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  • 1. Betts, Marissa, J.
    et al.
    Paterson, John, R.
    Jacquet, Sarah, M.
    Andrew, Anita S.
    Hall, Philip A.
    Jago, James, B.
    Jagodzinski, Elisabeth A.
    Preiss, Wolfgang V.
    Crowley, James L.
    Brougham, Tom
    Mathewson, Ciaran P.
    Garcia-Bellido, Diego C.
    Topper, Timothy, P.
    Skovsted, Christian
    Swedish Museum of Natural History, Department of Paleobiology.
    Brock, Glenn, A.
    Early Cambrian chronostratigraphy and geochronology of South Australia2018In: Earth-Science Reviews, ISSN 0012-8252, E-ISSN 1872-6828, Vol. 185, p. 498-543Article in journal (Refereed)
    Abstract [en]

    The most successful chronostratigraphic correlation methods enlist multiple proxies such as biostratigraphy and chemostratigraphy to constrain the timing of globally important bio- and geo-events. Here we present the first regional, high-resolution shelly fossil biostratigraphy integrated with δ13C chemostratigraphy (and corresponding δ18O data) from the traditional lower Cambrian (Terreneuvian and provisional Cambrian Series 2) of South Australia. The global ZHUCE, SHICE, positive excursions II and III and the CARE are captured in lower Cambrian successions from the Arrowie and Stansbury basins. The South Australian shelly fossil biostratigraphy has a consistent relationship with the δ13C results, bolstering interpretation, identification and correlation of the excursions. Positive excursion II straddles the boundary between the Kulparina rostrata and Micrina etheridgei zones, and the CARE straddles the boundary between the M. etheridgei and Dailyatia odyssei zones, peaking in the lower parts of the latter zone. New CA-TIMS zircon dates from the upper Hawker Group and Billy Creek Formation provide geochronologic calibration points for the upper D. odyssei Zone and corresponding chemostratigraphic curve, embedding the lower Cambrian successions from South Australia into a global chronostratigraphic context. This multi-proxy investigation demonstrates the power of integrated methods for developing regional biostratigraphic schemes and facilitating robust global correlation of lower Cambrian successions from South Australia (part of East Gondwana) with coeval terranes on other Cambrian palaeocontinents, including South and North China, Siberia, Laurentia, Avalonia and West Gondwana.

  • 2. Betts, Marissa, J.
    et al.
    Paterson, John, R.
    Jago, James, B.
    Jacquet, Sarah, M.
    Skovsted, Christian
    Swedish Museum of Natural History, Department of Paleobiology.
    Topper, Timothy, P.
    Brock, Glenn, A.
    A new lower Cambrian shelly fossil biostratigraphy for South Australia2016In: Gondwana Research, ISSN 1342-937X, E-ISSN 1878-0571, Vol. 36, p. 163-195Article in journal (Refereed)
    Abstract [en]

    Definition of early Cambrian chronostratigraphic boundaries is problematic with many subdivisions stillawaiting ratification. Integrated multi-proxy data from well-resolved regional-scale schemes are ultimately the key to resolving broader issues of global correlationwithin the Cambrian. In Australia, early Cambrian biostratigraphy has been based predominantly on trilobites. Phosphatic shelly fauna have great potential as biostratigraphic tools, especially in pre-trilobitic strata because they are widespread and readily preserved, but they have remained underutilised. Here we demonstrate their value in a new biostratigraphic scheme for the early Cambrian of South Australia using a diverse shelly fauna including tommotiids, brachiopods, molluscs and bradoriids. Biostratigraphic data are derived from ten measured stratigraphic sections across the Arrowie Basin, targeting Hawker Group carbonates including the Wilkawillina, Wirrapowie and Ajax limestones and the Mernmerna Formation. The stratigraphic ranges of shelly fossils are predictable and repeatable across the Arrowie Basin, allowing three discrete shelly biozones to be identified, spanning Terreneuvian, Stage 2 to Series 2, Stages 3–4. The Kulparina rostrata Zone (new) and part of the overlyingMicrina etheridgei Zone (new) are pre-trilobitic (predominantly Terreneuvian). The Cambrian Series 2, Stage 3 Dailyatia odyssei Zone (new) features a very diverse shelly fauna and will be described in detail in a separate publication. These zones provide robust means to correlate Terreneuvian–Series 2 successions in neighbouring coeval basins in Australia, particularly the Stansbury Basin. Wider correlation is possible throughout East Gondwana, and especially with South China.

  • 3. Betts, Marissa, J.
    et al.
    Paterson, John, R.
    Jago, James, B.
    Jacquet, Sarah, M.
    Skovsted, Christian
    Swedish Museum of Natural History, Department of Paleobiology.
    Topper, Timothy, P.
    Brock, Glenn, A.
    A new lower Cambrian shelly fossil biostratigraphy for South Australia:Reply2017In: Gondwana Research, ISSN 1342-937X, E-ISSN 1878-0571, Vol. 44, p. 262-264Article in journal (Refereed)
  • 4.
    Betts, Marissa, J.
    et al.
    Department of Biological Sciences, Macquarie University, Sydney, 2109, Australia.
    Paterson, John, R.
    Palaeoscience Research Centre, School of Environmental and Rural Science, University of New England, Armidale, New South Wales 2351, Australia.
    Jago, James, B.
    School of Natural and Built Environments, University of South Australia, Mawson Lakes, South Australia 5095, Australia.
    Jacquet, Sarah, M.
    Department of Biological Sciences, Macquarie University, Sydney, 2109, Australia.
    Skovsted, Christian
    Swedish Museum of Natural History, Department of Paleobiology.
    Topper, Timothy, P.
    Palaeoecosystems Group, Department of Earth Sciences, Durham University, Durham, DH1 3LE, UK.
    Brock, Glenn, A.
    Department of Biological Sciences, Macquarie University, Sydney, 2109, Australia.
    Global correlation of the early Cambrian of South Australia: Shelly faunaof the Dailyatia odyssei Zone2017In: Gondwana Research, ISSN 1342-937X, E-ISSN 1878-0571, Vol. 46, p. 240-279Article in journal (Refereed)
    Abstract [en]

    A lack of well resolved biostratigraphic data has prevented robust regional and global correlation of lower Cambriansuccessions from South Australia. A new early Cambrian biostratigraphy, based on data derived from 21measured stratigraphic sections and drill cores (11 described herein) reveals the abundance and diversity ofshelly fauna from the Arrowie Basin, and the value of early Cambrian “small shelly fossils” (SSF) for biostratigraphicstudies. Here we examine shelly fauna associated with the youngest of three recently establishedbiozones, the Dailyatia odyssei Taxon Range Zone (hereafter D. odyssei Zone), and their correlative potential.The D. odyssei Zone features a diverse suite of tommotiids, organophosphatic brachiopods, bradoriid arthropods,molluscs and phosphatic problematica. This fauna permits strong correlation (often at species-level) with othermajor early Cambrian terranes, particularly Antarctica, South China and Laurentia, and suggest a Cambrian Series2, Stages 3–4 age for the D. odyssei Zone. Bradoriids have proven to be useful biostratigraphic tools. Four newspeciesand three new genera are described herein: Acutobalteus sinuosus gen. et sp. nov., Eozhexiella adnyamathanha gen. etsp. nov., Manawarra jonesi gen. et sp. nov. and Mongolitubulus descensus sp. nov. The description of Eohadrotreta sp.cf. zhenbaensis represents the first occurrence of the acrotretoid brachiopod Eohadrotreta from Australia.

