Catalog - Neoacarinina blowi

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Other pages this level: N. blowi, N. conglomerata ventriosa

Neoacarinina blowi

Citation: Neoacarinina blowi Thompson 1973

Type specimens: Holotype, USNM 187701 (plate 1, figure 1 a-c) & figured paratypes, USNM 187702-187703

Type sample (& lithostrat): Core RC8-39 at 120 cm;

Type age (chronostrat): Late Pleistocene

Type locality: western Crozet Basin (text-figure 1) of the southwest Indian Ocean, latitude 42° 53' S., longitude 42° 21' E., at a depth of 4330 meters.

Type repository: Washington; USNM

Test a large, low trochospire, consisting of 10-11 chambers arranged in 3 whorls in adult; usually 3-4 chambers in final whorl; chambers increasing in size rapidly in a globigeriniform manner; in axial profile, spiral side almost flat and umbilical side strongly convex; periphery rounded to subangular; chambers angulo-conical to globular, much embracing; final chamber less inflated, elongated, often extending across umbilical area like a large bulla; sutures on both spiral and umbilical sides radial and depressed, becoming less distinct with ontogeny; aperture a low, lipped arch, umbilical-extraumbilical, its shape being determined by extent of final chamber; wall calcareous, finely perforate; surface densely covered by thick multiple spines.

Maximum diameter of the holotype 0.5 mm.

In honor of the late Dr. Walter H. Blow.

Remarks: This form occurs rarely throughout core AC8-39, which does not penetrate sediments older than the G. truncatulinoides truncatulinoides Zone (N. 22). It was not noted above 30 em. No ancestral form was observed. Many globigerinids and globorotaliids develop spines or pustules of various sizes and densities during their ontogeny, but, with maturity and migration to deeper habitats, additionally secreted calcite cortex smoothes the relief of the test (Be, 1960, 1965; Be and Ericson, 1963; Be, Mclntyre and Breger, 1966). The only other spinose globorotaliid present in the samples is G. inflata. Juveniles of this species are quite hispid, but SEM study proved the spines to be single and non-branching. Neoacarinina, however, has spines which are cylindrical, stalagmitic projections (plate 1, figure 4) that are probably hollow. Typically, two or more intergrown spines arise from the same circular spine base; frequently, the spines branch with small additional spines near the apices. These multiple spines are found on all parts of the test, but are best preserved in the umbilicus, and are most abundant on the final chamber.

The holotype, USNM 187701 (plate 1, figure 1 a-c), is from core RC8-39 at 120 em. in depth. The figured paratypes, USNM 187702-187703 (plate 1, figures 2-3), are from core RC8-39 at 30 em. and 120 em. in depth, respectively.

References:

Thompson, P. R. (1973). Two new late Pleistocene foraminifera from a core in the southwest Indian Ocean. Micropaleontology. 19: 469-474. gs

CATALOG OF ORIGINAL DESCRIPTIONS: Neoacarinina blowi Thompson 1973

Neoacarinina blowi

References:

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