Catalog - Globigerina utilisindex

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Globigerina utilisindex

Citation: Globigerina utilisindex Jenkins & Orr 1973

Type sample (& lithostrat): Site 77B-51CC;

Type age (chronostrat): Early Oligocene Pseudohastigerina barbadoensis zone.

Type locality: Eastern equatorial Pacific at latitude 0.5N; longitude 133.2W.

Type repository: Washington; USNM

"Description of holotype.- Test free, low trochospiral, dextrally coiled, equatorial periphery trilobate, axial periphery rounded. Wall calcareous, perforate, a relatively coarse reticulate hexagonal pattern, with thickened inter-pore areas on the earliest part of the spiral side obscuring the chamber outline with a thickened area also present on the umbilical side just outside the aperture. Chambers spherical in outline with last chamber comprising slightly less than half the test. Sutures on both spiral and umbilical sides radial to slightly curved and slightly depressed. Umbilicus moderately shallow, open. Aperture a very low slit, interiomarginal, umbilical-extraumbilical.

Synonyms:

Globigerina sp. A,. Beckmann in, Tracey et al., 1971, p. 719, pl. 1, figs. 1-4.
Globigerina linaperta Finlay n. subsp. Jenkins and Orr, in Hays et al.,1972, p, 1089, pl. 10, figs. 6, 7, 8.

Recorded stratigraphic range: Beckmann (in Tracey et a/., 1971) recorded the stratigraphic range of Globigerina utilisindex S.S. (as Globigerina sp. A) in the Oligocene as Pseudohastigerina micra/Cassigerinella chipolensis zone to Globorotalia opima opima zone at the following sites of the Deep Sea Drilling Project Leg VIII in the eastern equatorial Pacific: Site 69: latitude 6°00.00'N., longitude 152"51,93'W.; Site 70: latitude 6'20.08'N., longitude 140'21.72'W.; Site 72: latitude 00"26.49'N., longitude 138'52.02'W.
Jenkins and Orr (in Hays et al., 1972) recorded the range of Globigerina utilisindex at site 77B. upper Eocene to lower Oligocene in the Globorotalia insolita zone to early Pseudohastigerina barbadoensis zone.
Coiling: In a count of 100 specimens of Globigerina utilisindex from the type sample, the ratio of dextral to sinistral is 52:48. Remarks: It is considered that Globigerina utilisindex belongs to the genus Globigerina and not Subbotina. At first when it was examined by optical microscopes, it was thought that Globigerina utilisindex was related to the middle-late Eocene Subbotina linaperta (Finlay) and it was referred to as “Globigerina linaperta Finlay n. subsp.” by Jenkins and Orr (in Hays et al.. 1972). Scanning-electron photomicrographs reveal very little similarity, in either wall ornamentation or apertural characters, between thc two taxa. The wall ornamentation in Globigerina is much less coarse than in the recorded species of Subbotina. and this is illustrated by topotypes of Subbotina linaperta (pl. 3, figs. 6, 7). Also Globigerina utilisindex lacks the distinct lip which is usually present in Subbotina species (Jenkins, 1971). Steineck (1971) recently has described Subbotina as including “globigerinid and triloculine species with an umbilical aperture bordered by a distinct lip. The wall texture is often referred to as “cancellate” and reflects deep, funnel-shaped pores surrounded by raised rims.”

References:

Jenkins, D. G. & Orr, W. N. (1973). Globigerina utilisindex n. sp. from the upper Eocene-Oligocene of the eastern equatorial Pacific. Journal of Foraminiferal Research. 3(3): 133-136. gs

Wade, B. S., Olsson, R. K., Pearson, P. N., Edgar, K. M. & Premoli Silva, I. (2018b). Taxonomy, biostratigraphy, and phylogeny of Oligocene Subbotina. In, Wade, B. S., Olsson, R. K., Pearson, P. N., Huber, B. T. & Berggren, W. A. (eds) Atlas of Oligocene Planktonic Foraminifera. Cushman Foundation for Foraminiferal Research, Special Publication . 46(Chap 10): 307-330. gs

CATALOG OF ORIGINAL DESCRIPTIONS: Globigerina utilisindex Jenkins & Orr 1973

Globigerina utilisindex

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