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Wyszukujesz frazę "Hoffmann, R." wg kryterium: Autor


Wyświetlanie 1-2 z 2
Tytuł:
Non-destructive analysis of pathological belemnite rostra by micro-CT techniques
Autorzy:
Hoffmann, R.
Stevens, K.
Picollier, M.-C.
Mutterlose, J.
Klug, C.
Powiązania:
https://bibliotekanauki.pl/articles/2082134.pdf
Data publikacji:
2020
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
Cephalopoda
Belemnitida
palaeopathology
rostra
micro computed-tomography
diagenesis
Jurassic
Cretaceous
Germany
Opis:
Previously, palaeopathological features of fossil hardparts were often difficult to interpret because it was impossible to decipher their internal structure without destroying the specimens. We applied high-resolution computedtomo graphy (CT) to document such internal structures. This enabled us to describe a variety of pathologies of Jurassic and Cretaceous belemnite rostra. The examined rostra have been assigned to the taxa ?Acrocoelites sp., Belemnello camax spp., Belemnitella sp., Duvalia emerici, Goniocamax sp., Gonioteuthis spp., Hibolithes jaculoides, Neoclavibelus subclavatus, and Pseudobelus sp. The studied pathologies comprise rostra with two apices, bulges, pearls, broken juvenile rostra, highly porous rostra with abnormal growth increments, blunt-rostra, rostra with callus- like structures, and bent- or knee-shaped rostra. In one rostrum the apex has been turned towards the anterior (alveolus) during ontogeny. Additionally, computed-tomography data were used to document diagenetic alterations of the rostra such as silification, sedimentary infill, pyrite formation. Specimens can also be tested for the presence or absence of internal elements (septa, siphuncle) and surface features. Palaeoecological studies clearly benefit from the application of computed-tomography to gain high resolution images of otherwise invisible internal features of extinct organisms, as demonstrated herein.
Źródło:
Acta Palaeontologica Polonica; 2020, 65, 1; 11-27
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Virtual 3D modeling of the ammonoid conch to study its hydrostatic properties
Autorzy:
Moron-Alfonso, D.A.
Peterman, D.J.
Cichowolski, M.
Hoffmann, R.
Lemanis, R.E.
Powiązania:
https://bibliotekanauki.pl/articles/2082232.pdf
Data publikacji:
2020
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
Cephalopoda
Ammonoidea
virtual modeling
3D
conch
CT-scan
morphometry
Cretaceous
Antarctica
Opis:
Computed tomography has provided a wealth of biological data that now stands beside a vast, more traditional, morphometric database. By exploiting these two resources, we present a novel methodology to construct intricate, virtual cephalopod shells. As a case of study, we applied this method to Maorites seymourianus using data obtained from a previous work. For this purpose, evaluation of the conch geometry, and the definition of new parameters such as the segment width expansion rate (SWER), segment height expansion rate (SHER), the segment thickness expansion rate (STER), and three indices related, were introduced. The conch geometry of M. seymourianus follows a spiral that can be defined by a polynomial function. While similar to a logarithmic function, a polynomial fit is preferred because it reveals higher values of whorl expansion at the early ontogenetic phase and lower values reaching the adult body chamber. Results on the hydrostatic properties of the virtual models indicate that M. seymourianus would have a near neutral buoyancy, ranging from slightly positive to slightly negative, depending upon parameters that influence organismal mass. Positions of the center of mass and the center of buoyancy indicate that the studied species would have a relatively low hydrostatic stability, estimating a shell orientation of approximately 74–76° with respect to the vertical, with the aperture slightly inclined downwards relative to the horizontal plain.
Źródło:
Acta Palaeontologica Polonica; 2020, 65, 3; 467-480
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
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