Thalmanninella globotruncanoides

Taxonomy

Original description: Translated from French: Test unequally biconvex with a lobate periphery. Spiral side slightly convex, comprising 2.5 to 3 whorls of chambers first separated by curved sutures, clearly raised compared to the flat to even slightly concave chambers surface; chambers clearly overlapping as in Globotruncana; toward the end of the last whorl, their surface is more or less globular and often sinking into a kind of small gutter near the following chamber or in contact with the previous whorl, the chambers are bigger, roughly semicircular and separated by weak ridge-like sutures that are lowered compared to the chambers surface. The sutural ridge extends toward the periphery into the carinal ridge, shaping a clear angle between them. In the posterior part of the chamber, the sutural ridge disappears under the overlapping previous chamber. Umbilical side showing the last whorl with 5 to 7 chambers, and rarely 8. Its first chambers are tightly arranged They have a tetrahedral shape and are twisted in the rotating direction of the spire, similarly to the imbricate pattern observed on the spiral side. The "nose" of this tetrahedron is marked by a ridge overhanging the umbilical area. This ridge becomes less perceptible along the sutures, then extends into the carinal ridge. The sutural depressions between the chambers are not very deep and open out only next to the umbilicus. While gradually moving from the first to the last chambers, the tetrahedral shape is still distinct. But the chambers become less angular and are separated by deep sutural depressions, sutures and chambers being slightly curved according to the rotating direction of the spire. The faint sutural ridge extends into the carinal ridge here too, each chamber overlaps its following one, and there is continuity between the anterior edge outline of a chamber and its periphery. The umbilicus is wide and deep, its diameter oscillating between 1/3 and 1/4 of the test diameter. Overhanging chambers around the umbilicus but the latter is partially filled with wall extensions shaped as calcareous decks, the last extension almost completely covering the previous ones. The interiomarginal aperture of the last chamber is the only visible aperture, at least in the unbroken specimens. It opens at the base of the septal face of the chamber and extends below the calcareous deck. The deck formed by the last chamber covers the previous ones, obscuring the interiomarginal aperture of the other chambers. The sutural aperture of the last chambers opens in the sutural depression; the aperture is capped by a lip. But, gradually, the sutural depression closing on itself, this aperture gets closer to the umbilicus and moves in such a way, that, when the chambers are set one on the other (that is, the first chambers of the last whorl) it( the aperture)is reduced to an orifice with one side bordered by a faint ridge clearly visible, even when the umbilical cavity is filled with a calcareous deposit of secondary origin. In this case, the orifice emerges in the shape of a small arc opening through the calcareous deck, posteriorly directed and almost facing the umbilical extremity of the previous chamber. The coiling direction is mostly sinistral, but one can find dextrally coiled specimens (pl. II, fig. 4a-b).

Entries in the Catalog of original descriptions: Rotalipora globotruncanoides

Geological Range:
Last occurrence (top): within R. cushmani zone (94.03-95.94Ma, top in Cenomanian stage). Data source: [copied from Chronos database]
First occurrence (base): at base of T. globotruncanoides zone (0% up, 100.5Ma, in Albian stage). Data source: zonal marker (from Timescale Creator)

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: Thalmanninella globotruncanoides, synonyms included - Rotalipora globotruncanoides; Thalmanninella globotruncanoides;
• See also space-time plot :: Samples map :: Parent: Thalmanninella

Thalmanninella globotruncanoides compiled by the pforams@mikrotax project team viewed: 11-12-2023 Taxon Search: Advanced Search Short stable page link: https://mikrotax.org/pforams/index.php?id=110546 Go to Archive.is to create a permanent copy of this page - citation notes

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