Catalog entries: Clavatorella nicobarensisType images:
Distinguishing features: Low trochospire; aperture extending from umbilicus to periphery but not onto spiral side, lip.NB These concise distinguishing features statements are used in the tables of daughter-taxa to act as quick summaries of the differences between e.g. species of one genus.
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 cancellate 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 chamber, showing individual variation in height, and bordered by distinct, uniform, perforate lip throughout length; aperture does not extend across the periphery onto dorsal side.
|test outline:||Stellate||chamber arrangement:||Planispiral||edge view:||Equally biconvex||aperture:||Extraumbilical-peripheral|
|sp chamber shape:||Elongate||coiling axis:||Very low||periphery:||N/A||aperture border:||Thick lip|
|umb chbr shape:||Elongate||umbilicus:||Wide||periph margin shape:||Moderately rounded||accessory apertures:||None|
|spiral sutures:||Weakly depressed||umb depth:||Shallow||wall texture:||Cancellate||shell porosity:||Macroperforate: >2.5µm|
|umbilical or test sutures:||Strongly depressed||final-whorl chambers:||5.0-6.0||N.B. These characters are used for advanced search. N/A - not applicable|
Geographic distribution: Tropical Tropical (Kennett & Srinivasan 1983)
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.
Most likely ancestor: Protentella prolixa - at confidence level 2 (out of 5). Data source: Aze et al. 2011. This is in disagreement with Kennett & Srinivasan (1983, fig 24) who inferred derivation from Clavatorella bermudezii, but that involved a long range gap..
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 & Srinivasan 1983, p.220
Aze, T. et al. (2011). A phylogeny of Cenozoic macroperforate planktonic foraminifera from fossil data. Biological Reviews. 86: 900-927. gs Kennett, J. P. & Srinivasan, M. S. (1983). Neogene Planktonic Foraminifera. Hutchinson Ross Publishing Co., Stroudsburg, Pennsylvania. 1-265. gs Srinivasan, M. S. & Kennett, J. P. (1974a). A planktonic foraminifer (Clavatorella) from the Pliocene. Journal of Foraminiferal Research. 4(2): 77-79. gs
Aze, T. et al. (2011). A phylogeny of Cenozoic macroperforate planktonic foraminifera from fossil data. Biological Reviews. 86: 900-927. gs
Kennett, J. P. & Srinivasan, M. S. (1983). Neogene Planktonic Foraminifera. Hutchinson Ross Publishing Co., Stroudsburg, Pennsylvania. 1-265. gs
Srinivasan, M. S. & Kennett, J. P. (1974a). A planktonic foraminifer (Clavatorella) from the Pliocene. Journal of Foraminiferal Research. 4(2): 77-79. gs
Protentella nicobarensis compiled by the pforams@mikrotax project team viewed: 22-10-2019
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