Globigerinatheka korotkovi

Classification: pf_cenozoic -> Globigerinidae -> Globigerinatheka -> Globigerinatheka korotkovi
Sister taxa: G. semiinvoluta, G. tropicalis, G. luterbacheri, G. euganea, G. index, G. curryi, G. barri, G. korotkovi, G. kugleri, G. mexicana, G. subconglobata, G. sp.,


Citation: Globigerinatheka korotkovi (Keller 1946)
Rank: Species
Basionym: Globigerinoides korotkovi
Variants: ko
Taxonomic discussion: Keller (1946), in the original discussion, stated that “the present species differs from the Paleogene Globigerinoides conglobatus Brady from the upper Eocene of the Sotchi region in its much smaller dimensions (0.35-0.37 mm for the Cretaceous form and 0.5-0.6 mm for the Paleogene) and in the single type of structure shown by the representatives of this species”. Keller (1946) also emphasized that his species korotkovi is represented only as “regularly constructed forms” contrary to the high morphological variations observed in what he called the Paleogene Globigerinoides conglobatus.
Subbotina (1953) reillustrated Keller’s specimen and provided the original description, and Bolli (1972) refigured Subbotina’s drawings. Both authors, however, did not mention whether they had found G. korotkovi, nor did they discuss the validity of Keller’s species. On the other hand, Bolli (1972) regarded G. korotkovi as a subspecies of G. index. Following Subbotina (1953), and partially Bolli (1972), later authors ignored korotkovi and attributed common, high-spired globigerinathekid specimens to the species Globigerinoides rubriformis erected by Subbotina in 1953. However, the illustrations of rubriformis, including the holotype (see Subbotina, 1953, pl. 14: figs. 6-9) do not show supplementary apertures. The exception is the specimen figured on Subbotina’s pl. 13, 19a-b, which is here included in G. tropicalis, but the species needs further study to determine its taxonomic validity.
The middle to early late Eocene globigerinathekid population contains common morphotypes that exhibit a sac-like test with a medium-long spire and one subcircular supplementary aperture almost identical to the primary one. So, despite Keller’s poor description, we think that these sac-like, high-spired morphologies are best represented by Keller’s species korotkovi. Keller’s species shows some similarities in general shape with the paratype of G. index illustrated by Finlay in his fig. 87, but redrawing of the latter by Hornibrook (1958) shows well incised sutures lacking in G. korotkovi.
Blow (1979) considered G. korotkovi as taxonomically indistinguishable from G. semiinvoluta (= Porticulasphaera semiinvoluta, Blow, 1979, p. 788), an attribution here rejected. In addition, Blow (1979) considered most of Subbotina’s specimens of G. rubriformis, including the holotype, as immature specimens of Porticulapshaera semiinvoluta (p. 813), which we also reject here. The specimen in Blow, 1979, pl. 181, fig. 3 annotated as a typical G. kugleri, as well as the specimen in Blow, 1979, pl. 174, fig. 3 considered as atypical G. index, seem close to G. korotkovi for their prominent high spire and high subcircular primary aperture, respectively. [Premoli Silva et al. 2006]

Catalog entries: Globigerinoides korotkovi

Type images:

Distinguishing features: Test high trochospire with three chambers in the last whorl, a rather compact peripheral outline and subcircular primary and supplementary apertures.

NB These concise distinguishing features statements are used in the tables of daughter-taxa to act as quick summaries of the differences between e.g. species of one genus.
They are being edited as the site is developed and comments on them are especially welcome.


Diagnostic characters: This morphotype is characterized by a high trochospire with three chambers in the last whorl, a rather compact peripheral outline and subcircular primary and supplementary apertures. Based on the presence of at least one supplementary aperture, the species korotkovi is included here in the genus Globigerinatheka. Globigerinatheka korotkovi differs from Subbotina’s species rubriformis in having a much shorter (not turreted) spire and at least one subcircular supplementary aperture; it differs from G. subconglobata in having a last chamber that is much larger, and subcircular openings much smaller than G. index. [Premoli Silva et al. 2006]

Wall type: Spinose, cancellate, moderately incrusted with pores about 4 mm in diameter. [Premoli Silva et al. 2006]

Test morphology: Test shape sack-like consisting of 2 to 3 whorls arranged in a high trochospire; chambers subglobular with three chambers in the last whorl; sutures distinct, depressed, straight to slightly curved; peripheral outline rather compact; primary aperture a medium-sized subcircular arch at the junction of the sutures of the last three chambers with one subcircular secondary aperture almost identical to the primary one; other much smaller secondary apertures may be present on the spiral side of the previous chambers. [Premoli Silva et al. 2006]

Size: Dimensions of the holotype: diameter 0.35 mm; thickness 0.58 mm. [Premoli Silva et al. 2006]

Character matrix

test outline:Subcircularchamber arrangement:Trochospiraledge view:Equally biconvexaperture:Umbilical-extraumbilical
sp chamber shape:Globularcoiling axis:Highperiphery:N/Aaperture border:N/A
umb chbr shape:Globularumbilicus:Narrowperiph margin shape:Broadly roundedaccessory apertures:Sutural
spiral sutures:Strongly depressedumb depth:Deepwall texture:Spinoseshell porosity:Macroperforate: >2.5µm
umbilical or test sutures:Strongly depressedfinal-whorl chambers:3.0-3.0 N.B. These characters are used for advanced search. N/A - not applicable

Biogeography and Palaeobiology

Geographic distribution: Described from the Caucasus, it is commonly found in low and middle latitudes from deep-sea and land sections. [Premoli Silva et al. 2006]

Isotope paleobiology: No data available. [Premoli Silva et al. 2006]

Phylogenetic relations: Bolli (1972) suggested that G. rubriformis (here G. korotkovi) may be regarded as a high-spired variant of G. index and G. tropicalis, a hypothesis not accepted here as we consider G. korotkovi to be a valid taxon which probably descended from G. subconglobata. [Premoli Silva et al. 2006]

Most likely ancestor: Globigerinatheka subconglobata - at confidence level 3 (out of 5). Data source: Premoli Silva et al. 2006 f7.1.

Biostratigraphic distribution

Geological Range:
Notes: Globigerinatheka korotkovi was originally reported from lower Senonian strata. In agreement with Bolli (1972), the age is not correct. According to the present study, high-spired morphotypes consistent with G. korotkovi range from lower E9 to lower E15 in the upper Eocene. [Premoli Silva et al. 2006]
Last occurrence (top): within E15 zone (34.68-35.89Ma, top in Priabonian stage). Data source: Premoli Silva et al. 2006 f7.1
First occurrence (base): in lower part of E9 zone (30% up, 43.7Ma, in Lutetian stage). Data source: Premoli Silva et al. 2006 f7.1

Plot of occurrence data:

Primary source for this page: Premoli Silva et al. 2006 - Eocene Atlas, chap. 7 p186


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Globigerinatheka korotkovi compiled by the pforams@mikrotax project team viewed: 4-6-2020

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