Catalog - Globigerina nilotica

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Globigerina nilotica

Citation: Globigerina nilotica Viotti & Mansour 1969

Type specimens: pl. 6, figs.1-8,; p. 443, tf. 4; holotype (fig. la-c), no. A-134-2668; and paratypes, no. A-134-2669.

Type sample (& lithostrat): None reported

Type age (chronostrat): Middle Miocene.

Type locality: A depth of 2205 meters in Abu Madi Well no. I, at lat. 31°26'17.396" N., long. 31°21'41.726" E., northern Nile Delta, Egypt.

Type repository: San Donato Milanese; AGIP Mineraria (Azienda Generale Italiana Petroli), San Donato Milanese, Italy;

"Diagnosis. - Test rhomboidal shaped, trochospiral. Dorsal side convex, ventral side slightly concave, axial periphery rounded. Wall calcareous and very finely perforate. About 8 chambers, 4 in the last whorl. Chambers more or less spherical, increasing moderately in size. The last chamber is generally smaller than the penultimate. Sutures dorsally and ventrally distinct, straight and radially arranged. Aperture umbilical, large and typically quadrangular with a distinct lip. According to statistical measurements made on 60 paratypes (D and d, tf. 4), the typical specimens representing our new species are those with D = d or nearly equal (see table and tf. 5). The aperture of the new species (large, quadrangular with a distinct lip) is the most significant feature characterizing it.

Annotations. - Some paratypes of the new species show transition to triangular shape, but the form and the position of the aperture are the same as in the holotype.
"Comparison. - Globigerina nilotica Viotti and Mansour has the general shape of the following Globigerina species: Globigerina microstoma Cita, Premoli-Silva and Rossi, 1965; G. nepenthes Todd, 1957; G. falconensis Blow, 1959; G. parva Bolli, 1957; G. officinalis Subbotina, 1953; G. eamesi Blow, 1959; G. druryi Akers, 1955; G. tetracamerata Bolli and Bermudez, 1965.
"The main features which would allow to group all these species together are: a- the general shape of the test; b - the position of the aperture centralized on the umbilicus; c- the 4-chamber arrangement of the last whorl.
"G. microstoma Cita, Premoli-Silva and Rossi differs from the new species in having a semicircular aperture, less spherical chambers and a low trochospiral test. G. nepenthes Todd differs from the new species in having an elongated and occasionally narrow test, and a rounded somewhat twisted aperture. G. falconensis Blow differs from the new species in having an elongated and a slitlike aperture and also an elongated test. G. parva Bolli differs from the new species in being smaller (largest diameter of holotype 0.25 mm.) and in having a quite different aperture. G. officinalis Subbotina differs from the new species in having a subrectangular and shallower umbilicus. G. eamesi Blow differs from the new species in having a very small umbilicus and a very small arcuate aperture as well. G. druryi Akers differs from the new species through the coarser perforation of the test, the smaller aperture and the elongated test. G. tetracamerata Bolli and Bermudez differs from the new species in having an elongated test and in being smaller in size (largest diameter of holotype = 0.23 mm.). The aperture is smaller and lacks a distinct lip.
"The form figured by Perconig (1968, Giom. Geol., ser. 2, vol. 35 (1967), fasc. 3, tf. 4) as G. diplostoma Reuss is -in our opinion - a form very much related to our species if not the same. Reuss characterized his G. diplostoma as follows 'Die zwei letzten Kammern tragen jede eine grosse Miindung, welche auf der Oberseite im Nabel hart an einander liegen und oft zu einer zusammenfliessen. Doch sind sie, wenn die Kammem der letzten Windung nicht in einer Ebene liegen, stets getrennt' (Reuss, 1850, K. Akad. Wiss., Math.-Nat. Cl., Denkschr., Bd. l, p. 373)."

References:

Viotti, C. & Mansour, A. (1969). Tertiary planktonic foraminiferal zonation from the Nile Delta, U.A.R., Part II. Globigerina nilotica, a new species of foraminifera from the Miocene of the Nile Delta. In, Said, R., Beckmann, J. P., Ghorab, M. A., El Ansary, S., Viotti, C. & Kerdany, M. T. (eds) Proceedings of the Third African Micropaleonotligical Colloquium, Cairo March 1968. National Information and Documentation Centre, Cairo 442-447. gs

CATALOG OF ORIGINAL DESCRIPTIONS: Globigerina nilotica Viotti & Mansour 1969

Globigerina nilotica

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