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Species Sphaeroidinellopsis paenedehiscens Blow 1969


Diagnosis / Definition:
Kennett & Srinivasan (1983):
Test large, low trochospiral, early chambers barely visible, ovate to smoothly rounded in equatorial periphery; chambers three in the final whorl, inflated; sutures largely obscured by the secondary test thickening; surface covered by thick, secondary calcareous material (cortex), which restricts the pores and provides a smooth and glossy appearance to the test; aperture an elongate umbilical opening following the line of suture between the last and first chamber of the final whorl, bordered by a crenulated lip, which are extensions of the cortex.
Discussion / Comments:
Kennett & Srinivasan (1983):
Ss. paenedehiscens is distinguished from its ancestor Ss. seminulina seminulina by its more spherical and tightly coiled test and in possessing a longer primary aperture. This species differs from Sphaeroidinella dehiscens by not having supplementary apertures on the spiral side.
Chaisson & Leckie (1993):
Remarks: This species has three chambers in the final whorl, but they are very embracing and completely covered with cortical overgrowth so that the test is oblate. Similar species: Sphaeroidinellopsis seminulina may also have three chambers in the final whorl, but its chambers are less embracing, giving the test a more lobate equatorial outline. S. paenedehiscens evolved into Sphaeroidinella dehiscens by developing a secondary aperture on the spiral side. Early S. dehiscens may have only the smallest crack in the spiral side and must be checked carefully
Synonym list:
Kennett & Srinivasan (1983):
1969 Sphaeroidinellopsis subdehiscens paenedehiscens Blow. - Blow : p.386 pl 30 figs 4,5,9
Chaisson & Pearson (1997):
1969 Sphaeroidinellopsis paenedehiscens Blow. - Blow : p.386 pl. 30; fig. 4, 5, 9,
1983 Sphaeroidinellopsis paenedehiscens Blow. - Kennett & Srinivasan : p.52 fig. 4-6
Chaisson & Leckie (1993):
1969 Sphaeroidinellopsis paenedehiscens Blow. - Blow : p.386 pl. 30; fig. 4, 5 and 9
1983 Sphaeroidinellopsis paenedehiscens Blow. - Kennett & Srinivasan : p.52 fig. 4-6
1993 Sphaeroidinellopsis paenedehiscens Blow. - Chaisson & Leckie : p.178 pl. 10; fig. 9
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

Kennett,J. and Srinivasan,M.S. (1983):
Neogene Planktonic Foraminifera - A Phylogenetic Atlas.

Chaisson,W.P. and Leckie,R.M. (1993):
High-Resolution Planktonic Foraminifer Biostratigraphy of Site 806, Ontong Java Plateau (Western Equatorial Pacific).
In: Proceedings of the Ocean Drilling Program, Scientific Results Vol. 130 Eds: Berger, W.H.Kroenke, L.W..Mayer, L.A..et al. p. 137-178

Chaisson,W.P. and Pearson,P.N. (1997):
Planktonic foraminifer biostratigraphy at Site 925: middle Miocene–Pleistocene.
In: Proceedings of the Ocean Drilling Program, Scientific Results Vol. 154 Eds: Shackleton, N.J.Curry, W.B.Richter, C.Bralower, T.J.
Anonymous: Unedited TaxonConcept data
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