Catalog - Pulleniatina primalis

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Pulleniatina primalis

Citation: Pulleniatina primalis Banner & Blow 1967

Type locality: Sample WHB 181B, Zone N. 18, Bowden Formation, Buff Bay, Jamaica, W. I

The holotype (plate 3, figure 2a- c) is a test consisting of approximately three complete whorls of chambers, not enlarging with continuous regularity. The last whorl consists of five chambers, the second whorl of four chambers, and the first whorl of four (or perhaps five) chambers. The test is completely evolute dorsally and completely involute ventrally. The chambers are globose and their peripheries are broadly rounded. The walls of the chambers are thick and wholly perforate except for a narrow ventral area facing the aperture. Dorsally, the wall is thickest over the early chambers, and these possess scattered large pores and approximately an equal number of evenly distributed low, rounded, scattered pustules. Throughout the last two whorls the dorsal surface becomes progressively smoother and more finely perforate exteriorly. The ventral surface is smooth except for a granular area immediately facing the aperture. The dorsal spiral and intercameral sutures of the last two whorls are depressed. The spiral suture, like the periphery of the test, is lobulate, but the dorsal intercameral sutures are only slightly curved, meeting both the spiral suture and the periphery nearly at right angles. In the last whorl, the mode of coiling deviates from the uniform trochospire apparently normal for the earlier whorls, and the chambers progressively increase their degree of ventral embracement. The ventral parts of successive chambers completely cover the umbilicus formed at the junction of the ventral ends of earlier chambers. Only a very shallow umbilical depression remains. The aperture is a low, interiomarginal arch, extending ventrally along the base of the low, rounded apertural face from a point ventral to the periphery of the first chamber of the last whorl to the anterior intercameral suture of the antepenultimate chamber of the last whorl. The aperture possesses no lip, but the narrow, convex apertural face is thickened, rimlike and hyaline immediately above and throughout the length of the aperture.

The maximum diameter is 0.43 mm., and the maximum thickness (i. e., height) is 0.33 mm.

Discussion of paratypes: The figured topotypic paratype (plate 1, figure 7 a-c) illustrates the maximum degree of dorsal convexity (spiral height) observed in the type assemblage of sample WHB 181B. Consequent upon this greater dorsal convexity, the radial breadth of the chambers of the last whorl appears less, and the later intercameral dorsal sutures are more oblique. The lastformed chamber of this specimen is smaller than normal, and its ventral margin incompletely covers the umbilical end of the penultimate chamber, forming a narrow, abnormal, false umbilicus. Even here, however, the increasing ventral embracement of the chambers of the last whorl can be observed.

The specimens from the Wana No. 1 Well, Papua, core at 6631 ft. (high in Zone N. 17), have four or five chambers in the last whorl (plate I, figures 3 and 4, respectively). These specimens are stratigraphically slightly older than the holotype population, and the degree of progressive ventral chamber embracement is often less. Streptospirality is present in the last few chambers, but such specimens may well have been wrongly included by past authors in Globorotalia (Turborotalia), e. g., in G. (T.) injlata (compare Australasian Petroleum Company, 1961, pp. 78- 80). The specimens of Pulleniatina primalis from the Cubagua No. I Well, core at 946- 953 ft. (also from high in Zone N. 17) (plate I, figures 5-6), are virtually identical with the specimens from Wan a No. 1 (plate 1, figures 3-4) in all respects except coiling direction and test size. These specimens were among those identified by Bolli ( 1964, pp. 544-546; see also Bolli and Bermudez, 1965, p. 132), from Cubagua as "Pulleniatina obliquiloculata"". Clearly, these specimens belong to neither Globorotalia (T.) inflata nor Pulleniatina obliquiloculata ( s. l.) but are conspecific with Pulleniatina primalis, n. sp., here described.

Dissected specimens of P. primalis disclose that the first whorl of chambers is turborotaline, with about five inflated chambers and a narrow, intraumbilical-extraumbilical, lipped aperture. At later growth stages, the umbilicus becomes closed by ventral chamber involution (plate I, figure 8), and the aperture becomes wholly extraumbilical. At this stage, it may be a high, rounded arch near the mid-point of the basal suture of the septum (plate I, figure 8). The ventral surfaces of the early chambers show continuously developed remains of dense, fine hispidity, but the exterior surface of adult specimens is smooth. Advanced adult specimens of P. primalis lose granulation on the dorsal surface over the early whorls, and develop a uniformly smooth exterior, except in a narrow ventral area immediately facing the aperture.

Comparison with other species: Pulleniatina primalis differs from P. obliquiloculata (s. l.) in its ventrally restricted primary aperture, which typically does not reach the periphery of the preceding whorl; in its lack of a broad umbilical depression; and in the innermost ventral ends of the adult chambers, which are narrow and meet without forming a distinct linear suture between the opposed chambers. All specimens of P. primalis which we have observed remain wholly evolute dorsally (with respect to the extent of the chamber lumina), and the apertural position is such that dorsal involution could not occur in normally growing specimens. P. primalis differs from P. spectabilis Parker, 1965, in lacking the narrowly angled, acute, frequently pseudocarinate periphery characteristic of that species.

Observed distribution: Pulleniatina primalis occurs in both the Caribbean and Indo-Pacific provinces (e. g., in Venezuela, Ecuador, Jamaica, marine cores off Trinidad and in the Atlantic, in Papua, New Guinea, Fiji, Saipan, Guam, Java, and in Pacific deep-sea cores). P. primalis first appears ·within Zone N. 17 (of Banner and Blow, 1965a) and persists to within early horizons of Zone . 20 (i. e., it is known to range from late Miocene until middle Pliocene). A form probably referable to P. primalis was illustrated by Stainforth (1948, pl. 26, figs. 21 - 23) from the ""Upper Miocene"" of Ecuador (probably the Punta Gorda beds). However, we have found both P. primalis and P. obliquiloculata /praecursor to be present in the Punta Gorda beds, and we cannot be fully certain of the taxonomic position of the form illustrated by Stainforth, since it is a broken, incomplete specimen."

References:

Banner, F. T. & Blow, W. H. (1967). The origin, evolution and taxonomy of the foraminiferal genus Pulleniatina Cushman, 1927. Micropaleontology. 13(2): 133-162. gs

CATALOG OF ORIGINAL DESCRIPTIONS: Pulleniatina primalis Banner & Blow 1967

Pulleniatina primalis

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