Catalog - Globigerinella liverovskae

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Globigerinella liverovskae

Citation: Globigerinella liverovskae Bykova 1960

Type age (chronostrat): lower Oligocene (Rupelian), Globigerinella liverovskae Zone (Pg1a-3),

Type locality: type locality not designated. Bykova’s and Subbotina’s figured specimens from Kazakhstan and northern Caucasus, respectively.

Description. Test flattened, consisting of two whorls. Chambers closely adjoining. In the last whorl are five chambers, uniformly increasing in size. The last chamber is little different in size from the preceding one. The first chamber of the last whorl is only half-visible. Rarely six chambers are seen in the last whorl. Sutures distinct, radial, depressed. In the center on the ventral side is a small umbilical depression. Peripheral margin rounded and lobate. Aperture semilunate, on the ventral side at the base of the last chamber. Wall thick, covered by barely discernible spines.

Diameter of the largest Carpathian tests not more than 0.20 mm. Originals from the Khadumian beds of Ossetia: diameter 0.15 mm., thickness 0.05 mm. (specimen no. 3987); diameter 0.13 mm., thickness 0.08 mm. (specimen no. 3988)

At the base of the series of sections in South Mangyshlak beds were observed with a large number of five-chambered globigerinids, referred by N. N. Subbotina (1953, pp. 60, 61, pi. 2, figs. 16-20) in the Caucasus to globigerina postcretacea Myatlyuk, but in reality belonging to a new species, globigerinella liverovskae. These forms occupy an intermediate position between Globigerinella and Globigerina and among them are completely symmetrical and involute tests, Globigerinella (Globigerinella) liverovskae (fig. 1), and tests with a weakly evolute dorsal side, Globigerinella (Globigerina) liverovskae (figs. 2, 3). The species resembles most closely the Lower Cretaceous Globigerina globigerinelloides Subbotina. (For further discussion see Globigerina khadumica Bykova, 1960).

In this species, as is clear from the above data, a large variation in the test size, also in the relative sizes of the first and last whorl, is observed. Forms are seen in which the first whorl is very weakly discernible, so that a doubt arose as to whether they belonged in Globigerina. However, the existence of a number of transitional forms led us to conclude that such Globigerinella-Iike tests belong to Globigerina. Caucasian specimens differ from the Carpathian ones by the more regular rosette-like disposition of the chambers and by the position of the aperture along the marginal suture, although specimens come to hand also which have an aperture below the umbilicus as in the Carpathian forms.

In the Khadumian beds of Ossetia, as in other deposits of the Northern Caucasus, tests are encountered which are almost like the Carpathian ones, with a less regular rosette-like arrangement of the chambers and with relatively larger chambers in the first whorl. But such forms are much scarcer than forms with the more regular rosette-like arrangement of the chambers.

Globigerina globigerinelloides Subbotina representatives from the Lower Cretaceous of the Northern Caucasus are quite close to this species. The regular rosette-like chamber arrangement in the last whorl and the small size of the chambers in the first whorl, which lies, moreover, always either below the surface of the last whorl or in the same plane with it, are points of resemblance. An important difference is that in G. globigerinelloides there are more chambers in the last whorl and a less marked increase in chamber size as they are added in the last whorl

Lectotype designated by Samuel and Salaj, 1968:122); also Subbotina, 1953:60, pl. 2, figs. 16a-20c from Dzagal-Don, Ossetia, northern Caucasus referred to Globigerina postcretacea Myatliuk but referable to liverovskae according to Bykova, 1960:322 [Berggren & Wade 2018]

Bykova, 1960:322 recognized a group of minute 5-6 chambered, weakly hispid/pustulose forms in basal Oligocene strata from southern Mangyshlak, Kazakhstan which she referred to her new taxon Globigerinella liverovskae. She noted that there was a gradation in assemblages between involute, symmetrical tests (pl. 7, fig. 1a-c) and weakly evolute tests (pl. 7, fig. 2a-c) which suggests to us that she was including pseudohastigerinid specimens from the terminal part of their range as well as tenuitellids in her concept of liverovskae. In including a suite of specimens illustrated by Subbotina (1953) from the northern Caucasus it is clear that Bykova (1960) had in mind predominantly forms with low trochoid tests in her concept of liverovskae. Bykova (1960) did not designate a holotype for her new taxon (nor for the related, if not conspecific) khadumica, nor was a depository for her material specified. The specimen designated as lectotype for liverovskae by Samuel and Salaj (1968) may be presumed lost, and thus we recommend that liverovskae like khadumica be considered nomen dubium non conservandum. Hamrsmid and Rögl (2000:41, pl. 1, figs. 6-8) identified low-trochoid 5 chambered forms as Tenuitella liverovskae from marls assigned to Zones NP24/P20 (upper Rupelian) in the Pabdel Formation, near the town of Baba Heydar, Zagros Mountains, Iran. Examination of the illustrations and descriptions of these taxa suggest that they may have been identifications/references to Tenuitella gemma (Jenkins) and/or T. patefacta (Li). [Berggren & Wade 2018]

References:

Berggren, W. A. & Wade, B. S. (2018). Problematica. 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 20): 511-524. gs

Bykova, N. K. (1960). K voprosy O tsiklichnosti filogeneticheskogo razvitiya u foraminifer. Trudy Vsesoyuznego Neftyanogo Nauchno-Issledovatel'skogo Geologo-Razvedochnogo Instituta (VNIGRI). 163: 309-336. gs

Subbotina, N. N. (1953). Foraminiferes fossiles d'URSS Globigerinidae, Globorotaliidae, Hantkeninidae. Bureau de Recherches Geologiques et Minieres. 2239: 1-144. gs

CATALOG OF ORIGINAL DESCRIPTIONS: Globigerinella liverovskae Bykova 1960

Globigerinella liverovskae

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