Globotruncanella semsalensis

Taxonomy

Original description: Translated from French:
Test trochoidal, lobate, dextral in all the examined specimens (47). 2½ - 3 whorls. 4½ - 7, generally six, chambers per whorl, compressed, generally increasing slowly in size. One or several chambers of the last whorl may be smaller in size than the previous chambers or they all are the same size. The last-formed chamber is usually larger, sometimes the same size or even smaller than the penultimate chamber. Rounded or slightly elongate, or spine-like pustules densely present on the two sides of the test. On the first chambers of the last whorl they are thick, gradually becoming thinner and thinner on the following chambers so that the last chamber(s) may be more or less smooth.

Spiral side convex. The chambers of the first whorl look like buttons tightly fit one against the other. In the second whorl, they become more distinct.They have a flat or slightly convex surface with thick rounded, spiky or slightly elongate pustules concentrating along the periphery and roughly shaping spiral and septal ridges, the two ridges forming a curve or an "u" between them . This ornamentation often remains present in the two or three first chambers of the last whorl; then it disappears, resulting in a depressed, radial, or curved in a frontward direction septal suture. The spiral side of the chambers of this last whorl is weakly to moderately convex.

Umbilical side: due to this side being strongly inflated, its shape is convex from the periphery toward the center of the chambers and concave from there toward the umbilicus. Sutures radial, depressed. Strong and thick pustules on the first chambers of the last whorl, either randomly distributed or aligned in the coiling direction or else perpendicular to that direction and, in this case, appearing like short costae spreading out from the umbilical edge toward the margin. In some specimens ,(presence of) one or two rows of pustules set in the coiling direction , becoming stronger on the two or three first chambers of the last coil and doubling or tripling the already existing peripheral row.

The primary aperture of the chambers is umbilical but often extends slightly toward the edge. It is covered by a tegillum directed toward the umbilicus, each tegillum is provided with a main aperture in the front and with one or two secondary apertures in the back. The infralaminal apertures (main and secondary) are provided - or not - with a thin lip. Each tegillum partly or totally extending over the tegillum of the preceding chamber, the tegillum of the last chamber sometimes sealing the whole umbilicus. I did not notice the presence of secondary intralaminal apertures.

Entries in the Catalog of original descriptions: Globotruncana semsalensis

Geological Range:
Last occurrence (top): within R. calcarata zone (75.06-75.91Ma, top in Campanian stage). Data source: [copied from Chronos database]
First occurrence (base): within R. calcarata zone (75.06-75.91Ma, base in Campanian 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: Globotruncanella semsalensis, synonyms included - Globotruncana semsalensis; Praeglobotruncana semsalensis;
• See also space-time plot :: Samples map :: Parent: Globotruncanella

Globotruncanella semsalensis compiled by the pforams@mikrotax project team viewed: 14-12-2024 Taxon Search: Advanced Search Short stable page link: https://mikrotax.org/pforams/index.php?id=110186 Go to Archive.is to create a permanent copy of this page - citation notes

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