Seediscussions,stats,andauthorprofilesforthispublicationat:https://www.researchgate.net/publication/264167367

CorumbellaandinsituCloudinainassociationwiththrombolitesintheEdiacaranItapucumiGroup,Paraguay

ArticleinTerraNova·January2012

ImpactFactor:2.64·DOI:10.13140/2.1.2928.1924

CITATIONS

11

READS

79

7authors,including:

L.V.Warren

SãoPauloStateUniversity

38PUBLICATIONS114CITATIONS

SEEPROFILE

ThomasRichFairchild

UniversityofSãoPaulo

55PUBLICATIONS569CITATIONS

SEEPROFILE

PauloC.Boggiani

UniversityofSãoPaulo

71PUBLICATIONS500CITATIONS

SEEPROFILE

DanielG.Poiré

NationalUniversityofLaPlata

126PUBLICATIONS1,064CITATIONS

SEEPROFILE

Allin-textreferencesunderlinedinbluearelinkedtopublicationsonResearchGate,

lettingyouaccessandreadthemimmediately.

Availablefrom:L.V.Warren

Retrievedon:09May2016

Corumbella and in situ Cloudina in association with thrombolites inthe Ediacaran Itapucumi Group, Paraguay

Lucas V. Warren,1 Thomas R. Fairchild,1 Claudio Gaucher,2 Paulo C. Boggiani,1 Daniel G. Poire,3

Luıs E. Anelli1 and Julio C. G. Inchausti41Instituto de Geociencias, Universidade de Sao Paulo (USP), Rua do Lago, 562, Sao Paulo 05508-080, Brazil; 2Departamento de Geologıa,

Facultad de Ciencias, calle Igua 4225, Montevideo 11400, Uruguay; 3Centro de Investigaciones Geologicas, UNLP-CONICET, calle 1, n. 644,

La Plata 1900, Argentina; 4Viceministerio de Minas y Energıa, Ministerio de Obras Publicas y Comunicaciones, calle Oliva, n. 411, Assuncion

1221, Paraguay

Introduction

Recent years have seen significantadvances in our understanding ofclimatic, tectonic and evolutionaryevents that marked the end of theNeoproterozoic era. Low-latitudeglaciation (Hoffman et al., 1998; Hoff-man and Schrag, 2002) and the break-up of the supercontinent Rodinia(Hoffman, 1999; Li et al., 2008) setthe stage for the appearance ofincreasingly varied macroscopicorganisms (Grotzinger et al., 1995;Knoll and Carroll, 1999; Grey et al.,2003) and the subsequent escalation ofthe influence of the biosphere in theexternal dynamics of the Earth (Knolland Bambach, 2000). It was withinthis context that the macroscopicorganisms of the Ediacara biotaappeared around 575 Ma (Narbonneand Gehling, 2003), followed at about550 Ma by the worldwide advent oforganisms capable of producing min-eralized skeletal parts, putatively inresponse to the appearance of preda-tors (Germs, 1972; Grant, 1990;Hofmann and Mountjoy, 2001;Bengtson, 2002). These innovationsquickly led to a new plateau in eco-logical dynamics that ultimately re-sulted in the explosive radiation of

shelly faunas at the beginning of theCambrian.Initial access to this plateau,

although widely recorded by bioclastsof the late Ediacaran calcareous tubu-lar fossil Cloudina in grainstones fromwave- and tide-dominated deposi-tional settings, is most faithfully rep-resented by associations of skeletalremains of Cloudina sp. plus Nama-calathus, with or without biomineral-ized metazoan Namapoikia andpossible calcareous algae, in microbialbuild-ups (stromatolites, thrombo-lites) in Namibia (Nama Group;Germs, 1972; Grant, 1990; Woodet al., 2002), Canada (Miette Group;Hofmann and Mountjoy, 2001), andOman (Huqf Supergroup; Conway-Morris et al., 1990; Grotzinger et al.,2000), as well as by associations ofCloudina and Corumbella in Brazil(Corumba Group; Hahn et al., 1982;Zaine and Fairchild, 1987) and Clou-dina and Sinotubulites in China(Dengying and Gaojiashan forma-tions, Wood et al., 2002; Hua et al.,2007). Cloudina apparently occupiedlow-energy settings protected bymicrobial build-ups or banks of ooidsand surrounding areas, whereasNamacalathus inhabited the microbialbioherms themselves (Conway-Morriset al., 1990; Grotzinger et al., 2000;Hofmann and Mountjoy, 2001; Oliveira,2010; Wood, 2011).Hence, the discovery of thromboli-

tic biostrome outcrops and entireindividuals of Cloudina apparently

preserved in place, together with con-centrated bioclasts of Cloudina andfragments of the supposed scypho-zoan Corumbella, within the Itapuc-umi Group of eastern Paraguay notonly confirms the previous report(Boggiani and Gaucher, 2004) ofCloudina in this country from lime-stone but also corroborates the obser-vations mentioned above on thehabitat of Cloudina, and significantlyextends the geographical range inSouth America of Corumbella some400 km to the south of its type-area insouthwestern Brazil (Hahn et al.,1982;Zaine and Fairchild, 1985; Zaine,1991; Gaucher, 2000; Gaucher et al.,2005). These observations, plus thepresence of trace fossils and possiblebiomat structures within this associa-tion open an important new frontierin South America for research on lifein the latest Ediacaran.

