Praeglobotruncana gibba

Taxonomy

Original description: Translated from French: The characters of this variety are those of the type species. However, the spire is higher, and the ratio of the height of the ventral convexity to the combined heights of the spire and ventral convexity is lower. We have not observed an increase in size for the specimens from level 56, we have not noticed the presence of a septal keel in the chambers of the last whorl, and the last chamber does not always feature a marginal keel. Because of the height of the spire in dorsal view, the outline seems less lobate since the dorsal side of the chambers meets the observer's eye obliquely. This variety (the differentiation of which remains a little subjective) represents nearly less than 15% of the Late Cenomanian Praeglobotruncana population (level 56 of the Breggia River section).

Les caractères de cette variété sont ceux du type de l'espèce. Cependant, la spire est plus haute, et le rapport de la hauteur de la convexité ventrale à la somme de celles de la spire et de cette convexité ventrale est moins élevé. Nous n'avons pas observé d'augmentation sensible de la taille des individus au niveau 56. Nous n'avons pas remarqué de carène septale dans les loges du dernier tour, et la dernière loge ne présente pas toujours de carène marginale. A cause de la spire haute, le pourtour paraît en vue dorsale moins lobé, puisque le côté dorsal des loges se présente obliquement à l'observateur.
Cette variété représente environ (la discrimination de ses représentants reste quelque peu subjective) 15% de la population des Praeglobotruncana au Cénomanien supérieur (niveau 56 de la Breggia).

Entries in the Catalog of original descriptions: Praeglobotruncana stephani gibba, Globotruncana stephani turbinata

Geological Range:
Last occurrence (top): within H. helvetica zone (92.51-93.52Ma, top in Turonian stage). Data source: [copied from Chronos database]
First occurrence (base): within R. cushmani zone (94.03-98.69Ma, base in Cenomanian stage). Data source: [copied from Chronos database]

Plot of range and occurrence data:

• Range-bar - range as quoted above, pink interval top occurs in, green interval base occurs in.
• Triangles indicate an event for which a precise placement has been suggested
• Histogram - Neptune occurrence data from DSDP and ODP proceedings. Pale shading <50 samples in time bin. Interpret with caution & read these notes
• Taxon plotted: Praeglobotruncana gibba, synonyms included - Globotruncana stephani turbinata; Praeglobotruncana gibba; Praeglobotruncana hilalensis; Praeglobotruncana turbinata;
• See also space-time plot :: Samples map :: Parent: Praeglobotruncana

Praeglobotruncana gibba compiled by the pforams@mikrotax project team viewed: 20-9-2024 Taxon Search: Advanced Search Short stable page link: https://mikrotax.org/pforams/index.php?id=110430 Go to Archive.is to create a permanent copy of this page - citation notes

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