Clavatorella nicobarensis

NB TAXA WHICH ORIGINATE IN THE OLIGOCENE ARE NOT INCLUDED YET
Classification: pf_neogene -> Globigerinidae -> Clavatorella -> Clavatorella nicobarensis
Sister taxa: C. bermudezi, C. nicobarensis, C. sp.,

Taxonomy

Citation: Clavatorella nicobarensis Kennett & Srinivasan 1974
Rank: species
Basionym: Clavatorella nicobarensis Kennett & Srinivasan 1974

Catalog entries: Clavatorella nicobarensis;

Type images:

Description


Test morphology: Test small, outline deeply lobulate, coiled in low trochospire; spiral side evolute, umbilical side involute with moderately shallow umbilicus. The spire is mostly level or depressed below spiral surface of final whorl of chambers (pI. 55 , fig. 7), giving false impression of biumbilicate, planispiral test; large specimens consist of nearly two whorls containing nine or more chambers with 5 (or rarely 6) in final whorl; early chambers spherical to subspherical, with later chambers progressively more radially elon- gate ; sutures essentially radial, slightly curved , and depressed; wall penetrated by closely spaced pores and surface roughened by can- cellate ridges between pores and by irregular calcite growths on ridges (PI. 55, Fig. 2); aperture simple, extending from the umbilicus to the periphery along base of final cham- ber, showing individual variation in height, and bordered by distinct, uniform , perforate lip throughout length; aperture does not extend across the periphery onto dorsal side.

Biogeography and Palaeobiology


Geographic distribution: Tropical

Phylogenetic relations: Cl. bermudezi (Bolli) (PI. 54, Figs. 6-8) is most closely related to Cl. nicobarensis but differs in swollen extremities of later chambers, which are much more separated at their attenuated proximal ends. Also the wall surface of Cl. bermudezi (Bolli) is distinctly pitted. The former species also has similar depressed trochoid coiling and shallow umbilical depression and a comparably placed but more elevated aperture. It appears to be the direct ancestor of Cl. nicobarensis.
Protentella prolixa Lipps differs in being planispiral and in having an equatorial symmetrical aperture.

Biostratigraphic distribution

Geological Range:
Last occurrence (top): within N19 zone (4.37-5.20Ma, top in Zanclean stage). Data source: Kennett & Srinivasan 1983
First occurrence (base): within N16 zone (8.58-9.83Ma, base in Tortonian stage). Data source: Kennett & Srinivasan 1983

Plot of occurrence data:

Primary source for this page: Kennett & Srinivisan 1983, p.220

References:

Kennett & Srinivasan 1974 [sorry, not in our bibliography yet]

Kennett, J.P. & Srinivasan, M.S., (1983). Neogene Planktonic Foraminifera. Hutchinson Ross Publishing Co., Stroudsburg, Pennsylvania, 1-265 pp.


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Clavatorella nicobarensis compiled by the pforams@mikrotax project team viewed: 23-7-2017

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