Catalog - Globigerina rudis

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Globigerina rudis

Citation: Globigerina rudis Voloshinova 1960

Type specimens: pl. 29, fig. 9a-c, "original," type specimen, dorsal, ventral, and peripheral margins, X 7 5.

Type sample (& lithostrat): Figured "original" (fig. 9a-c) from the upper Miocene, lower Okobykay Formation; and also occurs in the middle Miocene, Pil' Formation.

Type age (chronostrat): upper Miocene

Type locality: Figured "original" (fig. 9a-c) from Okha, Sakhalin Island, U.S.S.R.; and also found on Sakhalin Island north and south of the Pil' River, on the westem shore of the Shmidt Peninsula; and at a number of points along its eastem coast from Sevemaya Okha to Katang1i.

Type repository: Leningrad; All-Union Petroleum Scientific-Research Geological-Prospecting Institute (VNIGRI), Leningrad, U.S.S.R.; figured "original" (fig. 9a-c), no. 11 3/454.

Translation from the Russian. - Test medium-sized, not strongly inflated, with a very convex ventral side and slightly convex, sometimes almost flat, dorsal side. Outline weakly lobate or almost smooth, rectangular. Spire consists of 2-2 1/2 whorls. Initial part very unclear, weakly convex; in the last whorl are four elongated chambers, weakly convex on the dorsal side and strongly convex on the ventral side, and touching closely one another. Chambers slightly and uniformly increase in size as they are added, the last chamber is usually not much larger than the penultimate chamber. Umbilicus distinct, small, but deep. Aperture not large, slit-shaped, shows as a narrow excision of the umbilical margin of the last chamber. Apertures of preceding chambers not visible. The wall is typical: very coarsely perforate, and spinose in places.

Dimensions, in mm. - Diameter 0.35-0.40; thickness 0.20-0.25.

Basis for erecting the species. - In a number of features (the flattening of the test on the dorsal side, the elongated chambers, the rough, coarsely reticulate, spinose wall) this species is reminiscent of the round Acarinina's (N. N. Subbotina, 1953, Leningrad: Vses. Neft. Nauchno-lssled. Geol.-Razved. Inst. (VNIGRI), Trudy, n. s., vypusk 76, p. 226). However the genus Acarinina typically has a slit-shaped aperture, which lies along the marginal suture. In Globigerina rudis Voloshinova the aperture is distinctly umbilical, typical for Globigerina, and the peripheral margin is smoothly rounded and not angular as in Acarinina. In the shape of the chambers and the overall look o f the test the species described is somewhat reminiscent of the American late Oligocene-early Miocene Globigerina venezuelana Hedberg (1937, Jour. Pal., vol. 11 , no. 8, p. 681, pl. 92, fig. 7), which, as E. V. Myatlyuk has told me, is found in beds of that age in Albania. However G. rudis very distinctively differs from G. venezuelana Hedberg by its flatter test and the larger fourth chamber in the last whorl. The test of G. rudis is similar to tests of G. quadrilatera Galloway and Wissler ( 1927, Jour. Pal. , vol. 1, no. I, p. 44, pl. 7, fig. II) found in the higher horizons of the Okobykay Formation, beds which are transitional from Miocene to Pliocene, and in the Nutovo Formation (Pliocene), differing clearly by the more elongate and closely joined chambers, the small umbilicus, and the much more coarsely reticulate wall

References:

Voloshinova, N. A. (1960). Novye neogenovye rotaliidy ostrova Sakhalin. In, Markovsky, B. P. (ed.) Novye vidy drevnihk rasteniy i bespozvonochnyhk SSSR, Chast Pervaya, vypusk 1, chasti 1. Vsesoyuznyy Nauchno-Issledovatel'skiy Geologicheskiy Institut,, Moscow 163-169. gs

CATALOG OF ORIGINAL DESCRIPTIONS: Globigerina rudis Voloshinova 1960

Globigerina rudis

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