Catalog - Globorotalia munda

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Globorotalia munda

Citation: Globorotalia munda Jenkins 1966

Type specimens: TF 1507: holotype and 1 paratype.

Type age (chronostrat): Whaingaroan-Duntroonian Stages (Oligocene)

Type locality: S127/422, F 11444, grid ref. 242931, Sheet 127, Earthquakes, very base of greensands. Collected by A. C. Amies.

Type repository: Lower Hutt, New Zealand; New Zealand Geological Survey

Test free, small, low trochospiral, sinistrally coiled; equatorial periphery, quadrilobate, axial periphery rounded. Wall
calcareous, finely perforate, fairly smooth with minute pustules. Chambers ovate, slightly compressed, 10 arranged in just under 2 whorls, proloculus diameter about 0.02 mm. Sutures on the spiral side curved, depressed; on the umbilical side, radial, depressed. Umbilicus shallow. Aperture, low arch with a thin lip, interiomarginal, umbilical-extraumbilical.

REMARKS: Globorotalia munda n. sp. has a short stratigraphic range, limited to the upper part of G.angiporoides angiporoides zone to lower G. euapertura zone of the Whaingaroan-Duntroonian Stages of the Earthquakes Marl and Kokoamu Greensand in the Waitaki Valley. Its ancestry is not known but G. munda evolved directly into Globigerina juvenilis Bolli.
This evolutionary lineage has been observed in the closely sampled Earthquakes Marl of Duntroon where 7 samples were collected at two-foot vertical intervals by the late A. C. Amies. A series of specimens from the 7 successive samples have been illustrated to demonstrate the evolution of the test morphology (Nos. 134--136).
There is a change in the position of the aperture from an extraumbilical-umbilical position in Globorotalia munda to an umbilical position in Globigerina juvenilis (Nos. 134--166), this being a rare instance of a Globorotalia evolving into a Globigerina. After evolving into G. juvenilis. G. munda became extinct.
Concomitant with the adoption of an umbilical position by the aperture there is also a change in the final chamber, which moves towards the umbilicus, increasing the height of the test spire and eventually producing Globigerina bradyi-like forms in the uppermost sample (No. 137). In sample S127/427 there is a specimen with a bulla-like final chamber in an umbilical position (No. 140). The writer' suggests that the first G. juvenilis appears in the sample S127/425 (Nos. 147-151), and that the change of position of the final chamber occurs first in the juveniles of G. juvenilis
in sample S127/424 (No. 156). Transitional forms connecting the two taxa exist in the two samples S127/425 and S127/424.
The same evolutionary change has also been observed in samples from the Earthquakes section of Gage (1957) and in the Kokoamu Cliff section, Waitaki Valley. In the type sample (S127/422) the coiling ratio of G. munda is 57 dextral and 43 sinistral The most variable feature in the type population is the final chamber, which in most specimens is slightly larger than the penultimate chamber. In a minority of individuals it is smaller, with a corresponding reduction in the size of the aperture as in the figured paratype (No. 133).
It should be noted that Mr Hornibrook is of the opinion that the Earthquakes Marl and Kokoamu Greensand at the Earthquakes section contain a mixed Whaingaroan and Duntroonian benthonic foraminiferal fauna. As far as can be ascertained there does not appear to be a similar mixed planktonic foraminiferal fauna. The specific name is derived from the Latin word mundus meaning "neat""."

The article was published in the December 1965 issue of the journal but appeared in early 1966, so for taxonomy the correct date is 1966

References:

Jenkins, D. G. (1966b). Jenkins, D. G. (1966b). Planktonic foraminiferal zones and new taxa from the Danian to lower Miocene of New Zealand. New Zealand Journal of Geology and Geophysics. 8 [1965](6): 1088-1126. New Zealand Journal of Geology and Geophysics. 8 [1965](6): 1088-1126. gs

Pearson, P. N., Wade, B. S. & Huber, B. T. (2018c). Pearson, P. N., Wade, B. S. & Huber, B. T. (2018). Taxonomy, biostratigraphy, and phylogeny of Oligocene Globigerinitidae (Dipsidripella, Globigerinita, and Tenuitella). In, Wade, B. S. , Olsson, R. K. , Pearson, P. N. , Huber, B. T. & Berggren, W. A. (eds) Atlas of Oligocene Planktonic Foraminifera. Cushman Foundation for Foraminiferal Research, Special Publication. 46(Chap 16): 429-458. In, Wade, B. S., Olsson, R. K., Pearson, P. N., Huber, B. T. & Berggren, W. A. (eds) Atlas of Oligocene Planktonic Foraminifera. Cushman Foundation for Foraminiferal Research, Special Publication . 46(Chap 16): 429-458. gs O

CATALOG OF ORIGINAL DESCRIPTIONS: Globorotalia munda Jenkins 1966

Globorotalia munda

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