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Species Globigerina nepenthes Todd 1957


Alternative name:
Globigerina (Zeaglobigerina) nepenthes Todd 1957
Diagnosis / Definition:
Bolli & Saunders (1985):
G. nepenthes is used as a zonal marker, for example by Blow (1959 and 1969, definition of N 14), Cati et al. (1968) and Kennett (1973), but it is erratic in its appearance, and may be virtually absent from whole sections. However, it is a distinctive, easily recognizable form which, when present, is of value.The coiling pattern of G. nepenthes suggests a distinction between it and other members of that genus but also does not fit elsewhere. There is some tendency towards Sphaeroidinellopsis but the species of that genus had formed distinct cortexes before the first appearance of G. nepenthes.
Discussion / Comments:
Bolli & Saunders (1985):
The coiling of G. nepenthes begins tightly but the last few chambers become more spiral producing the characteristic elongate outline. The high, cap shaped last chamber has a large aperture usually bordered by a thickened rim. Some workers record transitions at the beginning of the range of G. nepenthes between it and such forms as G. druryi (Akers) and G. woodi Jenkins. Within its range, G. nepenthes can show considerable morphological variation in closeness of coiling and thickness of test wall, which has led to a number of subspecies being proposed; for example, G. nepenthes delicatula Brönnimann & Resig (1971) here illustrated as Figs. 25.2 4. As variations can often be ascribed to environmental conditions and as they seem of little stratigraphic value, we retain these forms under the name nepenthes as do Stainforth et al., 1975.
Bolli (1957):
Globigerina nepenthes is restricted in Trinidad to the upper part of the Globorotalia mayeri zone and to the Globorotalia menardii zone. Although it is found in the transitional beds of the Lengua and Cruse formations and would under more favourable conditions probably have a longer range, it is here an excellent index fossil for the Lengua formation.
Srinivasan (1975):
lntergradational forms between Globigerina druryi and G. nepenthes are common in most samples, supporting the observation of Blow (1969) that G. nepenthes evolved from G. druryi Akers. Globigerina nepenthes is an important Zone fossil, as its initial appearance marks the base of Zone N.14 (Blow, 1969; Brönnimann and Resig, 1971), and its last appearance within Zone N.19 corresponds to Datum Vlll of Hays et al. (1969) and to the top of PL 1 Zone of Berggren (1973). In Little Andaman, the range of G. nepenthes stratigraphically overlaps the range of Globorotalia fohsi lobata and G. fohsi robusta.
Chaisson & Leckie (1993):
Remarks: The usual form of Globigerina nepenthes has a protruding last chamber, an oblate test outline, and a distinct apertural rim. It is rare at this site. What are found instead are very small globigerinid specimens with radially elongate final chambers that are skewed out the regular trochospiral curve and toward the umbilicus. Brönnimann and Resig (1971) called this form G. nepenthoides. We have treated it as an ecophenotype of G. nepenthes. Also included under this species concept were globigerinid specimens with "kümmerform" final chambers with apertural rims (cf. Jenkins and Orr, 1972, pi. 10, fig. 9). Similar species: Specimens of G. apertura with a high narrow final chamber can resemble G. nepenthes, but the trochospire of G. apertura is usually more regular, its final chamber closer to the size of the penultimate chamber, and its aperture is typically much larger than G. nepenthes. G. nepenthes is gradational with G. druryi, but it can be distinquished by its elongated final chamber and more oblate equatorial outline.
Synonym list:
Bolli & Saunders (1985):
1957 Globigerina nepenthes Todd. - Todd : p.301 pl.78, fig.7
1985 Globigerina nepenthes Todd. - Bolli & Saunders : p.201 figs. 25; 7,10,11
Bolli (1957):
1957 Globigerina nepenthes Todd. - Bolli : pl. 24, figs. 2a-c
1957 Globigerina nepenthes Todd. - Todd : p. 301 pl. 78, fig. 7
Srinivasan (1975):
1957 Globigerina nepenthes Todd. - Todd : 301-302 Pl. 78; Fig. 7a-b
1975 Globigerina nepenthes Todd. - Srinivasan : p.143 Pl. 1; Fig. 10-11
Chaisson & Leckie (1993):
1957 Globigerina nepenthes Todd. - Todd : p.301 fig. 7a-b
1983 Globigerina (Zeaglobigerina) nepenthes Todd. - Kennett & Srinivasan : p.48 pl. 9; fig. 1-3
1993 Globigerina nepenthes Todd. - Chaisson & Leckie : p.169 pl. 1; fig. 12
Was used in synonym list of:
Globoturborotalita nepenthes Todd 1957
Globigerina (Zeaglobigerina) nepenthes Todd 1957
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

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
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