Specimens which cannot be assigned to established species
| Daughter taxa (time control age-window is: 0-800Ma) | ||||
| | | Paracostellagerina libyca | |
| Paracostellagerina sp. Specimens which cannot be assigned to established species | ||||
Taxonomy
Differences in test ornamentation, position of the primary aperture, and nature of the periapertural structures provide the impetus to distinguish Hedbergella libyca and Rugoglobigerina pilula as the type species of the two monospecific genera Paracostellagerina nov. gen. and Costellagerina. The two species were considered congeneric in the past by Loeblich and Tappan (1988, p. 462) and Premoli Silva and Sliter (1995, pl. 1, fig. 8) under Costellagerina, and by El-Nakhal (2002) under his genus Meridionalla. Meridionalla was based on the figures of the holotype of Hedbergella murphyi, which was named by Douglas (1969). Re-examination of the SEM photographs of the Hedbergella murphyi holotype by Petrizzo and Premoli Silva (2000) showed that there is no meridional ornamentation as was illustrated in the original figure. Therefore Meridionalla lacks taxonomic significance. Separation of Costellagerina and Paracostellagerina nov. gen. is supported by absence of forms with similar test morphology between the extinction of Paracostellagerina libyca and the first occurrence of Costellagerina pilula. This stratigraphic interval ranges from the earliest Cenomanian to the earliest Santonian and spans approximately 13 myr.
Original description: Test low to moderate trochospiral, globular chambers with a broadly rounded periphery, lacking peripheral structures;
primary aperture extraumbilical-umbilical, bordered by a narrow, imperforate lip; test ornamentation asymmetrical with respect to the peripheral plane, rugosities and sharp costellae arranged following a meridional pattern on the umbilical side, and parallel to the periphery on the spiral side.
Entries in the Catalog of original descriptions: Paracostellagerina
Distinguishing features:
Parent taxon (Hedbergellidae): Test trochospirally coiled, primary aperture interiomarginal, extraumbilical-umbilical, with prominent apertural lip, apertures of earlier chambers remain visible around the umbilical region; no sutural secondary apertures.
This taxon: Test low to moderate trochospiral, globular chambers with a broadly rounded periphery, lacking peripheral structures; primary aperture extraumbilical-umbilical, bordered by a narrow, imperforate lip; test ornamentation asymmetrical with respect to the peripheral plane, rugosities and sharp costellae arranged following a meridional pattern on the umbilical side, and parallel to the periphery on the spiral side.
Geological Range:
Last occurrence (top): at top of T. globotruncanoides zone (100% up, 98.9Ma, in Cenomanian stage). Data source: Total of ranges of the species in this database
First occurrence (base): within P. appenninica zone (100.50-101.92Ma, base in Albian stage). Data source: Total of ranges of species in this database
Plot of range and occurrence data:
Georgescu, M. D. & Huber, B. T. (2006). Paracostellagerina nov. gen., a meridionally costellate planktonic foraminiferal genus of the middle Cretaceous (latest Albian- earliest Cenomanian). Journal of Foraminiferal Research. 36(4): 368-373. gsReferences:
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Paracostellagerina compiled by the pforams@mikrotax project team viewed: 11-10-2024
Short stable page link: https://mikrotax.org/pforams/index.php?id=110379 Go to Archive.is to create a permanent copy of this page - citation notes |
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