Chiloguembelina


Classification: pf_cenozoic -> microperforate -> Chiloguembelinidae -> Chiloguembelina
Sister taxa: Chiloguembelina, Streptochilus,
Daughter taxa - species arranged by first occurrence (blue => in age window 0-300Ma)
Distinguished from C. ototara by presence of fine costae parallel to the long axis of the test.
Test short to somewhat elongate, moderately to rapidly expanding, subtriangular, periphery rounded rather than compressed; usually 11-12, up to 15 chambers; sutures depressed, perpendicular to slightly oblique to growth axis; Aperture moderately narrow to broad symmetrical arch centered or slightly off-center, bordered on one side by a narrow lip.
Differs from other chiloguembelinids by its short, thick test that tapers rapidly toward its base and its centrally located, symmetrical, high and narrow aperture.
Test biserial with chambers that increase uniformly in breadth and height. Aperture symmetrically centered, low-arched with a narrow, equidimensional lip. [Olsson et al. 1999]
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.
Test biserial throughout with the characteristic chiloguembelinid apertural asymmetry; its aperture is marked by a narrow lip, infolded on one side, and expanded into a distinct apertural flange on the opposite side. Later chambers are subglobular. The sutures distinct and depressed. Test is microperforate and last chambers are finely hispid.
Test small, biserial with subangular periphery, subtriangular in side view. Chambers, slightly inflated,broadening though ontogeny, successive chambers slightly overlapping the previous one. Sutures somewhat depressed, nearly straight, at low angle with the growth axis. Aperture a low, asymmetrically positioned, interiomarginal arch with a lip that narrows toward the center of the chamber. Length 140-220 um.
Test small, compressed, and rapidly tapering. Early chambers subspherical, later chambers broader. Late-stage chambers cross the coiling axis and overlap the immediately preceding chambers, can extend almost across test. Surface with numerous small pustules, fewer on the last two chambers. Aperture of each chamber exhibits only one distinct lateral flange
The test biserial throughout. Sutures are distinct and depressed, initially sub-horizontal, oblique between later chambers. Successive chambers overlap, particularly in late ontogeny. Initial chambers sub-spherical, later chambers broader Wall surface with numerous small pustules, especially on early chambers. Aperture with a single distinct lateral flange.
Specimens which cannot be assigned to established species

Taxonomy

Citation: Chiloguembelina Loeblich and Tappan, 1956
Rank: Genus
Type species: Guembelina midwayensis Cushman, 1940
Taxonomic discussion: The microperforate surface texture, apertural asymmetry, and twisted coiling axis are the primary features that unite Chiloguembelina species with woodringinids and other Paleocene descendants of Guembelitria cretacea. The biserial first whorl of Chiloguembelina species distinguishes them from Woodringina species.
Beckmann (1957) proposed that Guembelina trinitatensis Cushman and Renz and Guembelina wilcoxensis Cushman and Ponton descended from Chiloguembelina crinita (Glaessner). On this basis, Beckmann (1957) assigned trinitatensis and wilcoxensis to the genus Chiloguembelina. [Olsson et al. 1999]

Catalog entries: Chiloguembelina;

Type images:

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.

Description


Diagnostic characters: The original description is diagnostic of many Chiloguembelina species (i.e., Chiloguembelina midwayensis (Cushman, 1940), C. crinita (Glaessner, 1937b), and C. morsei (Kline, 1943)). The diagnostic characters of Chiloguembelina species include the microperforate surface texture, slight twisting of the coiling axis, and infolding of the apertural lip on one side. The apertural flap noted by Loeblich and Tappan (1956) and Reiss (1963) characterizes C. midwayensis and closely related taxa (C. morsei and C. crinita). This flap is located on the apertural side that is not infolded and results from extension of the apertural lip (and its trailing chamber wall) over the preceding chamber. The apertural infolding and opposing flap render the chiloguembelinid aperture distinctly asymmetric with respect to the plane of biserial symmetry. This apertural asymmetry and twisting of the coiling axis are much reduced in the late Paleocene taxa Chiloguembelina trinitatensis (Cushman and Renz, 1942) and Chiloguembelina wilcoxensis (Cushman and Ponton, 1932). Apertural asymmetry is variably expressed in C. wilcoxensis; although apertural asymmetry occurs in early ontogeny, the apertures of terminal chambers appear to be symmetric in some C. wilcoxensis specimens and asymmetric in others (Plate 70: Figures 11, 12, 16, 17). [Olsson et al. 1999]

