Catalog - Globigerina hevensis

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Globigerina hevensis

Citation: Globigerina hevensis Shutskaya 1970

Type specimens: holotype (fig. 4a-c), no. 662-1-62.

Type age (chronostrat): Lower Eocene, Bakhchisarayan Stage, upper Globorotalia subbotinae Zone

Type locality: Along the Kheu River, NaJ'chik region, Northern Caucasus, USSR

Type repository: probably deposited in the collec- tions of the All-Union Scientific-Research Geological-Prospecting Petroleum Institute (VNIGNI), Moscow

Translation from the Russian. - Test medium-sized (0.3-0.35 mm.), flattened dorsally. high ventrally, oald - coefficient of elonga-tion around 1.3. coefficient or broadening 1.1-1.2. Structure of initial part globigerinoid, low-trochoid. Number of chambers in initial part around 5-6. 3-3.5 chambers in the last whorl. Chambers increase in size rapidly. Last chamber set off from the previous ones and makes up almost half of the entire whorl: a) ratio of width of next-to-last chamber to width of last chamber 0.8-0.9: b) length of base of last chamber greater than width- co- efficient 1.1-1.3. Height of last chamber close to height of earlier part of test. Shape of chambers of last whorl: first chamber of last whorl round, second one subquadrate, perpendicular to last chamber, shape of which is hemispherical or oval. Outer contour of last chamber broadly rounded. Surface of chambers flattened-inflated. Arrangement of chambers of last whorl free, second chamber often extends beyond the outline of the test. Inter- cameral sutures thin. not too deep. Outer margin scalloped. Umbilical depression varies from narrow to broad. Apertural opening marginal, horizontal, arcuate, short. Test wall coarsely perforate: interpore spaces narrow and higher than the depth of the pore (frequent coarse perforation).

Variation is expressed mainly by the circumstance that in some specimens the Jast chamber of the preceding whorl (half-chamber) is only noticeable on the ventral side, and does not take part in building the last whorl of the test (tf. 2, figs. 3, 4). In other specimens (tf. 2, figs. 1, 2) this chamber enters into the last whorl, and the first chamber projects beyond the outline of the test. Simultaneously the umbilical depression becomes broad.

Comparison. - From the other species of the Globigerina pseudotriloba group (G. pseudotriloba White, G. uruchaensis Shutskaya) (Shutskaya, 1970, table 2) G. hevensis differs by its arcuate aperture, freer chamber arrangement, and frequent, coarse perforation.

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

CATALOG OF ORIGINAL DESCRIPTIONS: Globigerina hevensis Shutskaya 1970

Globigerina hevensis

References:

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