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  • Biagioni, Cristian
    et al.
    Università di Pisa, Italy.
    Bindi, Luca
    Università di Firenze, Italy.
    Mauro, Daniela
    Università di Pisa.
    Hålenius, Ulf
    Swedish Museum of Natural History, Department of Geology.
    Crystal chemistry of sulfates from the Apuan Alps (Tuscany, Italy). V. Scordariite, K8(Fe3+0.67ο0.33)[Fe3+3O(SO4)6(H2O)3)]2(H2O)11 , a new metavoltine-related mineral2019In: Minerals, ISSN 2075-163X, E-ISSN 2075-163X, Vol. 9, no 11, p. 1-14, article id 0702Article in journal (Refereed)
  • Topper, Timothy, P.
    et al.
    Guo, Junfeng
    Clausen, Sébastien
    Skovsted, Christian
    Swedish Museum of Natural History, Department of Paleobiology.
    Zhang, Zhifei
    A stem group echinoderm from the basal Cambrian of China and the origins of Ambulacraria2019In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 10, article id 1366Article in journal (Refereed)
    Abstract [en]

    Deuterostomes are a morphologically disparate clade, encompassing the chordates (including vertebrates), the hemichordates (the vermiform enteropneusts and the colonial tube-dwelling pterobranchs) and the echinoderms (including starfish). Although deuterostomes are considered monophyletic, the inter-relationships between the three clades remain highly contentious. Here we report, Yanjiahella biscarpa, a bilaterally symmetrical, solitary metazoan from the early Cambrian (Fortunian) of China with a characteristic echinoderm-like plated theca, a muscular stalk reminiscent of the hemichordates and a pair of feeding appendages. Our phylogenetic analysis indicates that Y. biscarpa is a stem-echinoderm and not only is this species the oldest and most basal echinoderm, but it also predates all known hemichordates, and is among the earliest deuterostomes. This taxon confirms that echinoderms acquired plating before pentaradial symmetry and that their history is rooted in bilateral forms. Yanjiahella biscarpa shares morphological similarities with both enteropneusts and echinoderms, indicating that the enteropneust body plan is ancestral within hemichordates.

  • Li, Luoyang
    et al.
    Zhang, Xingliang
    Skovsted, Christian
    Swedish Museum of Natural History, Department of Paleobiology.
    Yun, Hao
    Li, Guoxiang
    Bing, Pan
    Shell microstructures of the helcionelloid mollusc Anabarella australis from the lower Cambrian (Series 2) Xinji Formation of North China2019In: Journal of Systematic Palaeontology, ISSN 1477-2019, E-ISSN 1478-0941, Vol. 17, p. 1699-1709Article in journal (Refereed)
    Abstract [en]

    Although various types of shell microstructures are documented from Cambrian molluscs, the precise organization and mineralogical composition of Terreneuvian molluscs are relatively unknown. Anabarella was one of the first helcionellid molluscs to appear in the Terreneuvian, with the genus surviving until the third epoch of the Cambrian. Here, shell microstructures of Anabarella australis have been studied based on new collections from the lower Cambrian (Series 2) Xinji Formation of the North China Block. Results show that A. australis has a laminar inner shell layer that consists of crossed foliated lamellar microstructure (CFL). Nacreous, crossed-lamellar and foliated aragonite microstructures previously documented in the older (Terreneuvian) species A. plana are here revised as preservational artefacts of the CFL layers. This complex skeletal organization of Anabarella suggests that mechanisms of molluscan biomineralization evolved very rapidly. Morphologically, specimens from the Chaijiawa section show a pattern of distinct ‘pseudo-dimorphism’ as external coatings are identical to Anabarella, while associated internal moulds are similar to the helcionelloid genus Planutenia. In contrast, internal moulds from the Shangzhangwan section show considerable morphological variation owing to preservational bias and show greater similarities to specimens from South Australia, Northeast Greenland and Germany. These observations demonstrate that the extensive morphological variation seen in the internal moulds of the cosmopolitan genus Anabarella are primarily preservational artefacts and are unlikely to represent the real intra- and interspecific variability of the animal. In these cases, Planutenia is here confirmed to be a subjective synonym of Anabarella.

