Chiloguembelina wilcoxensis

Classification: pf_cenozoic -> microperforate -> Chiloguembelinidae -> Chiloguembelina -> Chiloguembelina wilcoxensis
Sister taxa: C. cubensis, C. ototara, C. parallela, C. trinitatensis, C. wilcoxensis, C. crinita, C. subtriangularis, C. midwayensis, C. morsei, C. sp.,


Citation: Chiloguembelina wilcoxensis (Cushman and Ponton 1932)
Rank: Species
Basionym: Guembelina wilcoxensis
Taxonomic discussion: The final chamber in adult Chiloguembelinawilcoxensis may be normalform to strongly kummerform. The aperture on the final chamber may be a symmetrical low to moderately high semicircular arch, centered on the chamber face and bordered by an equidimensional lip, or they may be slightly asymmetrical, off-centered on the final chamber face, and bordered by an inequidimensional lip that is slightly infolded on one side. The symmetrical shape and positioning of the aperture and equidimensional bordering lip on adult specimens of C. wilcoxensis are reminiscent of the Cretaceous Heterohelicidae. However, dissection of adult tests with symmetrical apertures in the center of the final chamber reveal that the apertures on pre-adult chambers are asymmetrical in position and shape and the bordering lip in infolded on one side. Apertural asymmetry in early ontogeny is taken to represent a primitive feature shared with the chiloguembelinid stock, whereas apertural symmetry in adult specimens is considered a derived character that first appeared in C. trinitatensis. Chiloguembelinawilcoxensis differs from this species by its larger less tapering test. [Olsson et al. 1999]

Catalog entries: Guembelina wilcoxensis;

Type images:

Short diagnosis: Test large, with broadly rounded periphery, rapid chamber size increase in the initial portion of the test. Aperture symmetrically centered, low-arched to semicircular with an equidimensional lip.

NB The short diagnoses are used in the tables of daughter-taxa to act as quick summaries of the differences between e.g. species of one genus. They have initially been copied from the diagnostic characters/distinguishing features sections of the Eocene and Paleocene Atlases, they will be edited as the site is developed.


Diagnostic characters: Distinguished by the large test size, broadly rounded periphery, rapid chamber size increase in the initial portion of the test, and symmetrically centered, low-arched to semicircular aperture surrounded by an equidimensional lip. [Olsson et al. 1999]

Character matrix

test outline:Subtriangularchamber arrangement:Biserialedge view:Equally biconvexaperture:Terminal
umb chamber shape:Inflatedcoiling axis:N/Aperiphery:N/Aaperture border:Thin lip
sp chbr shape:N/Aumbilicus:N/Aperiph margin shape:Broadly roundedaccessory apertures:None
umbilical or test sutures:Moderately depressedumb depth:N/Awall texture:shell porosity:
spiral sutures:N/Adiameter mm:0.45width mm:0.35breadth mm:0.25
final-whorl chambers:2.0-2.0

Biogeography and Palaeobiology

Phylogenetic relations: Although Beckmann (1957) suggested that C. wilcoxensis descended from C. crinita during the late Paleocene, it is more likely that C. wilcoxensis was derived from C. trinitatensis during the late Paleocene since C. wilcoxensis and C. trinitatensis are more similar morphologically and study of Caribbean DSDP Site 152 indicates that the first occurrence of the latter species is older than that of the former species (B. Huber, pers. observ., 1995). Both species have a similar pustulose wall texture which suggests that they are phylogenetically related. [Olsson et al. 1999]

Most likely ancestor: Chiloguembelina crinita - at confidence level 4 (out of 5). Data source: Olsson et al. 1999, f6.

Biostratigraphic distribution

Geological Range:
Notes: Upper Paleocene Zone P4b through lower Eocene Zone E4. At middle latitude sites on the New Jersey coastal margin Liu and others (1997) recorded the HO of C. wilcoxensis in the middle of their Zone P6a (~Zone E2). For the southern high latitudes the LO of C. wilcoxensis was reported slightly earlier than at low latitudes, within middle Zone AP2 (~Zone P4b), and the extinction of this species marks the top of the Chiloguembelina wilcoxensis Zone (AE1) of Huber and Quille_ve_re_ (2005).
Last occurrence (top): in mid part of E4 zone (50% up, 53.6Ma, in Ypresian stage). Data source: Huber et al. 2006, f16.2
First occurrence (base): in mid part of P4b subzone (50% up, 59.2Ma, in Selandian stage). Data source: Olsson et al. 1999

Plot of occurrence data:

Primary source for this page: Olsson et al. 1999 - Atlas of Paleocene Planktonic Foraminifera, p. 92


Beckmann, J.P., (1957). Chiloguembelina Loeblich and Tappan and related foraminifera from the Lower Tertiay of Trinidad, B.W.I. In: Loeblich, A.R., Jr. et al. (Editors), Studies in Foraminifera: U.S. National Museum Bulletin 215. U.S. Government Printing Office, Washington, D.C., pp. 83-95.

Cushman, J.A. & Ponton, G.M., (1932). An Eocene foraminiferal fauna of Wilcox age from Alabama. Contributions from the Cushman Laboratory for Foraminiferal Research, 8: 51-72.

Olsson, R.K.; Hemleben, C.; Berggren, W.A. & Huber, B.T., (1999). Atlas of Paleocene Planktonic Foraminifera. Smithsonian Contributions to Paleobiology. Smithsonian Institution Press, Washington, DC, 1-252 pp.


Chiloguembelina wilcoxensis compiled by the pforams@mikrotax project team viewed: 23-1-2018

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