds predominate in the basal unitsof Niutitang and Hetang Formations, which also containrare SSFs. The phosphorites of the Niutitang and Hetangformations largely comprise concretionary and lentic-ular/banded phosphorites (autochems), whereas thethick Meishucunian carbonates of the shallow shelf re-gion largely comprise granular phosphorites (allochems,transported). Differences in faunal composition andlithofacies between the shallow-shelf region and thedeeper shelf region indicate that little lateral transport ofsediments occurred, and no major downslope gravityslides of phosphorites occurred in the Meishucunian.This also rules out shoreward-migrating phosphate sandwaves during the Niutitang transgression. It supports awinnowing of phosphates by removal of the fine grainedmaterial in the major phosphate deposits of easternYunnan and Sichuan (Siegmund, 1995).

8. Toward an international correlation of the LowerCambrian

An international correlation of pre-trilobitic stratabased on SSF occurrences is more problematic thanregional correlations, because of faunal provincialismand facies dependence ofmany species. Additionally, theapplication of different taxonomic concepts in the de-scription of regional faunas has contributed to confusionabout the stratigraphic utility of important SSFs. How-

ever, with mounting evidence for the occurrence of SSFsonmajor platforms and some progress toward taxonomicrevision of SSFs, intercontinental correlation appearsfeasible at least for some platforms such as South China,Siberia, and Avalonia.

Correlation of pre-trilobitic strata between SouthChina and Siberia is best constrained using the rich SSFrecord from both regions and a predominantly carbonatefacies. Our correlation is mainly based on SSFs havingthe best potential for international correlation (proto-conodonts and molluscs) but omits many problematictaxa (tubular fossils, hyolith-like SSFs, and other simpleforms) for this purpose. The cosmopolitan distribution ofprotoconodonts (e.g., Protohertzina, Mongolodus) andsome molluscs (Watsonella, Aldanella, Oelandiella) isprobably due to a pelagic lifestyle or dispersal byplanktonic larval stages. Although conclusive revision ofnumerous described molluscan taxa is not available foreither Siberia or South China, recent revisions allow therecognition of pre-trilobitic zones mainly based on cos-mopolitan molluscs (Gubanov, 1998, 2002). With ourrecent revision of Chinese SSF zonation it becomesobvious that the sequential stratigraphic appearance ofindex fossils and zones is similar in South China andSiberia (Fig. 11).

In Siberia the critical index taxa indicate a strongerstratigraphic overlap than in China (Fig. 11), whichmight be indicative of more hiatuses or ecologicalchanges (more siliciclastics in the geological sequence)in South China. Although the presence of hiatuses can-not be neglected (Figs. 9 and 10), it appears moreprobable that stronger ecological fluctuations occurredon the Yangtze Platform. Due to a stronger siliciclasticinfluence on the carbonate platform, archaeocyathans arealso more limited in the Lower Cambrian of South China(Yuan et al., 2001) than in Siberia.

The Nemakit–Daldynian and lower TommotianAnabarites trisulcatus Zone, Purella antiqua Zone andWatsonella crosbyi (=Heraultipegma sibirica) Zone ofSiberia are easily correlated with the Anabaritestrisulcatus–Purella anabarica Zone, P. subglobosus–P.squamulosa Zone andWatsonella crosbyi Zone of SouthChina. Thus the lower Meishucunian is correlative withthe Nemakit–Daldynian Stage of Siberia. The mid-Meishucunian and lower Tommotian W. crosbyi Zonecan be recognized in many parts of the world andrepresents an intercontinental time marker interval.

The upper Meishucunian is characterized by thedominance of siliciclastic sediments in South China andthus SSFs are rare due to ecological reasons. The upperMeishucunian S. flabelliformis–T. zhangwentangi Zoneis rather endemic and does not support international

Fig. 11. Distribution of SSFs and international correlation between Yangtze Platform and Siberian Platform (stippled line indicates Precambrian–Cambrian boundary according to the FADof Protohertzina anabarica; dash-dotted line indicates Precambrian–Cambrian boundary according to the FAD of Treptichnus pedum; data from Siberia from Brasier, 1989; Khomentovsky andKarlova, 1993; Gubanov, 1998, 2002).

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correlation. The Qiongzhusian P. subangulata Zone canbe considered as time equivalent with the Pelagiellalorenzi Zone of the upper Atdabanian Stage of Siberia(an assignment of individuals from Siberia wronglyplaced within the Middle Cambrian species P. lorenziwith P. subangulata is probable). The exact tracing ofthe Atdabanian/Botoman boundary into South China isnot yet possible. However, it can be assumed thatthe top of Qiongzhusian may correlate with the basalBotoman. This correlation in principle confirms earli-er attempts at correlation between South China andSiberia (Khomentovsky and Karlova, 1993; Qian et al.,2001); however, it also clearly rejects other proposalsthat overestimated the duration of hiatuses (Landing,1994) and correlated the Qiongzhusian with the Boto-man (Zhuravlev, 1995), mainly due to fewer recordedSSFs and based on the occurrence of trilobites. Ourcorrelation indicates that the FAD of trilobites at thebase of Qiongzhusian in South China is not timeequivalent with the FAD of trilobites at the base of theAtdabanian in Siberia.

Correlation into Avalonia is even more complicated(Fig. 12) because the SSF record from the PlacentianSeries of Newfoundland and Massachusetts is limitedand the intra-provincial correlation of Avalonian se-quences is problematic. SSFs of Nemakit–Daldynianassemblages are largely missing in Newfoundland andMassachusetts, probably because siliciclastic-dominatedfacies and high palaeolatitudes inhibited precipitation ofwarm water carbonates (Landing and Westrop, 2004).Occurrences of Anabarites (Tiksitheca) korobovi (=? A.trisulcatus) and P. anabarica within theW. crosbyi Zoneand partly even the Sunnaginia imbricata Zone (alsocontaining W. crosbyi; Landing et al., 1989) remainquestionable in terms of their biostratigraphic implica-tions. The only specimen assigned to P. anabarica wasrecovered from the top ofMember 4 of the Chapel IslandFormation (=top of Watsonella Zone sensu Landing,1994); however, it remains uncertain if it actuallyrepresents the species to which it was assigned due topoor preservation. Also it cannot be ruled out that thespecimen was reworked because the sample containedangular intraclasts. A. trisulcatus also reaches into theW.crosbyi Zone of Siberia and Mongolia (Brasier et al.,1996; Gubanov, 1998, 2002). However, with an un-derstanding of the SSF zones of Siberia as interval zones,this does not diminish the possibility for a correlationwith the assemblage zones of South China. Consider-ing the stratigraphic overlap of Anabarites (Tiksitheca)korobovi with W. crosbyi and Aldanella attleborensis inNewfoundland, the W. crosbyi Zone also has to be un-derstood as an interval zone and can be correlated with

the lower Tommotian. SSFs of the underlying “La-datheca” cylindrica Zone are too unspecific for inter-national correlation. It can be concluded that theupper part of the Chapel Island Formation is of lowerTommotian or mid-Meishucunian age (Fig. 12).

