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Species Pseudohastigerina barbadoensis Blow 1969 |
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| Diagnosis / Definition: |
Blow (1969):
Description of holotype: The small test is composed of about 17 chambers coiled in an evolute planispire with 71 chambers visible in the final whorl. The test is moderately laterally compressed but the periphery is gently rounded. The chambers of the last whorl are slightly inflated and the intercameral sutures only shallowly depressed; the intercameral sutures between the last few chambers of the final whorl show a banded appearance due to a greater degree of smoothness of the wall and to a reduction in the density of the pores. In some parts of the intercameral sutures, pores seem to be virtually absent or very fine.
In optical appearance the test seems to be finely perforate but stereoscan electron microscopy shows comparatively large pores moderately densely scattered over the test surface. The pores seem to open to the exterior without any distinct pore pits. The evolute test possesses a wide umbilicus and the relict apertures of the last two chambers can be seen. The apertural porticus is well developed and the junction of the porticus and the test wall in the apertural region forms a virtual right angle. The aperture is a moderately low arch and is completely bordered by the porticus which seems to be imperforate. The wall is calcareous, radial hyaline [62a] and slightly pustulose but the surface is without distinct pore pits. Maximum diameter of holotype 0.20 mm. |
| Discussion / Comments: |
Blow (1969):
Description of holotype: The small test is composed of about 17 chambers coiled in an evolute planispire with 71 chambers visible in the final whorl. The test is moderately laterally compressed but the periphery is gently rounded. The chambers of the last whorl are slightly inflated and the intercameral sutures only shallowly depressed; the intercameral sutures between the last few chambers of the final whorl show a banded appearance due to a greater degree of smoothness of the wall and to a reduction in the density of the pores. In some parts of the intercameral sutures, pores seem to be virtually absent or very fine.
In optical appearance the test seems to be finely perforate but stereoscan electron microscopy shows comparatively large pores moderately densely scattered over the test surface. The pores seem to open to the exterior without any distinct pore pits. The evolute test possesses a wide umbilicus and the relict apertures of the last two chambers can be seen. The apertural porticus is well developed and the junction of the porticus and the test wall in the apertural region forms a virtual right angle. The aperture is a moderately low arch and is completely bordered by the porticus which seems to be imperforate. The wall is calcareous, radial hyaline [62a] and slightly pustulose but the surface is without distinct pore pits. Maximum diameter of holotype 0.20 mm. |
| Systematics: |
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Familia Globigerinelloididae
Genus Schackoina
Species Schackoina cabri
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| Synonym list: |
Blow (1969):
Spezzaferri & Silva (1990):
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| Was used in synonym list of: |
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| References: |
Blow,W.H. (1969):
Late middle Eocene to Recent planktonic foraminiferal biostratigraphy.
In: Proceedings of the First International Conference on Planktonic Microfossils, Geneva 1967 Vol. 1 Eds: Bronnimann, P.Renz, H.H. p. 199-422
Spezzaferri,S. and Silva,I.S.. (1990):
Oligocene planktonic foraminiferal biostratigraphy and paleoclimatic interpretation from Hole 538A, DSDP Leg 77, Gulf of Mexico . Palaeogeography, Palaeoclimatology, Palaeoecology Vol. 83 p. 217-263
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