Catalog - Globigerina triloculinoides parva

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 triloculinoides parva

Citation: Globigerina triloculinoides subsp. parva El-Naggar 1966

Type specimens: holotype (fig. 4a-c) P.45587; unfigured paratypes, P.45588.

Type sample (& lithostrat): upper Owaina Shale. Rare in the upper Lower Paleocene (Danian), Globorotalia compressa/ Globigerinoides daubjergensis Zone, common throughout the Middle and Upper Paleocene, reaching its acme in the upper part of the Globorotalia velascoensis Zone. and dying out at the top of that zone.

Type age (chronostrat): Upper Paleocene, Globorotalia velascoensis Zone

Type locality: Holotype (fig. 4a-c) and unfigured paratypes from approximately 66 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 Mahamicl, Esna-ldfu region, Upper Egypt.

Diagnosis. - A Globigerina triloculinoides with much smaller, more tightly coiled, compressed test, chambers increasing less rapidly in size and more strongly elonga ted in direction of coiling.

Description.- Test small, coiled in a low trochospire; dorsal side weakly inflated with the early chambers slightly ra ised above the level of the last whorl; ventral side moderately inflated; equatorial periphery roughly ovoid, modera tely lobate; ax ial periphery subrounded; chambers on the dorsal side are not all clear, but appear to be 12 in number, arranged in 2½ dextrally coiled whorls; initial chambers are very small, closely coiled, indistinct and almost masked by the surface pitting; the last whorl is composed of 3½, roughly crescentic, narrow ch ambers which increase modera tely in size and are strongly elongated in the direction of coiling : on the ventral side the chambers are 3½, relatively large, roughly globular, moderately inflated but slightly compressed, especially the last one, and increase so rapidly in size that the last chamber constitutes about half of the test; sutures on the dorsal side, curved depressed in the early part, almost straight, st rongly incised later; on the ventral side they are straight. radial and strongly depressed; umbilicus very small, n arrow and open, with the last chamber sligh tly pushed over it; aperture interiomarginal, umbilical, in the form of a long, narrow slit, with a narrow delicate flap: wall calcareous, perforate; surface densely pitted.

Maximum diameter 0.3 1 mm.; minimum diameter 0.27 mm.; thickness 0.25 mm. "

Remarks. Globigerina triloculinoides parva is distinguished from G. triloculinoides Plummer, from which it is believed to have evolved, by its much smaller, less lobulate, tightly coiled, slightly compressed test: its roughly cresce tic, narrow chambers which are elongated in the direction of coiling, and which increase less rapidly in size; by its weakly raised early whorls and slightly compressed last chamber.
Bronnimann (1952, p.15, pl.2, figs.4-6) described as G. hornibrooki n.sp., a form which appears to be closely related to the present subspecies. However, Loeblich and Tappan (1957) considered G. hornibrooki to be a junior synonym of G. triloculinoides Plummer, while Bolli (1957, pp. 70-71. pl.15, figs.12-14) considered it to be a junior synonym of G. triangularis White. Indeed G. triangularis White appears to be closely related to G. triloculinoides parva although it is much larger, but White's description is incomplete and the form figured by Bolli who had examined White's holotype, is most probably G. triloculinoides Plummer.
Khalilov (1956, pp. 236-7, pl.1, fig.4a-c) described as G. triloculinoides var. nanus, a form which only differs from typical G. triloculinoides Plummer in its smaller size and slightly deep ened sept al sutures. Khalilov's form should probably be included within G. triloculinoides Plummer, and is believed to be transitional to G. triloculinoides parva. It is distinguished from the present subspecies by its triglobular test and strongly inflated last chamber, characteristic of typical G. triloculinoides Plummer.""

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

Brönnimann, P. (1952d). Trinidad Paleocene and lower Eocene Globigerinidae. Bulletins of American Paleontology. 34(143): 1-34. 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

Khalilov, D. M. (1956). 0 pelagicheskoy faune foraminifer Paleogenovykh otlozheniy Azerbaydzhana [Pelagic Foraminifera of the Paleogene Deposits of the Azerbaizhan SSR]. Trudy Instituta Geologii, Akademiya Nauk Azerbaidzhanskoi SSR. 17: 234-255. gs

CATALOG OF ORIGINAL DESCRIPTIONS: Globigerina triloculinoides subsp. parva El-Naggar 1966

Globigerina triloculinoides parva

References:

Add Comment

Comments