Eoglobigerina eobulloides


Classification: pf_cenozoic -> spinose -> Globigerinidae -> Eoglobigerina -> Eoglobigerina eobulloides
Sister taxa: E. edita, E. eobulloides, E. spiralis, E. sp.,

Taxonomy

Citation: Eoglobigerina eobulloides Morozova 1959
Rank: Species
Basionym: Globigerina (Eoglobigerina) eobulloides
Synonyms:
Taxonomic discussion: Considerable uncertainty and confusion surrounds the identification of this species and Globigerina fringa Subbotina, 1953, due to the very small size and generalized drawing of the holotype of G. fringa. Examination of the holotype (WAB and FR) under a light microscope shows it to be similar to E. eobulloides in general morphology and, thus, a possible senior synonynm. Scanning electron micrographs (SEM) taken by FR (Plate 8: Figures 10-12, Plate 9: Figures 7-9) of the two holotypes, however, show that they are distinctly different species. "Globigerina" fringa has a coarsely cancellate wall similar to that of Subbotina cancellata Blow, 1979 (Plate 24: Figures 1-14). This type of cancellate wall texture is more advanced than that seen in Zone Pa globigerinids, which suggests thatfringa was described from a higher Danian stratigraphic level. See "Discussion" under Subbotina cancellata for additional data on this species.
Four-chambered forms of E. eobulloides were named by Blow (1979) as the subspecies E. eobulloides simplicissima. This form seems to be the same as Globigerina moskvini Shutskaya, 1953, a name that could be used for E. eobulloides except that some of the Shutskaya collections were destroyed during the 1960s, and, thus, the usage of this name is not advisable. Blow's (1979) illustrations of E. eobulloides agree well with the holotype (Plate 8: Figures 10-12). The small size of E. eobulloides and its very thin pore-filled walls make this species very susceptible to dissolution, which is common in lowermost Danian sections. [Olsson et al. 1999]

Catalog entries: Globigerina (Eoglobigerina) eobulloides;

Type images:

Short diagnosis: 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.

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: 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. [Olsson et al. 1999]

Character matrix

test outline:Lobatechamber arrangement:Trochospiraledge view:Inequally biconvexaperture:Umbilical
umb chamber shape:Inflatedcoiling axis:Lowperiphery:N/Aaperture border:Thick lip
sp chbr shape:Inflatedumbilicus:Narrowperiph margin shape:Broadly roundedaccessory apertures:None
umbilical or test sutures:Strongly depressedumb depth:Deepwall texture:Spinoseshell porosity:Finely Perforate: 1-2.5µm
spiral sutures:Strongly depresseddiameter mm:0.225width mm:0.13breadth mm:-
final-whorl chambers:4.0-4.5

Biogeography and Palaeobiology


Geographic distribution: Worldwide in high to low latitudes (Figure 8). [Olsson et al. 1999]
Aze et al. 2011 summary: Cosmopolitan; based on Olsson et al. (1999)

Isotope paleobiology: Eoglobigerina eobulloides has a ∂13C and ∂18O signature similar to Parasubbotina and Globanomalina but typically with heavier ∂18O and more negative ∂13C than coexisting Praemurica and Woodringina (D'Hondt and Zachos, 1993; Berggren and Norris, 1997). The species shows little change in ∂18O or ∂13C over a large size range (Berggren and Norris, 1997), although a positive size/∂13C relationship has been reported for the species at small shell sizes from the early Danian (D'Hondt and Zachos, 1993). [Olsson et al. 1999]
Aze et al. 2011 ecogroup 3 - Open ocean thermocline. Based on light δ13C and relatively heavy δ18O. Sources cited by Aze et al. 2011 (appendix S3): Berggren & Norris (1997); D'hondt & Zachos (1993)

Phylogenetic relations: Eoglobigerina eobulloides evolved from Hedbergella monmouthensis (Olsson) in late Biochron P0 by the development of a spinose cancellate wall texture (Liu and Olsson, 1994). It is the earliest spinose taxon of the Cenozoic, and, as such, it represents a completely new adaptive innovation (carnivory?) following the terminal Cretaceous event(s). Olsson et al. (1992) suggested that the spinose E. eobulloides lies at the base of an early Paleocene (Danian) radiation of normal perforate, cancellate spinose forms referable to Eoglobigerina and Subbotina (see also Pearson, 1993). [Olsson et al. 1999]

Biostratigraphic distribution

Geological Range:
Notes: Upper Zone P0 to Zone Plb. [Olsson et al. 1999]
Last occurrence (top): within P1b subzone (63.90-65.25Ma, top in Danian stage). Data source: Olsson et al. 1999
First occurrence (base): within P0 zone (66.00-66.04Ma, base in Danian stage). Data source: Olsson et al. 1999

Plot of occurrence data:

Primary source for this page: Olsson et al. 1999 - Atlas of Paleocene Planktonic Foraminifera, p. 20

References:

Olsson, R.K.; Hemleben, C.; Berggren, W.A. & Huber, B.T., (1999). Atlas of Paleocene Planktonic Foraminifera. Smithsonian Contributions to Paleobiology. Smithsonian Institution Press, Washington, DC, 1-252 pp.


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Eoglobigerina eobulloides compiled by the pforams@mikrotax project team viewed: 20-9-2017

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