  • 5.
    Betts, Marissa J.
    et al.
    Macquarie University, Sydney, Australia.
    Topper, Timothy P.
    Geological Museum, Copenhagen.
    Valentine, James L.
    Macquarie University, Sydney, Australia.
    Skovsted, Christian
    Swedish Museum of Natural History, Department of Paleobiology.
    Brock, Glenn A.
    Macquarie university, Australia.
    A new early Cambrian bradoriid (Arthropoda) assemblage from the northern Flinders Ranges, South Australia2014In: Gondwana Research, ISSN 1342-937X, E-ISSN 1878-0571, Vol. 25, p. 420-437Article in journal (Refereed)
    Abstract [en]

    A new assemblage of early Cambrian bivalved arthropods (Bradoriida) is described from the Arrowie Syncline in the northern Flinders Ranges, South Australia. The well preserved, largely endemic fauna comprises a total of six taxa (including five new species): Jiucunella phaseloa sp. nov., Jixinlingella daimonikoa sp. nov., Mongolitubulus anthelios sp. nov., Neokunmingella moroensis sp. nov., Phasoia cf. spicata ( Öpik, 1968), and Sinskolutella cuspidata sp. nov. This assemblage is derived from a carbonate sedimentary package representing a high energy, shallow water archaeocyath-Renalcis biohermal facies of Terreneuvian, Stage 2 age which transitions up-section to a more restricted, low energy, intra-shelf lagoonal environment that correlates with a Cambrian Series 2, Stage 3 age. The new taxon J. phaseloa sp. nov., has a first appearance datum (FAD) in shallow water biohermal facies of the Hideaway Well Member of the Wilkawillina Limestone at a level 47 m below the FAD of Pelagiella subangulata which is taken to approximate the base of Series 2, Stage 3 in South Australia. Along with Liangshanella circumbolina, this makes J. phaseloa sp. nov. amongst the oldest bivalved arthropods in South Australia and potentially greater Gondwana. The presence of 25 bradoriid taxa from the early Cambrian of South Australia suggests East Gondwana represents a major centre of origin for the Bradoriida.

  • 6. Bicknell, Russell D.C.
    et al.
    Paterson, John, R.
    Caron, Jean-Bernhard
    Skovsted, Christian
    Swedish Museum of Natural History, Department of Paleobiology.
    The gnathobasic spine microstructure of recent and Silurian chelicerates and the Cambrian artiopodan Sidneyia: Functional and evolutionary implications2018In: Arthropod structure & development, ISSN 1467-8039, E-ISSN 1873-5495, Vol. 47, p. 12-24Article in journal (Refereed)
    Abstract [en]

    Gnathobasic spines are located on the protopodal segments of the appendages of various euarthropod taxa, notably chelicerates. Although they are used to crush shells and masticate soft food items, the microstructure of these spines are relatively poorly known in both extant and extinct forms. Here we compare the gnathobasic spine microstructures of the Silurian eurypterid Eurypterus tetragonophthalmus from Estonia and the Cambrian artiopodan Sidneyia inexpectans from Canada with those of the Recent xiphosuran chelicerate Limulus polyphemus to infer potential variations in functional morphology through time. The thickened fibrous exocuticle in L. polyphemus spine tips enables effective prey mastication and shell crushing, while also reducing pressure on nerve endings that fill the spine cavities. The spine cuticle of E. tetragonophthalmus has a laminate structure and lacks the fibrous layers seen in L. polyphemus spines, suggesting that E. tetragonophthalmus may not have been capable of crushing thick shells, but a durophagous habit cannot be precluded. Conversely, the cuticle of S. inexpectans spines has asimilar fibrous microstructure to L. polyphemus, suggesting that S. inexpectans was a competent shell crusher. This conclusion is consistent with specimens showing preserved gut contents containing various shelly fragments. The shape and arrangement of the gnathobasic spines is similar for both L. polyphemusand S. inexpectans, with stouter spines in the posterior cephalothoracic or trunk appendages, respectively.This differentiation indicates that crushing occurs posteriorly, while the gnathobases on anterior appendages continue mastication and push food towards and into the mouth. The results of recent phylogenetic analyses that considered both modern and fossil euarthropod clades show that xiphosurans and eurypterids are united as crown-group euchelicerates, with S. inexpectans placed within more basalartiopodan clades. These relationships suggest that gnathobases with thickened fibrous exocuticle, if not homoplasious, may be plesiomorphic for chelicerates and deeper relatives within Arachnomorpha. This study shows that the gnathobasic spine microstructure best adapted for durophagy has remained remarkably constant since the Cambrian.

  • 7. Devaere, Lea
    et al.
    Skovsted, Christian
    Swedish Museum of Natural History, Department of Paleobiology.
    New early Cambrian sclerites of Lapworthella schodakensis from NE Greenland: advancements in knowledge of lapworthellid taxonomy, sclerite growth and scleritome organization2017In: Geological Magazine, ISSN 0016-7568, E-ISSN 1469-5081, Vol. 154, no 5, p. 1061-1072Article in journal (Refereed)
    Abstract [en]

    The Cambrian Stage 4 upper Bastion Formation of Albert Heim Bjerge and CH Ostenfeld Nunatak, NE Greenland, yielded 34 excellently preserved sclerites of Lapworthella schodackensis among other small shelly fossils. Lapworthellids have been interpreted as members of the camenellans,a basal tommotiid group. Little is known about this group although the morphological andultrastructural features of their sclerites allow a potential reconstruction of a lophophorate body plan.The exquisite material from Greenland provides significant new data for the revision of the species taxonomy, but also for the comprehension of the scleritome structure of lapworthellids and the modeof formation of their sclerites. Two morphotypes of L. schodackensis sclerites are identified: one with asimple apex, occurring in sinistral and dextral forms; and one bilaterally symmetrical sclerite with twoapices. All bear a similar ornamentation constructed of repeated growth sets consisting of a reticulate inter-rib groove with tubercles, a densely denticulate rib and a striated sub-rib area. The new data onthe ornamentation and observations of the laminar shell microstructure of L. schodackensis enable us to improve the reconstruction of growth in lapworthellids. Finally, the morphological features of the two types of sclerites provide new information for the reconstruction of the bilaterally symmetrical multi-component lapworthellid scleritome with evidence of the fusion of adjacent sclerites duringearly ontogeny.

  • 8. Jacquet, Sarah, M.
    et al.
    Brougham, Thomas
    Skovsted, Christian
    Swedish Museum of Natural History, Department of Paleobiology.
    Jago, James, B.
    Laurie, John, R.
    Betts, Marissa, J.
    Topper, Timothy, P.
    Brock, Glenn, A.
    Watsonella crosbyi from the lower Cambrian (Terreneuvian, Stage 2) Normanville Group in South Australia2016In: Geological Magazine, ISSN 0016-7568, E-ISSN 1469-5081, p. 1-17Article in journal (Refereed)
    Abstract [en]

    Correlation of lower Cambrian strata is often confounded by provincialism of key fauna. The widespread occurrence of themicromollusc Watsonella crosbyi Grabau, 1900 is therefore an important biostratigraphic signpost with potential for international correlation of lower Cambrian successions. Previous correlations of W. crosbyi from Australia (Normanville Group) suggested an Atdabanian- to Botoman-equivalent age. However, in the upper part of the Mount Terrible Formation, stratigraphic ranges of W. crosbyi and Aldanella sp. cf. golubevi overlap prior to the incoming of vertically burrowed ‘piperock’, which is indicative of an age no earlier than Cambrian Stage 2. The stratigraphic range of W. crosbyi in the Normanville Group, South Australia correlates with the ranges of the taxon in China, France, Mongolia and Siberia (though not Newfoundland). The new Australian data add further support for considering the first occurrence of W. crosbyi a good potential candidate for defining the base of Cambrian Stage 2. The stratigraphic range of W. crosbyi through the lower Cambrian Normanville Group has been determined based on collections from measured sections. Although rare, W. crosbyi is part of an assemblage of micromolluscs including Bemella sp., Parailsanella sp. cf. murenica and a sinistral form of Aldanella (A. sp. cf. A. golubevi). Other fauna present include Australohalkieria sp., Eremactis mawsoni, chancelloriids and Cupitheca sp.

