Globigerinoides mitra Todd 1957 from: Bolli, H.M. (1957): Planktonic foraminifera from the Oligocene-Miocene Cipero and Lengua formations of Trinidad, B.W.I.. In: Studies in Foraminifery, Bulletin of the U.S. National Museum Vol. 215 Eds: Loeblich, A.R.Tappan, H.Beckmann, J.P.Bolli, H.M.Gallitelli, E.M.Troelsen, J.C. p. 97-123 . |
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Species Globigerinoides mitra Todd 1957 |
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Diagnosis / Definition: |
Kennett & Srinivasan (1983):
Test large, high spired, chambers spherical to suhspherical, three or four in the final whorl; sutures depressed, surface hummocky on earlier chambers but perforate on later chambers; primary aperture interiomarginal, umbilical, a large semicircular opening occupying most of the umbilical edge of the final chamber; small supplementary apertures at the intersection of the vertical sutures with the spiral sutures. |
Discussion / Comments: |
Kennett & Srinivasan (1983):
Gs. mitra is distinguished by its large test size, very high spire, and large, asymmetric primary aperture. Except for its
distinct asymmetrically developed adult chambers, Gs. mitra is morphologically close to Gs. subquadratus and Gs. ruber and possibly is intermediate between them.
Bolli & Saunders (1985):
This species occurs infrequently but is easily recognized because of its exceptionally large size (according to Todd up to 1.4 mm). Characteristic is the high spire formed by loosely arranged chambers, those of the last whorl often elongate, grape shaped. As has been noted in Trinidad, G. mitra tests are often preserved in a pyritic state.
Bolli (1957):
Scarce specimens of the large Globigerinoides mitra may occur from the Catapsydrax dissimilis zone onward. In the transitional beds between the Lengua formation and the Cruse formation, where they are more often encountered than deeper in the section, the tests of Globigerinoides mitra are usually pyritized. It appears possible that these abnormally large forms have developed from Globigerinoides obliqua, new species, by the development of additional chambers. The large specimen of Globigerinoides obliqua (pl. 25, figs. 9a c) and Globigerinoides species (pl. 26 figs. 5a c) (USNM P5641) are possibly transitional forms.
Srinivasan (1975):
Sporadic occurrences of this large, high-spired
species of Globigerinoides have been recorded in the
Caribbean, GuIf of Mexico, and equatorial Pacific regions.
It appears to be restricted to tropical and warm subtropical regions. |
Systematics: |
21 Genus Globigerinoides
Species Globigerinoides mitra
Species Globorotalia minutissima
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Synonym list: |
Kennett & Srinivasan (1983):
Bolli & Saunders (1985):
Bolli (1957):
Srinivasan (1975):
Vincent & Toumarkine (1990):
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References: |
Todd,R. (1957): Smaller foraminifers. In: Geology of Saipan, Mariana Islands (Pt. 3) Paleontology, US. Geological Survey Professional Papers280-H p. 265-320
Bolli,H.M. (1957): Planktonic foraminifera from the Oligocene-Miocene Cipero and Lengua formations of Trinidad, B.W.I.. In: Studies in Foraminifery, Bulletin of the U.S. National Museum Vol. 215 Eds: Loeblich, A.R.Tappan, H.Beckmann, J.P.Bolli, H.M.Gallitelli, E.M.Troelsen, J.C. p. 97-123
Srinivasan,M.S. (1975): Middle Miocene Planktonic Foraminifera from the Hut Bay Formation, Little Andaman Island, Bay of Bengal . Micropaleontology Vol. 21(2) p. 133-150
Kennett,J. and Srinivasan,M.S. (1983): Neogene Planktonic Foraminifera - A Phylogenetic Atlas.
Bolli,H.M. and Saunders,J.B. (1985): Oligocene to Holocene low latitude planktic foraminifers. In: Plankton Stratigraphy Eds: Bolli, H.M.Saunders, J.B. p. 155-262
Vincent,E. and Toumarkine,M. (1990): Neogene planktonic foraminifers from the Western Tropical Indian Ocean, Leg 115. In: Proceedings of the Ocean Drilling Program, Scientific Results Vol. 115 Eds: Duncan, R.A..Backman, J.Peterson, L.C. p. 795-836
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