Geological setting

The Itapucumi Group (Harrington,1950) crops out within the Rio ApaBlock in an area 40 · 60 km east ofand paralleling the Paraguay river innortheastern Paraguay (Fig. 1A). Thewestern portion of this unit exhibitslocal low-grade (chlorite zone) meta-morphism and intense deformation,with E-vergent reverse faults andinverted folds (Campanha et al.,2010). This succession (Fig. 1B) ismade up of sandstones and siltstonesof the Vallemi Formation that grade

ABSTRACT

An in situ assemblage of Cloudina, thrombolites and an ichno-fossil (cf. Archaeonassa), together with fragments of Corumbellawerneri, is reported here, from a tidally influenced, shallow,lagoonal setting on a carbonate ramp within the ItapucumiGroup, Paraguay. The association of Cloudina with thrombolitesis comparable to other terminal Neoproterozoic occurrences,but the coexistence of shelly fossils in situ with trace fossils and

microbially induced sedimentary structures is apparentlyunique. This discovery extends the record of Cloudina andCorumbella in South America and further elucidates the diversity,distribution and palaeoecology of shelled organisms in lateEdiacaran time.

Terra Nova, 23, 382–389, 2011

Correspondence: Dr. Lucas V. Warren,

Instituto de Geociencias, Universidade de

Sao Paulo (USP), Rua do Lago, 562, Sao

Paulo, SP, 05508-080, Brazil. Tel.: (55-11)

3091-4116; e-mail: warren@usp.br

382 � 2011 Blackwell Publishing Ltd

doi: 10.1111/j.1365-3121.2011.01023.x

upward into grey oolitic limestonesand dolostones of the Camba JhopoFormation, culminating in the marls,pelites and dolostones of the Cerro

Curuzu Formation (Warren, 2011).Further east, the Tagatiya GuazuFormation, considered the lateralequivalent of the Camba Jhopo

Formation, comprises an extensiveunmetamorphosed, undeformed cra-tonic sedimentary cover composedmainly of carbonates exhibiting mas-

(A)

(C)

(B)

Fig. 1 (A and B) Locality map and stratigraphic sections from the Ediacaran-age Itapucumi Group, northeastern Paraguay. (C)Biostratigraphic, chemostratigraphic and geochronologic correlation between the Itapucumi Group and other terminalNeoproterozoic successions worldwide. The grey band corresponds to the Cloudina biozone (data from Grotzinger et al., 1995,2000; Brasier et al., 2000; Amthor et al., 2003; Gaucher et al., 2003; Peral et al., 2007; Zhou and Xiao, 2007; Boggiani et al., 2010;Warren, 2011). (1) P.Nolloth, Port Nolloth Group; Nu., Numees Formation; Hol., Holgat Formation; (2) AD., Algal Dolomite;Zhuiaq., Zhujiaqing Formation; Zh., Zhongyicun Member; (4) BN, Barriga Negra; CSF, Cerros San Francisco; CV, CerroVictoria; (6) V.Monica, Villa Monica; L.Negra, Loma Negra; (7) T.Guazu, Tagatiya Guazu; C. Jhopo, Camba Jhopo.

Terra Nova, Vol 23, No. 6, 382–389 L. V. Warren et al. • Corumbella and In situ Cloudina in South America

.............................................................................................................................................................

� 2011 Blackwell Publishing Ltd 383

sive, cross-stratified grainstones andooid grainstones, oncoids, mudstonesand heterolithic facies intercalatedwith breccias and microbialites (Fig. 1B).The fossils described here are from

two outcrops 10 km apart inthe TagatiyaGuazu Formation (Fig. 1Band C) in the eastern portion ofthe Itapucumi Group (22�46.18¢S ⁄57�29.10¢W; 22�42.57¢S ⁄57�30.35¢W).In both sections, massive and cross-stratified calcareous grainstones giveway upward to heterolithic facies ofgrainstones and calcareous mudstones(Fig. 1B), exhibiting tidal bundles.Intercalated within these facies are cen-timetre-thick beds of intraformationalbreccias, including tepee structures,laminated microbialites plus thrombo-litic biostromes (Fig. 2A and B),consisting of extensive, laterally con-tinuous low domes up to 10 cm highrelief and irregular nodules. The bio-stromesmay be and are covered by limemud containing dispersed grains ofquartz sand (Fig. 2C) and platy intra-clasts evidently eroded from nearbymicrobial mats and thrombolites withminimal abrasion and redepositededgewise, without imbrication. Thepresence of convoluted and laterallyinterrupted stratiform microbialiticlaminae (Fig. 2C and D), pseudo-

morphs of gypsum (Boggiani, 1998;Boggiani and Gaucher, 2004), tepeestructures, intraformational brecciaswith mudstone curls and small desic-cation cracks suggest sedimentationunder evaporitic conditions with spo-radic subaerial exposure of sedimentsand microbial mats. This facies associ-ation represents a shallow intertidal tosupratidal setting on a rimmed carbon-ate ramp.The presence of the Cloudina ⁄