  • Bing, Pan
    et al.
    Skovsted, Christian
    Swedish Museum of Natural History, Department of Paleobiology.
    Sun, Haijing
    Li, Guoxiang
    Biostratigraphical and palaeogeographical implications of Early Cambrian hyoliths from the North China Platform2019In: Alcheringa, ISSN 0311-5518, E-ISSN 1752-0754, Vol. 43, p. 351-380Article in journal (Refereed)
    Abstract [en]

    A succession of diverse hyolith assemblages comprising 10 genera and 14 species are reported from the lower Cambrian Shangwan and Sanjianfang sections of the Xinji Formation, and Xiaomeiyao section of the Houjiashan Formation, which crop out along the southern margin of the North China Platform. Most of the specimens are represented by both conchs and opercula. The identified orthothecids include Conotheca australiensis, Cupitheca holocyclata, C. costellata, Neogloborilus applanatus, N. spinatus, Tegminites hymenodes, Triplicatella disdoma, T. xinjia sp. nov. and Paratriplicatella shangwanensis gen. et sp. nov. The hyolithids comprise Protomicrocornus triplicensis gen. et sp. nov., Microcornus eximius, M. petilus, Parkula bounites and Parakorilithes mammillatus. Some anomalous taxa possess characteristics of both Hyolithida and Orthothecida, such as C. australiensis, Neogloborilus and P. triplicensis. Protomicrocornus may constitute a sister group of other hyolithids. The teeth of Parkula bounites and clavicles of Parakorilithes mammillatus are documented for the first time. The hyolith assemblages from North China are probably coeval, and can be correlated with the Cambrian upper Stage 3–lower Stage 4. Many taxa are also globally distributed and have significant potential for biostratigraphical correlations. In accordance, the hyoliths from North China reveal closest compositional similarities to faunas from eastern Gondwana, and especially South Australia. However, some taxa are shared with Laurentian assemblages suggesting cosmopolitanism, and possibly planktonic larval dispersal.

  • Betts, Marissa, J.
    et al.
    Claybourn, Thomas M.
    Brock, Glenn, A.
    Jago, James, B.
    Skovsted, Christian
    Swedish Museum of Natural History, Department of Paleobiology.
    Paterson, John, R.
    Shelly fossils from the lower Cambrian White Point Conglomerate, Kangaroo Island, South Australia2019In: Acta Palaeontologica Polonica, ISSN 0567-7920, E-ISSN 1732-2421, Vol. 64, no 3, p. 489-522Article in journal (Refereed)
    Abstract [en]

    The lower Cambrian (Series 2) White Point Conglomerate (WPC) on Kangaroo Island, South Australia contains exoticclasts representing a diverse array of lithologies, including metamorphics, chert, sandstone, and abundant carbonates,notably archaeocyath-rich bioclastic limestone. Acetic acid digestion of the WPC bioclastic limestone clasts reveals adiverse shelly fauna. This assemblage includes abundant organophosphatic brachiopods such as Cordatia erinae Brockand Claybourn gen. et sp. nov., Curdus pararaensis, Eodicellomus elkaniformiis, Eohadrotreta sp. cf. E. zhenbaensis,Eoobolus sp., Kyrshabaktella davidii, and Schizopholis yorkensis. Additional shelly taxa include the solenopleurid trilobiteTrachoparia? sp., the tommotiids Dailyatia odyssei, Dailyatia decobruta Betts sp. nov., Kelanella sp., and Lapworthellafasciculata, spines of the bradoriid arthropod Mongolitubulus squamifer, and several problematica, such as Stoibostrombuscrenulatus and a variety of tubular forms. The upper age limit for the WPC is constrained by biostratigraphic data fromthe overlying Marsden Sandstone and Emu Bay Shale, which are no younger than the Pararaia janeae Trilobite Zone(Cambrian Series 2, Stage 4). The shelly fossil assemblage from the WPC limestone clasts indicates an upper Dailyatiaodyssei Zone (= Pararaia tatei to lower P. janeae trilobite zones), equivalent to the Atdabanian–early Botoman of theSiberian scheme. This contrasts with the previously suggested late Botoman age for the limestone clasts, based on the diversearchaeocyath assemblage. The minor age difference between the WPC and its fossiliferous limestone clasts suggestsrelatively rapid reworking of biohermal buildups during tectonically-active phases of deposition in the Stansbury Basin.

