pforams@mikrotax - Rugotruncana circumnodifer

Citation: Rugotruncana circumnodifer (Finlay, 1940)

Basionym: Globigerina circumnodifer

Synonyms: Globotruncana (Rugoglobigerina) ornata subornata;
Globotruncana subpennyi = Rugotruncana subpennyi
Rugotruncana ellisi;
Rugotruncana tilevi;
Globotruncana rugosa subrugosa

Original description: "Large, loosely coiled, 4 chambers per coil, about 2 coils visible dorsally, ventrally nearly involute; spire flatly depressed, second coil more descending, chambers sub-globular, smooth, shining above and below but with faint peripheral sulcus margined by low nodules increasing in extent posteriorly to cover most of early chambers; umbilicus widely open, about one-third of shell diameter, aperture opening laterally into it, apertures of all ventral chambers probably visible if matrix absent. Size, 0.47 mm. Evidently a close relative of the abundant Navarro Globigerina rugosa Plummer, which has 5 chambers per coil and more ornament of a different character. It is a moot point whether these are not Globotruncana, as they differ only in the absence of keels and feebler sculpture"

Emended description: From Georgescu and Huber, 2007 (Jour. Foram. Res.): "Test low to medium high trochospiral. The test consists of 12 to 14 chambers, which increase slowly to moderately in size as added; 4.5 to 6 chambers in the final whorl. Sutures are distinct, depressed, straight, and radial on both spiral and umbilical sides. Umbilicus is wide, its diameter representing approximately 30% to 40% of the maximum test diameter. Main aperture is umbilical in position, and bordered by a tegillum; successive tegilla can completely cover the umbilical area. Periphery is broadly rounded with two more or less developed, quasi-equal keels bordering an imperforate band, which is better developed on the earlier chambers of the final whorl. The two keels can be situated at the equatorial periphery or be slightly offset towards the spiral side. The imperforate peripheral band is pustulose on the earlier chambers; pustules can fuse in some specimens, resulting in the development of an intercarinal ridge, occasionally giving the appearance of a third keel. Ornamentation is highly variable, ranging from meridional on both sides of the test to asymmetrical, meridional on the umbilical side and parallel to the periphery on the spiral side. Ornamentation patterns can be lost on the earlier chambers of the test due to the addition of calcite material during ontogenetic development. The last formed chambers are less ornamented than the previous ones. The last formed chambers often show the best development of the asymmetrical ornamentation because they are not obscured by ontogenetic calcite." [copied from Chronos database]

Geological Range:
Last occurrence (top): within A. mayaroensis zone (67.30-69.18Ma, top in Maastrichtian stage). Data source: [copied from Chronos database]
First occurrence (base): within G. gansseri zone (71.75-72.97Ma, base in Campanian stage). Data source: [copied from Chronos database]

References:

Finlay, H. J. (1940). New Zealand foraminifera: Key species in stratigraphy - no. 4. Transactions of the Royal Society of New Zealand. 69(4): 448-472. gs

test outline:	Lobate	chamber arrangement:	Trochospiral	edge view:	Spiroconvex	aperture:	Umbilical
sp chamber shape:	Inflated	coiling axis:	Low	periphery:	Double keel	aperture border:	Tegilla
umb chbr shape:	Inflated	umbilicus:	Narrow	periph margin shape:	Moderately rounded	accessory apertures:	Infralaminal
spiral sutures:	Moderately depressed	umb depth:	Deep	wall texture:	Meridional costellae	shell porosity:	-
umbilical or test sutures:	Moderately depressed	final-whorl chambers:	4.5-5.5	N.B. These characters are used for advanced search. N/A - not applicable

Rugotruncana circumnodifer

References:

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