Corumbella assemblage associatedwith thrombolites (Fig. 2D) in theeastern portion of the ItapucumiGroup and the Tamengo Formationof southwest Brazil not only confirmsthe long-held view that these two unitsare lateral equivalents but also allowscorrelation with stratigraphic units inUruguay and Argentina. In the Tam-engo Formation, Cloudina occurs gen-erally as bioclasts in grainstones ormore rarely as fragments in poorlyfossiliferous, thinly bedded fine grain-stone ⁄marl rhythmites. Shales in thisformation harbour Corumbella wer-neri Hahn et al., 1982; vendotaenidsand a depauperate acritarch assem-blage dominated by Bavlinella (Zaine,1991; Gaucher et al., 2003). In Uru-guay, Cloudina has been described insiltstones of the Yerbal Formation,

Arroyo del Soldado Group (Gaucherand Sprechmann, 1999; Gaucher,2000), putatively in living position;better preserved, silicified specimenshave been observed in limestones ofthe overlying Polanco Formation(Fig. 1C). Siltstones of the YerbalFormation also host other skeletalfossils, most notably Titanothecacoimbrae, interpreted as an aggluti-nated foraminifera, andWaltheria mar-burgensis, purportedly possessing aphosphatic shell (Gaucher, 2000).Cloudina has also been reported fromlimestones of the Loma Negra Forma-tion in Tandilia, Argentina (Fig. 1C,Gaucher et al., 2005).The presence of the index fossil

Cloudina (Grant, 1990) indicates aterminal Ediacaran age for these SouthAmerican successions somewhere be-tween 548 and 542 Ma (Grotzingeret al., 1995; Amthor et al., 2003), anage recently confirmed for the Tam-engo Formation by geocronologicaland chemostratigraphical studies byBabinski et al. (2008) and Boggianiet al. (2010), respectively. The Cloudi-na-bearing units of South America arethus biostratigraphically equivalent tosuccessions around the world (Fig. 1C)within the Nama Group (Namibia),Dengying Formation (China), Ara

(A) (B)

(C) (D)

Fig. 2 (A and B) Domical thrombolites with small microbialitic intraclasts in the irregular depressions between domes. (C)Photomicrograph of thrombolite microstructure as seen in petrographic thin section. The light fragments are quartz grains. (D)Polished slab showing obliquely oriented shell of Cloudina lucianoi filled by sparry calcite cement (square at top) and mesoscopicclotted fabric (rectangle) at the lower right of the specimen. Scale bar represents 100 lm and 1 cm for C and D, respectively.

Corumbella and In situ Cloudina in South America • L. V. Warren et al. Terra Nova, Vol 23, No. 6, 382–389

.............................................................................................................................................................

384 � 2011 Blackwell Publishing Ltd

Group (Oman), Miette Group (Can-ada), Ibor-Navalpino group (Spain,Cortijo et al., 2010) and Ko-todzha ⁄Raiga Formations (Russia,Kontorovich et al., 2008).

Description of the fossils

The fossils identified here as Cloudinain the Itapucumi Group are frag-mented to entire, straight to markedlycurved, generally cylindrical tubes,closed at their rounded proximal(basal) end and open at their distal(apical) end (Fig. 3A–C). The succes-

sion of nested, commonly eccentricring-like wall segments observed inthese specimens is typical of the genusCloudina Germs, 1972. Wall segmentsdo not always overlap regularly andmay flare outward slightly at theirdistal ends (Fig. 3B and C), thusimparting an annular ornamentationto the tubes. In transverse cross-section, the tubes are slightly ellipticalto circular with diameters from 1.0 to3.5 mm (Fig. 3D). Complete speci-mens may reach 35 mm in length(Fig. 3A, G–I). Smaller than C. hart-mannae Germs, 1972, and larger than

C. riemkeae Germs, 1972, from Nam-bia, these fossils are comparable to thespecies Cloudina lucianoi Beurlen andSommer, 1957, of the Tamengo For-mation, to which they are assignedhere (Beurlen and Sommer, 1957;Zaine and Fairchild, 1985). They arecommonly filled by sparry calcite(Fig. 3E) and preserved parallel,perpendicular or oblique to bedding.A second metazoan in the Itapuc-

umi Group occurs as fragments,3.0–4.6 mm long and flattened, 1.4and 2.9 mm wide, made up of articu-lated, non-phosphatic, non-calcare-

(A)

(F)

(J) (K)

(L)