  • Lindh, Anders
    et al.
    Geologiska institutionen, Lunds universitet.
    Abu El-Rus, Mohamed A.
    Department of Geology, Assiut University, Assiut, Egypt.
    Mohamed, Mohamed Abdel‑Moneim
    Department of Geology, Assiut University, Assiut, Egypt.
    Persson, Per-Olof
    Swedish Museum of Natural History, Department of Geology.
    Scherstén, Anders
    Geologiska institutionen, Lunds universitet.
    A model for granite evolution based on non‑equilibrium magmaseparation: evidence from the Gharib and Qattar fluorite‑bearing granites, Eastern Desert, Egypt2019In: International journal of earth sciences, ISSN 1437-3254, E-ISSN 1437-3262, Vol. 108, no 4, p. 1201-1232Article in journal (Refereed)
    Abstract [en]

    We present 77 new granite whole-rock analyses from the Qattar and Gharib areas, Eastern Desert, Egypt. Both areas includea “normal” granite and either a hypersolvus (Gharib) or an almost plagioclase-free granite (Qattar) enriched in fluorite. According to earlier results, F influences element distribution in granitic melts forming complexes with specific elementsas Nb, Ta, Ga, Hf, Th, Zn, Sn, whereas F excludes Ba and Sr. We use principal component analyses to split the granite into chemical groups allowing an unbiased study of the inter-group element distribution. This adds the heavy REEs and Y to the earlier lists of elements with an affinity for F. The light REEs show a decreasing affinity with decreasing atomic mass; fluorine separates Sm from Nd, whereas Zr follows La. Opposite to some, but in accordance with other earlier results, the ratio Nb/Ta is higher in the fluorite-enriched than in the other granite. Weak tetrad effects are present. Zircon in the hypersolvus granite is high in common lead. We suggest F to be instrumental for separating Pb2+from Pb4+.Two hypotheses may explain the occurrence of the two contrasting granites: they have either different sources, or they are co-magmatic, but the magma was split into two discrete types. We apply the second hypothesis as our working hypothesis. The liquidus has a gentler slopewith pressure than the diapir requiring crystallisation to be most important in the lower part of the magma chamber. Our hypothesis suggests that globules of magma, enriched in volatile components, form during crystallisation due to slow diffusionrates in the crystallizing magma. Elements accompanying F are distributed into this magma batch, which has a lowered density and viscosity than the rest of the magma due to its increased contents of volatile components. A mushroom-formed diapir rises, forming the hypersolvus (or almost plagioclase-free) granite. Due to an edge effect, it is concentrated close to the wall of the magma chamber. The size and form of the outcropping granite depend on the intersection of the diapir with the erosion surface. Fluorine only makes it possible to follow the process. The model may be generalised to explain the diversification of non-F enriched granite, since the buoyancy of a magma batch several thousand m3 in size has a much larger impact on the system than the small negative buoyancy of crystals or small crystal aggregates. A-type granite classified merely from its trace element content may form from separated F-enriched magma batches. This may be the reason fo rtheir high frequency in the Eastern Desert.

  • Moksnes, Per-Olav
    et al.
    Eriander, Louise
    Hansen, Joakim
    Albertsson, Jan
    Andersson, Mathias
    Bergström, Ulf
    Carlström, Julia
    Swedish Museum of Natural History, Department of Environmental research and monitoring.
    Egardt, Jenny
    Fredriksson, Ronny
    Granhag, Lena
    Lindgren, Fredrik
    Nordberg, Kjell
    Wendt, Ida
    Wikström, Sofia
    Ytreberg, Erik
    Fritidsbåtars påverkan på grunda kustekosystem i Sverige2019Report (Other academic)