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Wyszukujesz frazę "early ontogeny" wg kryterium: Wszystkie pola


Wyświetlanie 1-2 z 2
Tytuł:
Early ontogeny and palaeoecology of the Mid-Miocene rissoid gastropods of the Central Paratethys
Autorzy:
Kowalke, T
Harzhauser, M.
Powiązania:
https://bibliotekanauki.pl/articles/21635.pdf
Data publikacji:
2004
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
Miocene
gastropod
Mohrensternia pfaffstaettensis
morphology
embryonic shell
Sarmatian
Mohrensternia hollabrunnensis
Gastropoda
ontogenesis
Caenogastropoda
rissoid gastropod
Badenian
paleoecology
Rissooidea
Littorinimorpha
Opis:
Twenty−six species of Rissoidae (Caenogastropoda: Littorinimorpha: Rissooidea) are described from the Badenian and Early Sarmatian of 14 localities in Austria and the Czech Republic (Molasse Basin, Styrian Basin, Vienna Basin) and from the Badenian of Coştei (Romania). For the first time, the early ontogenetic skeletal characters of these gastropods are described. Based on these features an indirect larval development with a planktotrophic veliger could be reconstructed for all investigated Mid−Miocene species. The status of Mohrensterniinae as a subfamily of the Rissoidae is confirmed by the morphology of the low conical protoconch, consisting of a fine spirally sculptured embryonic shell and a larval shell which is smooth except for growth lines. Transitions from embryonic shells to larval shells and from larval shells to teleoconchs are slightly thickened and indistinct. Whilst representatives of the subfamily Rissoinae characterise the marine Badenian assemblages, Mohrensterniinae predominate the Early Sarmatian faunas. We hypothesize that this take−over by the Mohrensterniinae was triggered by changes in the water chemistry towards polyhaline conditions. Consequently, the shift towards hypersaline conditions in the Late Sarmatian is mirrored by the abrupt decline of the subfamily. Four new species Rissoa costeiensis (Rissoinae) from the Badenian and Mohrensternia hollabrunnensis, Mohrensternia pfaffstaettensis, and Mohrensternia waldhofensis (Mohrensterniinae) from the Early Sarmatian are introduced.
Źródło:
Acta Palaeontologica Polonica; 2004, 49, 1
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Early ontogenetic growth stages of Middle Ordovician orthoceratoid cephalopods from Bohemia
Autorzy:
Aubrechtova, M.
Turek, V.
Zicha, O.
Powiązania:
https://bibliotekanauki.pl/articles/2082221.pdf
Data publikacji:
2020
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
Cephalopoda
Orthoceratida
early ontogeny
embryonic shell
Paleozoic
Darriwilian
Bohemia
Czech
Republic
Opis:
This study describes 18 specimens representing the earliest growth parts of orthoceratoid cephalopods, most of which have been recently obtained from the Middle Ordovician strata of the Prague Basin, central Bohemia. Only about 20 specimens of Ordovician orthoceratoids displaying embryonic shell are known globally and the Bohemian material thus significantly expands their current record. The studied collection includes twelve specimens assigned to the species Bactroceras sandbergeri and shows that the morphological variability in early ontogenetic growth stages of this species was rather low. The absence of a cicatrix was definitely confirmed in this phylogenetically important cephalopod. Six other specimens investigated herein are indeterminate orthoceratids. Initial chambers, where preserved, are generally large compared to known, stratigraphically younger specimens. This is interpreted here as supporting the previously postulated trend of decreasing the egg- and hatchling sizes in orthoceratoid cephalopods from mid-Ordovician times onwards. Alternatively, the large sizes of these Bohemian orthoceratids may be explained by the position of the Prague Basin in relatively cool-water high palaeolatitudes during the Middle Ordovician.
Źródło:
Acta Palaeontologica Polonica; 2020, 65, 3; 575-588
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-2 z 2

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