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Wyszukujesz frazę "Nagm, E." wg kryterium: Autor


Wyświetlanie 1-2 z 2
Tytuł:
Late Cenomanian.Turonian (Cretaceous) ammonites from Wadi Qena, central Eastern Desert, Egypt : taxonomy, biostratigraphy and palaeobiogeographic implications
Autorzy:
Nagm, E.
Wilmsen, M.
Powiązania:
https://bibliotekanauki.pl/articles/139381.pdf
Data publikacji:
2012
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
amonity
biostratygrafia
Egipt
górna kreda
paleobiogeografia
paleontologia systematyczna
ammonites
biostratigraphy
Egypt
palaeobiogeography
systematic palaeontology
Upper Cretaceous
Opis:
In Egypt, marine Upper Cenomanian.Turonian strata are well exposed in the Eastern Desert. The southernmost outcrops are located in the central part of Wadi Qena, where the lower Upper Cretaceous is represented by the fossiliferous Galala and Umm Omeiyid formations. From these strata, numerous ammonites have been collected bed-by-bed and 13 taxa have been identified, which are systematically described herein. Four of them (Euomphaloceras costatum, Vascoceras globosum globosum, Thomasites gongilensis and Pseudotissotia nigeriensis) are recorded from Egypt for the first time. The ammonite ranges are used for a biostratigraphic zonation of the lower Upper Cretaceous succession in the northern and central part of Wadi Qena: the Upper Cenomanian.Lower Turonian has been subdivided into five biozones (including a new upper Lower Turonian biozone based on the occurrence of Pseudotissotia nigeriensis), and one biozone has been recognized in the Upper Turonian. Palaeobiogeographically, the ammonite assemblage has a Tethyan character. During the Early Turonian, influences of the Vascoceratid Province were predominant with strong affinities to typical Nigerian faunas. This shows the significance of faunal exchange between Egypt and Central and West Africa via the Trans-Saharan Seaway. Compared to contemporaneous ammonoid faunas from the northern part of the Eastern Desert, Boreal influences are much less obvious in Wadi Qena. Thus, the present study greatly enhances the knowledge of the Late Cretaceous palaeobiogeography and biostratigraphy of Egypt and adjacent areas.
Źródło:
Acta Geologica Polonica; 2012, 62, 1; 63-89
0001-5709
Pojawia się w:
Acta Geologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Palaeobiology and evolutionary context of Angulithes mermeti, a streamlined early Late Cretaceous shallow - water nautiloid
Autorzy:
Wilmsen, M.
Nagm, E.
Powiązania:
https://bibliotekanauki.pl/articles/20639.pdf
Data publikacji:
2019
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Opis:
Cretaceous nautiloids are commonly characterized by inflated shells and prolonged stratigraphic ranges. In the Albian, the species of Angulithes appeared and compressed, short-lived forms with narrow venters emerged during the Cenomanian age. Based on a new description, the late Cenomanian nautiloid Angulithes mermeti is discussed with its palaeobiological background and placed in an evolutionary context of the Cenomanian lineage of Angulithes, considering contemporaneous palaeoenvironmental changes and inferred functional traits. A. mermeti is characterized by a nearly oxycone shell with sharp venter and narrow umbilicus, a fairly sinuous suture, low inter-septal distances, and an almost dorsal siphuncle. Its palaeobiogeographical occurrence was latitudinally restricted to shallow tropical–subtropical shelf seas with a preferred habitat depth between 5–50 m. Several morphological trends reflected by the Cenomanian species of the genus culminated in the late Cenomanian species A. mermeti, i.e., (i) increasing shell compression and sharpening of the venter, (ii) increasing folding of the septa, (iii) reduction of inter-septal distances, and (iv) dorsally directed migration of the siphuncle. The hydrodynamically efficient form was favorable to successfully populate the wide and shallow epicontinental seas that formed during the Cenomanian age. The increasing sutural sinuosity and the dense septal spacing aimed to buttress the shells against shell-breaking predators while the functional reason for the dorsal- directed migration of siphuncle is more elusive; it may have improved the efficiency of the hydrostatic apparatus and its internal position is beneficial in the case of predation, too. The gradual morphological change in the Cenomanian lineage of the genus Angulithes provides a well-constrained case study of rapid evolutionary response to major environmental pressure, i.e., the opening of newly available niches in the course of the great early Late Cretaceous transgression, in an otherwise rather bradytelic biotic group.
Źródło:
Acta Palaeontologica Polonica; 2019, 64, 4
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-2 z 2

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