Taxonomy
Original description: Test flabelliform, slightly compressed; Eight chambers in biserial portion; twenty-two chambers in multiserial portion. Chambers globular to pyriform. Sutures distinct, depressed. Fine, discontinuous segments of longitudinal costae cover majority of test, rearranging into a vermicular pattern on early chambers. Arched, basal apertures on front and back of all but outermost chambers in multiserial portion; outermost chambers usually with apertures on front only, facing inward.
Entries in the Catalog of original descriptions: Ventilabrella riograndensis
Morphology: Biserial chambers rapidly expanding in size; followed by up to 5 multiserial sets; surface covered with fine vermicular ornamentation; last set of chamberlets usually covered with fine, discontinuous costae.
Geological Range:
Last occurrence (top): within P. hariaensis zone (66.39-67.30Ma, top in Maastrichtian stage). Data source: [copied from Chronos database]
First occurrence (base): within R. calcarata zone (75.71-76.18Ma, base in Campanian stage). Data source: [copied from Chronos database]
Plot of range and occurrence data:
Character matrix
test outline: | Palmate | chamber arrangement: | Multiserial | edge view: | Compressed | aperture: | Multiple |
sp chamber shape: | Inflated | coiling axis: | N/A | periphery: | N/A | aperture border: | Thin flange |
umb chbr shape: | Inflated | umbilicus: | N/A | periph margin shape: | Moderately rounded | accessory apertures: | N/A |
spiral sutures: | Moderately depressed | umb depth: | N/A | wall texture: | Finely costate | shell porosity: | - |
umbilical or test sutures: | Moderately depressed | final-whorl chambers: | 5.0-8.0 | N.B. These characters are used for advanced search. N/A - not applicable |
Martin, S. E. (1972). Reexamination of the Upper Cretaceous planktonic foraminifera genera Planoglobulina and Ventilabrella Cushman. Journal of Foraminiferal Research. 2(2): 73-92. gsReferences:
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Planoglobulina riograndensis compiled by the pforams@mikrotax project team viewed: 21-4-2021
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