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    Wyświetlanie 1-4 z 4
    Tytuł:
    Trachyplax arctica, a new multiplated problematic fossil from the Lower Cambrian of North Greenland
    Autorzy:
    Larsson, C M
    Peel, J.S.
    Hogstrom, A.E.S.
    Powiązania:
    https://bibliotekanauki.pl/articles/20953.pdf
    Data publikacji:
    2009
    Wydawca:
    Polska Akademia Nauk. Instytut Paleobiologii PAN
    Tematy:
    Trachyplax arctica
    fossil
    paleontology
    Lower Cambrian
    Cambrian
    North Greenland
    Greenland
    Trachyplax
    Problematica
    sclerite
    scleritome
    Multiplacophora
    Paralledal Formation
    Opis:
    A new scleritome−bearing organism with eight sclerite types, Trachyplax arctica gen. et sp. nov., is described from the lower Cambrian Paralledal Formation of North Greenland. The originally calcareous sclerites are now silicified; no microstructures are preserved. The dominant sclerite type (A; maximum dimension 19.3 mm) is bilaterally symmetrical, strongly arched, with an oval shield showing co−marginal growth lines and a projecting rostrum with prominent radial ornamentation. A similar sclerite morphology can be identified in Silurian–Carboniferous multiplacophoran molluscs but the remaining sclerite types, which also display a combination of concentric and radial ornamentation, find no clear equivalents. Two models for scleritome reconstruction are presented, based on the relative abundance of the sclerites, but neither promotes a satisfactory assignment to a higher taxon. Despite the morphological dissimilarities, possibly reflecting the age discrepancy, reference to the Multiplacophora is most attractive and entails a substantial extension of the known geological range of that group.
    Źródło:
    Acta Palaeontologica Polonica; 2009, 54, 3; 513-523
    0567-7920
    Pojawia się w:
    Acta Palaeontologica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The earliest annelids: Lower Cambrian polychaetes from the Sirius Passet Lagerstatte, Peary Land, North Greenland
    Autorzy:
    Morris, S C
    Peel, J.S.
    Powiązania:
    https://bibliotekanauki.pl/articles/21486.pdf
    Data publikacji:
    2008
    Wydawca:
    Polska Akademia Nauk. Instytut Paleobiologii PAN
    Tematy:
    Polychaeta
    Annelida
    systematics
    annelid
    Greenland
    polychaete annelid
    paleontology
    metazoan evolution
    Sirius Passet Lagerstatte
    Phagmochaeta canicularis
    Lower Cambrian
    Cambrian
    Opis:
    Apart from the Phyllopod Bed of the Burgess Shale (Middle Cambrian) polychaete annelids are practically unknown from any of the Cambrian Lagerstätten. This is surprising both because their diversity in the Burgess Shale is considerable, while to date the Chengjiang Lagerstätte which is equally impressive in terms of faunal diversity has no reliable records of any annelids. Here we describe, on the basis of about 40 specimens, Phragmochaeta canicularis gen. et sp. nov. from the Lower Cambrian Sirius Passet Lagerstätte of Peary Land, North Greenland. This makes it by far the oldest known polychaete, with a likely age of lower to middle Atdabanian, The body consists of approximately 20 segments, each bearing notochaetae and neurochaetae. The former appeared to have formed a felt−like covering on the dorsum, whilst the neurochaetae projected obliquely to the longitudinal axis. Apart from minor differences in chaetal size at either end there is no other tagmosis. Details of the head are obscure, and presence of palps, tentacles and eyes are conjectural. Jaws appear to have been absent. The gut was straight, and flanked by massive longitudinal musculature. P. canicularis was evidently benthic, propelling itself on the neurochaetae, with the dorsal neurochaetae conferring protection. Its stratigraphic position and generalized appearance are consistent with P. canicularis being primitive, but the phylogenetic relationships within the polychaetes remain problematic, principally because of paucity of relevant morphological information.
    Źródło:
    Acta Palaeontologica Polonica; 2008, 53, 1
    0567-7920
    Pojawia się w:
    Acta Palaeontologica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    New palaeoscolecidan worms from the Lower Cambrian: Sirius Passet, Latham Shale and Kinzers Shale
    Autorzy:
    Morris, S.C.
    Peel, J.S.
