Eoglobigerina


Classification: pf_cenozoic -> spinose -> Globigerinidae -> Eoglobigerina
Sister taxa: Catapsydrax, Eoglobigerina, Globigerina, Globigerinatheka, Globorotaloides, Globoturborotalita, Guembelitrioides, Orbulinoides, Paragloborotalia, Parasubbotina, Pseudoglobigerinella, Subbotina, Turborotalita,
Daughter taxa (blue => in age window 0-300Ma)
The species is characterized by a moderately high trochospiral test with 4½ to 5 (occasionally up to 7) globular chambers which increase gradually in size in the ultimate whorl, and a strongly lobulate peripheral margin. The aperture is a rounded umbilical to slightly extraumbilical aperture which is bordered by a narrow lip. The umbilicus is small but open to the previous chambers. The cancellate wall is weakly developed and spinose with numerous spine holes along the cancellate ridges. The overall size of the test is generally less than 250 um.
This spinose species has a moderately elevated trochospire, globular chambers, an umbilical to slightly extraumbilical rounded aperture which is bordered by a narrow, slightly flaring lip. Four to 4½ chambers in the final whorl increase moderately in size. The umbilicus is small but open to the previous chambers. The cancellate wall texture is very weakly developed and difficult to view with the light microscope, especially where preservation of the wall is poor. The pores which are on average about 1 um in diameter at the narrowest point occur at the base of a shallow pit which is surrounded by the cancellate ridges. The wall ranges from 4 um to 7 um in thickness and the overall size of the test is generally less than 250 um.
This spinose species has a distinct elevated spire and 4½ to 5½ chambers in the ultimate whorl. The chambers are closely appressed with an umbilically directed aperture. The radially directed intercameral sutures on the umbilical side appear as distinct valleys when surrounded by gametogenetic calcification. A thin discontinuous lip borders the aperture. The wall texture is more strongly developed than in the ancestral species, E. edita. The umbilicus is very small and is often overlapped by the ultimate chamber. The spine holes which are set along the cancellate ridges appear not to be as numerous as in E. edita.
Specimens which cannot be assigned to established species

Taxonomy

Citation: Eoglobigerina Morozova, 1959
Rank: Genus
Type species: Globigerina (Eoglobigerina) eobulloides Morozova, 1959
Taxonomic discussion: Hemleben et al. (1991) demonstrated that Eoglobigerina had a spinose morphology, which separates it from other cancellate forms in the Danian that are nonspinose. The concept of Eoglobigerina followed herein is similar to that of previous workers except that it is emended to include the spinose character. [Olsson et al. 1999]

Catalog entries: Eoglobigerina;

Type images:

Short diagnosis: Low, trochospiral test with 10-16 chambers, 4-6½ globular chambers in ultimate whorl. Trochospire moderately to highly elevated; aperture interiomarginal, umbilical to slightly extraumbilical, a low, rounded arch bordered by a thin, narrow lip; umbilicus small and open to the apertures of surrounding chambers. Cancellate and spinose wall with spine holes situated along cancellate ridges.

NB The short diagnoses are used in the tables of daughter-taxa to act as quick summaries of the differences between e.g. species of one genus. They have initially been copied from the diagnostic characters/distinguishing features sections of the Eocene and Paleocene Atlases, they will be edited as the site is developed.

Description


Diagnostic characters: Low, trochospiral test with 10-16 chambers, 4-6½ globular chambers in ultimate whorl. Trochospire moderately to highly elevated; aperture interiomarginal, umbilical to slightly extraumbilical, a low, rounded arch bordered by a thin, narrow lip; umbilicus small and open to the apertures of surrounding chambers. Cancellate and spinose wall with spine holes situated along cancellate ridges.

Biogeography and Palaeobiology

Biostratigraphic distribution

Geological Range:
Last occurrence (top): within Danian Stage (61.61-66.04Ma, top in Danian stage). Data source: Total of range of species in this database
First occurrence (base): within Danian Stage (61.61-66.04Ma, base in Danian stage). Data source: Total of range of species in this database

Plot of occurrence data:

Primary source for this page: Olsson et al. 1999 - Atlas of Paleocene Planktonic Foraminifera, p. 199

References:

Hemleben, C.; Mhlen, D.; Olsson, R.K. & Berggren, W.A., (1991). Surface texture and the first occurrence of spines in planktonic foraminfera from the early Tertiary. Geologisch Jarhbuch, 128: 117-146.

Morozova, V.G., (1959). Stratigraphy of the Danian-Montian deposits of the Crimea according to the foraminifera. Doklady Akademii Nauk SSSR, 124(5): 1113-1115.


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Eoglobigerina compiled by the pforams@mikrotax project team viewed: 26-9-2017

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