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Linked specimens: USNM-219442
Current identification/main database link: Neogloboquadrina acostaensis (Blow, 1959)
The medium-sized test is a flat trochospire consisting of at least 12 subglobular chambers with five chambers in the final whorl. The early chambers increase rapidly,those of the final whorl only gradually and the ultimate chamber is slightly smaller than the penultimate one. The chambers of the final whorl in spiral view are tangentially slightly larger than radially with the exception of the ultimate one which is about equidimensional. The cameral and the spiral sutures are well defined and depressed, and the outline of the test is therefore lobate in spiral and umbilicate views. The early cameral sutures are oblique, whereas those between the chambers of the final whorl are radial. In lateral view the spiral side is virtually flat and the final chambers somewhat displaced ventrally; the umbilical side is faintly concave. The chambers are not compressed in axial direction. In umbilical view, five chambers are visible; the fifth is partially masked by a large tegilla, as shown by the scanning micrograph (Plate 33, Figure 3). The tegilla starts as a strong peripheral lip and, toward the umbilicus, develops into an angular plate covering most of the umbilicus, which is about 120 microns in diameter. The tegillate umbilical coverying is densely but finely pustulate in its central portion. Its maximum diameter is about 100 microns. The corners of the umbilical plate extend into the sutural depressions. They are tangentially-wide end-chamber from Globorotalis tumida tumida (Brady), 1877, and radially directed. The aperture is a low umbilical-extraumbilical arch of about a 15-microns height covered in its umbilical portion by the strong tegilla. The wall is calcareous, perforate, and the surface is pustulate. The scanning micrograph of the umbilical side shows strong, pointed, individual pustules in the vicinity of the umbilicus on the early chambers of the final whorl. On the other portion of the surface, the pustules are fused in their basal portions, blunt, and form polygonal walls around the deeply set poral openings of the 2- to 4-micron diameter. The ventral side of the penultimate chamber exhibits details of the pustular structures. As in the case of Globorotalia (T.) pseudopumilio Brönnimann and Resig, n. sp., and Globorotalia (T.) planespira Brönnimann and Resig, n. sp., here also the pustules are made up of small elements or "crystallites" discernible as clearer points on the darker background of the scanning micrograph.
Size: The maximum diameter of the holotype is about 355 microns. The specimen coils to the right, and is illustrated on Plate 33, Figure 3. It is from Hole 62.1, Core 15, Section 1, 15-17 centimeters, Zone N. 18.
Extra details from original publication
Globorotalia (T.) acostaensis tegillata, n. subsp., differs from Globorotalia acostaensis acostaensis Blow, 1959,as typified by Blow (1969, pi. 9, fig. 13-15), by the umbilical tegilla which in well-preserved individuals covers not only the axial cavity but may extend into the umbilical sutural depressions. Globorotalia (T.) acostaensis tegillata occurs stratigraphically first in Hole 62.1 at the base of Zone N. 16, whereas typical representatives of Globorotalia (T.) acostaensis acostaensis appear in Hole 62.1 for the first time in the uppermost part of Zone N. 16. The tegillate subspecies is the older form from which the non-tegillate subspecies seems to have evolved by reduction of the tegilla into a thick rim-like lip, as exhibited by the holotype of Globorotalia (T.) acostaensis acostaensis.
The evolutionary sequence from Globorotalia (T.) acostaensis tegillata to Globorotalia acostaensis acostaensis seems to be fairly well-established, as in our material transitional forms are well represented. Parker (1967) has figured a series of the tegillate subspecies as Globoquadrina acostaensis (Blow) on Plate 24, Figures 3, 5, 6, 7 and 8. These figures show the tegilla in extreme modification, masking not only the umbilicus but extending deeply into the radial umbilical sutures.
The number of chambers in the final whorl varies in Parker's specimens from 4 to 6. This variation is also found in our paratypes of Globorotalia (T.) acostaensis tegillata. We believe that Parker's (1967) individual illustrated on Plate 24, Figures 10 and 11, referred by her to Globoquadrina humerosa (Takayanagi and Saito), represents Globorotalia (T.) acostaensis tegillata. A questionable individual of the new subspecies seems to be also illustrated by Parker's (1967) Plate 25, Figure 4, also placed by her in Globoquadrina humerosa. It should be noted that the tegilla of Globorotalia (T.) acostaensis tegillata is morphologically an umbilical-sutural extension of the apertural lip and not a development of an isolated tooth-like structure, as in known to occur in Globorotalia (T.) dutertrei and in Globorotalia (T.) acostaensis humerosa as shown by the scanning micrograph Plate 33, Figure 1. Such tooth-like structures, if fused, would not form a simple extension of the rim of the final aperture but a structure of spiral nature following from one aperture to the next one. Paratypes of Globorotalia (T.) acostaensis tegillata coil randomly. Maximum diameters of seven paratypes from Core 15, Section 1, and Core 16, Section 1, range from about 200 to 400 microns.
Globorotalia (Turborotalia) acostaensis tegillata compiled by the pforams@mikrotax project team viewed: 25-10-2020
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