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Linked specimens: USNM-219447
Current identification/main database link:
The very small turborotaliid is a low trochospire of more than 12 chambers with 5 chambers in the last whorl. The outline of the test is elongate-subcircular and more or less lobate in spiral and umbilical views. In side view, the initial portion of the test is spirally strongly convex and raised as a minute obtuse cone over the level of the chamber surfaces of the final whorl. The chambers of the last whorl increase rapidly in size so that the ultimate chamber together with the penultimate chamber about equals in size the preceding portion of the test. The chambers of the final whorl are flattened on the dorsal side and strongly convex on the ventral side. The cameral and spiral sutures of the final whorl are well-incised, those of the early trochospire are masked by secondary shell substance. The inter-cameral sutures between the chambers of the last whorl are oblique on the spiral side and radial on the ventral side. The umbilicus is very small. The umbilical-peripheral interiomarginal aperture is an elongate, low-arched opening with an imperforate border which
can be faintly differentiated from the apertural face.
The calcareous walls are coarsely perforate, and the umbilically directed surfaces of the early chambers of the final whorl and the imperforate region of the apertural face just above the apertural border are covered with irregularly distributed, irregular-sized,blunt to pointed individual pustules. On the spiral side low, rounded probably composite pustules are still detectable on the surfaces of the early chambers of the initial cone of the trochospire. On the chambers of the final whorl, they are completely incorporated in the heavy unstructured walls surrounding the large wall pores. There is no longer any clear polygonal mesh-work. Under the light microscope, the wall surface seems to be non-pustulate, smooth, and the large,widely spaced wall pores, which on the early coil measure up to 6 microns across, represent the dominant wall formation. The maximum diameter of the wall pores of the dorsal side of the final chamber is about 3 microns. The wall pores are in funnel-shaped depressions of small diameter. The walls are not transparent.
Size: The maximum diameter of the holotype is about 175 microns, its maximum axial height about 125 microns. It is illustrated on Plate 41, Figure 4. The specimen coils to the left. It is from Hole 62.1,Core 32, Section 1, 15-17 centimeters; Zone N. 14. The new species is named for W. R. Riedel, Scripps Institution of Oceanography, La Jolla, California.
Extra details from original publication
Globorotalia riedeli, n.sp., differs in its outer wall formation, by its small raised central cone, and by its usually plano-convex morphology from all other small turborotaliids encountered in Hole 62.1. It seems to be represented by a plexus of forms related by the same outer wall formations but somewhat differing in the development of the initial raised cone. Together with the form as typified by the holotype, Plate 41,Figure 4, and also by a paratype, Plate 41, Figure 2,there exist more lobate specimens which are flat or even depressed over the center of the trochospire. Such a specimen is illustrated on Plate 41, Figure 1. In spiral view, the related but slightly more elongate and less lobate turborotalias, with the same outer wall formations but possessing chambers with a subacute periphery, as seen in side view, have also been referred to Globorotalia (T.) riedeli. Paratypes from Hole 62.1,Core 32, Section 1, 15-17 centimeters, Zone N. 14, with raised central cone and lobate outlines, corresponding well in outer wall formation and wall pores, with the holotype, have maximum diameters from 112 to 175 microns. Detailed scanning microscope observation of surface and apertural features of stratigraphically successive forms may prove that this group of minute turborotalias could perhaps be further subdivided. The more elongate, flat forms were first believed to be small representatives of Globorotalia (T.) siakensis LeRoy, 1939. Examination of specimens of Globorotalia (T.) siakensis in the collections of W. H. Blow by one of the writers (P.B.) however has shown that Globorotalia (T.) riedeli is not only much smaller than typical Globorotalia (T.) siakensis but also lacks the characteristic "comma""-shaped aperture of the siakensis group of forms. The outer wall formations are also completely different in Globorotalia (T.) siakensis as illustrated on Plate 35, Figures 1 through 8.
Another turborotaliid species, Globorotalia (Turborotalia) minutissima Bolli, 1957, in its general morphology, but not in its outer wall formations, resembles somewhat the peripherally more rounded individuals of Globorotalia (T.) riedeli. Globorotalia (T.) minutissima ranges from Zone N. 9 to Zone N. 16, and hence overlaps typical Globorotalia (T.) riedeli in Hole 62.1.According to Blow (1969, p. 352), Globorotalia (T.) minutissima seems to be particularly common in cold-water areas, such as the Vienna Basin, Italy and California. In Hole 62.1, this species has tentatively been recorded in Core 39, Zone N. 13. Other small turborotaliids which come close to Globorotalia (T.) riedeli are Globorotalia (Turborotalia) postcretacea (Myatluk), 1953, and Globorotalia (Turborotalia) permicra Blow and Banner, 1962. However, both of these species have different apertural features, recalling the ""comma""-shaped aperture of the siakensis group,and different outer wall formations. In addition, Globorotalia (T.) postcretacea has a translucent or transparent test, a feature never observed in Globorotalia (T.) riedeli."
Globorotalia (Turborotalia) riedeli compiled by the pforams@mikrotax project team viewed: 25-10-2020
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