Emended description: "Test biserial, may become staggered uniserial, sometimes twisted; wall calcareous, perforate; aperture a high arch, eccen- tric in position, extending from the base of the last chamber onto the apertural face. On the outside margin, a collar borders the aperture. Near the base of the inside margin, the collar and apertural edge are turned inward, producing a plate-like con- nection with the proximal margin of the collar of the previous aperture. Aperture may be obscured by a thickening of the wall including the rim of the aperture. The length of the test varies between 75 and 300 µm." [Smart & Thomas 2007]

Wall type: Bilamellar, generally microperforate, though low latitude forms may have larger pores; wall texture smooth, finely to moderately pustulose, or finely striate; [Eocene Atlas]

Test morphology: Test subtriangular in outline, biserial throughout or rarely with multiserial final chambers, initial chambers sometimes slightly twisting; chambers slightly to moderately inflated, increasing slowly to moderately in size; aperture a simple arched opening at base of the final chamber, symmetrically or asymmetrically centered on chamber face, with an inturned, narrow bordering rim on one margin and a broad collar or flange that is directed toward one of the flat sides of the test, lacking an infolded margin or internal plate. Multiple apertures rarely occur on specimens assigned to this genus.
[Eocene Atlas]

Biogeography and Palaeobiology


Phylogenetic relations: Descended from Woodringina by loss of the initial triserial coiling (Olsson and others, 1999).
[Eocene Atlas]

Similar species: Differs from Heterohelix Ehrenberg (1843) and Laeviheterohelix Nederbragt (1991) by the presence of an asymmetric infolding of the apertural collar; differs from Streptochilus Bronnimann and Resig (1971) by having a narrower and more equal thickness of the apertural collar, lacking an internal plate connecting successive foramina of all chambers, and by having a surface texture that is pustulose or striate rather than smooth to granular. Pore mounds are not present on any species of Chiloguembelina.
[Eocene Atlas]

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

Biostratigraphic distribution

Geological Range:
Notes: Lower Danian through middle Oligocene (Zones P -O4).
[Eocene Atlas]
Last occurrence (top): at top of Rupelian Stage (100% up, 28.1Ma, in Rupelian stage). Data source: Total of range of species in this database
First occurrence (base): at base of Danian Stage (0% up, 66Ma, in Danian stage). Data source: Total of range of species in this database

Plot of occurrence data:

Primary source for this page: Olsson et al. 1999 - Atlas of Paleocene Planktonic Foraminifera, p. 89

References:

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.

Brönnimann, P. & Resig, J., (1971). A Neogene globigerinacean biochronologic time-scale of the southwestern Pacific. Deep Sea Drilling Project, 7(2): 1235-1469.

Cushman, J.A., (1940). Midway foraminifera from Alabama. Contributions from the Cushman Laboratory for Foraminiferal Research, 16: 51-73.

Ehrenberg, C.G., (1843). Verbreitung und Einfluss des mikroscopischen Lebens in Sd- und Nord Amerika. Bericht k. preuss. Akad. Wiss. Berlin, 1841: 291-446.

Ehrenberg, C.G., (1843). Neue Beobachtungen ber den sichtlichen Einfluss der mikroskopischen Meeres-Organismen auf den Boden des Elbbettes bis oberhalb Hamburg. Bericht k. preuss. Akad. Wiss. Berlin: 161-167.

El-Naggar, Z.R., (1971). On the classification, evolution and stratigraphical distribution of the Globigerinacea. In: Farinacci, A. (Editor), Proceedings of the II Planktonic Conference, Roma 1970. Edizioni Tecnoscienza, Rome, pp. 421-476.

Loeblich, A.R., Jr. & Tappan, H., (1956). Chiloguembelina, a new Tertiary genus of the Heterohelicidae (Foraminifera). Journal of the Washington Academy of Sciences, 46: 340.

Nederbragt, A.J., (1991). Late Cretaceous biostratigraphy and development of Heterohelicidae (planktic foraminifera). Micropaleontology, 37: 329-372.

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.

Smart, C.W. & Thomas, E., (2007). Emendation of the genus Streptochilus Brönnimann and Resig 1971 (Foraminifera) and new species from the lower Miocene of the Atlantic and Indian Oceans. Micropaleontology, 53(1-2): 73-103, 3 figures, 13 plates, 1 table.


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

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