    Powiązania:
    https://bibliotekanauki.pl/articles/23022.pdf
    Data publikacji:
    2010
    Wydawca:
    Polska Akademia Nauk. Instytut Paleobiologii PAN
    Tematy:
    new worm
    worm
    palaeoscolecidan worm
    Lower Cambrian
    Sirius Passet
    Latham Shale
    Kinzers Formation
    paleontology
    Palaeoscolecida
    Chalazoscolex
    Xystoscolex
    Cycloneuralia
    Cambrian
    Greenland
    California
    Pennsylvania
    Opis:
    Palaeoscolecidan worms are an important component of many Lower Palaeozoic marine assemblages, with notable occurrences in a number of Burgess Shale−type Fossil−Lagerstätten. In addition to material from the lower Cambrian Kinzers Formation and Latham Shale, we also describe two new palaeoscolecidan taxa from the lower Cambrian Sirius Passet Fossil−Lagerstätte of North Greenland: Chalazoscolex pharkus gen. et sp. nov and Xystoscolex boreogyrus gen. et sp. nov. These palaeoscolecidans appear to be the oldest known (Cambrian Series 2, Stage 3) soft−bodied examples, being somewhat older than the diverse assemblages from the Chengjiang Fossil−Lagerstätte of China. In the Sirius Passet taxa the body is composed of a spinose introvert (or proboscis), trunk with ornamentation that includes regions bearing cuticular ridges and sclerites, and a caudal zone with prominent circles of sclerites. The taxa are evidently quite closely related; generic differentiation is based on degree of trunk ornamentation, details of introvert structure and nature of the caudal region. The worms were probably infaunal or semi−epifaunal; gut contents suggest that at least X. boreogyrus may have preyed on the arthropod Isoxys. Comparison with other palaeoscolecidans is relatively straightforward in terms of comparable examples in other Burgess Shale−type occurrences, but is much more tenuous with respect to the important record of isolated sclerites. These finds from Greenland provide further evidence that palaeoscolecidans possessed a complex anterior introvert directly comparable to a number of priapulid−like taxa from other Burgess Shale−type assemblages. Although these palaeoscolecidans have been allied with the nematomorphs, molecular data in conjunction with our observations suggest that this hypothesis is untenable. Palaeoscolecidans and similar priapulid−like taxa are probably primitive cycloneuralians and as such may indicate the original bodyplan of this important group of ecdysozoans. In addition, we describe another sclerite−bearing fossil from the Sirius Passet Fossil−Lagerstätte that may be related to the cambroclaves.
    Źródło:
    Acta Palaeontologica Polonica; 2010, 55, 1
    0567-7920
    Pojawia się w:
    Acta Palaeontologica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Small shelly fossils from the argillaceous facies of the Lower Cambrian Forteau Formation of Western Newfoundland
    Autorzy:
    Skovsted, C.B.
    Peel, J.S.
    Powiązania:
    https://bibliotekanauki.pl/articles/20504.pdf
    Data publikacji:
    2007
    Wydawca:
    Polska Akademia Nauk. Instytut Paleobiologii PAN
    Tematy:
    Brachiopoda
    Cambrian
    Forteau Formation
    geological setting
    Helcionellidae
    Hyolitha
    Lower Cambrian
    Newfoundland
    argillaceous facies
    brachiopod
    facies
    fossil
    helcionelloid mollusc
    hyolith
    mollusc
    paleontology
    small shelly fossil
    systematics
    Opis:
    A diverse fauna of helcionelloid molluscs, hyoliths, and other small shelly fossils is described from limestone layers within the Forteau Formation of the Bonne Bay region in western Newfoundland. The fauna is dominated by internal moulds of various molluscs and tubular problematica, but also includes hyolith opercula, echinoderm ossicles, and other calcareous small shelly fossils preserved by phosphatisation. Originally organophosphatic shells are comparatively rare, but are represented by brachiopods, hyolithelminths, and tommotiids. The fauna is similar to other late Early Cambrian faunas from slope and outer shelf settings along the eastern margin of Laurentia and may be of middle Dyeran age. The similarity of these faunas indicates that at least by the late Early Cambrian, a distinctive and laterally continuous outer shelf fauna had evolved. The Forteau Formation also shares elements with faunas from other Early Cambrian provinces, strengthening ties between Laurentia and Australia, China, and Europe during the late Early Cambrian. Two new taxa of problematic fossil organisms are described, the conical Clavitella curvata gen. et sp. nov. and the wedge−shaped Sphenopteron boomerang gen. et sp. nov.
    Źródło:
    Acta Palaeontologica Polonica; 2007, 52, 4
    0567-7920
    Pojawia się w:
    Acta Palaeontologica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-4 z 4

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