Another problem arises from the SSF record of theSunnaginia imbricata Zone of the lower BonavistaGroup, specifically the mid-Weymouth Formation(Landing, 1988). This SSF assemblage is not signifi-cantly different from that of the underlying W. crosbyiZone. Sunnaginia imbricata has a long range ofoccurrence throughout most of the Tommotian in Siberiaand partly co-occurs there with W. crosbyi (Brasier,1989; Gubanov, 1998; Khomentovsky and Karlova,1993). Thus, it would be possible to consider the S.imbricata Zone as a subzone of theW. crosbyi Zone andto correlate it with the lower Tommotian and mid-Meishucunian. This is in contrast to previous correlationattempts where these strata were thought to be correlativewith an interval between the Tommotian and Nemakit–Daldynian (=Manykaian), which was postulated to bemissing in Siberia (Landing, 1994) or alternatively withthe upper Nemakit–Daldynian (Landing and Westrop,2004). Due to the fact that in South China theW. crosbyiZone is overlain by poorly fossiliferous strata, it cannotbe excluded that part of this upperMeishucunian “poorlyfossiliferous interzone” also correlates with the barreninterval and S. imbricata Zone of the mid-PlacentianSeries (Fig. 12).

Our new correlation implies the existence of an un-recognized hiatus between the S. imbricata Zone andthe Camenella baltica Zone, because the appearanceof Pelagiella sp. (aff. subangulata), R. cancellatum,and Microdictyon sp. allows correlation of the upperBonavista Group with the upper Atdabanian andQiongzhusian (Fig. 12). Although C. baltica is a typicalAcado-Baltic species not recognized in Siberia, thegenus Camenella has a stratigraphic range from thelower Tommotian to the mid-Atdabanian in Siberia(Brasier, 1989). In South China, records of Camenellafrom the upper Meishucunian (Luo et al., 1984) remainequivocal. Other tommotiids occur in the mid-Meishu-cunian, but most genera, such as Tannuolina and So-nella, are known from the upper Meishucunian toQiongzhusian (Yuan and Zhang, 1983; Qian, 1989;Qian and Bengtson, 1989; Li and Xiao, 2004).

Absolute age dating of an ash bed from the middlePlacentian Series of Avalon (barren interval underlyingthe S. imbricata Zone) provided an age of 530.7±0.9Ma(Isachsen et al., 1994). Dating of cobbles of a con-glomerate underlying a sandy limestone of the supposed“Heraultipegma–Lapworthella tortuosa Zone”

Fig. 12. Distribution of SSFs and international correlation between Yangtze Platform and West Avalonia (stippled line indicates Precambrian–Cambrian boundary according to the FAD ofProtohertzina anabarica; dash-dotted line indicates Precambrian–Cambrian boundary according to the FAD of Treptichnus pedum; fossil occurrence data of Newfoundland and Massachusettsfrom Landing, 1988; Landing et al., 1980).

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(however, without record of W. crosbyi = H. sibirica;thus probably assignable to the L. tortuosa Zone) of themiddle Tommotian from Kharaulakh (Siberia) providedamaximum age of 534.6±0.5Ma (Bowring et al., 1993).Together, these values were used to set the Nemakit–Daldynian (Manykaian)–Tommotian boundary at ap-proximately 530 Ma (Bowring et al., 1993). However, inthe light of revision of biostratigraphic interpretation ofSSFs in Siberia and Newfoundland, the Nemakit–Daldynian–Tommotian boundary must be expected atan earlier age, possibly around 531–535 Ma.

The postulation of large depositional gaps within theLower Cambrian of South China (Landing, 1994) isrejected here by the application of platform-wide inter-regional and international correlation based on the SSFrecord (Figs. 9–12). Although in a later correlation(Landing and Westrop, 2004) the existence of large pre-Tommotian gaps in Siberia was relativised, no suchrevision exists for the Avalon–South China correlation.The overestimation of definitively existing unconformi-ties in South China mainly resulted from the fact thatprevious correlations mainly based on data from theMeishucun section of eastern Yunnan, important SSFzones (W. crosbyi Zone=former H. yunnanensis Zone)and large barren zones were not taken into consideration,and important SSF occurrences (e.g., P. subangulatafrom the Qiongzhusian) were only relatively recentlyrecognized.

Correlation of the Lower Cambrian strata of SouthChina with those of India, Iran, and Tarim are based onsimilar lithofacies and SSF associations. However, theSSF record is far less studied in this Himalayan region,which only allows a tentative correlation. In Tarim,SSFs have mainly been reported from the carbonateupper part of the Yurtus Formation (Qian and Xiao,1984; Yue and Gao, 1992, 1994; Conway Morris andChapman, 1996, 1997). The upper Yurtus Formationcontains N. tarimensis, C. fangxianensis (reported asSugaites soleiformis), Z. longistriatus, and T. zhang-wentangi (reported as T. minuta). Thus it was inferredthat the Yurtus Formation is equivalent to the mid-Meishucunian to lower Qiongzhusian (Yue and Gao,1992; Conway Morris and Chapman, 1996) or only tothe Qiongzhusian (Yue and Gao, 1992). Most of thelower to mid-Meishucunian and thus the wholeNemakit–Daldynian was thought to be missing (Con-way Morris and Chapman, 1996). However, the reportof Anabarites sp. from the basal Yurtus Formation andrecent finds of K. novilis from the basal cherty andphosphatic unit of Yurtus Formation (Yao et al., 2005)indicate that at least part of the lower Meishucunian isalso present in Tarim. Here we consider the Yurtus

Formation to be correlative with strata covering theinterval from the A. trisulcatus–P. anabarica Zone topossibly lower P. subangulata Zone. Stratigraphic gapsmay occur at the base and top of the Yurtus Forma-tion, and possibly also at the top of lower member. Theoverlying Xiaoerbulak Formation contains in its lowerpart R. cancellatum and the trilobite Shizhudiscussugaitensis. Together these fossils suggest an upperQiongzhusian to Canglangpuian age (Yue and Gao,1992).