  • 9. Knight, Ian
    Skovsted, Christian
    Swedish Museum of Natural History, Department of Paleobiology.
    Balthasar, Uwe
    The Lower Cambrian Forteau Formation, southern Labrador and Great Northern Peninsula, western Newfoundland: Lithostratigraphy, trilobites, and depositional setting.2017Report (Other academic)
    Abstract [en]

    The upper Lower Cambrian Forteau Formation in southern Labrador and the Great Northern Peninsula (GNP) is a successionof shale, limestone, siltstone and sandstone accommodated by rising sea levels during the early drift stages ofNewfoundland’s Laurentian passive margin. Its Dyeran trilobite fauna, characterized by Elliptocephala logani (Walcott, 1910)that ranges throughout the formation, indicates it was mostly deposited in the middle Bonnia‒Olenellus Zone. Its three lithostratigraphicdivisions, the Devils Cove member, Middle shale and Upper limestone, preserve a transgressive system tract(TST; Devils Cove and lower part of the Middle shale) and the early stages of a regressive high-stand system tract (HST; upper Middle shale and Upper limestone) that hosts a carbonate ramp shelf.A mudstone-dominated succession characterizes the TST, comprised of an inner belt of archeocyathid patch reef andcyclic, well-stratified, fine-grained mixed clastic and carbonate shelf rocks in southern Labrador. To the southeast on the GNP,the shale succession along with minor limestone and no reefs suggests a deeper water shelf basin in which shale accumulated across the GNP. Maximum flooding on the GNP is linked to dark shale midway through the basinal succession, and to athick shale bed that overlies the reefal strata in Labrador.Thin-bedded siltstone, sandstone and limestone in Labrador, and extensively bioturbated siltstone, sandstone and rare limestone on the GNP, support a shelf shallowing above storm-wave base as it prograded during the early stages of regression. Shallow-water carbonate of the Upper limestone supports a prograding shelf, at first dominated by an archeocyathid reefal tract and oolitic shoal complex. The reef tract and carbonate sand shoal complex prograded southeastward to justbeyond the northeast-trending Ten Mile Lake–Long Range fault system. Evidence of slumping in the underlying fine clastic sediment in the same area suggest that this fault zone may coincide with a hinge zone, beyond which the shelf steepened intomostly deep-water clastic sedimentation. The archeocyathid tract in southern Labrador is a broad biostromal complex confined within an erosional recess in the shelf. On the GNP, however, the tract is characterized by high-energy bioherms associated with crossbedded grainstone channels that can be traced for over 60 km along a northeast strike length. East of the reef tract‒shoal complex, the succession appears to be dominated by deeper water shelf mudrock, nodular carbonate and little evidence of shallow-water carbonate facies. The facies transition suggests the Forteau Formation insouthern Labrador and the GNP was laid down in a high-energy shallow-water, inner ramp setting that was up to 75 km wide. Above the carbonate sand shoal complex, the succession is marked by decametre-thick parasequences of intercalated carbonateand clastic intervals. The sequences support a shelf of fine grained to grainy carbonate deposited on an open shelframp overlain by intervals dominated by coarsening upward high-energy siliciclastics that suggest barrier complexes alongthe landward margin of the ramp. Thick units of crossbedded quartz arenite, in the upper half of the Upper limestone, suggest terrigenous sediments initially encroached along the inner part of the shelf, and eventually smothered the Forteau shelf leading to the low-stand deposits of the overlying Hawke Bay Formation. Trilobites recovered from this transition throughout the GNP, indicate that it occurred very late in the upper part of the Bonnia‒Olenellus Zone, likely between the Bristolia mohavensis Biozone and the top of the zone.

  • 10.
    Kouchinsky, Artem
    et al.
    Swedish Museum of Natural History, Department of Paleobiology.
    Bengtson, Stefan
    Swedish Museum of Natural History, Department of Paleobiology.
    Runnegar, Bruce
    Skovsted, Christian
    Swedish Museum of Natural History, Department of Paleobiology.
    Steiner, Michael
    Vendrasco, Michael
    Chronology of early Cambrian biomineralization.2012In: Geological Magazine, ISSN 0016-7568, Vol. 149, no 2, p. 221-251Article in journal (Refereed)
    Abstract [en]

    Data on the first appearances of major animal groups with mineralized skeletons on the Siberian Platform and worldwide are revised and summarized herein with references to an improved carbon isotope stratigraphy and radiometric dating in order to reconstruct the Cambrian radiation (popularly known as the ‘Cambrian explosion’) with a higher precision and provide a basis for the definition of Cambrian Stages 2 to 4. The Lophotrochozoa and, probably, Chaetognatha were first among protostomians to achieve biomineralization during the Terreneuvian Epoch, mainly the Fortunian Age. Fast evolutionary radiation within the Lophotrochozoa was followed by radiation of the sclerotized and biomineralized Ecdysozoa during Stage 3. The first mineralized skeletons of the Deuterostomia, represented by echinoderms, appeared in the middle of Cambrian Stage 3. The fossil record of sponges and cnidarians suggests that they acquired biomineralized skeletons in the late Neoproterozoic, but diversification of both definite sponges and cnidarians was in parallel to that of bilaterians. The distribution of calcium carbonate skeletal mineralogies from the upper Ediacaran to lower Cambrian reflects fluctuations in the global ocean chemistry and shows that the Cambrian radiation occurred mainly during a time of aragonite and high-magnesium calcite seas.

  • 11.
    Larsson, Cecilia M.
    et al.
    Uppsala Universitet.
    Skovsted, Christian
    Swedish Museum of Natural History, Department of Paleobiology.
    Brock, Glenn A.
    Macquarie University, Sydney, Australia.
    Balthasar, Uwe
    University of Glasgow.
    Topper, Timothy P.
    Geological Museum, Copenhagen.
    Holmer, Lars E.
    Uppsala Universitet.
    Paterimitra pyramidalis from South Australia: scleritome, shell structure and evolution of a Lower Cambrian Ssten group brachiopod2014In: Palaeontology, ISSN 0031-0239, E-ISSN 1475-4983, Vol. 57, no 2, p. 417-446Article in journal (Refereed)
    Abstract [en]

    The tommotiid Paterimitra pyramidalis Laurie, 1986, is redescribed based on well-preserved material from the lower Cambrian Wilkawillina, Wirrapowie and Ajax limestones of the Flinders Ranges, South Australia. The material shows that the scleritome of Paterimitra pyramidalis includes three sclerite morphotypes (S1, S2 and L). Detailed shell microstructure studies show striking similarities with both the paterinid brachiopod Askepasma toddense and the tommotiid Eccentrotheca helenia, which strengthens the suggested evolutionary link between tommotiids and brachiopods. Based on the partly articulated specimens and similarities in shell microstructure and sclerite morphology with Eccentrotheca, Paterimitra pyramidalis is reconstructed as a tube-dwelling, epifaunal, sessile, filter-feeder with an organic pedicle-like attachment structure. The proposed reconstruction of the scleritome comprises a basal unit composed of one S1 and one S2 sclerite, as well as an unresolved number of L sclerites lining a coniform tubular structure.

  • 12. Luo, Q.
    Skovsted, Christian
    Swedish Museum of Natural History, Department of Paleobiology.
    Xu, Y.
    Liu, Y.
    Wu, J.
    Zhang, S.
    Wang, W.
    Zhong, N.
    Optical characteristics of graptolite-bearing sediments and its implication for thermal maturity assessment2018In: International Journal of Coal Geology, ISSN 0166-5162, E-ISSN 1872-7840, Vol. 195, p. 386-401Article in journal (Refereed)
    Abstract [en]

    Graptolite reflectance was thought to be one of the most useful thermal maturity indicators for graptolite bearing sediments, however, the relationship between graptolite reflectance and vitrinite reflectance is not well established. Graptolites, especially in the Wufeng–Longmaxi Formations from the Ordovician to Silurian of SouthChina, have been mistaken for vitrinite-like particles or solid bitumen, which results in inconsistent data on the thermal maturity. In this paper, we have employed optical microscope techniques to describe the detailed optical characteristics of graptolites and solid bitumen in the Wufeng–Longmaxi Formations. Laboratory simulation ofmaturation was used to determine the relationship between graptolite reflectance and vitrinite reflectance. The organic constituents in the Wufeng–Longmaxi Formations are mainly composed of graptolites and solid bitumen. Granular and non-granular graptolites were observed in the Wufeng–Longmaxi Formations, with nongranular as the most common texture. Solid bitumen can be distinguished from non-granular graptolites by its coarse surface, weaker anisotropy, and lower random reflectance. The combination of non-polarized and polarized light is very helpful to distinguish solid bitumen from graptolite. For comparison, organic material from the early Ordovician Alum Shale Formation of Sweden and Estonia was also studied. The macerals of the Alum shales are mainly composed of lamalginites, mineral-bituminous groundmasses, graptolites, and solid bitumen.The major textures of the graptolites in the Sweden and Estonia sediments are non-granular and granular, respectively.Both non-granular graptolite and vitrinite reflectances display a systematic increase with the increase of heating temperature and time. The granular graptolites in the Estonian sample were gradually changed to nongranular graptolites following laboratory simulated maturation, indicating that granular graptolites can transform into non-granular graptolites with maturation. Solid bitumen in the Wufeng–Longmaxi Formations was derived from the solid residue of kerogen and/or post-oil bitumen. The graptolite random reflectance is a better thermal maturity indicator than graptolite maximum reflectance and is more precise due to the smaller standard deviation. Several equations are proposed to determine the thermal maturity of the graptolite-bearing sediments based on graptolite random reflectance, graptolite maximum reflectance and solid bitumen random reflectance.

