Catalog - Globuligerina glinskikhae

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Globuligerina glinskikhae

Citation: Globuligerina glinskikhae Gradstein & Waskowska 2021

Type sample (& lithostrat): sample GN 6 in the lower part of the Gnaszyn section; a grey and slightly sandy claystone with numerous bioclasts, mainly of mollusks shells

Type age (chronostrat): Morrisi Ammonite Zone - Middle Bathonian

Type locality: Gnaszyn section of the Częstochowa area of Poland (Gradstein et al. 2017a, Figures 12 and 13)

Type repository: Krakow; European Micropalaeontology Reference Centre of the MicroPress Europe Foundation at AGH, Krakow, Poland.

Test diameter generally in the 100–125 μm range, with 2–3 whorls in a compact trochoid shape. Relatively large, last whorl with three, globular chambers, slowly increasing in size, with the last globular chamber taking up about half of the final whorl. Coiling direction mostly dextral. Sutures depressed, umbilicus tight, aperture a low slit with rim at the base of the last chamber in the umbilical area. Test wall microperforate with numerous small pustules and scattered pore mounds

Test diameter generally in the 100–125 μm range

The new species is named in honour of Dr. Larisa Glinskikh, Novosibirsk, Russia, who supplied the sample material from Dagestan, and provided valuable stratigraphic information.

In the Gnaszyn section, the new species is relatively rare, but many paratype specimens occur in the marine clays of the Khouroukra section of central Dagestan (Gradstein et al. 2017a, Figure 9), particularly in sample 8 of Bed 19, assigned to the Parkinsonii Ammonite Zone, Upper Bajocian.

Discussion Globuligerina glinskikhae nov. sp. may be readily distinguished from Globuligerina oxfordiana (Grigelis) because of its tight, three-chambered and highly globular last whorl (Fig. 1, no. 1). G. oxfordiana has four chambers (and only rarely 3.5 or 4.5) in the last whorl with the second chamber in the last whorl characteristically protruding (see Fig. 1, no. 1 and Fig. 1, nos. 2 and 3 for a comparison of the two test shapes). We have not observed morphological intermediates between the two taxa, but consider it likely that G. glinskikhae evolved from G. oxfordiana, perhaps during the Bajocian in Dagestan time and then spread to for example Poland, where it is rare in Bathonian strata. We have not observed the new taxon in clay-prone planktonic foraminiferal assem- blages from the Middle Jurassic of Portugal or the Grand Banks of Newfoundland, but co-author AW had correspondence with palynology colleague Dr. Elahe Aarei (School of Earth Sciences, Damghan University, Iran) who showed pictures of Bathonian specimens closely resembling G. glinskikhae. We failed to obtain Iranian sample material.
Because of its prominent globular chambers, arranged in a large, three chambered last whorl, we consider it feasible to recognize this taxon in thin sections; it maybe a possible index for Upper Bajocian to Bathonian strata.

References:

Gradstein, F. & Waskowska, A. (2021). New insights into the taxonomy and evolution of Jurassic planktonic foraminifera. Swiss Journal of Palaeontology. 140(1): 1-12. gs O

Gradstein, F. M., Gale, A. S., Kopaevich, L., Waskowska, A., Grigelis, A. & Glinskikh, L. (2017b). The planktonic foraminifera of the Jurassic. Part I: material and taxonomy. Swiss Journal of Palaeontology. 136(2): 187-257. gs O

CATALOG OF ORIGINAL DESCRIPTIONS: Globuligerina glinskikhae Gradstein & Waskowska 2021

Globuligerina glinskikhae

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