Catalog - Globigerinoides quadrilobatus primordius

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Globigerinoides quadrilobatus primordius

Citation: Globigerinoides quadrilobatus primordius Blow & Banner 1962

Type locality: from the type locality of the Globorotalia kugleri Zone, Cipero formation southern Trinidad (see Bolli, I957b, p. 100).

Type specimens: Plate IX Dd-Ff; Fig. 14 (iii-viii)

Original Description
The test consists of about nine chambers arranged in a low, fairly loose trochospire of two to three whorls, each whorl consisting of about four chambers. The chambers are fairly rapidly and almost uniformly enlarging, and are distinctly inflated. The degree of embrace between the chambers decreases during ontogeny. The equatorial profile is ovoid and the equatorial periphery is lobulate. The axial profile is suboval, and the axial periphery is broadly and smoothly rounded. The chambers are subglobular and the intercameral sutures become increasingly deeply depressed during ontogeny, becoming almost incised between the last few chambers. The dorsal intercameral sutures, like the ventral ones, are subradial through. out the greater part of the test. The spiral suture is lobulate. The umbilicus is open, but is narrow and shallow; as the apertural face is of equal convexity to the rest of the chamber surface, the umbilical margins are not sharply delimited. Only two apertures are present on the test exterior. The primary aperture is a low intraumbilical arch, lacking a distinct lip or rim. The single dorsal supplementary sutural aperture is a small hole or very low arch situated in the wall of the last chamber at the junction of the last intercameral suture and the spiral suture; it lacks a lip or rim. The relict aperture of the penultimate chamber may sometimes be observed within the ventral umbilicus. The wall is fairly thick and is uniformly perforate, the surface is markedly cancellate and punctate, and this is strongest on the dorsal surfaces of the earlier chambers.

Size: Maximum diameter of holotype: 0.41 mm;

Extra details from original publication
Remarks: As this form possesses a dorsal sutural supplementary aperture, together with a distinct ventral (umbilical) primary aperture, it is referable to the genus Globigerinoides Cushman, I927, as emended by Bolli et al. (I957) (see also Banner & Blow 1959, 1960a). It is distinguished from G. quadrilobatus quadrilobatus (d'Orbigny) (see Banner & Blow, 1960a, pp. I7-I9, pl. 4, for description of lectotype) by its possession of only one single dorsal sutural supplementary aperture in the adult test. We consider that this form is worthy of formal taxonomic recognition because it has a very restricted stratigraphical occurrence, and because it clearly demonstrates the transition between the genera Globigerina and Globigerinoides. It is distinguished from advanced forms of its immediate ancestor, Globigerina praebul!oides occlusa, solely on its possession of a dorsal supplementary aperture; it also differs from typical (i.e. Oligocene) forms of G. praebulloides occlusa by being a little less tightly coiled and more coarsely cancellate, With broader punctae on the surface of the test, into which open pores still closely comparable to those of G. praebulloides occlusa (see also §VII, p. 136, and Fig. I4).

Stratigraphical range: This form is confined to the Globorotalia kugleri Zone in southern Trinidad, and it also occurs in stratigraphically sharply limited horizons in the Ragusa area of south-east Sicily and in East Africa, where it occurs in the Aquitanian, probably near the middle part. It does not occur, so far as is known, in the lower Aquitanian of Escornebeou or Moulin de l'Eglise, Aquitaine, nor has it ever been observed in any Oligocene samples from Germany, France or East Africa.

References:

Blow, W. H. & Banner, F. T. (1962). The mid-Tertiary (Upper Eocene to Aquitanian) Globigerinaceae. In, Eames, F. E., Banner, F. T., Blow, W. H. & Clarke, W. J. (eds) Fundamentals of mid-Tertiary Stratigraphical Correlation. Cambridge University Press, Cambridge 61-151. 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 V O

CATALOG OF ORIGINAL DESCRIPTIONS: Globigerinoides quadrilobatus primordius Blow & Banner 1962

Globigerinoides quadrilobatus primordius

References:

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