  • 13. Luo, Qingyong
    Skovsted, Christian
    Swedish Museum of Natural History, Department of Paleobiology.
    Luo, Peng
    Khan, Imran
    Wu, Jin
    Zhong, Ningning
    The organic petrology of graptolites and maturity assessment of the Wufeng–Longmaxi Formations from Chongqing, China: Insights from reflectance cross-plot analysis2017In: International Journal of Coal Geology, ISSN 0166-5162, E-ISSN 1872-7840, Vol. 183, p. 161-173Article in journal (Refereed)
    Abstract [en]

    The Wufeng–Longmaxi Formations (Ordovician-Silurian) contain abundant graptolite-bearing shales, which have proven to be one of the most successful shale gas exploration targets in China and can provide an opportunity to study the organic petrology of graptolites. Organic petrology analysis has been conducted on these organic-rich shales in order to depict the shape of graptolite reflectance indicating surface (GRIS) and their organic maturity. Granular and non-granular graptolites have been observed in the studied sediments, and nongranular graptolites were the major graptolite species. The strong positive correlation between the maximum reflectance (Rmax) and bireflectance of graptolites indicates that the graptolites display stronger anisotropy with maturation. A linear coalification path of graptolite fragments was observed in the studied sediments. A remarkable decrease in the minimum reflectance (Rmin) values of graptolites was observed when Rmax exceeds 6%.The samples with lower thermal maturity (Rmax ≤2%) tend to be biaxial neutral, whereas higher rank samples display biaxial negative characteristics. The GRIS shape becomes more oblate with maturation. The Wufeng–Longmaxi shales from the southeastern Chongqing and Wuxi areas of the Chongqing municipality, China, are post mature and in the dry gas zone, whereas samples from the Chengkou area of the Chongqing municipality, China, are still in the oil window. Their different burial and thermal histories controlled their thermal maturity.

  • 14. Pan, Bing
    et al.
    Brock, Glenn, A.
    Skovsted, Christian
    Swedish Museum of Natural History, Department of Paleobiology.
    Betts, Marissa, J.
    Topper, Timothy, P.
    Li, Guoxiang
    Paterimitra pyramidalis Laurie, 1986, the first tommotiid discovered from the early Cambrian of North China2018In: Gondwana Research, ISSN 1342-937X, E-ISSN 1878-0571, Vol. 63, p. 179-185Article in journal (Refereed)
    Abstract [en]

    The eccentrothecimorph tommotiid Paterimitra pyramidalis Laurie, 1986, was previously only known from lower Cambrian rocks of the Northern Territory and South Australia. Herein, we document the first occurrence of P. pyramidalis from the Xinji Formation in the Shuiyu section at Ruicheng County, Shanxi Province, located at the southwestern margin of the North China Platform. This represents the first report of a tommotiid taxon from lower Cambrian strata of the North China Platform. All three sclerite types that characterise the scleritome of P. pyramidalis have been recovered and are described, permitting definitive identification to species level. The discovery of P. pyramidalis fromthe North China Platformnot only greatly extends the palaeogeographic range of this distinctive tommotiid taxon, but also supports planktotrophic development of larvae in Paterimitra as a stem group brachiopod. The discovery of P. pyramidalis supports a Cambrian, Epoch 2, late Age 3 to early Age 4 age for the shelly fossil fauna from the Xinji Formation and indicates a close palaeogeographic position between the North China Platform and Australian East Gondwana during the early Cambrian.

  • 15. Pan, Bing
    et al.
    Topper, Timothy, P.
    Skovsted, Christian
    Swedish Museum of Natural History, Department of Paleobiology.
    Miao, Lanyun
    Li, Guoxiang
    Occurrence of Microdictyon from the lower Cambrian Xinji Formationalong the southern margin of the North China Platform2018In: Journal of Paleontology, ISSN 0022-3360, E-ISSN 1937-2337, Vol. 91, no 1, p. 59-70Article in journal (Refereed)
    Abstract [en]

    Disarticulated net-like plates of the lobopod Microdictyon had a near cosmopolitan distribution from the early to middle Cambrian, but are yet to be documented from the North China Platform. Here we report isolated plates of Microdictyon from the lower Cambrian Xinji Formation (Stage 4, Series 2) of the North China Platform, extending the paleogeographic distribution of Microdictyon in the early Cambrian. The plates of Microdictyon from the Xinji Formation are similar to those of other species established on the basis of isolated plates, but do bear some new characters, such as mushroom-shaped nodes with a single inclined platform-like apex, and an upper surface that displays radial lines. However, the plates documented here are left under open nomenclature due to an inadequate knowledge of intraspecific and ontogenetic variation and low specimen numbers. Through comparison of the node shapes of the isolated plates of different Microdictyon species, we consider that low mushroom-shaped nodes could be a primitive and conservative character of Microdictyon, while tall mushroom-shaped nodes may be derived character. Subtle differences in shape and number of node apices may also represent intraspecific or ontogenetic variation.

  • 16. Peel, John, S.
    et al.
    Streng, Michael
    Geyer, Gerd
    Kouchinsky, Artem
    Swedish Museum of Natural History, Department of Paleobiology.
    Skovsted, Christian
    Swedish Museum of Natural History, Department of Paleobiology.
    Ovatoryctocara granulata assemblage (Cambrian Series 2–Series 3 boundary) of Løndal, North Greenland2016In: Australasian Palaeontological Memoirs, Vol. 49, p. 241-282Article in journal (Refereed)
    Abstract [en]

    Ovatoryctocara granulata Chernysheva 1962, a key trilobite in discussions concerning intercontinental correlation and the placement of the Cambrian Series 2–Series 3 boundary, occurs together with more than 60 other species in a fossil assemblage from the Henson Gletscher Formation of Løndal, Peary Land, North Greenland. Most taxa are described from acid residues in which diverse protoconodonts, helcionellid molluscs and hyoliths occur together with linguliformean brachiopods, bradoriids and other fossils. Recognition of an earlier First Appearance Datum for O. granulata in Løndal consolidates the biostratigraphic relationship between the assemblage and other partly co-occurring trilobites valuable for correlation within Laurentia and beyond. The assemblage can be correlated with the Ovatoryctocara Biozone, the basal biozone of the Molodian Stage in the Republic of Sakha (Yakutia, north-eastern Siberia), proposed as the earliest stage of Cambrian Series 3. New taxa are Tulenicornus? frykmani sp. nov., Conotheca hensoni sp. nov., Capitoconus borealis sp. nov., ‘Hipponicharion’ pearylandica sp. nov. and Liangshanella? nivalis sp. nov.

  • 17.
    Skovsted, Christian
    Swedish Museum of Natural History, Department of Paleobiology.
    A silicified tommotiid from the lower Cambrian of Greenland2016In: Bulletin of Geosciences, ISSN 1214-1119, E-ISSN 1802-8225Article in journal (Refereed)
    Abstract [en]

    Three specimens of a new eccentrothecimorph tommotiid are described from the Paralelldal Formation of North Greenland. The specimens are all tubular structures composed of a number of individual sclerites. The sclerites were arranged in rings which fused to form a rigid tube during ontogeny. The tube has a basal aperture presumably allowing attachment to a hard substrate. In morphology, both individual sclerites and the tubular scleritome are remarkably similar to specimens of Eccentrotheca from South Australia. However, the Greenland specimens are silicified and may have been either weakly mineralized or calcareous in original composition. In this respect they differ from all previously known tommotiids, considerably expanding the ultrastructural disparity of the Tommotiida and allowing comparison to a new range of possible lophotrochozoan fossils.

