Catalog - Globorotalia (Globorotalia) praefohsi

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Globorotalia (Globorotalia) praefohsi

Citation: Globorotalia (Globorotalia) praefohsi Blow & Banner 1966

Type specimens: pl. I, figs. 3, 4; pl. 2, figs. 6, 7, 10, 11: Fig. 3a-c, paratype, dorsal, axial-apertural, and ventral views, X 87: 4a-c, holotype, dorsal, axial-apertural, and ventral views, X 87; 6, paratype, morphologically and phylogenetically very primitive, X 135; 7, topotypic paratype, X 135; 1Oa-b, specimen illustrated in fig. 6, showing the acute periphery with a very narrow imperforate peripheral carina (breadth approximately four times the average distance between pores in this peripheral, later part of the test) developed in the last-formed chamber (a), X ca. 1000, and the rounded, fully perforate periphery of the early part of the last whorl (b), X ca. 500; 11, specimen illustrated in fig. 7, showing the well-developed carina in the last-formed chambers, X ca. 1000. Holotype (fig. 4a-c) deposited in the collections of the British Museum (Natural History), London, England, no. P45691; two paratypes (figs. 6, 1Oa-b and 7, 11) deposited in the collections of the British Petroleum Co., Ltd., Research Centre, Exploration and Production Division, Sunbury-on-Thames. England; one paratype (fig. 3a-c) deposited in the collections of the U. S. National Museum, Washington, D. C., no. USNM ex 38164.

Type locality: Holotype (fig. 4a-c) and two paratypes (figs. 6, 10a-b and 7, 11) from the El Mene - Pozon Road traverse, eastern Falcon, Venezuela (see Blow, 1959, op. cit.. map no. 4 ). One paratype (fig. 3a-c) from a depth of 3.5 m. in an auger hole 2.4 km. N30°E from Kampong Loebeckram-bahan, Tapoeng-Kiri area, Rokan-Tapunoeli region, Central Sumatra, Indonesia.

The test of the holotype (pl. 1, fig. 4a-c) consists of about two and one-half whorls of chambers, with six chambers in the first whorl and seven in the last. Successive whorl heights (measured dorsally from the proloculus) are in the approximate ratio 1:4:12. The test is completely evolute dorsally, with no conspicuous deposit of secondary laminae to obscure the early whorls. The dorsal surface is slightly convex and the dorsal sutures are narrowly and shallowly depressed, the dorsal walls of the chambers being but weakly, if at all, inflated. The dorsal intercameral sutures meet the lobulate spiral suture approximately at right angles. Their proximal ends are nearly radial, but distally they are recurved, meeting the weakly lobulate periphery at angles of about 45° . The periphery, in axial view, is bluntly acute in the early part of the last whorl, but it becomes progressively more compressed during ontogeny, and by the fourth chamber of the last whorl the periphery becomes sharply acute. The first four chambers of the last whorl are uniformly perforate; in this part of the test, no carina is formed. although the fourth chamber possesses a thickened (pseudocarinate) periphery. The fifth chamber of the last whorl (the antepenultimate chamber) develops a true carina, and this carina is present also on the peripheries of the penultimate and the last chambers. The penultimate and the ultimate dorsal intercameral sutures are limbate, possessing throughout their length deposits of imperforate shell material developed in continuity with the peripheral carina. The ventral surface is more convex than the dorsal surface, the ratio of ventral to dorsal convexity being about 3:1. The ventral side is completely involute, only six and one-half chambers of the last whorl being visible. The ventral intercameral sutures are narrowly and shallowly depressed, and they are smoothly curved or sinuous. meeting both the periphery and the narrow umbilicus at right angles or at very obtuse angles. The ventral walls of the chambers are uniformly perforate, and smooth except for a granular area of the earlier chambers immediately facing the aperture. The umbilical shoulders of the ventral chambers are very low. In the earlier chambers, the area between the umbilicus ancl the periphery is slightly convex, but this area becomes first flattened and then concave during ontogeny. The apertural face is not separated from the ventral face of the last chamber by any change in texture or structure. nor is it separated by an abrupt change of slope. It is well delimited along the periphery of the test by the sharply developed carina, and the area of the apertural face just ventral to the carina is slightly concave. the remainder of the apertural face being smoothly convex. The apcrtural race is narrowest at its umbilical end, and, at its mid-point, its breadth is approximately equal to one-half its total length. The narrow interiomarginal aperture extends from the umbilicus to the ventral margin of the carinate periphery and is furnished throughout its length with a strong lip. which is broadest near the umbilicus. In the holotype, the lip of the penultimate aperture (relict) is exposed and is contiguous with the final apertural lip.

The maximum diameter of the test is 0.55 mm.

Globorotalia barisanensis [sic] LeRoy. - LeRoy, 1944 (part), Colorado School Mines. Quart., vol. 39. no. 3, pt. I. p. 41, pl. 2, figs. 43-45 only.
Globorotalia fohsi fohsi Cushman and Ellisor. - Bolli, 1957 (part), U. S. Nat. Mus., Bull., no. 215, p. 119, pl. 28, fig. 9a-b only.
Globorotalia fohsi lobata (Bermudez). - Blow, 1959, Bull. Amer. Pal., vol. 39, no. 178. p. 213, pl. 16, figs. 113a-c.
Globorotalia (Globorotalia) lobata lobata Bermudez. - Banner and Blow, 1959, Palaeontology, vol. 2, pt. 1, p. 22, pl. 1, fig. 3a-c.
Not Globorotalia lobata Bermudez, 1949.
Not Globorotalia barisanensis LeRoy, 1939 = G. fohsi Cushman and Ellisor, 1939

Comparison of species: G. (G.) praefohsi differs from G. (G.) fohsi (and from G. barisanensis, G. lobata and G. robusta) principally in possessing a carina on the later chambers only of the adult last whorl, the early chambers of the adult final whorl being uniformly perforate and non-carinate. Unlike G. (G.) fohsi, only the last few dorsal intercameral sutures are limbate. Conversely, G. (G.) praefohsi differs from G. (Turborotalia) peripheroacuta in possessing a true imperforate carina in the later part of the last whorl.

Discussion of figured paratype: The paratype here illutrated (plate I, figure 3a-c), which is deposited in the U. S. National Museum, Washington, D. C. (Cushman Coll, ex no. 38164), is one of the seven partially carinate specimens deposited in that museum which were originally included by LeRoy in his paratype series of his species G. barisanensis. This specimen, which is now transferred to the paratype series of G. (G.) praefohsi, was obtained by LeRoy from sample Ho. 862A, the same sample from which the holotype of G. barisanensis was obtained. This paratype, however, is carinate only in its last two chambers, and the periphery of the first two chambers is bluntly rounded and fully perforate. It is not conspecific with the fully carinate G. (G.) barisanensis ( = G. (G.) fohsi), but it is morphologically essentially the same as the holotype of G. (G.) praefohsi.

References:

Blow, W. H. & Banner, F. T. (1966). The morphology, taxonomy and biostratigraphy of Globorotalia barisanensis LeRoy, Globorotalia fohsi Cushman and Ellisor, and related taxa. Micropaleontology. 12(3): 286-302. gs

CATALOG OF ORIGINAL DESCRIPTIONS: Globorotalia (Globorotalia) praefohsi Blow & Banner 1966

Globorotalia (Globorotalia) praefohsi

References:

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