Catalog - Globigerina prolonga

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Globigerina prolonga

Citation: Globigerina prolonga Shutskaya 1964

Type specimens: pl. 2, fig. 1a-c, X 78.

Type age (chronostrat): Lower Paleocene, Globorotalia angulata Zone. Ranges from the Danian to the lower part of the Upper Paleocene.

Type locality: Malyy Balkhan Mts., western Turkmenia, USSR. Also found in the Northern Caucasus.

[Translation from the Russian. - Test small, not more than 0.3 mm. long, oblong. Its sides are parallel, with the elongation index 1.3. since the width of the initial part of the last whorl and the length across the middle of the last chamber are the same. Broadening index (ratio of width of test to length of base of last chamber) not large (1.2- 1.4). Initial part globigerinoid in structure, consists of one-and-a-half whorls. Coiling in a single plane. Three chambers in the last whorl, first two nearly the same size, last one very large and stands apart from the preceding chambers. Width of penultimate chamber consistently less than that of the last one (ratio about 0.7-0.8), which is strongly extended in width (ratio of length of base of last chamber to its width 1.0-1.1). There is a great distance between the first and last chambers of the last whorl. A half-chamber is sometimes noted in the last whorl. Shape of chambers hemispherical, inflated, sutures thin. depressed, outer margin scalloped. Umbilical ends of first two chambers are far removed from the inner margin of the last chamber. but the umbilical depression is not clearly outlined. Aperture marginal, horizontal, slitlike, short, covered by a flat lip. It extends from the center of the test laterally to the ventral side of the outer margin. Lateral surface of last chamber broadly rounded and the highest part of the test. Wall distinctly perforate.

Comparison. - This species differs from Globigerina triloculinoides by its oblong test - a feature which is maintained over a very large number of specimens and appears only beginning with the late Danian (Acarinina inconstans Zone).

Distribution. Appears in the Acarinina zone inconstans zone where it is very important in the association of planktonic foraminifera. In the older layers of the Danian stage, oblong shells of the described species are absent. Characteristic of the lower and lower Upper Paleocene. North Caucasus, Western Turkmenistan.

References:

Shutskaya, E. K. (1964). Видовые критерии нижнепалеогеновых представителей рода Globigerina - Species criteria of the Lower Paleogene genus Globigerina. . Voprosyi Mikropaleontologii. 8: 118-137. gs

CATALOG OF ORIGINAL DESCRIPTIONS: Globigerina prolonga Shutskaya 1964

Globigerina prolonga

References:

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