  • 18.
    Skovsted, Christian
    Swedish Museum of Natural History, Department of Paleobiology.
    Betts, Marissa J.
    Macquarie university.
    Brock, Glenn A.
    Macquarie University.
    Associated conchs and opercula of Triplicatella disdoma (Hyolitha) from the early Cambrian of South Australia2013In: Alcheringa, ISSN 0311-5518, E-ISSN 1752-0754, Vol. 38, no 1, p. 148-153Article in journal (Refereed)
    Abstract [en]

    Internal moulds of complete shells, including conch and associated opercula, of the hyolith Triplicatella disdoma from Cambrian Series 2, Stages 3–4 of South Australia are described. The conch of T. disdoma is shown to be narrow and cone-shaped, and with a rounded triangular cross-section. The conch shows a gentle dorsal curvature in lateral view. The fossils lack evidence of helens, and the operculum was smaller than the apertural diameter of the conch and could be withdrawn a short distance into the conch. Triplicatella was probably closely related to orthothecid hyoliths.

  • 19.
    Skovsted, Christian
    Swedish Museum of Natural History, Department of Paleobiology.
    Topper, Timothy, P.
    Brock, Glenn, A.
    The early Cambrian tommotiid genus Dailyatia from South Australia2015In: Association of Australiasian Palaeontologists, Memoir, ISSN 0810-8889, Vol. 48, p. 1-117Article in journal (Refereed)
    Abstract [en]

    The camenellan tommotiid Dailyatia is one of the most common fossils in shallow water carbonates from Cambrian Stages 2-4 in South Australia (Arrowie and Stansbury basins). Six species of Dailyatia are analysed and new terminology for describing camenellan sclerites is introduced. Dailyatia sclerites are found in three fundamental sclerite types (A-C), each of which may be present in one to three sub-types depending on species. The previously described species Dailyatia ajax Bischoff 1976 and D. macroptera (Tate 1892) are revised and four additional species are described for the first time from South Australia. These include D. odyssei Evans & Rowell 1990, previously known only from Antarctica, and two new species; D. bacata sp. nov. and D. helica sp. nov. as well as a species left under open nomenclature. Two of the recognised species (D. macroptera and D. helica) occur in two different ecophenotypic variants. Species and variants are defined by differences in sclerite types present in the scleritome, sclerite morphology and ornament. The sclerites of Dailyatia are finely laminated with distal expansion of laminae supporting the prominent concentric ribs. The external surface is covered by a fine reticulate network which indicates that the sclerites were at least partly embedded in soft integument. The pattern of incremental growth reveals specific initial and possible gerontic growth stages with unique surface sculptures. Evidence of physical damage and growth disturbances is common in Dailyatia sclerites and many specimens reveal preferential abrasion of the apex. Apical canals are present in all sclerites and are connected to specialised internal apical structures.

    The internal surface of the sclerites in most species reveals raised platforms and depressed, scar like areas forming unique patterns in each sclerite type, presumably representing muscular attachment. Two specimens revealing ontogenetic fusion of Dailyatia sclerites have been recovered. Based on all available evidence, a new reconstruction of the Dailyatia scleritome is proposed. In the reconstruction, a central row of A and paired B sclerites is flanked on both sides by one or two lateral rows of C sclerites. The exact number of sclerites may vary between species. This reconstruction is based on an assumed slug-like bodyplan and the Dailyatia animal is considered to be a vagrant, benthic animal living in and around archaeocyathan-microbial buildups and in other shallow water carbonate environments.

  • 20.
    Skovsted, Christian B.
    et al.
    Swedish Museum of Natural History, Department of Paleobiology.
    Kouchinsky, Artem
    Swedish Museum of Natural History, Department of Paleobiology.
    Bengtson, Stefan
    Swedish Museum of Natural History, Department of Paleobiology.
    Holmer, Lars E.
    The problematic early Cambrian fossil Tumulduria incomperta represents the detached ventral interarea of a paterinid brachiopod.2014In: Acta Palaeontologica Polonica, ISSN 0567-7920, E-ISSN 1732-2421, Vol. 59, no 2, p. 359-365Article in journal (Refereed)
    Abstract [en]

    The organophosphatic early Cambrian (Terreneuvian, Cambrian Stage 2) fossil Tumulduria incomperta has been problematic ever since its original description in 1969. Comparison of abundant specimens from the Lower Cambrian of Siberia with co-occurring brachiopod valves show that T. incomperta represents the central portion of the ventral interarea of a paterinid brachiopod similar to Cryptotreta neguertchenensis, and that the domed central portion of typical Tumulduria specimens represents the ridge-like pseudodeltidium of the interarea.

  • 21.
    Skovsted, Christian
    et al.
    Swedish Museum of Natural History, Department of Paleobiology.
    Bing, Pan
    Topper, Timothy, P.
    Betts, Marissa, J.
    Li, Guoxiang
    Brock, Glenn, A.
    The operculum andmode of life of the lower Cambrian hyolith Cupitheca from South Australia and North China2016In: Palaeogeography, Palaeoclimatology, Palaeoecology, ISSN 0031-0182, E-ISSN 1872-616X, Vol. 443, p. 123-130Article in journal (Refereed)
    Abstract [en]

    The operculum of the problematic tubular fossil Cupitheca holocyclata Bengtson in Bengtson et al., (1990) is described for the first time based on collections from South Australia and North China. The phosphatized sub-circular operculum exhibits well defined cardinal processes and a narrow cardinal shield unequivocally demonstrating that Cupitheca is a hyolith, probably an orthothecid. C. holocyclata has an almost global distribution in Cambrian Stages 3–4. The apical structure of the operculum is an elevated, disc-shaped platform with a concave base and a marginal rim that could represent the scar of a specialized larval attachment structure, perhaps anchoring the larval hyolith to a sediment grain, algae or other benthic substrate. Cupitheca probably had a pelagic larval stage and settled on the seafloor by attachment of the apical disc to suitable substrates before developing a free-living benthic adult lifestyle. This contrasting mode of life compared to other hyolith genera suggests that the group had already evolved a range of distinct lifestyles in the Cambrian, providing significant clues into their ecology and distribution.

  • 22.
    Skovsted, Christian
    et al.
    Swedish Museum of Natural History, Department of Paleobiology.
    Brock, Glenn A.
    Macquarie University.
    First occurrence of a new Ocruranus-like helcionelloid mollusc from the lower Cambrian of East Gondwana2012In: Gondwana Research, ISSN 1342-937X, E-ISSN 1878-0571, Vol. 22, p. 256-261Article in journal (Refereed)
    Abstract [en]

    A new cap-shaped mollusc, Emargimantus angulatus gen. et sp. nov. is described from the Arrowie Basin of South Australia. The new species is closely comparable to mollusc species from South China and North-East Greenland previously described under the generic name Ocruranus Liu, a genus recently reinterpreted as a multiplated, possibly polyplacophoran mollusc. Emargimantus is interpreted as a univalved helcionelloid mollusc and differs from Ocruranus in both morphology and function. E. angulatus represents the first discovery of Ocruranus-like helcionelloids in the lower Cambrian of eastern Gondwana and demonstrates that these molluscs had a global distribution during the early Cambrian.

  • 23.
    Skovsted, Christian
    et al.
    Swedish Museum of Natural History, Department of Paleobiology.
    Brock, Glenn, A.
    Holmer, Lars, E.
    Topper, Timothy, P.
    Larsson, Cecilia, M.
    The early Cambrian tommotiid Kulparina rostrata from South Australia2016In: Journal of Paleontology, ISSN 0022-3360, E-ISSN 1937-2337, Vol. 89, no 6, p. 920-932Article in journal (Refereed)
    Abstract [en]

    The early Cambrian (Terreneuvian, Stage 2) tommotiid Kulparina rostrata Conway Morris and Bengtson in Bengtson et al., 1990 is revised. The pyramidal sclerites of K. rostrata are shown to be bilaterally symmetrical and homologues of the symmetrical S1 sclerites of Paterimitra pyramidalis Laurie, 1986. The scleritome of K. rostrata is also shown to include flattened asymmetrical sclerites that were originally described under the name Eccentrotheca guano Bengtson in Bengtson et al., 1990 and which correspond to the L-sclerites of Paterimitra. A modified tubular scleritome and a sessile filter-feeding mode of life is envisaged for Kulparina rostrata.