The Lower Cambrian succession in Lesser Himalaya,India, can be roughly correlated with time-equivalentstrata of South China by the occurrence of SSFs in thelower Tal Formation (Brasier and Singh, 1987; Kumaret al., 1987). The lower Chert-Phosphorite Member ofthe lower Tal Formation contains protoconodonts of theP. anabarica–P. unguliformis group, fragments of Hex-angulaconularia cf. formosa (Brasier and Singh, 1987),and the anabaritid A. trisulcatus (Kumar et al., 1987), allof which are characteristic of the A. trisulcatus–P. anabarica Zone in South China. The uppermost cal-careous member of the lower Tal Formation yieldedP. lorenzi (Kumar et al. (1987), probably wrongly placedwithin the Middle Cambrian species P. lorenzi, butcan be assigned to P. subangulata), indicating that thelower Tal Formation embraces a sequence equivalent tothe lower Meishucunian to Qiongzhusian of SouthChina. However, it cannot be ruled out that the mainlysiliciclastic sequence also contains stratigraphic gapsbecause only the basal A. trisulcatus–P. anabarica Zoneand the upper P. subangulata Zone can be recognized.

A comparable sequence of fossiliferous Precambri-an–Cambrian boundary strata has been described fromthe Elburz Mountains, Iran (Hamdi et al., 1989). TheMiddle Dolomite Member of Soltanieh Formationcontains an SSF association, including P. unguliformis,A. trisulcatus, and M. multa. These SSF species aretypical of the lower Meishucunian A. trisulcatus–P. anabarica Zone in South China. The top part of theUpper Shale Member of the Soltanieh Formation yieldsOelandiella (Latouchella) korobkovi and Pelagiellasubangulata (described as P. lorenzi; Hamdi et al.,1989). Therefore, most of the Soltanieh Formation iscorrelative with the lower Meishucunian to Qiongzhu-sian of South China. Its Upper Dolomite Member maybe comparable to Canglangpuian and younger strata.

9. Palaeobiogeographic implications

Palaeobiogeographic analyses of the Cambrian havemainly been based on the distribution of polymeridtrilobites and resulted in the recognition of three major

Fig. 13. Palaeogeographic reconstruction for the Early Cambrian. (A) Base map with most important continental blocks and terrains (slightlymodified from Brock et al. (2000) and Eldridge et al. (1997)). (B) Palaeogeographic map indicating a closer relationship of the SE Shaanxi–NWHubei Region of Yangtze Platform with the East Gondwanan realm (stippled areas indicate stratigraphical gaps or strata barren of SSFs during theNemakit–Daldynian to Tommotian or equivalent stages).


faunal realms (Redlichiid; Olenellid; Bigotinid; Jell,1974; Pillola, 1990). Results of palaeobiogeographicstudies on Cambrian trilobites have been taken intoconsideration in various palaeogeographic reconstruc-tions (McKerrow et al., 1992; Brasier, 1995). SSFshave only rarely been utilized for palaeobiogeographic

considerations (Gubanov, 2002). This may be dueto the fact that little is known of the biological affinitiesof SSFs, that taxonomy of SSFs from differentplatforms and regions was often inconsistent, and thatdata are widely dispersed. Relatively recently, fossilgroups other than trilobites (such as archaeocyaths,

Fig. 14. Palaeobiogeographic relationships between the Yangtze craton and other blocks and terrains during the Early Cambrian. (A) Joint occurrenceof taxa between Yangtze Platform and selected regions in absolute numbers (species/genera). (B) Joint occurrence of taxa between Yangtze Platformand selected regions in relative numbers (species/genera).


brachiopods, and other small shelly fossils) have alsobeen used to draw palaeobiogeographic conclusions forthe pre-trilobitic Early Cambrian (Brock et al., 2000).These studies reveal close relationships between EastGondwana and a terrain in East Germany based on theSSF record. A close palaeogeographic relationshipduring the Early Cambrian was also drawn for Siberia

and the Iberian Massif by micro-molluscs (Gubanov,2002).

Most palaeogeographic reconstructions indicate aposition of South China within the tropical zone ofwestern Gondwana during the Early Cambrian (Kirsch-vink, 1992; McKerrow et al., 1992). Alternative recon-structions have shown a position at around 30°N along


the eastern side of Gondwana, between Australia andSiberia (Li et al., 1995; Li, 1998; Li and Powell, 1999).However, this hypothesis has found no support fromstudies of comparative stratigraphy (Metcalfe, 1996),palaeomagnetics (Zhang and Piper, 1997), and palaeo-biogeography (Brock et al., 2000). Therefore, ourpalaeobiogeographic comparison of SSF assemblagefrom South China with those of other cratons is basedon palaeogeographic maps given by Eldridge et al.(1997) and Brock et al. (2000), which place SouthChina at the western margin of Gondwana.

