Catalog - Globigerina tricamerata

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Globigerina tricamerata

Citation: Globigerina tricamerata Tolmachoff 1934

Type specimens: Plate XLI, fig. 21; C. M. I. F. No. 7040-7041.

Type sample (& lithostrat): A specimen of black fossiliferous lime occurring at the base of a thick section of shallow fresh-water shales and sands

Type locality: Atrato Valley, Colombia, on the west flank of the western Cordillera of the Andes Mountains, about thirty kilometers due east from the town of Quibdo.

Type repository: Pittsburgh, Carnegie Museum

Test subovoidal composed of three large final chambers, closely connected together, the last one of which almost equals in its size two other ones, or may be even larger than those. Sutures depressed, but not so deeply as usually in Globigerinae. Aperture not well known, apparently single and small on the last chamber, and opens into the umbilicus. Wall perforated rather coarsely.

1884. Globigerina bulloides var. triloba Brady, Report on the Foraminifera dredged by H.M.S. Challenger, during the years 1873-1876: Challenger Report, Zoology, IX, p. 595 , pl. LXXXI, figs. 2-3 , Edinburgh.
1931. Globigerina bulloides var. tribloba Hanzawa, Notes on some Eocene Foraminifera found in Taiwan (Formosa), with Remarks on the Age of the Hori Slate Formation and crystalline Schists: Sc. Rep. Tohoku Imp. Univ., 2nd Ser. (Geology), XII, No. 2A, p. 182, pl. XXIX, fig. 12 (Synonymy).
1932. Sphaeroidina (?) peruviana Berry, The Foraminifera of the Heath Formation of Northwestern Peru, South America: Eel. Geol. Helvetiae, XXV, No. r, p. 29, pl. II , fig. 4·

A great confusion exists in the literature with reference to Globigerina triloba Reuss. As may be seen on Reuss' figures, he described a form composed chiefly of three large chambers of the last formed whorl, but displayed also the small chambers of the preceding convolutions, and accessory apertures on the dorsal side of the test. Brady describing this form, as a variety of Globigerina bulloides D'Orb., gave figures of several rather different forms. His following description of forms "with final convolutions consisting of three relatively very large segments which sometimes form the entire visible shell," refers to figures 2 and 3 of Plate LXXXI, quoted above, and representing "bottom species." Varieties figured on Plate LXXIX are entirely different. There are, further, no supplementary apertures, represented on Brady's figures, and he did not mention them in his description. Macfadyen was, probably, quite right in suggesting that supplemental apertures were probably not present in the specimens studied by Brady. In the Egyptian specimens closely related to those of Austria, supplemental apertures were found often more numerous than stated by Reuss. Apparently Brady had in his hands forms similar to Reuss' species, but distinct enough to be considered specifically different. To the same conclusion apparently came Macfadyen. At least he did not include Challenger's forms in the synonymy of Globigerina triloba Reuss.

As a matter of fact, in most cases it is impossible to decide to which form the mention of Globigerina triloba Reuss refers, unless the description is accompanied by good figures. It may be the species under consideration, or Globigerina bulloides D'Orb., or Globigerina trilocularis D'Orb, next described. All three forms are closely related to each other, sometimes found together, and when not, may be considered vicarious from the stratigraphical point of view. The following data on the distribution of Globigerina triloba Reuss should be accepted, while keeping in mind these considerations. In the north Pacific Ocean, Globigerina triloba Reuss is found nearly everywhere with Globigerina bulloides D'Orb., but seems to be much less common. It seems to be rare in the seas in the area of the Philippine Islands. The species was found occasionally in the Panama Canal Zone in three localities of the Gatun Formation. It was described from the Vicksburg Group of Mississippi. In the Atlantic Ocean, according to Cushman, "Variety triloba Reuss is very nearly wanting".

Possibly this species was described by Hanzawa from the Japanese Eocene as a variety of Globigerina bulloides D'Orb. Into the above synonymy is included also Sphaeroidina (?) peruviana Berry from the Upper Oligocene of Peru, South America, which may belong to the variety described by Brady as, indeed, was suggested by Berry himself. In the fauna under consideration this species is almost as common as Globigerina bulloides D'Orb.

References:

Reuss, A. E. (1850). Neue Foraminiferen aus den Schichten des Osterreichischen Tertiarbeckens. Denkschriften der kaiserlichen Akademie der Wissenschaften zu Wien. 1: 365-390. gs O

Tolmachoff, I. P. (1934). A Miocene microfauna and flora from the Atrato River, Colombia, South America. Annals of the Carnegie Museum. 23: 275-356. gs

CATALOG OF ORIGINAL DESCRIPTIONS: Globigerina tricamerata Tolmachoff 1934

Globigerina tricamerata

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