CATALOG OF ORIGINAL DESCRIPTIONS: Globotruncana tricarinata colombiana Gandolfi 1955
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Citation: Globotruncana tricarinata colombiana Gandolfi 1955Taxonomic rank: sub-speciesType specimens: PI. 1, fig. 3a-c, 4a-c, Text figs. 5(la-c), 5(2a-c), 6(4a-b); 20827: type description p.20Type sample (& lithostrat): Molino section, S. 12141. Type age (chronostrat): Campanian-MaastrichtianType locality: Cesar Valley, Rio Molino, 200 km. NE of Villanueva; Northern ColombiaType repository: Ithaca, New York; Paleontological Research Institution
Current identification: Globotruncana linneiana (DOrbigny 1839)
Original Description The form is flat dorsally with protruding umbilical side, sidewall making a large angle with the roof of the chambers, as in Glt. tricarinata tricarinata (Quereau, 1893) and Glt. stuarti. The peripheral band is wide, perpendicular to the plane of coiling, with two well-developed, parallel keels. The chambers are generally arched, considerably overlapping, and rapidly increasing in size as
added. The sutures are curved, generally thick, and continuously raised; on the ventral side the sutural elevations are running sigmoidal around the umbilicus (lapparenti type) thickening considerably around the same umbilicus ("bourrelet umbilical," Mornod, 1949) which appears in side view or axial section as a third well-developed keel. The umbilicus is large and open.
In some specimens (PI. 1, fig. 4, Text fig. 5 (la-c) the early chambers of the last coil are slightly inflated, gradually becoming flat in the more adult stage; the keels are finely beaded becoming increasingly raised in the adult stage; the test is spinose; on the umbilical side, the sutures are radial and depressed, the chambers slightly inflated. The forms are quite similar to Glt. ventricosa (White), as described in detail by Mornod, 1949. The only remaining distinctive characteristic: the strongly developed umbilical thickening. Glt. ventricosa of Mornod (op. cit. fig. 85/3 a-c) may belong to this type of transitional form, but due to the strong umbilical thickening should still belong to the Glt. tricarinata, type. Size: Dimensions of holotype. Width 0.44 x 0.32 mm.; thickness, 0.16 mm. Extra details from original publication Remarks.—The form shows a side view which is identical to Glt. tricarinata ( (Juereau 1893, pi. 5, fig. 3). As is known, this form is named only from thin section. Later the authors made pictures of Glt. tricarinata which show all the same typical axial sections, but the number, shape, and arrangement of chambers ( fig. 6) differ considerably. Therefore, the problem arises which of those forms, including ours, is to be identified with the original of Quereau. Since, however, it is here believed that many forms of "tricarinata type" are perhaps present in the original material, and since there is no possibility for the writer to check it, the forms figured by Cushman.1936 (pi. 61, fig. 18a-c) are considered as holotype of Glt. tricarinata tricarinata in spite of some apparently evolved characteristics.
It is of particular phylogenetic interest to describe in detail a single specimen which was found high and isolated in the section and is shown in fig. 4 (2a-c). The side view shows the identical profile which is common to all tricarinata forms with the third keel well developed. Peculiar, however, is the extreme development of the last chamber, the spinose test, the radially depressed umbilical sutures in the early stages and the slight inflation of the chambers. In accordance with our procedure of not creating any new nomenclatural units without having a sufficient number of specimens, this specimen has been considered as a Glt. tricarinata colombiana and was consequently not named. It is believed, however, that it may represent a stage of a well-defined line of. evolution and, accordingly, a new species or subspecies for the following reasons:
1. It cannot be interpreted as an immature form of Glt. colombiana because of the extremely peculiar development of the last chambers.
2. It was found isolated and high in the section where no Glt. colombiana was found.
A similar tendency toward such forms with few chambers in the last whorl is shown in other groups ( cf. Glt. cesarensis, PI. 2, fig. 10a-c).
References:
Gandolfi, R. (1955). The genus Globotruncana in northeastern Colombia. Bulletins of American Paleontology. 36: 1-118. gs
Globotruncana tricarinata colombiana compiled by the pforams@mikrotax project teamviewed: 11-2-2025
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