Our results show that the SE Shaanxi–NW Hubeiregion of the Yangtze Platform is more comparablewith the East Gondwanan realm (North China, SouthAustralia, Antarctica; Fig. 13B), based mainly on thefact that most of the lower and middle Meishucunian(equivalent to Nemakit–Daldynian to Tommotian) strataare missing or barren of SSFs. Most other shallow anddeeper shelf sequences of the Yangtze Platform indicateclose relationships with regions of the western margin ofGondwana, in particular the Tarim Platform, India, andIran. The numbers of species/genera co-occurrences ofMeishucunian to Qiongzhusian (Nemakit–Daldynian toAtdabanian) SSFs are recorded as a measure of thesimilarity between the Yangtze Platform and otherplatform regions of the world (Fig. 14A). The relativecontent of species/genera co-occurring in both faunas(in %) represents a more critical parameter characteriz-ing the palaeobiogeographic relationship (Fig. 14B)because faunas differ in absolute species numbers andhave been studied with different intensity. Although adifferent taxonomic treatment (e.g., oversplitting of taxain specific regions) of the different regional faunas maycontribute to obscuring original biogeographic connec-tions, our preliminary results show a conclusive pattern(Figs. 13 and 14). The strongest faunal similarity withSouth China exists with Tarim (88% species similarity,95% generic similarity), India (92% species similarity,82% generic similarity), and Iran (62% speciessimilarity, 77% generic similarity; Fig. 14). The SSFassociations of East Gondwana, Siberia, and Kazakh-stan are far less similar in taxic composition with SouthChina (Fig. 14). Here especially generic similarity ismoderate for West Avalonia (61%), Kazakhstan (52%),and Antarctica (52%), although their species similarityranges only between 12 and 26%. The lowest com-parability exists between South China and Siberia (16%species similarity, 29% generic similarity) and SouthChina and Australia (8% species similarity, 29% genericsimilarity). Both faunas are characterized by species-rich assemblages having more than 100 species of SSFs,which seem to indicate incomplete endemism.

Our palaeobiogeographic data support the conclusionthat the South China Block was arranged at the westernGondwanan edge rather than along East Gondwanaduring the Early Cambrian. This further rejects the pro-posed position of South China between Australia andSiberia for the Neoproterozoic to Cambrian (Li, 1998;Li et al., 1995).

Acknowledgements

We thank Bernd Weber (Berlin), Tatiana Goldberg,Harald Strauss (both Münster), He Tingui, Yang Xianhe(both Chengdu), Guo Qingjun (Guiyang), He Shengce(Xiaoshan), Zhang Junming, Yang Aihua, He Hongwei(all Nanjing) for the discussions and joint fieldwork.Support with literature from Olaf Elicki (Freiberg) isgreatly appreciated. Technical assistance with fossilpicking and acid treatment by Sandra Schochardt andwith SEM from Jörg Nissen (both TU Berlin) is warmlyacknowledged. We are grateful for the reviews byAlexander Gubanov (Uppsala) and Loren E. Babcock(Columbus). This study was financially supported byDFG (grant ER 96/32-1, -2, -3), CAS (grant no. KZCX3-SW-141), and NSFC (grants no. 40232020 and40572006), and MOST of China (2006CB806400)with contributions of the Max-Planck-Gesellschaft,Munich. This is a contribution to the Sino-German bun-dle project “From Snowball Earth to the Cambrian Bio-radiation—AMultidisciplinary Analysis of the YangtzePlatform, China.”

Appendix A. Supplementary data

Supplementary data associated with this articlecan be found, in the on line version, at doi:10.1016/j.palaeo.2007.03.046.

References

Amthor, J.E., Grotzinger, J.P., Schröder, S., Bowring, S.A., Ramezani,J., Martin, M.W., Matter, A., 2003. Extinction of Cloudina andNamacalathus at the Precambrian–Cambrian boundary in Oman.Geology 31 (5), 431–434.

Bengtson, S., 1985. Taxonomy of disarticulated fossils. Journal ofPaleontology 59 (6), 1350–1358.

Bengtson, S., 1994. The advent of animal skeletons. In: Bengtson, S.(Ed.), Early Life on Earth. Nobel Symposium No., vol. 84.Columbia University Press, New York, pp. 412–425.

Bengtson, S., Yue, Z., 1992. Predatorial borings in Late Precambrianmineralized exoskeletons. Science 257, 367–369.

Bengtson, S., Conway Morris, S., Cooper, B.J., Jell, P.A.,Runnegar, B.N., 1990. Early Cambrian fossils from SouthAustralia. Association of Australasian Palaeontologists, Bris-bane. 364 pp.



Bowring, S.A., Grotzinger, J.P., Isachsen, C.E., Knoll, A.H.,Pelechaty, S.M., Kolosov, P., 1993. Calibrating rates of EarlyCambrian evolution. Science 261, 1293–1298.

Brain, C.K., 2001. Some observations on Cloudina, a terminalProterozoic index fossil from Namibia. Journal of African EarthSciences 33, 475–480.

Brasier, M.D., 1989. Towards a biostratigraphy of the earliestskeletal biotas. In: Cowie, J.W., Brasier, M.D. (Eds.), ThePrecambrian–Cambrian Boundary. Clarendon Press, Oxford,pp. 117–165.

Brasier, M.D., 1995. The basal Cambrian transition and Cambrian bio-events. In: Walliser, O.H. (Ed.), Global Events and EventStratigraphy. Springer, Berlin, pp. 113–138.

Brasier, M.D., Singh, P., 1987. Microfossils and Precambrian–Cambrian boundary stratigraphy at Maldeota, Lesser Himalaya.Geological Magazine 124 (4), 323–345.

Brasier, M.D., Shields, G., Kuleshov, V.N., Zhegallo, E.A., 1996.Integrated chemo- and biostratigraphic calibration of early animalevolution: Neoproterozoic–Early Cambrian of southwest Mongo-lia. Geological Magazine 133 (4), 445–485.

Brock, G.A., Engelbretsen, M.J., Jago, J.B., Kruse, P.D., Laurie, J.R.,Shergold, J.H., Shi, G.R., Sorauf, J.E., 2000. Palaeobiogeographicaffinities of Australian Cambrian faunas. Memoir of the Associ-ation of Australasian Palaeontologists 23, 1–61.

Budd, G.E., 2003. The Cambrian fossil record and the origin of thephyla. Integrative and Comparative Biology 43, 157–165.

Butterfield, N.J., Nicholas, C.J., 1996. Burgess shale-type preservationof both non-mineralizing and ‘shelly’Cambrian organisms from theMackenzie mountains, Northwestern Canada. Journal of Paleon-tology 70 (6), 893–899.

Chen, P., 1984. Discovery of Lower Cambrian small shelly fossilsfrom Jijiapo, Yichang, West Hubei and its significance. Profes-sional Papers of Stratigraphy and Palaeontology 13, 49–66.

Chen, Z., Sun, W., 2001. Late Sinian (tubular) metazoan fossils:Cloudina and Sinotubulites from southern Shaanxi. Acta Micro-palaeontologica Sinica 18 (2), 180–202.

