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Conoglobigerina


Classification: pf_mesozoic -> Conoglobigerinidae -> Conoglobigerina
Sister taxa: Conoglobigerina, Globuligerina,
Daughter taxa: (blue => in age window 0-300Ma)

Low to medium high conical test with a compact spire and 3.5 to 4 chambers in the last whorl. H/D ratio 0.5 to 1, and rarely over 1. No preferred coiling direction observed. The chambers of the last whorl are large and have deeply incised sutures. Last whorl strongly embraces previous (? 2) whorls such that the earlier part of the test may hardly be visible. Apex generally blunt, rarely pointed. Umbilical area depressed. Aperture generally a more or less symmetrical arch with lip, rarely comma-shaped. Specimens may have a small bulla over the umbilicus with one or two, low-arch apertures; it may resemble the bulla structure of Cenozoic Catapsydrax taxa. Wall microperforate, strongly pustulose; pustules form low and broken ridges that create an imperfectly reticulate pattern over the surface of the chambers.



Low to medium high trochospiral, with an H/D ratio of 0.5 to 1. The trochospire axis may be slightly curved, such that the chambers of the final whorl sit oblique of the chambers of the previous whorl. No preferred coiling direction observed. Last whorl flaring out and much larger than previous (2) whorls. Spherical-circular chambers (nicely ball shaped), four in the last whorl; chambers in the last whorl not much increasing in size. Umbilicus generally open and wide, rarely narrow. Sutures depressed, mostly straight. Aperture variable in shape, low to medium high arch, umbilical to slightly extraumbilical; a looped aperture was rarely observed also. The aperture often has a thickened rim around it. A bulla is observed in some specimens. Wall pustulose and reticulate to strongly reticulate
Specimens which cannot be assigned to established species

Taxonomy

Citation: Conoglobigerina Morozova 1961
Rank: Genus
Basionym: Globigerina (Conoglobigerina) dagestanica
Type species: Globigerina (Conoglobigerina) dagestanica Morozova, in Morozova and Moskalenko, 1961;
Taxonomic discussion: The taxonomic concpets of this genus has varied. Morozova and Moskalenko (1961) used it for species with test diameter < test height. Simmons et al. (1997) used it for forms with an intraumbilical, interiomarginal and low arch aperture. Gradstein et al. (2017) used it for froms with an irregularly reticulate wall surface pattern. This has resulted in the species assigned to the genus changing. See Gradstein et al. (2017) for full discussion.

Type images:

Original description: Conoglobigerina Morozova in Morozova and Moskalenko, 1961:

Entries in the Catalog of original descriptions: Conoglobigerina;

Distinguishing features: Chambers of the last whorl strongly embrace previous whorls; irregularly reticulate wall surface pattern


Test morphology:

Test trochospiral, low to medium high spired (H/D ratio 0.5–1, rarely over 1); final whorl may be compact or more open in shape. Chamber shape globular, rounded, rarely slightly irregular with 3.5–4 chambers in last whorl. Chambers of the last whorl strongly embrace previous whorls. Apertural shape variable, low arch or slit; mostly umbilical, but may be slightly extraumbilical in position. Wall microperforate, with small or larger, blunt pustules; pustules fuse to form ridges that are organized in broken cells that form an imperfect reticulate pattern. [Gradstein et al 2017]

Most likely ancestor: Globuligerina - at confidence level 2 (out of 5). Data source: Gradstein et al. (2017) p. 263.

Geological Range:
Last occurrence (top): within Valanginian Stage (133.88-139.39Ma, top in Valanginian stage). Data source: Total of range of species in this database
First occurrence (base): within Oxfordian Stage (157.25-163.47Ma, base in Oxfordian stage). Data source: Total of range of species in this database

Plot of occurrence data:

Dec 2017 - Plotting of Neptune data has been re-enabled on the Mesozoic pages following revision of the age-models in Neptune. The data is, however, still very sparse for the Early Cretaceous

Character matrix

test outline:Lobatechamber arrangement:Trochospiraledge view:Spiroconvexaperture:Umbilical
umb chamber shape:Globularcoiling axis:Low-moderateperiphery:N/Aaperture border:
sp chbr shape:Globularumbilicus:periph margin shape:Broadly roundedaccessory apertures:None
umbilical or test sutures:Moderately depressedumb depth:wall texture:Finely pustuloseshell porosity:Microperforate: <1µm
spiral sutures:Moderately depressedfinal-whorl chambers:0.0-0.0

References:

Gradstein, F.M.; Gale, A.S.; Kopaevich, L.; Waskowska, A.; Grigelis, A. & Glinskikh, L., (2017). The planktonic foraminifera of the Jurassic. Part I: material and taxonomy. Swiss Journal of Palaeontology, 136(2): 187-257.

Loeblich, A.R. & Tappan, H., (1988). Foraminiferal Genera and Their Classification (Volume I-II)Van Nostrand Reinhold Co., New York, 1059 pp.

Morozova, V.G. & Moskalenko, T.A., (1961). Планктонные фораминиферы пограничных отложений байосского и батского ярусов Центрального Дагестана (Северо-Восточный Кавказ) [Foraminiferes planctoniques des depots limitrophes du Bajocien et du Bathonien du Daghestan central (Nord-Est du Caucase)]. Voprosy Mikropaleontol., U.S.S.R., 5: 3-30.

Simmons, M.D.; Boudagher-Fadel, M.K.; Banner, F.T. & Whittaker, J.E., (1997). The Jurassic Favusellacea, the earliest Globigerina. In: Boudagher-Fadel, M.K., Banner, F.T. and Whittaker, J.E. (Editors), The Early Evolutionary History of Planktonic Foraminifera. British Micropaleontological Society Publication Series. Chapman & Hall, Lonodon.


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Conoglobigerina compiled by the pforams@mikrotax project team viewed: 12-11-2018

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