CATALOG OF ORIGINAL DESCRIPTIONS: Globigerina (Conoglobigerina) dagestanica Balakhmatova & Morozova, in Morozova & Moskalenko 1961

This page provides data from the catalog of type descriptions. The catalog is sorted alphabetically. Use the current identification link to go back to the main database.


Higher levels: pf_cat -> G -> Globigerina (Conoglobigerina) -> Globigerina (Conoglobigerina) dagestanica
Other pages this level: G. (Conoglobigerina) avarica, G. (Conoglobigerina) dagestanica, G. (Conoglobigerina) gaurdakensis

Globigerina (Conoglobigerina) dagestanica

Citation: Globigerina (Conoglobigerina) dagestanica Balakhmatova & Morozova, in Morozova & Moskalenko 1961
Rank: Species
Type locality: The villages of Chokh and Gunib, central Dagestan, Soviet Russia.
Type age (chronostrat): Middle Jurassic, Bathonian, Globigerina (Conoglobigerina) dagestanica - Globigerina (Conoglobigerina) auarica Zone. Abundant.
Type sample (& lithostrat): Mogokh beds, in the upper band of an argillite,
Type specimens: Pl. 1 figs 13-15; Pl2. figs 14-19; holotype 3513/2
Type repository: Moscow, Russia; Museum of the Geological Institute of the Academy of Sciences
Described on page(s) : 26-27

Current identification/main database link: Globuligerina dagestanica (Morozova in Morozova & Moskalenko, 1961)


Original Description
Test small, high, its diameter equal to or greater than the height. Chambers arranged in a high, very steep spiral consisting of three whorls. The final whorl consists of three or four spherical chambers differing but little in size. The penultimate and final whorls usually have the same number of chambers, the first whorl often having up to five chambers. Sutures between the chambers of late whorls depressed, straight; those between the chambers of the first whorl weakly depressed, straight or slightly oblique. Aperture umbilical, an elongate slit, or low, crescentic. Wall radiate, thin, moderately porous. Surface matte.

Size: Greatest diameter 0.15-0.12mm; Smallest diameter 0.12-0.08mm; Height 0-17-0.07mm

Extra details from original publication

Variability - The present species is very variable, as expressed in the number of chambers, their arrangement, the shape of the spiral side, and the ratio of diameter to length of the test. The sharpest morphologic differences have been observed between the micro-band megalospheric generations. The microspheric forms possess a larger, inflated test with a roundly obtuse in itial end. The number of chambers in the initial whorl is up to five or five and one-half; in the second whorl, four; and in the lasbt, three or four (see tf. 7, figs. 1- 12). The megalospheric forms are represented by smaller, subconical tests, with the initial whorl usually comprising four chambers (see tf. 7, figs. 13-24).

Comparison. - The described species is closest to Globigerina jurassica Gofman, from the Bathonian- Callovian of the Crimea; however, the Bathonian specimens from central Dagestan differ from Globigerina jurassica in that their chambers are arranged in a spiral (and not "almost glomospirally, according to Gofman). The essential distinctive characteristic is the multichambered initial whorl (usually five - chambered) in the microspheric forms and the great range of individual variability which indicates a great plasticity for the species. A form close to the present species is Globigerina sp. of Balakhmatova, from the upper Bajocian of Turkmenia, which has been herein described as a new species, Globigerina (Conoglobigerina) gaurdakensis Balakhmatova and Morozova. The main difference between the two species consists in that the Dagestan form has a higher spiral and more loosely arranged chambers.

Another similar species is Globigerina bradyi Wiesner, which was originally described by Brady as Globigerina sp.; it was named by Wiesner and redescribed by Banner and Blow. The holotype being lost, they selected as the lectotype of the species one of the two specimens of Globigerina sp. from the collections of the ""Challenger"" Expedition, deposited at the British Museum of Natural History. The species, which ranges from the middle Aquitanian to Recent, has a high test formed by four whorls. The first whorl is low, multichambered, formed bv four or five chambers closely embracing the small initial chamber. Each of the following three whorls consists of four chambers (in the figured lectotype only three chambers are visible in the final whorl, which may only appear because of the foreshortened test; unfortunately, there is no illustration of either the initial or apertural ends). Wall thin, semitransparent; weakly rugose. The distinctive features of the species are the inflated, spherical chambers, their gradual increase in size, and the smooth, slightly convex outline of the test. The Middle Jurassic form is distinguished by the slowly increasing chambers within each whorl and sharply differing in size from the chambers of the adjoining whorls, due to which the periphery of the test is very uneven; its aperture is low, small, slit like, often indiscernible, unlike the large, high, arcuate aperture of the Recent species. An essential distinctive characteristic of our species is the wide range of variability, as expressed in the number of chambers per whorl, and in that it is one and one-half times smaller than the Recent species. A common feature of the two species is evidently the thin, fine-grained, slightly rugose or spinous wall.


Editors' Notes
content migrated from chronos

References:

Morozova, V. G. & Moskalenko, T. A. (1961). Планктонные фораминиферы пограничных отложений байосского и батского ярусов Центрального Дагестана (Северо-Восточный Кавказ) [Foraminiferes planctoniques des depots limitrophes du Bajocien et du Bathonien du Daghestan central (Nord-Est du Caucase)]. Voprosyi Mikropaleontologii. 5: 3-30. gs


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Globigerina (Conoglobigerina) dagestanica compiled by the pforams@mikrotax project team viewed: 24-7-2021

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