(G) (H) (I)

(B) (C) (D)

(E)

Fig. 3 Fossil assemblage of the Itapucumi Group. (A) Autochthonous assemblage of toppled specimens and in-place circular basalsections of Cloudina lucianoi. (B and C) C. lucianoi exhibiting typical cone-in-cone construction. (D) Photomicrograph oftransverse section of C. lucianoi showing excentric emplacement of successive shell segments. (E) Photomicrograph of longitudinalsection of C. lucianoi shell filled by sparry calcite cement. (F and G) Fragments of Corumbella werneri. (H) Bed-parallel trace fossil,cf. Archaeonassa (centre of photograph) associated with in situ specimens of C. lucianoi. (I and J) Discoidal pseudofossil exhibitinga small ellipsoidal central elevation interpreted as a rimmed microbially induced sedimentary structure (MISS of Noffke et al.,1996). (K and L) Relatively long, nearly straight tubular structures. Note the subtle segmentation of the specimen in (K). Scale barrepresents 1 cm for A and H; 5 mm for K and L; 2 mm for B, I and J; 1 mm for E; 500 lm for D, F and G; 300 lm for C.

Terra Nova, Vol 23, No. 6, 382–389 L. V. Warren et al. • Corumbella and In situ Cloudina in South America

.............................................................................................................................................................

� 2011 Blackwell Publishing Ltd 385

ous, apparently organic, narrow annu-lar elements, approximately four permillimetre of length. These elementsmay also occur as submillimetric, lath-like fragments and isolated rings, nothicker than 0.25 mm (Fig. 3F and G)within the rock and possibly corre-spond to transverse rod-like skeletalelements that occur in conulariid scy-phozoan cnidarians (Babcock et al.,2005). These fossils are attributed toCorumbella werneri (Hahn et al.,1982), described from the TamengoFormation, rather than a possiblesecond species, Corumbella sp., pro-posed by Hagadorn and Waggoner(2000) for rare specimens in sand-stones from the Wood Canyon For-mation, California, USA, becausethey are nearly identical in size,organization and preservation to theBrazilian species.A single, slightly curved, unorna-

mented, unbranched, linear horizon-tal structure preserved in positiveepirelief (Fig. 3H) amidst abundantfragments of C. lucianoi is interpretedas a trace fossil similar to Archaeon-assa (Yochelson and Fedonkin,1997). The structure is 27.1 mm longand varies in width from 2.5 mm atone extremity to 5.3 mm at the other.A slightly offset flat central depres-sion separates the structure longitu-dinally into two narrow raised lobes(Fig. 3H). This mark is interpreted asa feeding trace of a soft-bodiedworm-like organism or a locomotiontrace of a mollusc-like animal madenear the sediment–water interface(Valentine, 1995; Jensen, 2003).Figure 3I and J shows an elliptical

structure measuring 6.6 · 8.6 mmwith slightly elevated borders 1.7mm wide and a central, slightly ele-vated elliptical structure, 3.8· 1.3 mm, preserved in positivehyporelief in a fine grainstone.Although similar to moulds of soft-bodied medusoid cnidarians reportedfrom the Ediacaran, such as Nimbiaocclusa (Fedonkin, 1980; Hagadornand Waggoner, 2000), this simplestructure is known from a single,poorly preserved specimen in theItapucumi Group and more likelyrepresents a microbially induced sed-imentary structure (MISS; Noffkeet al., 1996; Grazhdankin and Ger-des, 2000).Millimetric to centimetric fragments

of elongate, roughly cylindrical struc-

tures with tapering terminations wereobserved in depressions betweenthrombolitic domes (Fig. 3K and L).Some specimens present a subtle seg-mentation suggestive of equallyspaced ring-like structures (Fig. 3K).Although possibly representing poorlypreserved C. lucianoi, their length-to-diameter ratio, straightness and apicaltermini suggest other affinities, per-haps calcareous algae.

Discussion

Fossils in the Itapucumi Group in-clude abundant fragments and com-plete specimens of Cloudina, much lessabundant, short segments of Corum-bella and single specimen of a sus-pected trace fossil and a pseudofossil

interpreted here as a MISS (Noffkeet al.,1996).Cloudina may be preserved parallel,

perpendicular or oblique to beddingand occurs in three different wayswithin the Itapucumi Group: (1) asthin, lenticular coquinas in shallowtidal channels and in troughs betweenlow-amplitude dunes and current rip-ples (Fig. 4A and B); (2) as fragments(fine bioclasts) in very fine grainstonesbetween thrombolitic domes; andmost importantly, (3) as articulatedsegments and prostrate whole speci-mens apparently in situ and associatedwith thrombolites (Figs 2D, 3A and4C–G). Several spar-filled tubes ofCloudina oblique or perpendicular tothe bedding appear to be the basalportions of relatively long, nearly

(A)

(C)

(E) (F)

(G)

(D)

(B)

Fig. 4 Autochthonous Cloudina lucianoi. (A and B) Overview (A) and detail ofcoquina of C. lucianoi in a shallow trough. Note random arrangement of the shells inB. (C and D) Oblique view of sample (A) and graphic interpretation (B) showingsparry internal moulds in relief parallel to bedding plane (light grey) and normal tobedding (arrows) on the nearly vertical broken margin (darker grey). (E) Beddingplane view of transverse cross-sections of several specimens of C. lucianoi orientedperpendicular to bedding. (F and G) Side views of a polished carbonate slab showingspar-filled tubes of Cloudina in presumed living position in the sediment. Scale barrepresents 1 cm for B, C and D; 5 mm for E, F and G.

