Catalog - Polyperibola

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Polyperibola

Citation: Polyperibola Liska 1980

Type species: Polyperibola christiani Liska 1980

Diagnosis. Initial portion of test trochoidal, with two to three whorls; chambers globular, lightly appressed; umbilical area covered by final chamber(s); supplementary chambers and bullae develop over dorsal intercameral sutures tending to envelop earlier trochoid whorls; no visible primary aperture, nor supplementary apertures on dorsal portion of trochoid test; final chamber, all supplementary chambers, and bullae with multiple, semicircular, sutural apertures, bordered by imperforate rims; apertures restricted to added chamber or bullae and do not develop on, or with, covered surface; test wall radial calcite, thin, finely porous and lightly pustulose in trochoid portion of test; walls of supplementary chambers and bullae thinner walled, with smoother, more vitreous appearance and a similar to slightly finer pore pattern than walls of trochoid chambers.

The generic name Polyperibola is Latin, meaning, “many enclosing features.”

Remarks. Polyperibola is, at present, a monotypic genus exhibiting an extreme variation in test size and shape, and the number and shape of supplementary chambers and bullae. Diagnostic features are a pustulose trochoid initial growth stage, supplementary chambers and bullae enveloping earlier portions of the test, and hemispherical, multiple, sutural, apertures with imperforate rims. The apertures are restricted to the final chambers, all supplemental chambers and bullae.
Although this morphology is distinct and not easily confused with other genera, Polyperibola exhibits growth tendencies of earlier genera. The Eocene genus Globigerinatheka Bronnimann, also developed a final chamber over the umbilicus and developed chambers and bullae on the earlier portion of the test (Bronnimann 1952, Bolli 1972). Polyperibola differs from Globigerinatheka in having a smaller, more globose, morphologically variable test, a smoother test wall, and a larger number of smaller sutural apertures.
In Globigerinatella Cushman and Stainforth, from sediments of early Miocene age, as in Polyperibola, the earlier portion of the test is enveloped by later growth stages and has multiple rimmed apertures (Bronnimann 1950). Globigerinatella is larger than Polyperibola, has a coarser test wall, is less enveloped by numerous bullae and supplementary chambers and lacks the multiple, sutural, rimmed apertures on all bullae and supplemental chambers, as found in Polyperibola.
The writer examined specimens of the Tortonian genus Velapertina Popescu (1969). Polyperibola has a different wall structure, a smaller test, and no secondary apertures on the spiral side of the test. Velapertina has umbilical and sutural bullae which do not envelop the earlier portion of the test. The infralaminal apertures of the bullae in Velapertina differ from the diagnostic, sutural apertures of Polyperibola.
Globigerinoita Bronnimann has a less globose but coarser test than Polyperibola. The bullae which cover the primary and supplementary apertures have two to three openings and differ considerably from the supplementary chambers and bullae, with multiple sutural apertures, which envelope the earlier portion of the test of Polyperibola.
A comparison of Polyperibola with Pliocene and Recent specimens of Candeina d’Orbigny was made and certain significant differences were found. Candeina has secondary “apertures” in the dorsal portion of the test which are not present in Polyperibola. This suggests the two genera have dissimilar ancestors, a “Globigerinoides type” for Candeina (as stated by Blow 1969), and a globigerine (Globigerinita?) ancestor for Polyperibola. Candeina has a similar test wall, but lacks the development of pustules and supplementary chambers or bullae enveloping the early portions of the test. In addition, the sutural apertures of Candeina are developed within the suture, are elliptical, completely rimmed, and develop both within the added and earlier chamber. The sutural apertures of Polyperibola are semicircular and restricted to the added chamber. From this, it appears that there is no direct evolutionary lineage between the two genera.
The most closely related genus however, seems to be Globigerinita Bronnimann (1951). Globigerinita (middle Miocene to Recent) could evolve to Polyperibola by the development of the bulla in Globigerinita into a final chamber, the retention of multiple, sutural openings developing imperforate rims, the envelopment of the globigerine portion of the test by additional chambers and bullae which retain the sutural apertures, and the addition of pustules to the test wall. Because it appears to be closely related to Globigerinita, Polyperibola is tentatively placed in the family Candeinidae, and the author here follows the classification used by Parker (1967).

References:

Liska, R. D. (1980). Polyperibola, a new planktonic foraminiferal genus from the late Miocene of Trinidad and Tobago. Journal of Foraminiferal Research. 10(2): 136-142. gs

CATALOG OF ORIGINAL DESCRIPTIONS: Polyperibola Liska 1980

Polyperibola

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