Chen, M., Chen, Y., Qian, Y., 1981. Some tubular fossils fromSinian–Lower Cambrian boundary sequences, Yangtze Gorge.Bulletin of the Chinese Academy of Geological Sciences 3,117–124.

Chen, J., Zhou, G., Ramsköld, L., 1995. The Cambrian LobopodianMicrodictyon sinicum. Bulletin of the National Museum of NaturalScience 5, 1–93.

Chen, J., Oliveri, P., Li, C., Zhou, G., Gao, F., Hagadorn, J.W.,Peterson, K.J., Davidson, E.H., 2000. Precambrian animaldiversity: putative phosphatized embryos from the DoushantuoFormation of China. PNAS 97 (9), 4457–4462.

Chen, J., Oliveri, P., Gao, F., Dornbos, S.Q., Li, C., Bottjer, D.J.,Davidson, E.H., 2002. Precambrian animal life: probable devel-opmental and adult cnidarian forms from Southwest China.Developmental Biology 248, 182–196.

Conway Morris, S., 1988. Metazoan evolution near the Precambrian–Cambrian boundary: use and misuse of small shelly fossils. NewYork State Museum Bulletin 463, 9–10.

Conway Morris, S., Chapman, A.J., 1996. Lower Cambrian coelo-scleritophorans (Ninella, Siphogonuchites) from Xinjiang andShaanxi, China. Geological Magazine 133 (1), 33–51.

Conway Morris, S., Chapman, A.J., 1997. Lower CambrianHalkieriids and other Coeloscleritophorans from Aksu-Wushi,Xinjiang, China. Journal of Paleontology 71 (1), 06–22.

Conway Morris, S., Chen, M., 1989. Lower Cambrian anabaritidsfrom south China. Geological Magazine 126 (6), 615–632.

Conway Morris, S., Chen, M., 1992. Carinachitiids, Hexangulaconu-lariids, and Punctatus: problematic metazoans from the EarlyCambrian of South China. Journal of Paleontology 66 (3),384–406.

Conway Morris, S., Mattes, B.W., Chen, M., 1990. The early skeletalorganism Cloudina: new occurrences from Oman and possiblyChina. American Journal of Science 290-A, 245–260.

Ding, W., Qian, Y., 1988. Late Sinian to Early Cambrian small shellyfossils from Yangjiaping, Shimen, Hunan. Acta Micropalaeonto-logica Sinica 5 (1), 39–55.

Ding, L., Zhang, L., Li, Y., Dong, J., 1992. The Study of the LateSinian–Early Cambrian Biota from the Northern Margin ofYangtze Platform. Scientific and Technical Documents PublishingHouse, Beijing. 156 pp.

Dong, X., Bergström, S.M., 2001. Middle and Upper Cambrianprotoconodonts and paraconodonts from Hunan, South China.Palaeontology 44 (5), 949–985.

Dzik, J., 1994. Evolution of “small shelly fossil” assemblages. ActaPalaeontologica Polonica 39 (3), 247–313.

Eldridge, J., Walsh, D., Scotese, C.R., 1997. Plate Tracker. (Windows95/NT).

Gehling, J.G., Jensen, S., Droser, M.L., Myrow, P.M., Narbonne, G.M.,2001. Burrowing below the basal Cambrian GSSP, Fortune Head,Newfoundland. Geological Magazine 138 (2), 213–218.

Geyer, G., Uchman, A., 1995. Ichnofossil assemblages from the NamaGroup (Neoproterozoic–Lower Cambrian) in Namibia and theProterozoic–Cambrian boundary problem revisited. BeringeriaSpecial Issue 2, 175–202.

Geyer, G., Shergold, J.H., 2000. The quest for internationallyrecognized divisions of Cambrian time. Episodes 23 (3), 188–195.

Goedert, J.L., Peckmann, J., Reitner, J., 2000. Worm tubes in anallochthonous cold-seep carbonate from lower Oligocene rocks ofwestern Washington. Journal of Paleontology 74 (6), 992–999.

Grant, S.W.F., 1990. Shell structure and distribution of Cloudina, apotential index fossil for the Terminal Proterozoic. AmericanJournal of Science 290-A, 261–294.

Grotzinger, J.P., Watters, W., Knoll, A.H., 2000. Calcified metazoansin thrombolite–stromatolite reefs of the terminal Proterozoic NamaGroup, Namibia. Paleobiology 26, 334–359.

Gubanov, A., 1998. The Early Cambrian molluscan evolution and itspalaeogeographic implications. Acta Universitatis Carolinae–Geologica 42 (3/4), 419–422.

Gubanov, A.P., 2002. Early Cambrian palaeogeography and theprobable Iberia–Siberia connection. Tectonophysics 352,153–168.

Gubanov, A.P., Peel, J.S., 2000. Cambrian monoplacophoran molluscs(Class Helcionelloida). American Malacological Bulletin 15 (2),139–145.

Hamdi, B., Brasier, M.D., Jiang, Z., 1989. Earliest skeletal fossils fromPrecambrian–Cambrian boundary strata, Elburz Mountains, Iran.Geological Magazine 126 (3), 283–289.

He, T., Yang, X., 1982. Lower Cambrian Meishucun stage of westernYangtze stratigraphic region and its small shelly fossils. Bulletin ofthe Chengdu Institute of Geology and Mineral Resources. ChineseAcademy of Geological Sciences 3, 69–95.

Hofmann, H.J., Mountjoy, E.W., 2001. Namacalathus–Cloudinaassemblage in Neoproterozoic Miette Group (Byng Formation),British Columbia: Canada's oldest shelly fossils. Geology 29 (12),1091–1094.

Hua, H., Zhang, L.-Y., Zhang, Z.-F., Wang, J.-P., 2000. Fossilevidences of Latest Neoproterozoic Gaojiashan biota and theircharacteristics. Acta Palaeontologica Sinica 39 (4), 507–515.


Hua, H., Pratt, B.R., Zhang, L., 2003. Borings in Cloudina shells:complex predator–prey dynamics in the terminal Neoproterozoic.Palaios 18, 454–459.

Isachsen, C.E., Bowring, S.A., Landing, E., Samson, S.D., 1994.New constraint on the devision of Cambrian time. Geology 22,496–498.