Corumbella and In situ Cloudina in South America • L. V. Warren et al. Terra Nova, Vol 23, No. 6, 382–389

.............................................................................................................................................................

386 � 2011 Blackwell Publishing Ltd

complete, prostrate shells lying uponthe suprajacent bedding surface (Fig. 4C–G). Many of the circular sections ofshells observed on bedding planes(Fig. 4E) may represent a similar sit-uation. In several of the prostratespecimens, the upper margin of someof the shell segments flares outwardfrom the axis of the shell as a verydelicate rim. Any transport wouldhave easily broken and abraded theserims and disarticulated the longerspecimens of Cloudina. Hence, thesefossils were most likely preserved inplace as obrution deposits, possiblywhen unconfined suspended lime mudand fine calcareous sand washed overnatural barriers, smothering the pro-tected areas where thrombolitic domesand Cloudina flourished. The deposi-tional history was much different forCloudina in the coquinas and as com-minuted bioclasts in grainstones, andevidently involved differing degrees oftransport, jostling, breakage and abra-sion directly related to their respectiveshort and long residence times withinthe taphonomically active zone.A large number of Cloudina shells

are filled by sparry calcite (Figs 3E,4F and G), not only in the ItapucumiGroup but also in the coquinoidtempestites within the CorumbaGroup. Given the thinness of the shellsegments in Cloudina (perhaps nomore than 50 lm according to Grant,1990), it is surprising, first, that thesefossils were not fragmented or crushedduring transport and, burial and,second, that they were not immedi-ately filled by sediment once they wereburied. We believe that many of thesespar-filled shells were originally occu-pied by the Cloudina animal smoth-ered during obrution or killed by thetempest responsible for their rapidtransport and concentration in stormbeds. The carcass of the animal wouldhave effectively inhibited breakageduring transport and blocking infillingof the shell by sediment until decom-position of the tissues resulted in avoid that was later filled by sparrycalcareous cement.Corumbella, on the other hand,

occurs as rare fragments and de-graded, disarticulated segments alongwith fragments of Cloudina, a situa-tion also described, but very rare, inthe Tamengo Formation (Zaine,1991). Differences in abundance andbiostratinomic signatures between

Cloudina and Corumbella in the Ita-pucumi Group may be related todifferences in their respective habitatpreferences, i.e. nearby protected car-bonate settings for Cloudina, and dis-tant shaley settings for Corumbellawerneri, as registered in the type local-ity in the Tamengo Formation (Zaine,1991; Babcock et al., 2005), as well asto the rigidity of the calcareous shellsof Cloudina and the plasticity of theapparently organic skeleton. For thesereasons, Corumbella occurs as flat-tened, often degraded parauchtho-nous ⁄alocthonous bioclasts andCloudina, as whole shells and brokenfragments are apparently preservedwithin or very near to its naturalhabitat.The Itapucumi Group thus provides

the sixth example of coquinoid lime-stones containing Cloudina plus atleast one other skeletal fossil in asso-ciation with microbial buildups onNeoproterozoic carbonate platforms,albeit on a smaller stratigraphic scalethan in that registered in Namibia,Canada, Oman, Brazil, Spain andRussia. For example, in Namibiaand Oman, and probably in Canada(Hofmann and Mountjoy, 2001) aswell, the Cloudina-Namacalathus–thrombolite-stromatolite, associationextends for several kilometres as bio-herms ⁄biostromes, tens to hundredsof metres in thickness. Given thedistance between the two sectionsreported here, the microbialites andskeletal fossils in the ItapucumiGroup may be as extensive as someof the examples cited above. Thepresently known thickness of thesedeposits, however, is on the order of10 m, but this may merely reflect thevery limited size of the fossiliferousoutcrops. Despite the influence ofcurrents in the reef-like buildups inNamibia and their effect upon theshapes of platey stromatolites andbioherms in Canada, the commonlygood preservation of the thin-walledcalcareous shells at all four localitiessuggests that Cloudina (and Nama-calathus) either grew within the build-ups themselves or were derived fromnearby protected areas.

