Guembelitria sergipensis

Taxonomy

Original description: This species is characterized by having a minute trochoid test, triserial throughout, with a short, moderately high trochospire, and a slight variability during ontogeny in the maximum height/diameter (H/D) ratio (e.g., from H/D around 1.1, elongate-conical neanic to early ephebic morphotypes-Pl.1, figs.5, 6, 15, Pl.2, fig.2; and H/D close or equal to 1, nearly as broad as long, globular trochoid, early ephebic and gerontic morphotypes-Pl.1, figs.1-2, 8, 12, 13, Pl.2, figs.1, 3, 4). Three inflated, gradually enlarging globular chambers in the last whorl, distinct, differing little in size and comprising about 2/3 of the test size. Chambers of previous whorl are indistinct, mostly obscured by overgrowth of test surface calcification. Ultimate chamber in mature specimens has smoother ornamentation and partially covers the umbilicus (e.g., Pl.1, figs.1, 8, 12, 13). Umbilicus small, shallow; periphery rounded. Sutures distinct and depressed, in the last whorl; indistinct in the previous whorls. Aperture a low to medium sized umbilical arch at the base of the last formed chamber, slightly asymmetrical. The aperture is nearly completely obscured by overgrowths of test ornamentation and deposited calcite particles. Test surface covered with blunt rounded or elongate poreless pustules, some forming elongate imperforate quadrangles (= short ridges)-(Pl.1, figs.3, 4, 5, 7, 9-11 and Pl.2, figs.5, 9, 10), several pore mounds (pores of maximum diameter around 1.0 microns; see Pl.1, figs.11, 14, 16 and Pl.2, figs.7, 12), and sporadic presence of pores on edges of pustules (Pl.2, figs.5, 10). The specimens show an irregular development of the pore mounds on the first two chambers of the last whorl (Pl.1, figs.14, 16, and Pl.2, fig.5, 7). The ultimate chamber may be densely covered with small poreless pustules and totally lack pore mounds (Pl.2, fig.10), whereas these may have been sealed on the earlier chambers by shell overgrowths. Morphologically intermediate forms between G. sergipensis and G. cenomana (Keller), with a more elongate test (WD from around 1.2 to 1.3). higher trochospire, and more developed pore mounds surface texture, are recorded in the middle Albian to lowermost upper Albian (PI. 2, figs. 6-12). Thirteen paratypes are illustrated by the lateral views in PI. 1, figs. 5-16, and PI. 2, figs. 1-12. The overall morphological features are similar to that of the holotype, varying only slightly in the WD ratio, coarseness of the test surface ornamentation and in the density and regularity of pore mounds.

Entries in the Catalog of original descriptions: Guembelitria sergipensis

Geological Range:
Last occurrence (top): within T. primula zone (107.39-111.84Ma, top in Albian stage). Data source: [copied from Chronos database]
First occurrence (base): within P. cheniourensis zone (118.02-118.93Ma, base in Aptian 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
• (NB There is no histogram as there are no occurrence records for the taxon in the Neptune database) Parent: Guembelitria

Guembelitria sergipensis compiled by the pforams@mikrotax project team viewed: 10-12-2023 Taxon Search: Advanced Search Short stable page link: https://mikrotax.org/pforams/index.php?id=110222 Go to Archive.is to create a permanent copy of this page - citation notes

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