Globanomalina planoconica


Classification: pf_cenozoic -> smooth non-spinose -> Hedbergellidae -> Globanomalina -> Globanomalina planoconica
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 planoconica (Subbotina 1953)
Rank: Species
Basionym: Globorotalia planoconica
Synonyms:
Taxonomic discussion: The specimens identified as this species by Tjalsma (1977) and Huber (1991b) from the South Atlantic and southern Indian oceans, respectively, differ from the holotype (Plate 10: Figures 15-17) by having only five chambers in the ultimate whorl and by the more sharply curved sutures on the spiral side. Tjalsma reported that transitional forms between "planoconica" and G. australiformis occurred at DSDP Site 329 in the upper Paleocene and lower Eocene, suggesting that the former species was derived from the latter. It would appear that these "planoconica" morphotypes may be a different species. This possibility needs further investigation. Blow (1979) figured specimens from Zone P10 in a North Atlantic piston core that he identified as G. planoconica. These specimens have 7 to 8 chambers in the ultimate whorl and a high arched aperture that extends slightly over the axial periphery onto the spiral side. He considered these forms ancestral to Pseudohastigerina danvillensis (Howe and Wallace, 1932). Except for the greater number of chambers, Blow's
specimens are similar to G. planoconica in that they possess a well-developed imperforate peripheral margin, but they differ in the apertural lip, which widens as a tooth-like projection into the umbilical area. It would appear that these morphotypes may be related to G. planoconica. The morphologic range of this species and its relationship to other species in the Eocene needs further study. [Olsson et al. 1999]

Catalog entries: Globorotalia planoconica;

Type images:

Short diagnosis: A small highly compressed species with a well developed, thickened, imperforate peripheral margin. The number of chambers in the ultimate whorl ranges from 5 to 6, occasionally 7. The aperture is a high umbilical-extraumbilical arch that is bordered by a thin continuous lip. The equatorial periphery is rounded in the early portions of the ultimate whorl and becomes more lobulate with the final few 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 highly compressed species with a well developed, thickened, imperforate peripheral margin. The number of chambers in the ultimate whorl ranges from 5 to 6, occasionally 7. The aperture is a high umbilical-extraumbilical arch that is bordered by a thin continuous lip. The equatorial periphery is rounded in the early portions of the ultimate whorl and becomes more lobulate with the final few chambers. [Olsson et al. 1999]

Character matrix

test outline:Ellipticalchamber arrangement:Planispiraledge view:Planoconvexaperture:Umb.-extraumbilical
umb chamber shape:Subtriangularcoiling axis:N/Aperiphery:Imperforate bandaperture border:Thin lip
sp chbr shape:Petaloidumbilicus:Wideperiph margin shape:Subangularaccessory apertures:None
umbilical or test sutures:Moderately depressedumb depth:Deepwall texture:Smoothshell porosity:Finely Perforate: 1-2.5µm
spiral sutures:Moderately depresseddiameter mm:0.23 - 0.26width mm:-breadth mm:0.06 - 0.08
final-whorl chambers:4.5-5.5

Biogeography and Palaeobiology


Geographic distribution: As discussed above, the taxonomy of this species needs further clarification before its distribution can be reliably plotted. At present, a middle to low latitude distribution is probable. [Olsson et al. 1999]
Aze et al. 2011 summary: Low to middle latitudes; 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: The strong imperforate peripheral margin allies this species with the chapmani lineage and suggests that it was derived from this species in upper Zone P4. [Olsson et al. 1999]

Biostratigraphic distribution

Geological Range:
Notes: Upper Zone P4 to lower Eocene. [Olsson et al. 1999]
Last occurrence (top): within E4 zone (52.54-54.61Ma, top in Ypresian stage). Data source: Olsson et al. 1999
First occurrence (base): within P4 zone (57.10-60.73Ma, base in Selandian 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. 44

References:

Blow, W.H., (1979). The Cainozoic Globigerinida: A study of the morphology, taxonomy, evolutionary relationships and stratigraphical distribution of some Globigerinida (mainly Globigerinacea). E. J. Brill, Leiden, 1413 pp.

Huber, B.T., (1991). Paleogene and early Neogene planktonic foraminifer biostratigraphy of ODP Leg 119 Sites 738 and 744, Kerguelen Plateau (southern Indian Ocean). Proceedings of the Ocean Drilling Program, Scientific Results, 119: 427-449.

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.

Subbotina, N., (1953). Foraminiferes fossiles d'URSS Globigerinidae, Globorotaliidae, Hantkeninidae. Bureau de Recherches Geologiques et Minieres, 2239: 1-144.

Tjalsma 1977 [sorry, not in our bibliography yet]


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Globanomalina planoconica compiled by the pforams@mikrotax project team viewed: 20-9-2017

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