Catalog - Globigerinoides fragilis

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Globigerinoides fragilis

Citation: Globigerinoides fragilis Borsetti & Cati 1972

Type locality: Holotype (pl. 79, fig. 1a-c, pl. 80, fig. 2a-c, tf. 1a-c) and figured paratypes (pl. 79, figs. 2a-c, 3a-c, 4c, pl. 80, figs. 1a, b, 3a, b) from a bottom trawl at a depth of 1140-921 m. made on cruise CT 1971 of the N/0 Bannock south of the Isola di Ventotene, from lat. 40° 3417'' N., long. 13°3 11211 E. to lat. 40° 37 1611 N., long. 13° 3514 1' E. (material designated as T 7 1-Leg l Station 7), in the west-central Tyrrhenian Sea; and other figured specimens (figs. Sa, 6c) from the section at Pasquasia-Capodarso, Sicily. Also occurs on the Italian mainland at Santerno, northeastern ltaly. The species is common where Sphaeroidinellopsis is common (Tyrrhenian Sea, Pasquasia-Capodarso (at the latter the specimens are always incomplete)), where the frequency of Sphaeroidine/lopsis goes down (Santerno section), Globigerinoides fragilis (there also found always as fragments) also declines in frequency.

Type age (chronostrat): Lower Pliocene

Type sample (& lithostrat): Globorotalia margaritae Zone; in an argillaceous grey-white marl. Very frequent in and basically limited to the Sphaeroidinellopsis Subzone; and also occurs rarely in the Globorotalia praehirsuta Subzone of the G. margaritae Zone.

Type specimens: pl. 79, figs. 1-6; pl. 80, figs. 1-3 ; p. 695, tf. 1a-c;

Type repository: Depository not given. [Probably deposited in the collections of the Laboratory of Marine Geology of the Consiglio Nazionale delle Ricerche, Bologna, Italy.]

Original Description

Translation from Italian using Google Translate original text below

Perforated calcareous test, consisting of 3.5-4 rounds of a trochoid spire not very high. The first turns of the coil are quite tight, while the last one tends to unfold so much that the last or the last two lodges are separate from those of the previous turn. Globose chambers, initially 4 per turn, in the last one there are 5-6; very thin wall, intensely perforated and with sparse spines but well developed especially in the initial portion. The sutures are radial, simple and depressed, the peripheral margin rounded and lobed. The main opening, in an extra-umbilical umbilical position, is always a broad, arched motto with a thin, clear lip; the dorsal openings, no more than one per loggia, are also wide, slightly arched and present only in the last 2-3 lodges.

Plasmostraco calcareo perforate, costituito da 3.5-4 giri di spira trocoide non molto elevata. I primi giri di spira sono abbastanza serrati, mentre l'ultimo tende a svolgersi tanto che l'ultima o le ultime due logge sono separate da quelle del giro precedente. Camere globose, inizialmente 4 per giro, nell'ultimo se ne contano 5-6; parete molto sottile, intensamente perforata e interessata da spine rade ma ben sviluppate specialmente nella porzione iniziale. Le suture sono radiali, semplici e depresse, il margine periferico arrotondato e lobato. L'apertura principale, in posizione ombelicale extra-ombelicale, e sempre motto ampia, arcuata e provvista di un sottile rna evidente labbro; le aperture dorsali, non piu di una per loggia, sono anch'esse ampie, leggermente arcuate e presenti solo nelle ultirne 2-3 logge.

Size: Diametro maggiore 0.56 mm.; diametro minore 0.45 mm.; altezza 0.37 mm.

Extra details from original publication

Translation from Italian using Google Translate original text below

Remarks. - None of the known species of gen. Globigerinoides and can be compared with G. fragilis, whose main characteristics are the accentuated thorny shell and above all the particular arrangement of the last or the last two chambers separated by that of the previous lap.

This last feature, together with the very thin thickness of the test wall, makes the specimens extremely fragile, so much so that great caution is required during the sediment washing process; the individuals of G. fragilis in fact generally present themselves without the last chambers or even in fragments. In this case, however, the recognition of the species is possible due to the particular appearance of the outer surface of the plasma layer.

Osservazioni. - Nessuna delle specie note del gen. Globigerinoides e raffrontabile con G. fragilis, le cui caratteristiche principali sono l'accentuata spinosita del guscio e soprattutto la particolare disposizione dell'ultima o delle ultime due logge separate da quellc del giro precedente.

Quest'ultima particolarita, unitamente allo spessore molto esile della parete del plasmostraco, rende estremamente fragili gli esemplari, tanto che occorre una grande cautela durante il processo di lavaggio del sedimento; gli individui di G. fragilis infatti si presentano generalmente privi delle ultime logge o atddirittura solo in frammenti. Anche in questo caso pero il riconoscirnento della specie e possibile per il particolare aspetto della superficie estema del plasmostraco.

References:

Borsetti, A. M. & Cati, F. (1972). Globigerinoides fragilis nuova specie del Pliocene inferiore. Giornale di Geologia. 38: 689-702. gs V O

CATALOG OF ORIGINAL DESCRIPTIONS: Globigerinoides fragilis Borsetti & Cati 1972

Globigerinoides fragilis

References:

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