Catalog - Globorotalia bollii

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Globorotalia bollii

Citation: Globorotalia bollii El Naggar 1966

Type specimens: holotype (fig. 5a-d) P.45599: and figured paratype (fig. 6a-d). P.45600.

Type sample (& lithostrat): Libya Group, Thebes Calcareous Shale. Common to rare.

Type age (chronostrat): Lower Eocene, Globorotalia wilcoxensis Zone

Type locality: Holotype (fig. Sa-d) and figured paratype (fig. 6a-d) from approximately 240.5 meters above the base of the Gebel Owaina section (27°45'N 32°45.7S'E), about 12 km. north of the Nile at El Mahamid, Esna-ldfu region, Upper Egypt.

"Diagnosis.- A Globorotalia with medium-sized test; perfectly flat dorsal side and protruding ventral one; distinctly well-developed, very broad, heavily beaded keel; narrow umbilicus and thick, curved, raised, heavily beaded dorsal sutures. "Description.- Test medium sized, plano-convex, coiled in a very low trochospire; dorsal side flat; ventral side strongly protruding; equatrorial periphery roughly quadrate, distinctly lobate with a well-developed, broad, heavily beaded marginal keel; axial periphery acute; chambers on the dorsal side about 10, arranged in 2 dextrally coiled whorls; the initial chambers are small, globular, compressed, almost masked by the surface rugosity, and are folowed by typically crescentic chambers wich increase gradually in size; the last whorl is composed of 4½, large, crescentic chambers which increase rapidly in size; on the ventral side the chambers are 4½ large, angular, conical, and strongly protruding, with their distal ends meeting closely around the small umbilicus; sutures on the dorsal side are thickened, raised, curved, and heavily beaded; on the ventral side the sutures are radial and strongly depressed; umbilicus small, deep and open; aperture interiomarginal, extraumbilical-umbilical; wall calcareous, perforate; surface delicately papillose on the dorsal side, more heavily so on the ventral.

Maximum diameter 0.46 mm.; minimum diameter 0.35 mm.; thickness 0.21 mm.

Remarks. Bolli (1957) described as Globorotalia rex Martin from the upper Lizard Springs formation of Trinidad, a form which differs from the holotype of Martin in its perfectly nat dor al side: extremely well-developed, much wider. heavily beaded marginal keel: thick. raised, beaded dorsal sutures and more tightly coiled chambers. Bolli stated that this form churacterizes the G. rex Zone at the base of the Eocene.
Globorotalia rex Martin is closely related to G. aequa Cushman and Renz, and may be a junior synonym of G. simulatilis (Schwager) [Discorbina simulatilis, 1882 ] although very little is known about Schwager's species. On the other hand, the form figured by Bolli (1957) appears to be more closely related to the G. velascoensis group, especially to G. velascoensis parva Rey. It differs from the latter, only in being smaller, having a rougher surface, a much smaller umbilicus, a less protruding ventral side and a weaker, less ornamented umbilical shoulder.
Careful examination of G. rex as described and figured by Martin (1943 p. 117-8, pl. 8, fig. 2a-c) from the Lodo formation of California, and by Mallory (1959, p. 257) from the same formation, showed that the form described by Bolli (1957) as G. rex Martin is different and should be considered separately.
A form with a much rougher surface than the holotype, sub-circular test, and more chambers in the last whorl (fig. 6a-d), may well be a transitional stage between G. velascoensis velascoensis and the present species. This substantiates the hypothesis that G. bollii evolved from G. velascoensis velascoensis in late Paleocene or early Eocene time, as suggested by their morphological features and stratigraphical ranges. Subbotina (1953 pp. 212-2 13, pl.18, fig. la-c) figured as G. marginodentata Subbotina, a form with a flat dorsal side, which may belong to G. bollii. Loeblich and Tappan (1957) described as G. rex Martin a form which appears to be different from the holotype of Martin (1943), the hypotype of Mallory (19S9) and the present form.

References:

Bolli, H. M. (1957d). The genera Globigerina and Globorotalia in the Paleocene-Lower Eocene Lizard Springs Formation of Trinidad. In, Loeblich, A. R. , Jr., Tappan, H., Beckmann, J. P., Bolli, H. M., Montanaro Gallitelli, E. & Troelsen, J. C. (eds) Studies in Foraminifera. U.S. National Museum Bulletin . 215: 61-82. 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

Mallory, V. S. (1959). Lower Tertiary biostratigraphy of the California Coast Ranges. American Association of Petroleum Geologists, Tulsa, Oklahoma. 1-416. gs

Martin, L. T. (1943). Eocene foraminifera from the type Lodo Formation, Fresno County, California. Stanford University Publications, Geological Sciences. 3(3): 1-35. gs

Subbotina, N. N. (1953). Foraminiferes fossiles d'URSS Globigerinidae, Globorotaliidae, Hantkeninidae. Bureau de Recherches Geologiques et Minieres. 2239: 1-144. gs

CATALOG OF ORIGINAL DESCRIPTIONS: Globorotalia bollii El Naggar 1966

Globorotalia bollii

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