Conclusions

The Paraguayan fossil occurrencesdescribed in this article are sedimen-tologically, taphonomically and pala-

eontologically comparable to similarEdiacaran successions worldwide. Thepresence of MISS structures (Noffkeet al., 1996), thrombolites and speci-mens of Cloudina preserved in situsuggests a shallow marine carbonateenvironment in which the substrate, inpart organic, was colonized by sessileand vagile benthos. Cloudina appar-ently lived as a flexible mat-stickerrising above the seafloor by partiallyanchoring itself in the sediment orattaching itself to small thrombolitedomes. This life style surely providedgreater efficiency for feeding, whereasthe presence of a mineralized organic-rich exoskeleton protected the organ-ism from possible predators (Huaet al., 2007; Wood, 2011). Theco-occurrence of shells of Cloudinaand fragments of the cnidarian Co-rumbella werneri, reported here foronly the second time outside its typearea, suggests that these organismsshared analogous or nearby environ-mental settings and colonized similarsubstrates. Furthermore, the presenceof an ichnofossil identified as Archae-onassa preserved among in situ Clou-dina specimens shows that soft-bodiedorganisms inhabited the same envi-ronment. These observations suggestthat at least locally there were noecological barriers impeding theco-occurrence of organic substrate,benthic microbial communities andsoft-bodied and shelly organismswithin the same environment. Hence,the lack of similar fossil assemblagesin the palaeontological record maypossibly reflect sedimentological ortaphonomical biases.The assemblage reported here sig-

nificantly extends the geographicalrange of the Cloudina–Corumbellaassociation in South America, indicat-ing that Corumbella is more commonin the Cloudina biozone in westernGondwana than previously registered.Thus, the Itapucumi assemblage rep-resents a potential landmark in SouthAmerican palaeontology that prom-ises to provide important new per-spectives on late Ediacaranpalaeoecology.

Acknowledgements

The authors thank the Viceministerio deMinas y Energıa de Paraguay and Indus-tria Nacional del Cemento (INC) forlogistic support in the field; and IGCP –

Terra Nova, Vol 23, No. 6, 382–389 L. V. Warren et al. • Corumbella and In situ Cloudina in South America

.............................................................................................................................................................

� 2011 Blackwell Publishing Ltd 387

478 �Neoproterozoic-Early Events in SWGondwana�, CNPq PROSUL (project490234/2005-4), CAPES and FAPESP(projects 2004/01233-0, 2010/02677-0,2010/19584-4) for financial support.

References

Amthor, J.E., Grotzinger, J.P., Schroder,S., Bowring, S.A., Ramezani, J., Martin,M.W. and Matter, A., 2003. Extinctionof Cloudina and Namacalathus at thePrecambrian-Cambrian boundary inOman. Geology, 31, 431–434.

Babcock, L.E., Grunow, A.M., Sadowski,G.R. and Leslie, S.A., 2005. Corumbella,an Ediacaran-grade organism fromthe Late Neoproterozoic of Brazil.Palageogr. Palaeoclimat. Palaeoecol.,220, 7–18.

Babinski, M., Boggiani, P.C., Fanning,C.M., Fairchild, T.R., Simon, C.M. andSial, A.N., 2008. U-PB SHRIMP geo-chronology and isotope chemostratigra-phy (C, O, Sr) of the TamengoFormation, Southern Paraguay Belt,Brazil. In: VI South American Sympo-sium on Isotope Geology, 160 pp. SanCarlos de Bariloche, Abstracts.

Bengtson, S., 2002. Origins and early evo-lution of predation. Paleont. Soc. Pap.,8, 289–317.

Beurlen, K. and Sommer, F.W., 1957.Observacoes estratigraficas e paleontol-ogicas sobre o Calcario Corumba.DNPM, Boletim da Divisao de Geologia eMineralogia, 168, 1–35.

Boggiani, P.C., 1998. Analise Estratigraficada Bacia Corumba (Neoproterozoico) –Mato Grosso do Sul. Unpublished Doc-toral dissertation, University of SaoPaulo, Sao Paulo, Brazil, 181 pp.

Boggiani, P.C. and Gaucher, C., 2004.Cloudina from the Itapucumi Group(Vendian, Paraguay): age andcorrelations. In: 1st Symposium onNeoproterozoic – Early Paleozoic Eventsin SW-Gondwana, pp. 13–15. Sao Paulo-Brazil, Abstracts.

Boggiani, P.C., Gaucher, C., Sial, A.N.,Babinski, M., Simona, C.M., Riccomini,C., Ferreira, V.P. and Fairchild, T.R.,2010. Chemostratigraphy of theTamengo Formation (Corumba Group,Brazil): a contribution to the calibrationof the Ediacaran carbon-isotope curve.Prec. Res., 182, 382–401.

Brasier, M., McCarron, G., Tucker, R.,Leather, J., Allen, P. and Shields, G.,2000. New U-Pb zircon dates for theNeoproterozoic Ghubrah glaciation andfor the top of the Huqf Supergroup,Oman. Geology, 28, 175–178.

