pforams@mikrotax - Globotruncanita stuartiformis

Citation: Globotruncanita stuartiformis (Dalbiez, 1955)

Basionym: Globotruncana stuarti stuartiformis

Synonyms:

Globotruncana bollii;
Globotruncana smithi
Globotruncana stuarti stuartiformis (used e.g. by El-Naggar 1966)
Kassabiana bangi Solakius & Salaj 1986 [our interpretation, BH 2021]

Original description: Test medium to large, periphery moderately to slightly lobate, acute transversally, single-keeled. Spiral side slightly convex, centrally more or less vaulted; chambers numerous, flat to slightly depressed, nearly triangular; 5 to 9 chambers in the last whorl; sutures nearly tangential to the preceding whorl, limbate. Umbilical side slightly convex at the beginning · of the last whorl, becoming strongly convex at the end of this whorl; chambers flat to slightly inflated; sutures even, limbate; periumbilical part of the chambers with a small keel. Umbilicus large and deep.

"Test medium-sized, almost planoconvex, coiled in a very low trochospire; dosal side very slightly convex to nearly flat, gently sloping towards the periphery; ventral side strongly protruding especially in the later part as the convexity of the ventral side increases gradually towards the last chamber; equatorial periphery nearly ovoid, moderatly lobate; axial periphery acute, with a single, well-developed, beaded keel; chambers on the dorsal side 15, arranged in 2.5 dextrally-coiled whorls; the initial chambers on the dorsal side slightly inflated, globigerine, and are followed by crescentic chambers towards the end of the second whorl; the last whorl is composed of 5 large chambers, the first 2 of which are nearly crescentic, while the last 3 are typically triangular; on the ventral side the chambers are 5, large, stuarti-form with the sutures more strongly curved forward, thus becoming nearly ovoid, strongly overlapping, distinctly outlined and strongly inflated, with the surface somewhat steeply sloping towards the periphery, especially in the last chambers; sutures on the dorsal side slightly curved in the early part, nearly straight and tangential to the preceding whorl in the last part, limbate, raised nad beasded, with the beading fading out gradually towards the last whorl; on the ventral side the sutures are strongly curved forward, limbate, raised and faintly beaded; umbilicus relatively small, roughly hexagonal in outline, moderately deep, surrounded by much thickened, strongly raised, faintly beaded ridges, and covered by complex tegilla of which remnants are still preserved; primary apertures interiomarginal, umbilical; tegilla with accessory apertures only poorly preserved; wall calcareous, perforate, except for the imperforate keel and tegilla; surface smooth. Dimensions of described specimen: max. diameter 0.51 mm, minimum diameter 0.39 mm; thichness 0.26 mm" [Naggar 1966]

Geological Range:
Last occurrence (top): within P. hariaensis zone (66.39-67.64Ma, top in Maastrichtian stage). Data source: [copied from Chronos database]
First occurrence (base): within D. asymetrica zone (83.65-85.60Ma, base in Santonian stage). Data source: [copied from Chronos database]

References:

Smith, C. C. & Pessagno, E. A. (1973). Planktonic foraminifera and stratigraphy of the Corsicana formation (Maestrichtian) North-central Texas. Cushman Foundation for Foraminiferal Research, Special Publication. 12: 1-67. gs O

Almogi-Labin, A., Reiss, Z & Caron, M. (1986). Senonian globotruncanidae from Israel. Eclogae Geologicae Helvetiae. 79(3): 849-895. gs O

Dalbiez, F. (1955). The genus Globotruncana in Tunisia. Micropaleontology. 1(2): 161-171. gs

El-Naggar, Z. R. (1966). Stratigraphy and planktonic foraminifera of the Upper Cretaceous-Lower Tertiary succession in the Esna-Idfu region, Nile Valley, Egypt, U. A. R. Bulletin of the British Museum (Natural History). supplement 2: 1-291. gs

Pessagno, E. A. (1967). Upper Cretaceous planktonic foraminifera from the western Gulf Coastal Plain. Palaeontographica Americana. 5: 245-445. gs O

Postuma, J. A. (1971). Manual of planktonic foraminifera. Elsevier for Shell Group, The Hague. 1-406. gs

Robaszynski, F., Caron, M., Gonzales Donoso, J. M., Wonders, A. A. H. & the European Working Group on Planktonic Foraminifera (1984). Atlas of Late Cretaceous globotruncanids. Revue de Micropaléontologie. 26(3-4): 145-305. gs

Solakius, N. & Salaj, J. (1986). A new Kassabiana species from the uppermost Maastrichtian of northeastern Tunisia. Revista Española de Micropaleontología. 18(1): 71-77. gs

test outline:	Subcircular	chamber arrangement:	Trochospiral	edge view:	Planoconvex	aperture:	Umbilical
sp chamber shape:	Subtriangular	coiling axis:	Moderate	periphery:	Single keel	aperture border:	Thin porticus
umb chbr shape:	Trapezoidal	umbilicus:	Wide	periph margin shape:	Subangular	accessory apertures:	Infralaminal
spiral sutures:	Raised beaded	umb depth:	Deep	wall texture:	Finely pustulose	shell porosity:	Finely Perforate: 1-2.5µm
umbilical or test sutures:	Raised beaded	final-whorl chambers:	5-7	N.B. These characters are used for advanced search. N/A - not applicable

Globotruncanita stuartiformis

References:

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