Catalog - Rugoglobigerina (Rugoglobigerina) bronnimanni

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Rugoglobigerina (Rugoglobigerina) bronnimanni

Citation: Rugoglobigerina (Rugoglobigerina) bronnimanni El Naggar 1971

Type specimens: Pl. 12, figs. 1-9; pl. 13, figs. 1-2e; pl. 14, figs. 14-16

Type sample (& lithostrat): Esna Group, Sharawna Shale Formation

Type age (chronostrat): Upper Cretaceous. Maastrichtian.

Type locality: Holotype (pl. 12, fig. 4 ) and two figured paraty pes (pl. 13. figs. 1, 2) from Gebel Owaina; and all other figured paratypes from Wadi El-Sharawna, on the western slopes of Gebel Owaina; south of Esna on the right bank of the Nile, Esna-Idfu region of the Nile Valley, Upper Egypt.

Diagnosis - A Rugoglobigerina (Rugoglobigerina) characterized by its large, very low trocho- piral test ; ovoid, lobate equatorial periphery, and subglobular, compressed axial one; almost fiat dorsal side and gently protruding ventral chambers; 5-6 constantly increasing chambers in the outer whorl, a large semicircular last chamber which is elongated in the direction of coiling; a medium-sized umbilicus and well developed meridional rugosities.

Description - Test large, coiled in a very low trochospire; dorsal side almost flat, with a slightly depressed early part; ventral side moderately inflated; equatorial periphery nearly ovoid, highly lobate; axial periphery rounded in the early part, subrounded later; chambers on the dorsal side about 15 arranged in 3 dextrally coiled whorls; the initial chambers are very small, globigerine and almost masked by surface rugosity; they increase slowly and regularly until the beginning of the last whorl, where the chambers start to increase rapidly and regularly in size with the result that the ultimate chamber becomes much larger than the penultimate and more elongated in the direction of coiling; the outer whorl is composed of 5.5 large, rapidly increasing chambers which are globigerine, inflated in the early part, becoming gently compressed later, with the penultimate chamber somewhat overlapping the ultimate one; chambers on the ventral side 5.5, globigerine moderately inflated and increase regularly in size; sutures on both sides slightly curved, almost radial, depressed in the early part, curved in the later part; umbilicus moderately sized, shallow, covered by tegilla which are only partly depressed; primary aperture interiomarginal umbilical, covered by tegilla, surface rough, covered by large pustules that nearly coalesce to produce more or less meridionally arranged costellae, but these are reduced on the last chamber; wall calcareous, perforate, hyaline, except for the relatively imperforate tegilla and surface rugosity.

Holotype: Maximum diameter 0.54 mm., minimum diameter 0.36 mm.; thickness of test 0.125 mm.; thickness of last chamber 0.150 mm

The species is named in honour of Professor PAUL BRONNIMANN of the Institute of Paleontology, University of Geneva

Remarks. - Rugoglobigerina (R.) bronnimanni El-Naggar shows a certain degree of similarity to R. (R.) scotti Bronnimann; although it is much larger in size and lacks the compressed, keeled later chamber or chambers and the angular periphery ascribed by Bronnimann (1952, p. 57) to his species. The writer was inclined to include this form in R. (R.) scotti, despite these morphologic dissimilarities, however due to the scarcity of typical forms of that species in the studied material, contrasted with the abundance of the present form, it was thought advisable to treat them separately. It is distinguished from R. (R.) badryi El-Naggar by its much larger test, more regularly increasing, and less inflated chambers in the outer whorl, a less depressed central spire, a smaller umbilicus and a rougher surface.

Stratigraphical range - The species is abundant in the Middle and Late Maastrichtian Globotruncana gansseri and Globotruncana esnehensis Zones of the studied sections, and dies out completely before the incoming of the Cainozoic.

References:

Brönnimann, P. (1952c). Globigerinidae from the Upper Cretaceous (Cenomanian-Maestrichtian) of Trinidad, B. W. I. Bulletins of American Paleontology. 34(140): 1-70. gs

El-Naggar, Z. R. (1971b). The genus Rugoglobigerina in the Maastrichtian Sharawna Shale of Egypt. In, Farinacci, A. (ed.) Proceedings of the Second Planktonic Conference, Roma 1970. Edizioni Tecnoscienza 477-537. gs

CATALOG OF ORIGINAL DESCRIPTIONS: Rugoglobigerina (Rugoglobigerina) bronnimanni El Naggar 1971

Rugoglobigerina (Rugoglobigerina) bronnimanni

References:

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