Catalog - Globigerinoides bispherica

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Globigerinoides bispherica

Citation: Globigerinoides bispherica Todd, in Todd et al. 1954

Type specimens: Plate 1, figures 1, 4; USNM-548876

Type age (chronostrat): upper Oligocene

Type locality: 1.6 miles northeast of the seaward tip of the southwest point of Saipan (loc. C-85, fig. 2).

Type repository: Washington; USNM

Test consists of two spheres of equal or nearly equal size, confluent in greater or less degree, one sphere consisting of the last-formed chamber, the other sphere consisting of the penultimate chamber strongly embracing all the previous ones, coiling dextral and sinistral. Sutures distinct and incised in individuals where the chambers are less embracing, indistinct in individuals where the chambers are more embracing. Wall calcareous, perforate, ornamented by a dense pattern of smalL delicate, round cancellations. Apertures two or more: in the case of individuals where the chambers are more embracing the apertures are irregular, narrow fissures appearing to result from the breaking apart of the test wall at the suture lines or suture junctions and usually bordered with irregular knobs of clear shell material: in the case of individuals where the chambers are less embracing the apertures are more distinct, low-arched openings into the final chamber, overhung by the rough, knobby edge of the chamber.

Length 0.55-0.65 mm, greater diameter 0.45-0.50 mm.

Globigerinoides conglobata Cushman and Stainforth (not Brady), 1945, Cushman Lab. Foram. Research Special Pub. 14, p. 68, pl. 13, fig. 6.
Globigerinoides cf. conglobata Cushman and Renz (in part) (not Brady), 1947, idem, Special Pub. 22, p. 41.
Globigerinoides conglobata Stainforth (not Brady), 1948, Jour. Paleontology, vol. 22. p. 121, pl. 26, fig. 4.

Remarks: This is the most abundant species in the upper Oligocene of Saipan. As described, it includes a rather wide range of shapes but is characterized by its bispherical form. Further studies of early Tertiary globigerinids are needed to determine the evolutionary relatives of this species.

The species has also been recorded under other names (see synonymy above) from the upper Oligocene of Trinidad and Ecuador. It is reported (R. M. Stainforth. letter of July 30, 1953, to Todd) to have had its acme during the short life-range of Globigerinatella insueta and to serve as a useful substitute marker for G. insueta in Venezuela where the latter is much less common than in Trinidad.

This species differs from Globigerinoides subquadrata Bronnimann, with which it occurs. in its circular, not compressed test, its less widely open apertures, and its finely cancellated wall. The individuals with strongly embracing chambers when poorly preserved may be confused with Orbulina suturalis Bronnimann and with Globigerinatella insueta Cushman and Stainforth but are distinguished by the faint trace of an equatorial suture line.

Name has often been corrected to Globigerinoides bisphericus Todd 1954 on the grounds that the genus is masculine

References:

Todd, R., Cloud, P. E., Low, D. & Schmidt, R. G. (1954). Probable occurrence of Oligocene in Saipan. American Journal of Science. 252: 673-682. gs

CATALOG OF ORIGINAL DESCRIPTIONS: Globigerinoides bispherica Todd, in Todd et al. 1954

Globigerinoides bispherica

References:

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