Jell, P.A., 1974. Faunal provinces and possible planetary recon-structions of the Middle Cambrian. Journal of Geology 82,319–350.

Jensen, S., 1997. Trace fossils from the Lower Cambrian Mickwitziasandstone, south-central Sweden. Fossils and Strata 42, 1–110.

Jensen, S., Saylor, B.Z., Gehling, J.G., Germs, G.J.B., 2000. Complextrace fossils from the terminal Proterozoic of Namibia. Geology 28(2), 143–146.

Jiang, Z., 1980a. The Meishucunian stage fauna of the Jinning County,Yunnan. Bulletin of Chinese Acadademy of Geological Sciences.Ser. I 2 (1), 75–92.

Jiang, Z., 1980b. Monoplacophorans and Gastropods fauna of theMeishucun Stage from the Meishucun section, Yunnan. ActaGeologica 112–123.

Jiang, Z., 1984. Evolution of early shelly metazoans and basiccharacteristics of Meishucun fauna. Professional Papers ofStratigraphy and Palaeontology 13, 1–22.

Jiang, Z., Brasier, M.D., Hamdi, B., 1988. Correlation of theMeishucunian Stage in South Asia. Acta Geologica Sinica 60 (3),191–199.

Khomentovsky, V.V., Karlova, G.A., 1993. Biostratigraphy of theVendian–Cambrian beds and the Lower Cambrian boundary inSiberia. Geological Magazine 130 (1), 29–45.

Kirschvink, J.L., 1992. A paleogeographic model for Vendian andCambrian time. In: Schopf, J.W., Klein, C. (Eds.), The ProterozoicBiosphere: An Interdisciplinary Study. Cambridge UniversityPress, pp. 569–581.

Koch, C.F., 1987. Prediction of sample size effects on the measuredtemporal and geographic distribution patterns of species. Paleobi-ology 13 (1), 100–107.

Kouchinsky, A., 2000. Shell microstructure in Early Cambrianmolluscs. Acta Palaeontologica Polonica 45 (2), 119–150.

Kouchinsky, A., Bengtson, S., 2002. The tube wall of Cambriananabaritids. Acta Palaeontologica Polonica 47 (3), 431–444.

Kumar, G., Bhatt, D.K., Raina, B.K., 1987. Skeletal microfauna ofMeishucunian and Qiongzhusian (Precambrian–Cambrian bound-ary) age from the GangaValley, Lesser Himalaya, India. GeologicalMagazine 124, 167–171.

Landing, E., 1988. Lower Cambrian of eastern Massachusetts:stratigraphy and small shelly fossils. Journal of Paleontology 62(5), 661–695.

Landing, E., 1994. Precambrian–Cambrian boundary global stratotyperatified and a new perspective of Cambrian time. Geology 22,179–182.

Landing, E., Westrop, S.R., 2004. Environmental patterns in the originand diversification loci of Early Cambrian skeletalized Metazoa:evidence from the Avalon microcontinent. Paleontological SocietyPapers 10, 93–106.

Landing, E., Myrow, P., Benus, A.P., Narbonne, G.M., 1989. ThePlacentian series: appearance of the oldest skeletalized faunas insoutheastern Newfoundland. Journal of Paleontology 63 (6),739–769.

Landing, E., Nowlan, G.S., Fletcher, T.P., 1980. A microfaunaassociated with Early Cambrian trilobites of the Callavia Zone,northern Antigonish Highlands, Nova Scotia. Canadian Journal ofEarth Sciences 17, 400–418.

Landing, E., et al., 1998. Duration of the Early Cambrian: U–Pb agesof volcanic ashes from Avalon and Gondwana. Canadian Journalof Earth Sciences 35, 329–338.

Li, Z.-X., 1998. Tectonic history of the major east Asian lithosphericblocks since the mid-Proterozoic — a synthesis. MantleDynamics and Plate Interactions in East Asia Geodynamics 27,221–243.

Li, Z.-X., Powell, C.M.A., 1999. Palaeomagnetic study of Neoproter-ozoic glacial rocks of the Yangzi Block: palaeolatitude andconfiguration of South China in the late Proterozoic Superconti-nent. Precambrian Research 94, 1–5.

Li, G., Xiao, S., 2004. Tannuolina and Micrina (Tannuolinidae)from the Lower Cambrian of Eastern Yunnan, South China, andtheir scleritome reconstruction. Journal of Paleontology 78 (5),900–913.

Li, Z.-X., Zhang, L., Powell, C.M., 1995. South China in Rodinia: partof the missing link between Australia–East Antarctica andLaurentia? Geology 23 (5), 407–410.

Li, C., Chen, J., Hua, T., 1998. Precambrian sponges with cellularstructures. Science 279, 879–882.

Li, G., Zhu, M., Steiner, M., Qian, Y., 2004. Skeletal faunas from theQiongzhusian of southern Shaanxi: biodiversity and lithofacies–biofacies links in the Lower Cambrian carbonate settings. Progressin Natural Science 14 (1), 91–96.

Li, G., Steiner, M., Zhu, M., Zhu, X., Erdtmann, B.-D., 2007. EarlyCambrian fossil record of metazoans in South China: genericdiversity and radiation patterns. Palaeogeography, Palaeoclimatol-ogy, Palaeoecology 254, 226–246 (this volume) , doi:10.1016/j.palaeo.2007.03.017.

Lowenstam, H.A., Margulis, L., 1980. Evolutionary prerequisites forearly Phanerozoic calcareous skeletons. BioSystems 12, 27–41.

Luo, H., et al., 1982. The Sinian–Cambrian boundary in easternYunnan, China., P.R. China. 265 pp.

Luo, H., Jiang, Z., Xu, Z., Song, X., Xu, X., 1980. On the Sinian–Cambrian boundary of Meishucun and Wangjiawan, JinningCounty, Yunnan. Acta Geologica Sinica 54 (2), 95–110.

Luo, H., et al., 1984. Sinian–Cambrian Boundary Stratotype Section atMeishucun, Jinning, Yunnan, China. Peoples Pub. House, Yunnan.154 pp.

Matthews, S.C., Missarzhevsky, V.V., 1975. Small shelly fossils of latePrecambrian and Early Cambrian age: a review of recent work.Journal of the Geological Society London 131, 289–304.