Campanha, G.A.C., Warren, L.V., Boggi-ani, P.C., Grohmann, C.H. and Caceres,A.A., 2010. Structural analysis of theItapucumı Group in the Vallemı region,northern Paraguay: evidence of a new

Brasiliano ⁄Pan-African mobile belt.J. S. Am. Earth Sci, 30, 1–11.

Conway-Morris, S., Mattes, B.W. andMenge, C., 1990. The early skeletalorganism Cloudina: new occurrencesfrom Oman and possibly China. Am.J. Sci., 290, 245–260.

Cortijo, I., Martı Mus, M., Jensen, S. andPalacios, T., 2010. A new species ofCloudina from the terminal Ediacaran ofSpain. Prec. Res., 176, 1–10.

Fedonkin, M.A., 1980. Novye predstavitelidokembriyskikh kishechnopolostnykhna severe Russkoy platformy (NewPrecambrian Coelenterata in the northof Russian platform). Paleont. Zhurnal,2, 7–15.

Gaucher, C., 2000. Sedimentology,palaeontology and stratigraphy ofthe Arroyo del Soldado Group(Vendian to Cambrian, Uruguay).Beringeria, 26, 1–120.

Gaucher, C. and Sprechmann, P., 1999.Upper Vendian skeletal fauna of theArroyo del Soldado Group, Uruguay.Beringeria, 23, 55–91.

Gaucher, C., Boggiani, P.C., Sprechmann,P., Sial, A.N. and Fairchild, T., 2003.Integrated correlation of the Vendian toCambrian Arroyo del Soldado and Co-rumba Groups (Uruguay and Brazil):palaeogeographic, palaeoclimatic andpalaeobiologic implications. Prec. Res.,120, 241–278.

Gaucher, C., Poire, D.G., Gomez Peral, L.and Chiglino, L., 2005. Litoestratigrafıa,bioestratigrafıa y correlaciones de lassucesiones sedimentarias del Neoproter-ozoico-Cambrico del Craton del Rio dela Plata (Uruguay y Argentina). Lat.Am. J. S. Basin. Ana., 12, 145–160.

Germs, G.J.B., 1972. New shelly fossilsfrom Nama Group, South West Africa.Am. J. Sci., 272, 752–761.

Grant, S.W.F., 1990. Shell structure anddistribution of Cloudina, a potential in-dex fossil for the terminal Proterozoic.Am. J. Sci., 290, 261–294.

Grazhdankin, D. and Gerdes, G., 2000.Ediacaran microbial colonies. Lethaia,40, 201–210.

Grey, K., Walter, M.R. and Calver, C.R.,2003. Neoproterozoic biotic diversifica-tion: Snowball Earth or aftermath of theAcraman impact? Geology, 31, 459–462.

Grotzinger, J.P., Bowring, S.A., Saylor,B.Z. and Kaufman, A.J., 1995.Biostratigraphic and geochronologicconstraints on early animal evolution.Science, 270, 598–604.

Grotzinger, J.P., Watters, W.A. and Knoll,A.H., 2000. Calcified metazoans inthrombolite stromatolite reefs of theterminal Proterozoic Nama Group,Namibia. Paleobiol., 26, 334–359.

Hagadorn, J.W. and Waggoner, B., 2000.Ediacaran fossils from the southwestern

Great Basin, United States. J. Paleont.,74, 349–359.

Hahn, G., Hahn, R., Leonardos, O.H.,Pflug, H.D. and Walde, D.H.G., 1982.Korperlich erhaltene Scyphozoen-Re-ste aus dem Jungprakambrium Brasil-iens. Geol. et Paleont. [Marburg], 16,1–18.

Harrington, H.J., 1950. Geologıa del Par-aguay Oriental. Facultad de CienciasExactas, Fisicas y Naturales de la Uni-versidad de Buenos Aires, Contribuici-ones Cientıficas, Buenos Aires.

Hoffman, P.F., 1999. The break-up ofRodinia, birth of Gondwana, true polarwander and the snowball Earth. J. Afr.Earth Sci., 28, 17–33.

Hoffman, P.F. and Schrag, D.P., 2002. Thesnowball Earth hypothesis: testing thelimits of global change. Terra Nova, 14,129–155.

Hoffman, P.F., Kaufman, A.J., Halverson,G.P. and Schrag, D.P., 1998. A Neo-proterozoic snowball earth. Science, 281,1342–1346.

Hofmann, H.J. and Mountjoy, E.W., 2001.Namacalathus-Cloudina assemblage inNeoproterozoic Miette Group (ByngFormation), British Columbia: Canada�soldest shelly fossils. Geology, 29, 1091–1094.

Hua, H., Zhe, C. and Xunlay, Y., 2007.The advent of mineralized skeletons inNeoproterozoic Metazoa – new fossilevidence from the Gaojiashan Fauna.Geol. J., 42, 263–279.

Jensen, S., 2003. The Proterozoic andearliest Cambrian trace fossil record;patterns, problems and perspectives.Integr. Comp. Biol., 43, 219–228.

