Globorotalia exilis


Classification: pf_cenozoic -> Globorotaliidae -> Globorotalia -> menardii lineage -> Globorotalia exilis
Sister taxa: G. pertenuis, G. exilis, G. multicamerata, G. miocenica, G. pseudomiocenica, G. limbata, G. menardii, G. praemenardii, G. archeomenardii,

Taxonomy

Citation: Globorotalia exilis Blow, 1969
Rank: species
Basionym: Globorotalia (Globorotalia) cultrata exilis Blow, 1969
Synonyms: Globorotalia (Menardella) exilis Blow, 1969 [e.g. Kennett & Srinivasan 1983]

Catalog entries: Globorotalia (Globorotalia) cultrata exilis

Type images:

Distinguishing features: Like G. limbata but with a more compressed, thinner, and delicate test.

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.
They are being edited as the site is developed and comments on them are especially welcome.

Description


Diagnostic characters: Lenticular, low trochospiral, prominent keel and densely perforate surface

Aperture: Interiomarginal umbilical-extraumbilical low-arched slit [Aze 2011, based on Kennett & Srinivasan 1983]


Wall type: Non-spinose; Smooth [Aze 2011]

Test morphology: Test large, thin, delicate, lenticular trochospire, 5 to 7 chambers in the final whorl, equatorial. periphery lobulate, axial periphery acute with thin keel; sutures on spiral side recurved , generally overlapped by succeeding chambers, limbate, merging into keel; umbilical side radial, depressed; surface smooth , finely perforate (PI. 28, Fig. 1); umbilicus narrow, deep; aperture a low-arched slit, interiomarginal, umbilical-extraumbilical. [Kennett & Srinivasan 1983]

Character matrix

test outline:Subcircularchamber arrangement:Trochospiraledge view:Compressedaperture:Umbilical-extraumbilical
sp chamber shape:Crescenticcoiling axis:Lowperiphery:Single keelaperture border:Thin flange
umb chbr shape:Subtriangularumbilicus:Narrowperiph margin shape:Subangularaccessory apertures:None
spiral sutures:Raisedumb depth:Shallowwall texture:Smoothshell porosity:Macroperforate: >2.5µm
umbilical or test sutures:Weakly depressedfinal-whorl chambers:5.0-7.0 N.B. These characters are used for advanced search. N/A - not applicable

Biogeography and Palaeobiology


Geographic distribution: Tropical; endemic to the Atlantic-Caribbean- Gulf of Mexico regions. [Kennett & Srinivasan 1983] Low latitudes [Aze et al. 2011, based on Kennett & Srinivasan (1983)]

[SCOR WG138]


Isotope paleobiology: Aze et al. 2011 ecogroup 3 - Open ocean thermocline. Based on light ∂13C and relatively heavy ∂18O. Sources cited by Aze et al. 2011 (appendix S3): this study

Phylogenetic relations: Gr. (Menardella) exilis is distinguished from Gr. (M.) limbata by having a more compressed, thinner, and delicate test. This species is closely related to Gr. (M.) pertenuis, which is larger and has a distinctly more lobate and compressed test. Globorotalia (M.) fimbriata (Brady) is morphologically very similar and may have priority.
Kaneps (1970) believed that Gr. (M.) exilis evolved from Gr. (M.) pertenuis, but this postulated evolution is not supported by stratigraphic data (Parker, 1973). Gr. (M.) exilis appears first in the Late Miocene as compared to the initial appearance of Gr. (M.) pertenuis during the Late Pliocene. [Kennett & Srinivasan 1983]

Most likely ancestor: Globorotalia limbata - at confidence level 3 (out of 5). Data source: Kennett & Srinivasan 1983, fig. 14; Stewart 2003 fig. 6.10; Aze et al. 2011, appendix 5.
Likely descendants: Globorotalia pertenuis;

Biostratigraphic distribution

Geological Range:
Last occurrence (top): in upper part of PL6 [Atl.] zone (57% up, 2.1Ma, in Gelasian stage). Data source: Wade et al. (2011), additional event; position within zone determined by linear interpolation from data in table 1 of Wade et al. (2011).
First occurrence (base): near top of PL1 [Atl.] zone (94% up, 4.5Ma, in Messinian stage). Data source: Wade et al. (2011), additional event; position within zone determined by linear interpolation from data in table 1 of Wade et al. (2011).

Plot of occurrence data:

Primary source for this page: Kennett & Srinivasan 1983, p.128

References:

Aze, T. et al. (2011). A phylogeny of Cenozoic macroperforate planktonic foraminifera from fossil data. Biological Reviews. 86: 900-927. gs

Blow, W. H. (1969). Late middle Eocene to Recent planktonic foraminiferal biostratigraphy. In, Bronnimann, P. & Renz, H. H. (eds) Proceedings of the First International Conference on Planktonic Microfossils, Geneva, 1967. E J Brill, Leiden 380-381. gs

Brady, H. B. (1884). Report on the Foraminifera dredged by H.M.S. Challenger, during the years 1873-1876. Rep. Sci. Results H.M.S. Challenger 1873-6. 9 (Zoology): 1-814. gs

Kaneps, A. G. (1970). Late Neogene biostratigraphy (planktonic foraminifera), biogeography, and depositional history,. In, p509 (ed.) . PhD thesis, Columbia University 1-509. gs

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

Norris, R. D. (1998). Planktonic foraminifer biostratigraphy: Eastern Equatorial Atlantic. Proceedings of the Ocean Drilling Program, Scientific Results. 159: 445-479. gs

Parker, F. L. (1973). Late Cenozoic biostratigraphy (Planktonic foraminfera) of Tropical Atlantic deep-sea sections. Revista Espanola de Micropaleontología. 5(2): 253-289. gs


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Globorotalia exilis compiled by the pforams@mikrotax project team viewed: 22-10-2019

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