Catalog - Globigerina alanwoodi

This page provides data from the catalog of type descriptions. The catalog is sorted alphabetically. Use the current identification link to go back to the main database.

Globigerina alanwoodi

Citation: Globigerina alanwoodi El-Naggar 1966

Type specimens: holotype (fig. 6a-c) P.45567; unfigured paratypes, P.45568

Type sample (& lithostrat): middle Owaina Chalk. Rare to very abundant.

Type age (chronostrat): Lower upper Paleocene, Globorotalia velascoensis Zone, Globorotalia pseudomenardii Subzone,

Type locality: Holotype (fig. 6a-c) and unfigured paratypes from approximately 133 meters above the base of the Gebel Owaina section (27°45'N 32°45.75'E), about 12 km. north of the Nile at El Mahamid, Esna-Idfu region, Upper Egypt.

Test large, robust, coiled in a low trochospire; dorsal side almost flat, slightly inflated, with the early chambers very weakly raised over the circumambient last whor l; ventral side strongly inflated and distinctly protruding; equatorial periphery circular, slightly lobate; axial periphery rounded; chambers on the dorsal side 17, arranged in 3 dextra lly coiled whorls; the initial chambers are compa ratively large, globular, slightly inflated and are followed by roughly ovoid, moderately inflated ones which are elongated in the direction of coiling and increase regularly in size; the last whorl is composed of 7 large chambers which are crescentic in the early part, roughly quadrangular later, strongly elongated in the direction of coiling and increase slowly and regularly in size, except for the last chamber which is slightly smaller than the penultimate; on the ventral side the chambers are 7, large, inflated and strongly protruding: sutures on the dorsal side slightly curved, depressed; on the ventral side they are straight, radial and strongly incised; umbilicus wide, deep and open, aperture interiomarginal, umbilical; wall calcareous, perforate; surface smooth, except around the umbilicus where it becomes delicately papillose.

Maximum diameter 0.47 mm.; minumum diameter 0.41 mm.; thickness 0.30 mm.

Remarks - Globigerina alanwoodi El-Naggar is closely related to G. mckannai White from which it is distinguished by its perfectly smooth surface, and distinct stratigraphical range. It probably evolved into G. mckannai in Upper Paleocene time by the development of the granular spinose surface. On the other hand, it possibly evolved from the smooth surfaced, multilocular, G. spiralis Bolli, by flattening the dorsal side, increasing the size of test and the number of chambers in the last whorl and by developing a much wider umbilicus. The stratigraphical ranges of these forms agree with this proposition, although no direct evidence was recorded.

References:

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

CATALOG OF ORIGINAL DESCRIPTIONS: Globigerina alanwoodi El-Naggar 1966

Globigerina alanwoodi

References:

Comments (0)

Add Comment