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Costellagerina bulbosa


Classification: pf_mesozoic -> Hedbergellidae -> Costellagerina -> Costellagerina bulbosa
Sister taxa: C. bulbosa, C. pilula,

Taxonomy

Citation: Costellagerina bulbosa (Belford, 1960)
Rank: Species
Basionym: Rugoglobigerina bulbosa
Similar species: Rugoglobigerina (Rugoglobigerina) bulbosa is close to the Rugoglobigerina macrocephala group than to any other described Upper Cretaceous Rugoglobigerinas, particularly to Rugoglobigerina macrocephala ornata Bronnimann. The chambers of Rugoglobigerina (Rugoglobigerina) bulbosa do not increase in size as rapidly as in Rugoglobigerina macrocephala subspp., the test is more rounded in outline, and it also lacks hispid ornamentation. Fifty-nine sinistrally coiled and thirty dextrally coiled forms have been found. [copied from Chronos database]

Type images:

Original description: Rugoglobigerina bulbosa Belford 1960: Test trochoid, both dextrally and sinistrally coiled forms known, with the latter the more common; umbilicus small, circular, usually infilled. Chambers globular, inflated, forming to two to two and one-half whorls, successive whorls strongly overlapping and spiral surface flat or only slightly convex; usually four but sometimes five chambers on last whorl increasing only slowly in size as added. Very rare specimens have last chamber smaller than penultimate chamber, formed to one side of test and always smooth. Earlier chambers and sutures on spiral side often obscured by surface ornamentation, the later sutures straight or slightly curved, depressed; sutures on umbilical side straight, depressed. Surface of test ornamented with small discontinuous ridges, irregularly arranged on earlier chambers and forming meridional pattern on chambers of last whorl. Vail of test calcareous, finely perforate, radiate in structure. Aperture interiomarginal umbilical, large and arcuate, not always observed; well-preserved specimens have distinct tegilla extending over umbilicus.

Entries in the Catalog of original descriptions: Rugoglobigerina bulbosa;

Geological Range:
Last occurrence (top): within G. elevata zone (79.20-84.19Ma, top in Campanian stage). Data source: [copied from Chronos database]
First occurrence (base): within D. asymetrica zone (84.19-86.71Ma, base in Coniacian stage). Data source: [copied from Chronos database]

Plot of occurrence data:

NB Plotting of Neptune data has been disabled on the Mesozoic pages because the dataset is both small and badly affected by a few sites with erroneous age models (our obs Huber, Petrizzo, Young, Nov 2016). The data can still be viewed via the range plottertool - tools menu.

Character matrix

test outline:Subcircularcoiling axis:Low-moderatechamber arrangement:Trochospiralumbilicus:Wide
edge view:umbilical or test sutures:Strongly depressedspiral sutures:Strongly depressedshell porosity:
wall texture:Meridional costellaeaperture:Umb.-extraumbilicalaperture border:Tegillaaccessory apertures:None
periphery:N/Aumb chamber shape:Inflatedsp chbr shape:Inflatedperiph margin shape:Broadly rounded
umb depth:Deepdiameter mm:0.34 to 0.39width mm:breadth mm:0.19 to 0.26
final-whorl chambers:4.0-5.0

References:

Belford, D.J., (1960). Upper Cretaceous foraminifera from the Toolonga Calcilutite and Gingin Chalk, Western Australia. Australia Bureau of Mineral Resources, Geology and Geophysics Bulletin, 57: 1-198.


Costellagerina bulbosa compiled by the pforams@mikrotax project team viewed: 23-5-2017

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