McKerrow, W.S., Scotese, C.R., Brasier, M.D., 1992. Early Cambriancontinental reconstructions. Journal of the Geological SocietyLondon 149, 599–606.

Metcalfe, I., 1996. Gondwanaland dispersion, Asian accretion andevolution of eastern Tethys. Australian Journal of Earth Sciences43, 605–623.

Missarzhevsky, V.V., 1982. Rastschlenenie i korrelatsija pogranitsch-nich tolz dokembrii i kembrija po nekotorym drewneischnymgruppam skeletnych organismov. Bull. MOIP, Otg. Geol., vol. 57(5), pp. 52–67.

Missarzhevsky, V.V., 1989. Oldest Sceletal Fossils and Stratigraphy ofPrecambrian and Cambrian Boundary Beds. Transactions, vol.443. Nauka, Moskow. 237 pp.

Missarzhevsky, V.V., Mambetov, A.M., 1981. Stratigraphy and Faunaof Cambrian and Precambrian Boundary Beds of Maly Karatau,vol. 326. Trudy Akademii Nauka SSSR, Moskow. 1–90 pp.

Murphy, M.A., Salvador, A., 1999. International Stratigraphic Guide—an abridged version. Episodes 22 (4), 255–271.

Peng, S., 2000. A new chronostratigraphic subdivision of Cambrianfor China. In: Acenolaza, G.F., Peralta, S. (Eds.), Cambrian from


the Southern Edge. Instituto Superior De Correlación Geológica,San Miguel de Tucumán, Argentinia, pp. 119–122.

Peng, S., Babcock, L.E., 2001. Cambrian of the Hunan–GuizhouRegion, South China. Palaeoworld 13, 3–51.

Pillola, G.L., 1990. Lithologie et trilobites du Cambrien inférieur duSW de la Sardaigne (Italie): implications paléobiogéographiques.Comptes Rendus de l'Académie des Sciences, Paris, Series II, vol.310, pp. 321–328.

Porter, S.M., 2004. Closing the phosphatization window: testing forthe influence of taphonomic megabias on the pattern of smallshelly fossil decline. Palaios 19, 178–183.

Qian, Y., 1978. The Early Cambrian hyolithids in central andSouthwest China and their stratigraphical significance. Memoirsof Nanjing Institute of Geology and Palaeontology. AcademiaSinica 11, 1–50.

Qian, Y., 1989. Early Cambrian small shelly fossils of China with specialreference to the Precambrian–Cambrian boundary. Stratigraphy andPalaeontology of Systematic Boundaries in China, vol. 2. NanjingUniversity Publishing House, Nanjing. 341 pp.

Qian, J., Xiao, B., 1984. An Early Cambrian small shelly fauna fromAksu-Wushi region, Xinjiang. Professional Papers of Stratigraphyand Palaeontology 13, 65–90.

Qian, Y., Yin, G., 1984. Small shelly fossils from the lowest Cambrianin Guizhou. Professional Papers of Stratigraphy and Palaeontology13, 91–124.

Qian, Y., Bengtson, S., 1989. Palaeontology and biostratigraphy of theEarly Cambrian Meishucunian Stage in Yunnan Province, SouthChina. Fossils and Strata 24, 1–156.

Qian, Y., Chen, M., Chen, Y.-Y., 1979. Hyolithids and other smallshelly fossils from the Lower Cambrian Huangshandong formationin the eastern part of the Yangtze Gorge. Acta PalaeontologicaSinica 18 (3), 207–229.

Qian, Y., Zhu, M., He, T., Jiang, Z., 1996. New investigation ofPrecambrian–Cambrian boundary sections in eastern Yunnan.Acta Micropalaeontologica Sinica 13 (3), 225–240.

Qian, Y., et al., 1999. Taxonomy and Biostratigraphy of Small ShellyFossils in China. Science Press, Beijing. 247 pp.

Qian, Y., Li, G., Zhu, M., 2001. The Meishucunian stage and its smallshelly fossil sequence in China. Acta Palaeontologica Sinica 40,54–62 (Sup.).

Rozanov, A.Y., Missarzhevsky, V.V., 1966. Biostratigraphy and faunaof Lower Cambrian horizons. Geol. Inst. Trudy, vol. 148. Nauka,Moscow, pp. 1–123.

Rozanov, A.Y., Missarzhevsky, V.V., Volkova, N.A., Voronova, L.G.,Krylov, I.N., Keller, B.M., Korolyuk, I.K., Lendzion, K.,Michniak, R., Pychova, N.G., Sidorov, A.D., 1969. The Tommo-tian Stage and the Cambrian lower boundary problem. Trudy Geol.Inst., vol. 206. Nauka, Moskow, pp. 1–380.

Runnegar, B., 1985. Shell microstructures of Cambrian molluscsreplicated by phosphorite. Alcheringa 9, 245–257.

Salvador, A. 1994. International Stratigraphic Guide, Second Edition.The International Union of Geological Sciences and TheGeological Society of America, Inc., Trondheim and Boulder,214 pp.

Seilacher, A., Buatois, L.A., Mángano, M.G., 2005. Trace fossils in theEdiacaran–Cambrian transition: behavioral diversification, eco-logical turnover and environmental shift. Palaeogeography,Palaeoclimatology, Palaeoecology 227, 323–356.

Sepkoski Jr., J.J., 1992. Proterozoic–Early Cambrian diversification ofmetazoans and metaphytes. In: Schopf, J.W., Klein, C. (Eds.), TheProterozoic Biosphere: A Multidisciplinary Study. CambridgeUniversity Press, Cambridge, pp. 553–561.

Siegmund, H., 1995. Fazies und Genese unterkambrischer Phos-phorite und mariner Sedimente der Yangtze-Plattform, Süd-china. Berliner Geowissenschaftliche Abhandlungen, Reihe A173, 1–114.

Steiner, M., Li, G., Qian, Y., Zhu, M., 2004. Lower Cambrian smallshelly fossils of northern Sichuan and southern Shaanxi (China),and their biostratigraphic importance. Geobios 37, 259–275.

Tipper, J.C., 1979. Rarefaction and rarefiction— the use and abuse ofa method in paleoecolgy. Paleobiology 5 (4), 423–434.

