Globanomalina imitata


Classification: pf_cenozoic -> smooth non-spinose -> Hedbergellidae -> Globanomalina -> Globanomalina imitata
Sister taxa: G. archeocompressa, G. australiformis, G. chapmani, G. compressa, G. ehrenbergi, G. imitata, G. luxorensis, G. ovalis, G. planocompressa, G. planoconica, G. pseudomenardii, G. sp.,

Taxonomy

Citation: Globanomalina imitata (Subbotina 1953)
Rank: Species
Basionym: Globorotalia imitata
Synonyms:
Taxonomic discussion: This is a distinctive species that is often overlooked because of its small size. It belongs to the perforate walled, inflated chamber lineage of planocompressa -imitata -ovalis. It also appears to have a phylogenetic link to G. australiformis (see "Discussion" under this species). The specimens illustrated as imitata by Blow (1979, pl. 81: figs. 8, 9, pl. 83: figs. 1,2, pl. 88:fig.5) are distinctly cancellate walled and do not belong to this species but probably belong to Praemurica. [Olsson et al. 1999]

Catalog entries: Globorotalia imitata;

Type images:

Short diagnosis: A small smooth-walled test with 4 to 4½, occasionally 5, inflated chambers in the ultimate whorl. The chambers are ovoid in shape with the long axis directed towards the umbilicus. In spiral and umbilical view the chambers are ovoid in shape with the long axis parallel to the coiling spire. The test walls are perforate throughout and the aperture is a high umbilical-extraumbilical arch that is bordered by a thin continuous lip. The wall is smooth in the adult chambers, but is covered with fine scattered to dense pustules in the early ontogenetic stages which possess anguloconical chambers.

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: A small smooth-walled test with 4 to 4½, occasionally 5, inflated chambers in the ultimate whorl. The chambers are ovoid in shape with the long axis directed towards the umbilicus. In spiral and umbilical view the chambers are ovoid in shape with the long axis parallel to the coiling spire. The test walls are perforate throughout and the aperture is a high umbilical-extraumbilical arch that is bordered by a thin continuous lip. The wall is smooth in the adult chambers, but is covered with fine scattered to dense pustules in the early ontogenetic stages which possess anguloconical chambers. [Olsson et al. 1999]

Character matrix

test outline:Ellipticalcoiling axis:Lowchamber arrangement:Trochospiralumbilicus:Narrow
edge view:Planoconvexumbilical or test sutures:Moderately depressedspiral sutures:Moderately depressedshell porosity:Microperforate: <1
wall texture:Smoothaperture:Interiomarginalaperture border:Thin lipaccessory apertures:None
periphery:N/Aumb chamber shape:Inflatedsp chbr shape:Inflatedperiph margin shape:Moderately rounded
umb depth:Deepdiameter mm:0.15 - 0.25width mm:-breadth mm:0.08 - 0.11
final-whorl chambers:4.0-5.0

Biogeography and Palaeobiology


Geographic distribution: Known from the northern Caucasus, southeast India, and the Atlantic and Gulf of Mexico coastal plains. [Olsson et al. 1999]
Aze et al. 2011 summary: Northern Caucasus, S.E. India, Atlantic and Gulf of Mexico coastal plains; based on Olsson et al. (1999)

Isotope paleobiology: No data available. [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): this study

Phylogenetic relations: This species probably evolved from Globanomalina planocompressa in Zone Pic. [Olsson et al. 1999]

Biostratigraphic distribution

Geological Range:
Notes: Zone Pic to Zone P4. [Olsson et al. 1999]
Last occurrence (top): within P4 zone (57.10-60.73Ma, top in Thanetian stage). Data source: Olsson et al. 1999
First occurrence (base): within P1c subzone (62.60-63.90Ma, 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. 42

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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Globanomalina imitata compiled by the pforams@mikrotax project team viewed: 22-7-2017

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