  • 24.
    Skovsted, Christian
    et al.
    Swedish Museum of Natural History, Department of Paleobiology.
    Clausen, Sebastien
    Universite Lille 1.
    Javier J., Alvaro
    Centro de Astrobiologıa (CSIC/INTA), Ctra. de Torrejon.
    Ponleve, Deborah
    Universite Lille 1.
    Tommotiids from the early Cambrian (Series 2, stage 3) of Morocco and the evolution of the tannuolinid scleritome and setigerous shell structures in stem group brachiopods.2014In: Palaeontology, ISSN 0031-0239, E-ISSN 1475-4983, Vol. 57, no 1, p. 171-192Article in journal (Refereed)
    Abstract [en]

    An assemblage of tannuolinid sclerites isdescribed from the Amouslek Formation (Souss Basin) of theAnti-Atlas Mountains in Morocco. The assemblage containstwo species, Tannuolina maroccana n. sp., which is representedby a small number of mitral and sellate sclerites, andMicrina sp., represented by a single mitral sclerite. Tannuolinamaroccana differs from other species of the genus in thepresence of both bilaterally symmetrical and strongly asymmetricalsellate sclerites. This observation suggests that thescleritome of Tannuolina was more complex than previouslythought and that this tommotiid may have held a more basalposition in the brachiopod stem group than previouslyassumed. The shell structure of both T. maroccana andMicrina sp. is well preserved and exhibits two fundamentallydifferent sets of tubular structures, only one of which waslikely to contain shell-penetrating setae. Based on these observations,the structure of the tannuolinid shell is discussed andits implications for the evolution of tubular microstructuresin stem and crown group brachiopods are analysed.

  • 25.
    Skovsted, Christian
    et al.
    Swedish Museum of Natural History, Department of Paleobiology.
    Knight, Ian
    Balthasar, Uwe
    Boyce, W. Douglas
    Depth related brachiopod faunas from the lower Cambrian Forteau Formation of southern Labrador and western Newfoundland, Canada2017In: Palaeontologia Electronica, ISSN 1935-3952, E-ISSN 1094-8074, Vol. 20, no 3, p. 1-52, article id 54AArticle in journal (Refereed)
    Abstract [en]

    A diverse fauna of organophosphatic brachiopods is described from the late early Cambrian (Series 2, Stage 3-4) Forteau Formation of southern Labrador and western Newfoundland. The total fauna includes 11 species representing a wide selection of Cambrian brachiopod groups. Three distinct assemblages are recognized: Assemblages1 and 2 are found in shallow water carbonates in association with archaeocyathans in southern Labrador and the western side of the Great Northern Peninsula of western Newfoundland. Assemblage 3 is found in a distal shelf setting of Gros Morne National Park. Assemblages 1 and 2 are found in stratigraphic continuity and definetwo brachiopod biozones, a lower Hadrotreta taconica zone and a higher Paterina zone, respectively. The presence of H. taconica in brachiopod Assemblage 3 possibly indicates time equivalence of Assemblage 1 but in a deep water setting. The identification of distinct time equivalent brachiopod Assemblages (1 and 3) in shallow and deep water environments of the Forteau Formation allow for the first time an analysis of environmental constraints determining the distribution of individual brachiopod taxa in the lower Cambrian succession of eastern Laurentia. Comparison to faunas from other areas indicates that the identified distributional patterns can be extended to other brachiopod faunas found along the Cambrian palaeocoast/margin of eastern Laurentia. The study indicates that specific brachiopod taxa can be used as indicators of palaeodepth; Botsfordia caelata in shallow environments and Eoobolus priscus and Eothele tubulus in deeper water. The following new taxa are described: Kyrshabaktella diabolan. sp., Pustulobolus triangulus n. gen et n. sp., Acrothyra bonnia n. sp.

  • 26.
    Skovsted, Christian
    et al.
    Swedish Museum of Natural History, Department of Paleobiology.
    Topper, Timothy, P.
    Mobergellans from the early Cambrian of Greenland and Labrador — new morphological details and implications for the functional morphology of mobergellans2018In: Journal of Paleontology, ISSN 0022-3360, E-ISSN 1937-2337, Vol. 92, no 1, p. 71-79Article in journal (Refereed)
    Abstract [en]

    New morphological features of the mobergellan Discinella micans (Billings, 1871) from the lower Cambrian (Stage 4) of North-East Greenland and southern Labrador are described. The new features include: (1) the morphology of the larval shell, which is shown to be cap-shaped, sub-circular and with impressions of the internal muscle attachment scars; (2) a range of unusual shell deformations (changes in growth direction resulting in thickened shells, partial detachment of shell laminae and subsequent regrowth, internal projections of shell material increasing the depth of the shell by up to 150%, disturbances and irregular fusion of muscle scars). In addition we provide new details about the variability in number and shape of the anteriormost internal muscle scars which often fuse and may vary in number from one to three (resulting in 9 to 11 scars in total). Together the new observations provide additional strength to the hypothesis that mobergellan shells represent opercula of an as yet unknown tubular organism.

  • 27.
    Skovsted, Christian
    et al.
    Swedish Museum of Natural History, Department of Paleobiology.
    Ushatinskaya, Galina
    Holmer, Lars, E.
    Popov, Leonid, E.
    Kouchinsky, Artem
    Swedish Museum of Natural History, Department of Paleobiology.
    Taxonomy, morphology, shell structure and early ontogeny of Pelmanotreta nom. nov. from the lower Cambrian of Siberia2015In: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 137, no 1, p. 1-8Article in journal (Refereed)
    Abstract [en]

    The new generic name Pelmanotreta is proposed under the provisions of the International Code of Zoological Nomenclature (ICZN) to replace Cryptotreta Pelman, 1977 (Brachiopoda), a junior homonym of Cryptotreta Blanc & Foote, 1961 (Arthropoda). This poorly known brachiopod genus and its type and only species, Pelmanotreta neguertchenensis (Pelman, 1977), from the early Cambrian of Siberia is redescribed. The family-level taxonomy of Pelmanotreta and other “cryptotretid” brachiopods is uncertain. In Pelmanotreta, dorsal valves vastly outnumber ventral valves in all collections but new specimens of the poorly known ventral valve reveal a possibly septate and poorly mineralized apical region. A prismatic hexagonal shell structure comparable to that of Salanygolina is described. P. neguertchenensis preserves the earliest known record of a larval shell in brachiopods.

  • 28. Sperling, Erik Anders
    et al.
    Balthasar, Uwe
    Skovsted, Christian
    Swedish Museum of Natural History, Department of Paleobiology.
    On the edge of exceptional preservation: insights into the role of redox state in Burgess Shale-type taphonomic windows from the Mural Formation, Alberta, Canada2018In: Emerging Topics In Life Sciences, ISSN 2397-8554, Vol. 2, no 2, p. 311-323Article in journal (Refereed)
    Abstract [en]

    Animals originated in the Neoproterozoic and ‘exploded’ into the fossil record in the Cambrian. The Cambrian also represents a high point in the animal fossil record for the preservation of soft tissues that are normally degraded. Specifically, fossils from Burgess Shale-type (BST) preservational windows give paleontologists an unparalleled view into early animal evolution. Why this time interval hosts such exceptional preservation, and why this preservational window declines in the early Paleozoic, have been long-standing questions. Anoxic conditions have been hypothesized to play a role in BST preservation, but recent geochemical investigations of these deposits have reached contradictory results with respect to the redox state of overlying bottom waters. Here, we report a multi-proxy geochemical study of the Lower Cambrian Mural Formation, Alberta, Canada. At the type section, the Mural Formation preserves rare recalcitrant organic tissues in shales that were deposited near storm wave-base (a Tier III deposit; the worst level of soft-tissue preservation). The geochemical signature of this section shows little to no evidence of anoxic conditions, in contrast to published multi-proxy studies of more celebrated Tier I and II deposits. These data help confirm that ‘decay limited’ BST biotas were deposited in more oxygenated conditions, and support a role for anoxic conditions in BST preservation. Finally, we discuss the role of iron reduction in BST preservation, including the formation of iron-rich clays and inducement of sealing seafloor carbonate cements. As oceans and sediment columns became more oxygenated and more sulfidic through the early Paleozoic, these geochemical changes may have helped close the BST taphonomic window.   

