Catalog - Globigerina gerpegensis

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Globigerina gerpegensis

Citation: Globigerina gerpegensis Shutskaya 1970

Type specimens: pl. 3. fig. 3a-c: p. 105, tf. 6, figs. 1-9: holotype (fig. 3a-c), no. 1583-1-62.

Type sample (& lithostrat): Lower Danat Subsuite

Type age (chronostrat): Upper Paleocene, Kachan Stage, upper Acarinina tadjikistanensis djanensis Zone.

Type locality: Malyy Balkhan Mts., western Turkmenia, USSR.

Type repository: Depository not given [probably All-Union Scientific-Research Geological-Prospecting Petroleum lnstitute (VNIGNI), Moscow];

Translation from the Russian. - Test average in size (0.3-0.4 mm.), flattened dorsally, convex ventrally, oval: a) elongation coefficient 1.1-1.3; b) broadness coefficient 1.1-1.6. Structure of initial part of test globigerinoid, low-trochoid. Number of chambers in initial part of test 4-6. 3.5 chambers in the last whorl, the half-chamber takes part in construction of the whorl. Increase in chamber size rapid. Last chamber the largest. Ratio of dimensions of the individual elements of the last whorl: a) width of penultimate chamber to width of last one 0.8-1; b) last chamber oblique relative to preceding one and more drawn out in length than in width, ratio of length of its base to its width is 1-1 .2. Outer contour broadly rounded. Lateral surface of last chamber high, subquadrate. lts height is greater than the height of the preceding part of the test. Shape of the first two chambers of the last whorl subquadrate and rounded; surface of chambers flattened-inflated. Chambers freely arranged. lntercameral sutures broad, not deep. Umbilical depression narrow or broader. Outer margin coarsely scalloped, narrow in the initial part of the last whorl. Aperture marginal, oblique, short, slitlike; extends from the center of the test to the beginning of the outer margin; covered by a flat lip. Test wall moderately perforate.

Globigerina triangularis White. - Bolli, 1957, U. S. Nat. Mus., Bull., no. 215, p. 71. pl. 15, figs. 12-14. - Bolli and Cita, 1960, Riv. Ital. Pal. Strat., vol. 66, no. 3, p. 372, pl. 33, fig. 3a-c.
Globigerina inaequispira Subbotina. - Loeblich and Tappan, 1957 (part), U.S. Nat. Mus., Bull., no. 215, p. 181, pl. 52, figs. l a-c, 2a-c.

Variation. - Expressed in the different degrees of broadening of the test, which often becomes broadly oval (tf. 6, figs. 4, 8, 9) with the ratio of the widths o[ the penultimate and last chambers approaching 1.

Comparison. - Bolli (1957) and Loeblich and Tappan (1957) describe entirely alike specimens but refer them either to Globigerina triangularis White or to G. inaequispira Subbotina. The new species is closer to the first of these. forming a group with it, but differs essentially by the constant position of the half-chamber, which forms, together with the last three chambers, the coil of the last whorl, and by the reverse relationship of constant position of the half-chamber, which forms, together with the last three chambers, the coil of the last whorl, and by the reverse relationship of the widths of the penultimate and last chambers (in G. triangularis this ratio is more than 1). The specimen shown by Loeblich and Tappan in their pl. 52, fig. 2 completely matches the short broad tests shown in tf. 6, figs. 4, 8 and 9.

Bolli and Cita (1960) describe as G. triangularis a 3½-chamberecl test in which the half-chamber together with the subsequent chambers composes the last whorl, the width of the last chamber is greater than that of the penultimate one. The combination of these features allow us to refer Bolli and Cita's specimen to G. gerpegensis.

Occurs in all three zones of the Kachan [Acarinina tadjikistanensis djanensis, A. subsphaerica and A. acarinata Zones] .

References:

Shutskaya, E. K. (1970a). Morphologic groups and descriptions of species of Globigerina and Acarinina in the lower Paleogene of the Crimea, the Caucasus Foreland, and western Central Asia. Trudy Vsesoyuznego Neftyanogo Nauchno-Issledovatel'skogo Geologo-Razvedochnogo Instituta (VNIGRI). 69: 79-113. gs

Missing or ambiguous references: 104-5;

CATALOG OF ORIGINAL DESCRIPTIONS: Globigerina gerpegensis Shutskaya 1970

Globigerina gerpegensis

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