Catalog - Globigerina soldadoensis

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Globigerina soldadoensis

Citation: Globigerina soldadoensis Bronnimann 1952

Type specimens: pl1 figs 1-9; 370085 Holotype:Plate 1,figures 4-6.Rz.287;T.L.L.,Cat.No.50506.

Type sample (& lithostrat): Lizard Springs Fm., Trinidad Soldado formation, Ramdat marl.

Type age (chronostrat): Palaeocene

Type locality: Lizard Springs Fm., Trinidad Soldado formation, Ramdat marl.

Type repository: Washington; USNM

The low trochoid test is composed of about two volutions. The four-chambered, occasionally five-chambered adult is lobulate in typical specimens. The spiral side is centrally more or less elevated, the umbilical side is convex. The umbilicus is large and deep showing the arcuate apertures of the latter formed chambers. The subglobular chambers increase gradually in size. They are rounded to slightly flattened peripherally and distinctly elongate in the direction of the axis of the test. At the umbilical side the chambers tend to be somewhat pointed. The end chamber can be smaller than the penultimate one or even rudimentary. Except for the indistinct sutures of the early ontogenetic stage, those of the spiral side are deep and curved in the direction of coiling, or they are oblique giving the impression of an overlapping arrangement of the chambers. The sutures of the umbilical side are straight throughout. The large arcuate apertures of the last formed chambers are provided with minute liplike boarders. The wall are perforate and rather thick. The surface is covered with irregularly distributed papillae which are stronger and more prominent on the early chambers of the adult whorl; they are absent or weakly developed near the aperture of the end chamber. The species is predominantly coiled sinistrally.

Holotype: Coiling: sinistral. Dimensions: maximum diameter of test, 0.35mm.; end chamber, radial diameter, 0.125mm.; tangential diameter, 0.23mm.; height, 0.25mm.

Remarks. At first, an attempt was made to differentiate three types on account of the number of chambers and rudimentary chambers, on the degree of peripheral flattening of the chambers, and on the general outline of the adult test. It was found, however, that this subdivision could not be maintained in a consistent way and, therefore, the three types, which are illustrated on Plate 1. figures 1-9, were united in the same species. The greatest diameters of the figured specimens are 0.3mm., 0.35mm.and 0.425mm. The radial diameter of the end chamber varies from 0.1mm.to 0.15mm. and the height of the end chamber from 0.25mm.to 0.32mm. The diameter of the aperture is from 0.05mm.to 0.1mm.
G. soldadoensis differs from Globigerina primitiva (Finlay), 1947 by the ellipsoid-lobulate outline, by the obliquely arranged chambers and their rounded margins, and by the less pointed umbilical portions of the chambers.
G.soldadoensis is one of the most characteristic Globigerinae of the Trinidad Paleoccne. It seems to be related to the spinose Globigerina decepta Martin, 1943 and Globigerina nitida Martin, 1943 both described from the Eocene Lodo formation of California. The comparison of the Trinidad forms with the holotypes of those species proved that G. soldadoensis is different from those forms. G. decepta Martin (holotype, Stanford University Collection, No.7399, Lodo formation, L.S.J.U. Loc.M-74, Sample, No.S-7-119, Lodo Gulch, Panoche Quad., Fresno Co., California, Coll. R.T.White) resembles G. soldadoensis in the granular surface, but it is clearly separated from G. soldadoensis by the much more pronounced planoconvex test, the oppressed chambers with distinct umbilical points, the rather rounded outline, the almost closed umbilicus and the small arcuate aperture. Globigerina nitida Martin (holotype, Stanford University Collection, No. 7400, L.S.J.U. Loc.M-74, Sample, No.S-7-47, Lodo Gulch, Panoche Quad., Fresno Co., California, Coll. R.T.White) is affined to G.decepta. The margin of G. decepta is more rounded and the chambers are more oppressed than in G. nitida, otherwise the two species are similar and possibly could be synonymous. This, however, can only be decided by the investigation of complete assemblages. The holotype of G. nitida is coiled dextrally, that of G. decepta sinistrally. Six out of eight topotypes of G. decepta and three out of eight topotypes of G. nitida are coiled to the right. Although these Californian forms and G. soldadoensis are separate species, they belong to a closely related group of Eocene Globigerinas with granulate surface.

Occurrence.—Both zones of the Lizard Springs formation, rare to abundant; Soldado formation, rare to common; Ramdat marl, abundant.

References:

Berggren, W. A., Pearson, P. N., Huber, B. T. & Wade, B. S. (2006b). Taxonomy, biostratigraphy, and phylogeny of Eocene Acarinina. In, Pearson, P. N., Olsson, R. K., Hemleben, C., Huber, B. T. & Berggren, W. A. (eds) Atlas of Eocene Planktonic Foraminifera. Cushman Foundation for Foraminiferal Research, Special Publication . 41(Chap 9): 257-326. gs O

Brönnimann, P. (1952d). Trinidad Paleocene and lower Eocene Globigerinidae. Bulletins of American Paleontology. 34(143): 1-34. gs

Olsson, R. K., Hemleben, C., Berggren, W. A. & Huber, B. T. (1999). Atlas of Paleocene Planktonic Foraminifera. Smithsonian Institution Press, Washington, DC. (85): 1-252. gs

CATALOG OF ORIGINAL DESCRIPTIONS: Globigerina soldadoensis Bronnimann 1952

Globigerina soldadoensis

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