Chiloguembelina midwayensis


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

Taxonomy

Citation: Chiloguembelina midwayensis (Cushman 1940)
Rank: Species
Basionym: Guembelina midwayensis
Synonyms:
Taxonomic discussion: Chiloguembelina midwayensis strombiformis Beckman, 1957, was erected as a Paleocene subspecies of Chiloguembelina midwayensis (Cushman, 1940). The chambers of the C. midwayensis strombiformis holotype (Plate
13: Figures 12, 13) expand much more rapidly in depth (thickness) than do those of C. midwayensis sensu stricto; in late-stage chambers of C. midwayensis sensu stricto, chamber breadth consistently exceeds chamber depth. [Olsson et al. 1999]

Catalog entries: Chiloguembelina midwayensis strombiformis;
Guembelina midwayensis;

Type images:

Short diagnosis: As originally described, the test is small, compressed in thickness (depth), and rapidly tapering. Although early chambers are subspherical, successive chambers increase more rapidly in breadth than in height. Each late-stage chamber crosses the coiling axis and overlaps the immediately preceding chamber. In the holotype, this overlap is so pronounced that the maximum breadth of its final chamber is nearly equal to the maximum breadth of the test. Although much of the holotype's surface is covered with numerous small pustules, the last two chambers contain few pustules. Despite the plural usage of the original description, the aperture of each chamber exhibits only one distinct lateral flange (the chiloguembelinid flap of Loeblich and Tappan, 1956).

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: As originally described, the test is small, compressed in thickness (depth), and rapidly tapering. Although early chambers are subspherical, successive chambers increase more rapidly in breadth than in height. Each late-stage chamber crosses the coiling axis and overlaps the immediately preceding chamber. In the holotype, this overlap is so pronounced that the maximum breadth of its final chamber is nearly equal to the maximum breadth of the test. Although much of the holotype's surface is covered with numerous small pustules, the last two chambers contain few pustules. Despite the plural usage of the original description, the aperture of each chamber exhibits only one distinct lateral flange (the chiloguembelinid flap of Loeblich and Tappan, 1956). [Olsson et al. 1999]

Character matrix

test outline:Triangularcoiling axis:N/Achamber arrangement:Biserialumbilicus:N/A
edge view:Hourglassumbilical or test sutures:Strongly depressedspiral sutures:N/Ashell porosity:Finely Perforate: 1-2.5
wall texture:Spinoseaperture:Terminalaperture border:Thick flangeaccessory apertures:None
periphery:N/Aumb chamber shape:Inflatedsp chbr shape:N/Aperiph margin shape:Moderately rounded
umb depth:N/Adiameter mm:0.18-0.22width mm:0.10-0.12breadth mm:0.05
final-whorl chambers:2.0-2.0

Biogeography and Palaeobiology


Geographic distribution: Chiloguembelina midwayensis occurred at low and middle latitudes (Beckmann, 1957; Boersma, 1984b; D'Hondt and Keller, 1991; Liu and Olsson,
1992) (Figure 35). [Olsson et al. 1999]

Isotope paleobiology: The stable isotopic signature of C. midwayensis suggests that this species inhabited a deeperwater or cooler-season habitat than most co-occurring taxa (Boersma and Premoli Silva, 1983; D'Hondt and Zachos, 1993). [Olsson et al. 1999]

Phylogenetic relations: Chiloguembelina midwayensis evolved from C. morsei (Kline) (D'Hondt, 1991). [Olsson et al. 1999]

Biostratigraphic distribution

Geological Range:
Notes: Zone P a (D'Hondt, 1991) to Zone P5 (Beckman, 1957; Boersma, 1984b). [Olsson et al. 1999]
Last occurrence (top): within P5 zone (55.96-57.10Ma, top in Thanetian stage). Data source: Olsson et al. 1999
First occurrence (base): within Pa zone (65.72-66.00Ma, base in Danian 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. 90

References:

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.


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Chiloguembelina midwayensis compiled by the pforams@mikrotax project team viewed: 23-7-2017

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