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    Wyświetlanie 1-3 z 3
    Tytuł:
    Acanthodians from the Lower Devonian (Emsian) ‘Placoderm Sandstone’, Holy Cross Mountains, Poland
    Autorzy:
    Burrow, C. J.
    Szrek, P.
    Powiązania:
    https://bibliotekanauki.pl/articles/139217.pdf
    Data publikacji:
    2018
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    Acanthodii
    Machaeracanthus
    Striacanthus
    Onchus
    Emsian
    Lower Devonian
    Polska
    fałdopłetwe
    akantody
    ems
    dewon dolny
    Polska
    Opis:
    The Lower Devonian ‘Placoderm Sandstone’ in the Holy Cross Mountains (HCM) is filled with abundant impressions of disarticulated vertebrate remains. The only acanthodian macroremains named to date are fin spines of Machaeracanthus polonicus Gürich. Fin spine impressions in slabs from the Winna Formation (Emsian) at Podłazie Hill (near Daleszyce) in the southern HCM, and also the Barcza Formation (?Lochkovian) at Barcza Quarry, Miedziana Góra Conglomerate (?Lochkovian), Gruchawka, and Zagórze Formation (middle–upper Emsian) at Bukowa Mountain in the northern HCM, reposited in the University of Warsaw, Polish Geological Institute-National Research Institute, Warsaw, and Natural History Museum, London collections, have been cast and studied in order to better document this poorly known taxon. As noted in other Machaeracanthus species, we have found that M. polonicus has two different morphotypes of spines, which abut lengthwise to form a pair of spines. Our investigations show that the fin spine assemblage includes Onchus overathensis as well as M. polonicus, and probably another undetermined acanthodian. The affinities of O. overathensis are reassessed. It is here considered to be a diplacanthiform, and reassigned to the genus Striacanthus, as S. overathensis. Acanthodian scapulocoracoids have also been identified, as well as tightly spiralled toothwhorls which could be from an acanthodian.
    Źródło:
    Acta Geologica Polonica; 2018, 68, 3; 307-320
    0001-5709
    Pojawia się w:
    Acta Geologica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Stem chondrichthyan microfossils from the Lower Old Red Sandstone of the Welsh Borderland
    Autorzy:
    Burrow, C. J.
    Turner, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/138801.pdf
    Data publikacji:
    2018
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    scale histology
    palaeobiogeography
    Lower Devonian
    Lochkovian
    stem gnatho stomes
    Altholepis
    Polymerolepis
    British Isles
    histologia
    paleobiogeografia
    dewon dolny
    lochkov
    Wyspy Brytyjskie
    Opis:
    Placoid and polyodontode scales of stem chondrichthyans have been found in the early Lochkovian “Ditton Group” of the Brown Clee Hill district, Shropshire, England and at Talgarth, south Wales. One of the forms is assigned to a new species of Altholepis Karatajūtė-Talimaa, 1997, a genus already recognised from Lochkovian shallow marine deposits in Celtiberia, Spain and the Northwest Territories, Canada as well as the type locality in Podolia, Ukraine. Altholepis salopensis sp. nov. is based on small polyodontode scales with typically three to eight high odontodes; the scale form was previously considered to belong to acanthodian “Nostolepis” robusta (Brotzen, 1934). The structure of other scales formerly assigned to “Nostolepis” robusta has led us to erect a new genus Jolepis for this scale form, which differs from Altholepis in lacking an ordered layout of odontodes. Jolepis robusta (Brotzen, 1934), originally (and possibly still) considered to be an acanthodian, is also known from the Baltic countries, Russia, and northern Germany (ex erratic limestones). Scales of acanthodian Parexus recurvus Agassiz, 1845, and/or possibly from the stem chondrichthyan Seretolepis elegans Karatajūtė-Talimaa, 1968 (scales of these two taxa are barely distinguishable), and of stem chondrichthyan Polymerolepis whitei Karatajūtė-Talimaa, 1968 are also present. Altholepis, Jolepis gen. nov., Seretolepis Karatajūtė-Talimaa, 1968 and Polymerolepis KaratajūtėTalimaa, 1968 are found in marine deposits elsewhere; the British occurrence of these taxa adds to the debate on the sedimentological origins of the Lower Old Red Sandstone deposits in the Welsh Borderland. The geographic range of several early sharks is now known to extend around the Old Red Sandstone continent and beyond.
    Źródło:
    Acta Geologica Polonica; 2018, 68, 3; 321-334
    0001-5709
    Pojawia się w:
    Acta Geologica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Vascular structure of the earliest shark teeth
    Autorzy:
    Martínez-Pérez, C.
    Martín-Lazaro, A.
    Ferrón, H. G.
    Kirstein, M.
    Donoghue, P. C. J.
    Botella, H.
    Powiązania:
    https://bibliotekanauki.pl/articles/139170.pdf
    Data publikacji:
    2018
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    Leonodus
    Celtiberina
    early chondrichthyans
    Lower Devonian
    synchrotron tomography
    vascular system
    ryby chrzęstnoszkieletowe
    ryby chrzęstne
    chrzęstniki
    dolny dewon
    tomografia
    układ naczyniowy
    Opis:
    Here we use synchrotron tomography to characterise dental vasculature in the oldest known tooth-bearing sharks, Leonodus carlsi Mader, 1986 and Celtiberina maderi Wang, 1993. Three dimensional reconstruction of the vascular system and microstructure of both taxa revealed a complex and dense network of canals, including horizontal, ascending and secondary bifurcated canals, as well as histological features consistent with an osteodont histotype. However, L. carlsi and C. maderi also exhibit significant morphological differences, showing Leonodus a typical diplodont tooth morphology with a linguo-labially elongated base, that contrast with Celtiberina’s teeth that show a single conical cusp curved lingually with a week developed flat base mesio-distally extended, perhaps reflecting distant relationship. These data are compatible with a pre-Devonian diversification of the two main tooth types traditionally recognised in Palaeozoic sharks (i.e., “cladodont” vs “diplodont”). Finally, our data demonstrate that existing dental classification schemes based on styles of vascularisation are over-simplified, especially when Palaeozoic taxa are considered.
    Źródło:
    Acta Geologica Polonica; 2018, 68, 3; 457-465
    0001-5709
    Pojawia się w:
    Acta Geologica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-3 z 3

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