    The full text will be freely available from 2019-10-01 18:09
  • 29.
    Topper, Timothy P.
    Geological Museum, Copenhagen.
    Peel, John S.
    Uppsala Universitet.
    Harper, David A.T.
    Durham University.
    Moulting in the lobopodian Onychodictyon from the lower Cambrian of Greenland2013In: Lethaia: an international journal of palaeontology and stratigraphy, ISSN 0024-1164, E-ISSN 1502-3931, Vol. 46, no 4, p. 490-495Article in journal (Refereed)
    Abstract [en]

    A number of lobopodian taxa from the Cambrian display pairs of sclerotized plates symmetrically positioned along the dorsum of the animal, predominantly above the walking appendages. Most genera were described from complete body fossils exquisitely preserved in the famous Cambrian Lagerstätten, but lobopodian phosphatized plates are found worldwide as typical components of Cambrian small shelly fossil assemblages (SSF). Details regarding intraspecific and ontogenetic variation in lobopod plates are elusive, and the lack of details of ornamentation in Lagerstätte specimens does not minimize the problem. We document here an assemblage of well-preserved isolated plates of Onychodictyon sp. from the Lower Cambrian (Cambrian Series 2, Stage 4) of North Greenland. Two specimens exhibit perfectly conjoined plates from successive moults. Details of ornamentation and the outline and profile of the fixed plates are identical, but width and length of the underlying plate are 24% larger. These specimens boost the body of evidence that lobopodians moulted but also show that plate outline and ornamentation did not vary during ontogeny.

  • 30.
    Topper, Timothy P.
    et al.
    Uppsala Universitet.
    Holmer, Lars E.
    Uppsala Universitet.
    Skovsted, Christian
    Swedish Museum of Natural History, Department of Paleobiology.
    Balthasar, Uwe
    University of Glasgow.
    Harper, David A.T.
    The oldest brachiopods from the lower Cambrian of South Australia2013In: Acta Palaeontologica Polonica, ISSN 0567-7920, E-ISSN 1732-2421, Vol. 58, no 1, p. 93-109Article in journal (Refereed)
    Abstract [en]

    The morphology and organophosphatic shell structure of the paterinate brachiopod Askepasma is documented using new and previously collected specimens from the lower Cambrian of South Australia. Lack of adequately preserved material has seen the majority of paterinate specimens previously reported from South Australia referred to the genus Askepasma and treated under open nomenclature. Large collections of paterinates from the lower Cambrian Wilkawillina, Ajax, and Wirrapowie limestones in the Arrowie Basin, South Australia have prompted redescription of the type species Askepasma toddense and the erection of a new species, Askepasma saproconcha sp. nov. Askepasma saproconcha sp. nov. currently represents the oldest known brachiopod from the lower Cambrian successions in South Australia with a FAD in pre−trilobitic (Terreneuvian, Cambrian Stage 2, lower Atdabanian) strata in the basal part of the Wilkawillina and Wirrapowie limestones. Askepasma toddense predominantly occurs in Abadiella huoi Zone equivalent strata (Unnamed Cambrian Series 2, Stage 3, middle–upper Atdabanian) in the upper part of the lower Wilkawillina, Wirrapowie, and Ajax limestones. The shell microstructure of Askepasma suggests a proximal stem group position within the Brachiopoda and similarities with tommotiid taxa provides further evidence that the ancestry of crown group brachiopods is firmly entrenched within the Tommotiida.

  • 31.
    Topper, Timothy P.
    et al.
    Geological Museum, Copenhagen.
    Skovsted, Christian
    Swedish Museum of Natural History, Department of Paleobiology.
    Ahlberg, Per
    Lunds Universitet.
    A Bradoriid and Brachiopod Dominated Shelly Fauna from the Furongian (Cambrian) of Västergötland, Sweden2013In: Journal of Paleontology, ISSN 0022-3360, E-ISSN 1937-2337, Vol. 87, no 1, p. 69-83Article in journal (Refereed)
    Abstract [en]

    A small assemblage of shelly fossils, dominated by the brachiopod Treptotreta jucunda and the bradoriid arthropod Mongolitubulus aspermachaera new species is described from a Furongian limestone of Västergötland, south-central Sweden. Mongolitubulus aspermachaera is represented in the assemblage by individual valves and numerous, ornamented spines. Valves and spines share identical ornament and microstructure leaving no doubt that the isolated spines were once attached to the bradoriid valves. Mongolitubulus aspermachaera adds to the increasing list of spinose Cambrian bradoriid arthropods, and Mongolitubulidae new family is erected here to incorporate the genera Mongolitubulus, Tubuterium and Spinospitella. Mongolitubulus aspermachaera represents the youngest member of the new family and supplements the biodiversity of bradoriids in the Furongian, an interval when bradoriid diversity is considered to be very much on the decline. The brachiopod Treptotreta jucunda described predominantly from the ‘middle' to ‘late' Cambrian of Australia is here documented for the first time from outside Gondwana, dramatically extending the biogeographical range of the species. Other elements of the faunal assemblage include typical Baltic Furongian representatives, such as the trilobite Parabolina, the agnostoid Agnostus and the phosphatocopids Hesslandona and Vestrogothia.

  • 32.
    Topper, Timothy P.
    et al.
    Geologisk Museum, Statens Naturhistoriske Museum, Danmark.
    Skovsted, Christian
    Swedish Museum of Natural History, Department of Paleobiology.
    A new name for a classic Cambrian Swedish brachiopod, Tallatella undosa (Moberg)2014In: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 136, no 3, p. 429-435Article in journal (Refereed)
    Abstract [en]

    The brachiopod originally described as Kuturgina undosa Moberg, 1892 from the early Cambrian (Cambrian Series 2, Stage 4) När Shale of Kalmarsund, Sweden, has experienced a long and turbulent history since the original description over 100 years ago. Uncertainties regarding key morphological characters have resulted in the species taxonomically hopping between genera until it wasrecently assigned to the poorly known genus Cryptotreta Pelman, 1977 and subsequently transferred to the problematic paterinate family Cryptotretidae. Despite members of this group representing the oldest brachiopods in the fossil record, they remain enigmatic, both taxonomically and phylogenetically. Theidentification of the brachiopod species from the När Shale as a cryptotretid means that this brachiopod was the first member of the family to be discovered, yet its systematic position is far from certain. Examination of type material in addition to supplementary material acquired from the Skäggenäs Peninsula, Sweden, has elucidated many of the previous ambiguous morphological characteristics of the species. The new morphological information acquired here has resulted in the erection of a new paterinate genus, Tallatella gen. nov., to accommodate the Swedish material previously described as Cryptotreta undosa.

  • 33. Topper, Timothy, P.
    et al.
    Skovsted, Christian
    Swedish Museum of Natural History, Department of Paleobiology.
    Keeping a lid on it: muscle scars and the mystery of the Mobergellidae2017In: Zoological Journal of the Linnean Society, ISSN 0024-4082, E-ISSN 1096-3642, Vol. 180, p. 717-731Article in journal (Refereed)
    Abstract [en]

    Mobergellans were one of the first Cambrian skeletal groups to be recognized yet have long remained one of the mostproblematic in terms of biological function and affinity. Characterized by a disc-shaped, phosphatic sclerite, the mostdistinctive character of the group is a prominent set of internal scars, interpreted as representing sites of former muscleattachment. Predominantly based on muscle scar distribution, mobergellans have been compared to brachiopods,bivalves and monoplacophorans; however, a recurring theory that the sclerites acted as an operculum remains untested.Rather than correlate the number of muscle scars between taxa, here we focus on the percentage of the inner surfaceshell area that the scars constitute. We investigate two mobergellan species, Mobergella holsti and Discinella micans,and compare the Cambrian taxa with the muscle scars of a variety of extant and fossil marine invertebrate taxa to testwhether the mobergellan muscle attachment area is compatible with an interpretation as operculum. The only skeletalelements in our study with a comparable muscle attachment percentage are gastropod opercula. Complemented withadditional morphological information, our analysis supports the theory that mobergellan sclerites acted as an operculumpresumably from a tube-living organism. The paucity of tubes co-occurring with mobergellan sclerites could beexplained by the transportation and sorting of detached opercula, while the corresponding tube remained attached tosubstrata in shallower water. The operculum perhaps performed a similar role to that seen in serpulid annelids and inneritid gastropods sealing the living chamber of the organism to avoid desiccation or for protection.

