Catalog - Globigerinoides bollii

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Globigerinoides bollii

Citation: Globigerinoides bollii Blow 1959

Type specimens: Holotype: Plate 10, figures 65a-c; No. 625717.

Type sample (& lithostrat): sample. No. RM 19697, auger line near Pozon, eastern Falcon

Type locality: near Pozon, eastern Falcon; Venzuela

Type repository: Washington; USNM

Test trochospiral with four chambers in the last whorl; equatorial periphery lobate; axial periphery rounded; chambers subspherical or ovate, much embracing; sutures of the spiral and umbilical sides depressed but often indistinct, radial to slightly curved; umbilicus small, often almost completely closed; primary aperture interiomarginal, umbilical, the opening almost completely circular but generally rather small; supplementary apertures on the spiral side, sutural, small; usually only one present, situated in the suture between the last chamber and its predecessor, although an additional supplementary aperture may be present in the suture between the penultmiate and antepenultimate chambers; wall calcareous, perforate, often rather thick.

maximum diameter of holotype, 0.34 mm.

This species is named after Dr. H. M. Bolli in recognition of the valuable training the writer received from him whilst in Trinidad.

Remarks: This species differs from Globigerinoides obliqua Bolli in having much more embracing chambers, a small, almost circular, primary aperture, and in the last few chambers not showing any lateral and oblique compression. A characteristic of this species is the "cut-in" nature of the umbilical margin of the primary aperture. Early forms of this species only show one supplementary aperture on the spiral side which is situated in the suture between the last and penultimate chambers. However, in later forms from the Globorotalia menardii menardii/Globigerina nepenthes Zone, an additional supplementary aperture appears in the suture between the penultimate and antepenultimate chambers.

This species seems to have a different origin from that of the Globigerinoides triloba group. According to Bolli (1957), Globigerinoides triloba (Reuss) appears to originate in the Globorotalia kugleri Zone and to develop from a form recorded by him as Globigerina cf. trilocidaris d'Orbigny. However, Globigerinoides bollii does not appear until the basal part of the Globorotalia mayeri/Globigerina nepenthes Subzone and seems to have originated from a Globigerina sp., which has an otherwise similar morphology to this species but does not have supplementary apertures. This Globigerina sp. is scarce and appears to be limited to the upper part of the Globorotalia fohsi robusta Zone.

Occurrence: Ranges from the base of the Globorotalia mayeri/Globorotalia lenguaensis Subzone to the Globigerina bulloides Zone, Pozon formation.

References:

Blow, W. H. (1959). Age, correlation, and biostratigraphy of the upper Tocuyo (San Lorenzo) and Pozon Formations, eastern Falcon, Venezuela. Bulletins of American Paleontology. 39(178): 67-251. gs

Spezzaferri, S., Olsson, R. K. & Hemleben, C. (2018c). Taxonomy, biostratigraphy, and phylogeny of Oligocene to Lower Miocene Globigerinoides and Trilobatus. In, Wade, B. S., Olsson, R. K., Pearson, P. N., Huber, B. T. & Berggren, W. A. (eds) Atlas of Oligocene Planktonic Foraminifera. Cushman Foundation for Foraminiferal Research, Special Publication . 46(Chap 9): 269-306. gs

CATALOG OF ORIGINAL DESCRIPTIONS: Globigerinoides bollii Blow 1959

Globigerinoides bollii

References:

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