Knoll, A.H. and Bambach, R.K., 2000.Directionality in the history of life:diffusion from the left wall or repeatedscaling of the right? Paleobiol., 26, 1–14.

Knoll, A.H. and Carroll, S.B., 1999. Earlyanimal evolution: emerging views fromcomparative biology and geology. Sci-ence, 284, 2129–2137.

Kontorovich, A.E., Varlamov, A.I.,Grazhdankin, D.V., Karlova, G.A.,Klets, A.G., Kontorovich, V.A., Saraev,S.V., Terleev, A.A., Belyaev, S.Y., Va-raksina, I.V., Efimov, A.S., Kochnev,B.B., Nagovitsin, K.E., Postnikov, A.A.and Filippov, Y.F., 2008. A section ofVendian in the east of West SiberianPlate (based on data from the BoreholeVostok 3). Rus. Geol. Geophy., 49, 932–939.

Li, Z.X., Bogdanova, S.V., Collins, A.S.,Davidson, A., De Waele, B., Ernst, R.E.,Fitzsimons, I.C.W., Fuck, R.A., Glad-kochub, D.P., Jacobs, J., Karlstrom,K.E., Lu, S., Natapov, L.M., Pease, V.,Pisarevsky, S.A., Thrane, K. and Verni-kovsky, V., 2008. Assembly, configura-tion, and break-up history of Rodinia:

Corumbella and In situ Cloudina in South America • L. V. Warren et al. Terra Nova, Vol 23, No. 6, 382–389

.............................................................................................................................................................

388 � 2011 Blackwell Publishing Ltd

a synthesis. Precambrian Res., 160, 179–210.

Narbonne, G.M. and Gehling, J.G., 2003.Life after snowball: the oldest complexEdiacaran fossils. Geology, 31, 27–30.

Noffke, N., Gerdes, G., Klenke, T. andKrumbein, W.E., 1996. Microbially in-duced sedimentary structures – examplesfrom modern sediments of siliciclastictidal flats. Zbl. Geol. Palaontol., I, 1995,307–316.

Oliveira, R.S., 2010. Depositos de RampaCarbonatica Ediacarana do Grupo Co-rumba, Regiao de Corumba, Mato Grossodo Sul. Unpublished Master�s thesis,Para Federal University, Belem, Brazil,88 pp.

Peral, L.E.G., Poire, G.D., Strauss, H. andZimmermann, U., 2007. Chemostrati-graphy and diagenetic constraints onNeoproterozoic carbonate successionsfrom the Sierras Bayas Group, TandiliaSystem, Argentina. Chem. Geol., 237,109–128.

Valentine, J.W., 1995. Late Precambrianbilaterians: grades and clades. In: Tempo

and Mode in Evolution: Genetics andPaleontology 50 Years After Simpson(W.M. Fitch and F.J. Ayala, eds),pp. 87–107. National Academy Press,Washington.

Warren, L.W., 2011. Tectonica e Sedimen-tacao do Grupo Itapucumi (Ediacarano,Paraguay Setentrional). UnpublishedDoctoral dissertation, University of SaoPaulo, Brazil, 215 pp.

Wood, R.W., 2011. Paleoecology of theearliest skeletal metazoan communities:implications for early biomineralization.Earth Sci. Rev., 106, 184–190.

Wood, R.A., Grotzinger, J.P. and Dickson,J.A.D., 2002. Proterozoic modular bio-mineralized metazoan from the NamaGroup, Namibia. Science, 296, 2383–2386.

Yochelson, E. and Fedonkin, M.A., 1997.The type specimens (Middle Cambrian)of the trace fossil Archaeonassa Fentonand Fenton. Can. J. Earth Sci., 34, 1210–1219.

Zaine, M.F., 1991. Analise dos Fosseis deParte da Faixa Paraguai (MS, MT) e

seu Contexto Temporal e Paleoambiental.Unpublished Doctoral dissertation,University of Sao Paulo, Sao Paulo,Brazil, 218 pp.

Zaine, M.F. and Fairchild, T.R., 1985.Comparison of Aulophycus lucianoiBeurlen & Sommer from Ladario (MS)and the genus Cloudina Germs, Ediaca-ran of Namibia. An. da Aca.Bras. deCien., 57, 130.

Zaine, M.F. and Fairchild, T.R., 1987.Novas consideracoes sobre os fosseis daFormacao Tamengo, Grupo Corumba,SW Brasil. In: Cong. Bras. Paleo., 10Anais, v.2, pp. 797–807. SociedadeBrasileira de Paleontologia, Rio deJaneiro, RJ.

Zhou, C. and Xiao, S., 2007. Ediacarand13C chemostratigraphy of SouthChina. Chem.Geol., 237, 89–108.

Received 1 March 2011; revised versionaccepted 11 August 2011

Terra Nova, Vol 23, No. 6, 382–389 L. V. Warren et al. • Corumbella and In situ Cloudina in South America

.............................................................................................................................................................

� 2011 Blackwell Publishing Ltd 389