Catalog - Globorotalia zealandica pseudomiozea

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Globorotalia zealandica pseudomiozea

Citation: Globorotalia zealandica pseudomiozea Walters 1965

Type specimens: Holotype(Fig. 6, P-R) Register No. TF 1488.

Type sample (& lithostrat): sample GMR 368,

Type locality: An unnamed, right-bank tributary of the Waiomoko River, Sheet N98/2, grid ref. 536552, approximately 13 miles north-east of Gisborne, N.Z.

Type repository: Lower Hutt; N.Z Geological Survey foraminiferal collections

Test a low trochospire consisting of 2½-3 whorls of slowly enlarging chambers, with 4-5 (usually 4) in the last whorl; equatorial profile subcircular, equatorial periphery very faintly lobate; dorsal surface of. the test flat or slightly convex; ventral side inflated and almost hemispherical; axial periphery rounded; wall of newly formed chambers moderately thin finely perforate, but older chambers show a progressive secondary thickening, especially on the ventral side and on the reriphery, giving a glassy appearance, often accompanied by a coarsening 0 the punctation, so that the ventral surface of the earliest chambers of the last formed whorl becomes quite knobbly; dorsally, chambers about twice as long as broad, separated by curved, rather tangential sutures which are slightly depressed between the weakly inflated later chambers; chambers triangular in outline on the domed ventral side, separated by more or less straight sutures which are not easily discernible near the periphery but which, towards the umbilical area, develop into jagged clefts in the thickened ventral wall, opening into the small, shallow umbilicus; aperture a low to moderately high arch, bordered by a thickened rim or a thick, narrow lip, situated in the middle of the fairly flattened terminal face of the last "normal" chamber, commonly obscured by the development of a small, finely punctate terminal chamberlet possessing a low, undistinctive, often irregular, aperture.

Maximum diameter = 0.37 mm; height = 0.25 mm.

Remarks: This subspecies differs from G. zealandica zealandica Hornibrook (at the opposite end of a continuous range of variation) in bemg larger and more coarsely punctate, in possessing a higher, more dome-like ventral side and a less lobulate periphery, and in possessing a distinctive thickening of the test wall, especially on the ventral side and on the periphery, frequently giving a somewhat glassy appearance to the ventral side as a whole and a knobbly surface to' the ventral surface of the earliest chambers of the last formed whorl.
It differs from G. zealandica incognita subsp. nov. (its immediate ancestor), in being larger, in possessing a more inflated and dome-like ventral side and a slightly less lobulate equatorial periphery, and in exhibiting the pronounced development of secondary thickening of the early chambers of the last whorl, which is only incipiently developed in G. zealandica incognita.
Some juveniles of the G. miozea lineage are relatively inflated and tend to resemble this subspecies, especially when the obscuring terminal chamberlet is developed. The difference in shape of the septal foramen, as seen in broken specimens, serves to prevent any confusion between the two, however.

Stratigraphic Range: From the upper third of the Awamoan ,up into< the base of the succeeding Altonian Stage.

References:

Walters, R. (1965). The Globorotalia zealandica and G. miozea lineages. New Zealand Journal of Geology and Geophysics. 8: 109-127. gs

CATALOG OF ORIGINAL DESCRIPTIONS: Globorotalia zealandica pseudomiozea Walters 1965

Globorotalia zealandica pseudomiozea

References:

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