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Species Globorotaloides variabilis Bolli 1957


Diagnosis / Definition:
Kennett & Srinivasan (1983):
Test low, trochospiral, spiral side almost flat, equatorial periphery lobulate, axial periphery subacute to subrounded; chambers subangular to ovate, five to six rapidly enlarging chambers in the final whorl; sutures on both spiral and umbilical sides distinctly curved in early stage, later becoming radial, depressed; surface distinctly cancellate ; umbilicus fairly wide; aperture a very low arch or slit interiomarginal, umbilical-extraumbilical in early stage, later becoming umbilical.
Bolli (1957):
Shape of test low trochospiral, biconvex; equatorial periphery lobate, in small specimens somewhat elongate; axial periphery subacute in immature specimens, rounded in mature specimens. Wall calcareous, perforate, surface very finely cancellate. Chambers subangular to ovate in early stage, later becoming ovate to spherical; about 1-18, arranged in 2-2 1/2 whorls; the 5-7 chambers of the last whorl increase fairly rapidly in size. Sutures on spiral side distinctly curved in early stage, later becoming more radial, depressed; on umbilical side slightly curved in early stage, later becoming radial, depressed. Umbilicus fairly wide, open in immature specimens, in mature specimens partly or completely covered by a bulla like chamber. Aperture a slit or low arch; interiomarginal, umbilical extraumbilical in early stage, later becoming umbilical, which in the mature stage becomes covered by a bullalike chamber with one infralaminal aperture. Coiling random. Largest diameter of holotype 0.45 mm.
Discussion / Comments:
Kennett & Srinivasan (1983):
This species is distinguished from Gd. suteri by having more compressed early chambers, more curved sutures, and a greater number of chambers in the final whorl.
Bolli & Saunders (1985):
G. variabilis is distinguished from G. suteri by its generally larger size and particularly by the more numerous and less inflated chambers of the early stage with their distinctly curved sutures and by the more rapidly increasing size of the last chambers.
Bolli (1957):
Globorotaloides variabilis, new species, is distinguished from G. suteri, new species, by having more compressed early chambers, more curved sutures and a greater number of chambers. It is likely that G. suteri, which is restricted to the lower and middle part of the Cipero formation, is the ancestor of G. variabilis, new species.
Chaisson & Leckie (1993):
Similar species: Globorotaloides variabilis can resemble juvenile specimens of Globoquadrina venezuelana and G. conglomerata, but it can be distinguished from these taxa by its distinctive subacute margin on the early chambers of the final whorl and the lack of an apertural tooth-plate. The chambers of G. variabilis are more embracing than those of G. hexagona. The subacute peripheral margin of G. variabilis also serves to distinguish these two taxa.
Systematics:

3
 Classis Foraminifera
  Genus Globorotaloides
   Species Globorotaloides variabilis

22
  Genus Globorotaloides
   Species Globorotaloides variabilis
Synonym list:
Kennett & Srinivasan (1983):
1957 Globorotaloides variabilis Bolli. - Bolli : p.117 pl 27 figs. 15a-20c
Bolli & Saunders (1985):
1957 Globorotaloides variabilis Bolli. - Bolli : p.117 pl. 27, figs. 20a-c
1985 Globorotaloides variabilis Bolli. - Bolli & Saunders : p.189 figs. 18.7-9; 7,9,12
Chaisson & Pearson (1997):
1957 Globorotaloides variabilis Bolli. - Bolli : p.117 pl. 27; fig. 15a-20c
1983 Globorotaloides variabilis Bolli. - Kennett & Srinivasan : p.214 pl. 53; fig. 2, 6-8
Bolli (1957):
1957 Globorotaloides variabilis Bolli. - Bolli : pl. 27, figs. 15a-20c new species
Vincent & Toumarkine (1990):
1957 Globorotaloides variabilis Bolli. - Bolli : p.117 pl.27, figs.15-20
1990 Globorotaloides variabilis Bolli. - Vincent & Toumarkine : p.834 pl.5, figs.25-27
Spezzaferri & Silva (1990):
1985 Globorotaloides variabilis Bolli. - Bolli & Saunders : fig. 18 (9a-c)
1990 Globorotaloides variabilis Bolli. - Spezzaferri & Silva : p.250 pl. X; fig. 2a-b
Chaisson & Leckie (1993):
1957 Globorotaloides variabilis Bolli. - Bolli : p.117 pl. 27; fig. 15a-20c
1983 Globorotaloides variabilis Bolli. - Kennett & Srinivasan : p.214 pl. 53; fig. 2 and 6-8
1993 Globorotaloides variabilis Bolli. - Chaisson & Leckie : p.177 pl. 9; fig. 3
References:

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

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

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

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

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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