Vidal, G., Palacios, T., Gámez-Vintaned, J.A., Balda, M.A.D., Grant,S.W.F., 1994. Neoproterozoic–Early Cambrian geology andpalaeontology of Iberia. Geological Magazine 131 (6), 729–765.

Xiao, S., Knoll, A.H., 2000. Phosphatized animal embryos from theNeoproterozoic Doushantuo Formation at Weng'an, Guizhou,South China. Journal of Paleontology 74 (5), 767–788.

Xiao, S., Zhang, Y., Knoll, A.H., 1998. Three-dimensional preserva-tion of algae and animal embryos in a Neoproterozoic phosphorite.Nature 391, 553–558.

Xiao, S., Yuan, X., Knoll, A.H., 2000. Eumetazoan fossils in terminalProterozoic phosphorites? Proceedings of the National Acadamyof Sciences, U. S. A. 97 (25), 13684–13689.

Xiao, S., Yuan, X., Steiner, M., Knoll, A.H., 2002. Macroscopiccarbonaceous compressions in a terminal Neoproterozoic shale:a systematic reassessment of the Miaohe biota, South China.Journal of Paleontology 76 (2), 347–376.

Xie, Y., 1990. The conodont-like fossils of Early Cambrian in Zhenba,Shanxi. Journal of Chengdu College of Geology 17 (4), 16–22.

Xing, Y., Ding, Q., Luo, H., He, T., Wang, Y., 1984. The Sinian–Cambrian boundary of China, 10. Bulletin of the Institute ofGeology. Chinese Academy of Geological Sciences (SpecialIssue).

Xing, Y., Yue, Z., 1984. The Sinian–Cambrian boundary insouthwestern part of Shaanxi. In: Xing, Y., Ding, Q., Luo, H.,He, T., Wang, Y. (Eds.), The Sinian–Cambrian Boundary of China.. Bulletin of the Institute of Geology, Chinese Academy ofGeological Sciences, Special Issue. Geological Publishing House,Beijing, pp. 111–125.

Xue, Y., Tang, T., Yu, C., 1992. Discovery of oldest skeletal fossilsfrom upper Sinian Doushantuo Formation in Weng'an, Guizhou,and its significance. Acta Palaeontologica Sinica 31 (5), 530–539.

Yang, X., He, Y., Deng, S., 1983. On the Sinian–Cambrian boundaryand the Small Shelly Fossil assemblages in Nanjiang area,Sichuan. Bulletin of the Chengdu Institute of Geology andMineral Resources. Chinese Academy of Geological Sciences 4,91–110.

Yang, A., Zhu, M., Zhang, J., Li, G., 2003. Early Cambrian eodiscoidtrilobites of the Yangtze Platform and their stratigraphic implica-tions. Progress in Natural Science 13 (11), 861–866.

Yao, J., Xiao, S., Yin, L., Li, G., Yuan, X., 2005. Basal Cambrianmicrofossils from the Yurtus and Xishanblaq formations (Tarim,North-west China): systematic revision and biostratigraphiccorrelation of Micrhystridium-like acritarchs. Palaeontology 48(4), 687–708.

Yuan, K., Zhang, S., 1983. Discovery of the Tommotia fauna in SWChina. Acta Palaeontologica Sinica 22 (1), 31–39.

Yuan, K., Zhu, M., Zhang, J., Van Iten, H., 2001. Biostratigraphy ofarchaeocyathan horizons in the Lower Cambrian Fuchengsection, South Shaanxi Province: implications for regionalcorrelations and archaeocyathan evolution. Acta PalaeontologicaSinica 40, 115–129 (Sup.).

Yue, Z., Gao, L., 1992. Paleontology, biostratigraphy and geologicalsignificance of the Early Cambrian protoconodonts and other


skeletal microfossils from Aksu-Wushi Region, Xinjiang, China.Bulletin of the Institute of Geology. Chinese Academy ofGeological Sciences 23, 133–160.

Yue, Z., Gao, L., 1994. A new Early Cambrian species of Tannuolinafrom Xinjiang region, China. Professional Papers of Stratigraphyand Palaeontology. Chinese Academy of Geological Sciences 24,66–78.

Zhang, L., 1986. A discovery and preliminary study of the latestage of late Gaojiashan biota from Sinian in Ningqiang County,Shaanxi. Bulletin of the Xian Institute of Geology and MineralResources. Chinese Academy of Geological Sciences 13,67–88.

Zhang, Q.R., Piper, J.D.A., 1997. Palaeomagnetic study of Neoproter-ozoic glacial rocks of the Yangzi Block: palaeolatitude andconfiguration of South China in the late Proterozoic Superconti-nent. Precambrian Research 85, 173–199.

Zhang, W., Babcock, L.E., 2002. Helcionelloid mollusk from theLower Cambrian Heilinpu Formation, Chengjiang, Yunnan. ActaPalaeontologica Sinica 41 (3), 303–307.

Zhu, M., 1997. Precambrian–Cambrian trace fossils from easternYunnan, China: implications for Cambrian explosion. Bulletin ofNational Museum of Natural Science 10, 275–312.

Zhu, M., Li, G., Zhang, J., Steiner, M., Qian, Y., Jiang, Z., 2001. EarlyCambrian Stratigraphy of East Yunnan, Southwestern China: asynthesis. Acta Palaeontologica Sinica 40, 4–39 (sup.).

Zhu, M., Li, G., Hu, S., Zhao, F., 2005. Ediacaran-Cambrianboundary stratigraphy at Meishucun, Jinning County, and fossilquarries of the Early Cambrian Chengjiang biota near Haikou,Kunming City, Yunnan, China. In: Peng, S., Babcock, L.E., Zhu,M. (Eds.), Cambrian System of China and Korea. Guide to FieldExcursions. University of Science and Technology of ChinaPress, Hefei, pp. 13–29.

Zhu, M., Qian, Y., Jiang, Z., He, T., 1996. A preliminary study on thepreservation, shell composition and microstructures of Cambriansmall shelly fossils. Acta Micropalaeontologica Sinica 13 (3),241–254.

Zhuravlev, A.Y., 1995. Preliminary suggestions on the global EarlyCambrian zonation. Beringeria Special Issue 2, 147–160.

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