  • 34. Topper, Timothy, P.
    et al.
    Strotz, Luke C.
    Skovsted, Christian
    Swedish Museum of Natural History, Department of Paleobiology.
    Holmer, Lars, E.
    DO BRACHIOPODS SHOW SUBSTRATE-RELATEDPHENOTYPIC VARIATION? A CASE STUDY FROM THE BURGESS SHALE2017In: Palaeontology, ISSN 0031-0239, E-ISSN 1475-4983, Vol. 60, no 2, p. 269-279Article in journal (Refereed)
    Abstract [en]

    As sessile, benthic filter feeders, brachiopods share an intimate relationship with their chosen substrate. Individuals of Micromitra burgessensis in the Burgess Shale Formation are preserved in life position, attached to a range of hard substrates, including skeletal debris, conspecific brachiopods, sponges and enigmatic tubes. Here we investigate the phenotypic variability of M. burgessensis associated with differing substrate attachments. We apply geometric morphometrics to test for variation by plotting landmarks on the exterior of ventral and dorsal valves of M. burgessensis specimens that are preserved attached to different substrates. Using principal component, canonical variate analyses and ANOVA, we determine that there is some variation in shape related to substrate. Canonical variate analyses, for ventral valves and dorsal valves, indicate that specimens attached to the same substrate are recognizable in shape from specimens attached to other substrate types. The strength of differentiation however, is not robust and combined with our discriminate analysis of separate populations suggests that there is the potential for substrates to exercise only weak control over the morphology of Brachiopoda.

  • 35. Topper, Timothy
    et al.
    Skovsted, Christian
    Swedish Museum of Natural History, Department of Paleobiology.
    A new name for a classic Cambrian Swedish brachiopod, Tallatella undosa (Moberg)2014In: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 136, no 4, p. 429-435Article in journal (Refereed)
    Abstract [en]

    The brachiopod originally described as Kuturgina undosa Moberg, 1892 from the early Cambrian (Cambrian Series 2, Stage 4) Nar Shale of Kalmarsund, Sweden, has experienced a long and turbulent history since the original description over 100 years ago. Uncertainties regarding key morphological characters have resulted in the species taxonomically hopping between genera until it was recently assigned to the poorly known genus Cryptotreta Pelman, 1977 and subsequently transferred to the problematic paterinate family Cryptotretidae. Despite members of this group representing the oldest brachiopods in the fossil record, they remain enigmatic, both taxonomically and phylogenetically. The identification of the brachiopod species from the Nar Shale as a cryptotretid means that this brachiopod was the first member of the family to be discovered, yet its systematic position is far from certain. Examination of type material in addition to supplementary material acquired from the Skaggenas Peninsula, Sweden, has elucidated many of the previous ambiguous morphological characteristics of the species. The new morphological information acquired here has resulted in the erection of a new paterinate genus, Tallatella gen. nov., to accommodate the Swedish material previously described as Cryptotreta undosa.

  • 36.
    Zhang, Zhifei
    et al.
    Northwest University, Xian, China.
    Holmer, Lars E.
    Uppsala Universitet.
    Brock, Glenn A.
    Macquarie University, Sydney, Australia.
    Budd, Graham E.
    Uppsala Universitet.
    Fu, Dongjing
    Northwest University, Xian, China.
    Zhang, Xingliang
    Northwest University, Xian, China.
    Shu, Degan
    Northwest University, Xian, China.
    Han, Jian
    Northwest University, Xian, China.
    Liu, Jianni
    Wang, Haizhou
    Uppsala Universitet.
    Butler, Aodhan
    Uppsala Universitet.
    Li, Guoxiang
    Nanjing Institute of Geology and Palaeontology, Nanjing, China.
    A sclerite-bearing stem group entoproct from the early Cambrian and its implications2013In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 3, no 1066, p. 1-7Article in journal (Refereed)
    Abstract [en]

    The Lophotrochozoa includes disparate tentacle-bearing sessile protostome animals, which apparently appeared in the Cambrian explosion, but lack an uncontested fossil record. Here we describe abundant well preserved material of Cotyledion tylodes Luo et Hu, 1999, from the Cambrian (Series 2) Chengjiang deposits, reinterpreted here as a stem-group entoproct. The entoproct affinity is supported by the sessile body plan and interior soft anatomy. The body consists of an upper calyx and a lower elongate stalk with a distal holdfast. The soft anatomy includes a U-shaped gut with a mouth and aboral anus ringed by retractable marginal tentacles. Cotyledion differs from extant entoprocts in being larger, and having the calyx and the stalk covered by numerous loosely-spaced external sclerites. The description of entoprocts from the Chengjiang biota traces the ancestry of yet another lophotrochozoan phylum back to the Cambrian radiation, and has important implications for the earliest evolution of lophotrochozoans.

  • 37.
    Zhang, Zhifei
    et al.
    Northwest University, Xian, China.
    Li, Guoxiang
    Nanjing Institute of Geology and Palaeontology, Nanjing, China.
    Holmer, Lars E.
    Uppsala Universitet.
    Brock, Glenn A.
    Macquarie University, Sydney, New South Wales.
    Balthasar, Uwe
    University of Glasgow.
    Skovsted, Christian
    Swedish Museum of Natural History, Department of Paleobiology.
    Fu, D.J.
    Northwest University, Xian, China.
    Zhang, X.L.
    Northwest University, Xian, China.
    Wang, Haizhou
    Uppsala Universitet.
    Butler, Aodhan
    Uppsala Universitet.
    Zhang, Z.L.
    Northwest University, Xian, China.
    Cao, C.Q.
    Nanjing Institute of Geology and Palaeontology, Nanjing, China.
    Han, J.
    Northwest University, Xian, China.
    Liu, J.N.
    Northwest University, Xian, China.
    Shu, D.G.
    Northwest University, Xian, China.
    An early Cambrian agglutinated tubular lophophorate with brachiopod characters2014In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 4, no 4682, p. 1-7Article in journal (Refereed)
    Abstract [en]

    The morphological disparity of lophotrochozoan phyla makes it difficult to predict the morphology of the last common ancestor. Only fossils of stem groups can help discover the morphological transitions that occurred along the roots of these phyla. Here, we describe a tubular fossil Yuganotheca elegans gen. et sp. nov. from the Cambrian (Stage 3) Chengjiang Lagersta¨tte (Yunnan, China) that exhibits an unusual combination of phoronid, brachiopod and tommotiid (Cambrian problematica) characters, notably a pair of agglutinated valves, enclosing a horseshoe-shaped lophophore, supported by a lower bipartite tubular attachment structure with a long pedicle with coelomic space. The terminal bulb of the pedicle provided anchorage in soft sediment. The discovery has important implications for the early evolution of lophotrochozoans, suggesting rooting of brachiopods into the sessile lophotrochozoans and the origination of their bivalved bauplan preceding the biomineralization of shell valves in crown brachiopods.

  • 38.
    Zhang, Zhiliang
    et al.
    Northwest university.
    Skovsted, Christian
    Swedish Museum of Natural History, Department of Paleobiology.
    Zhang, Zhifei
    Northwest University.
    A hyolithid without helens preserving the oldest hyolith muscle scars; palaeobiology of Paramicrocornus from the Shujingtuo Formation (Cambrian Series 2) of South China2018In: Palaeogeography, Palaeoclimatology, Palaeoecology, ISSN 0031-0182, E-ISSN 1872-616X, Vol. 489, p. 1-14Article in journal (Refereed)
    Abstract [en]

    The hyolithid Paramicrocornus zhenbaensis from the lower Cambrian (Cambrian Series 2) Shuijingtuo Formation of southern Shaanxi and western Hubei provinces of the Yangtze Platform is well-preserved in three dimensions. The morphology of the conch and operculum of P. zhenbaensis shows that this species lacked helens, which are considered to be characteristic of hyolithids and hence Paramicrocornus may belong to a sister group of other hyolithids. The shell structure of P. zhenbaensis reveals close similarities to the shell structure of other hyolithids. Furthermore, the smaller size and non-radial orientation of tubules in the shell structure of the operculum also differ from that in orthothecid hyoliths, suggesting that this characteristic may be used to differentiate hyolithids and orthothecids. The phosphatized opercula of P. zhenbaensis exhibit a pair of muscle scars located close to the apex of the internal surface. These muscle scars, as well as similar structures in other hyolithids, probably served as attachment sites of muscles controlling the retraction of the tentaculate feeding organ recently discovered inhyolithids. Without helens, P. zhenbaensis may have been sessile with the conch partly buried in the sea floor.

1 - 38 of 38
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